Matrix effects in quantitative pesticide analysis using liquid chromatography-mass spectrometry

Ultrasonic-induced grafted lanthanum sulfide decorated multi-walled carbon nanotube onto bacterial cellulose applied for adsorption of pesticides in environmental waters

A new biosorbent was fabricated by modification of bacterial cellulose biopolymer grafted with lanthanum sulfide decorated carboxylated multiwall carbon nanotube (La2S3@MWCNT@BC). The sorbent was employed in a green alternative dispersive-solid phase extraction of a variety of 14 pesticides in environmental water samples. The analyses were performed using GC-µECD. The properties and structure of La2S3@MWCNT@BC nanocomposite were characterized by scanning electron microscopy, energy-dispersive X-ray spectroscopy, Fourier transform infrared spectroscopy, and adsorption-desorption isotherms. The composition of the sorbent was also investigated to evaluate the adsorptive properties of its constituents. The impact of various parameters influencing extraction efficacies such as sorbent dose, adsorption time, sample pH, ionic strength, and desorption conditions was investigated. The method was validated by specificity, matrix effect % (-0.4 to -7.4), enrichment factor (4-10), limits of quantification (0.007-0.31 μg L-1), matrix-matched calibration linearity (0.01-200 µg L-1), determination coefficients (r2=0.9921-0.9998), and precision. The optimized method was applied for the analysis of multiclass pesticides in seven environmental and drinking waters and the recoveries were obtained in the 81-108 % range with RSDs of 2.5-4.7 %. This paper is the first report on the synthesis and use of La2S3@MWCNT@BC nanocomposite to extract pesticides from different water samples. The greenness of the procedure was evaluated by the AGREE protocols.

Post column infusion of an internal standard into LC-FT-ICR MS enables semi-quantitative comparison of dissolved organic matter in original samples

Ultrahigh resolution mass spectrometry hyphenated with liquid chromatography (LC) is an emerging tool to explore the isomeric composition of dissolved organic matter (DOM). However, matrix effects limit the potential for semi-quantitative comparison of DOM molecule abundances across samples. We introduce a post-column infused internal standard (PCI-IS) for reversed-phase LC-FT-ICR MS measurements of DOM and systematically evaluate matrix effects, detector linearity and the precision of mass peak intensities. Matrix effects for model compounds spiked into freshwater DOM samples ranging from a headwater stream to a major river were reduced by 5-10% for PCI-IS corrected mass peak intensities as compared to raw (i.e., untransformed) intensities. A linear regression of PCI-IS corrected DOM mass peak intensities across a typical DOM concentration range (2-15 mg dissolved organic carbon L-1) in original, non-extracted freshwater samples demonstrates excellent linearity of the detector response (r2 > 0.9 for 98% of detected molecular formulas across retention times). Importantly, PCI-IS could compensate for 80% of matrix effects across an environmental gradient of DOM composition from groundwater to surface water. This enabled studying the ionization efficiency of DOM isomers and linking the observed differences to the biogeochemical sources. With PCI-IS original, non-extracted DOM samples can be analysed by LC-FT-ICR MS without carbon load adjustment, and mass peak intensities can be reliably used to semi-quantitatively compare isomer abundances between compositionally similar DOM samples.

Development of an analytical method for the determination of more than 300 pesticides and metabolites in the particulate and gaseous phase of ambient air

Pesticides can enter the atmosphere during spraying or after application, resulting in environmental or human exposure. The study describes the optimisation and validation of analytical methods for the determination of more than 300 pesticides in the particulate and gaseous phases of the air. Pesticides were sampled with high-volume air samplers on glass-fibre filters (GFFs) and glass columns filled with polyurethane foam (PUF) and XAD-2 resin. Comparing different extraction methods, a QuEChERS extraction with acetonitrile was selected for the GFFs. For the PUF/XAD-2 columns, a cold-column extraction with dichloromethane was used. Instrumental determination was performed using liquid chromatography/electrospray ionisation-time-of-flight mass spectrometry (LC/ESI-QTOF) and gas chromatography/electron impact ionisation-tandem mass spectrometry (GC/EI-MS/MS). Recovery experiments showed recovery rates between 70 and 120% for 263 compounds on the GFFs and 75 compounds on the PUF/XAD-2 columns. Semi-quantitative determination was performed for 39 compounds on the GFFs and 110 compounds on the PUF/XAD-2 columns. Finally, 27 compounds on the GFFs and 138 compounds on the PUF/XAD-2 columns could be determined only qualitatively. For the determination of the PUF/XAD-2 samples, signal suppression (LC) or signal enhancement (GC) due to matrix effects were determined. Method quantification limits of the optimised methods ranged from 30 to 240 pg/m3 for the target compounds on the GFFs, and from 8 to 60 pg/m3 on the PUF/XAD-2 columns. The applicability of the method was demonstrated by means of environmental air samples from an agricultural area in the Netherlands.

Dissipation and Risk Assessment of Propaquizafop in Ginseng under Field Conditions

Propaquizafop is a highly efficient aryloxy phenoxy propionate chiral herbicide. However, the use of propaquizafop, including its safe use methods, residue patterns, dietary risk assessment, and maximum residue limits, for ginseng, a traditional Chinese medicinal plant, has not been studied. An analytical method was established for the simultaneous determination of propaquizafop and its four metabolites in ginseng soil, fresh ginseng, ginseng plant, and dried ginseng using HPLC-MS/MS. This approach showed good linearity (R2 ranging from 0.9827 to 0.9999) and limit of quantification ranging from 0.01 to 0.05 mg/kg. The intra- and interday recovery rates of this method ranged from 71.6 to 107.1% with relative standard deviation ranging from 1.3 to 23.2%. The method was applied to detect residual samples in the field, and it was found that the degradation of propaquizafop in ginseng plants and soil followed a first-order kinetic equation. R2 was between 0.8913 and 0.9666, and the half-life (t1/2) ranged from 5.04 to 8.05 days, indicating that it was an easily degradable pesticide (T1/2 < 30 days). The final propaquizafop residues in ginseng soil, plants, fresh ginseng, and dried ginseng ranged from 0.017 to 0.691 mg/kg. A dietary risk assessment was conducted on the final propaquizafop residue in fresh and dried ginseng. The results showed that the chronic exposure risk quotient values were less than 100% for fresh and dried ginseng (1.15% for fresh ginseng and 1.13% for dried ginseng). This illustrates that the dietary risk associated with the use of 10% propaquizafop emulsifiable concentrate in ginseng is very low. Thus, applying 750 mL/ha of propaquizafop on ginseng could not pose an unacceptable risk to public health. The results of the present study support the registration of propaquizafop in ginseng.

Dissipation behaviours, residues, and health risk of six herbicides in sugar beets under field conditions

This study established a residue detection method based on the QuEChERS pre-treatment method and combined it with high-performance liquid chromatography-tandem mass spectrometry to test six herbicides (metamitron, clopyralid, desmedipham, phenmedipham, ethofumesate, and haloxyfop-p-methyl) in sugar beet plants, soil, and roots. The degradation dynamics and terminal residues of each herbicide in sugar beets were analysed. Finally, the dietary risks of various herbicides in sugar beets were evaluated based on the dietary structure of Chinese people, and the risk quotient values were below 100%. Using this detection method, all reagents exhibited good linearity (0.9724 ≤ R2 ≤ 0.9998), The limit of quantification (LOQ) ranged from 0.01 to 0.05 mg/L, the matrix effect ranged from -1.2% to -50%, the addition recovery rate ranged from 77.00% to 103.48%, and the relative standard deviation ranged from 1.61% to 16.17%; therefore, all indicators of this method met the residue detection standards. Under field conditions, the half-lives (t1/2) ranged about 0.65 ∼ 2.96 d and 0.38 ∼ 27.59 d in sugar beet plants and soil, respectively. All herbicides were easily degraded in sugar beet plants and soil (t1/2 < 30 d). The terminal residue amounts in the beet plants, soil, and roots ranged from < LOQ to 0.243 mg/kg. The dietary risk assessment of each pesticide was conducted based on the residual median of the terminal residues and the highest residual values on the edible part of the beetroot. The chronic exposure risk quotient (RQc) and acute exposure risk quotient (RQa) values were < 100%, indicating that the residue of each pesticide in beetroot posed low risks to consumers in China at the recommended dosage.

Development, validation, and implementation of an ultratrace analysis method for the determination of moenomycin A, in aquatic animal products

Moenomycin A, an antimicrobial growth promoter widely used as an additive in aquaculture feedstuffs, has been restricted for use in the European Union and China due to its potential risk of promoting resistant strains of pathogenic bacteria and causing residues in aquatic animal products. Although methods for analyzing moenomycin A in feedstuffs have been developed, no established method exists for aquatic matrices. In this study, we present, for the first time, a sensitive and validated high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) method for the determination of moenomycin A in aquatic animal products. Samples were extracted using methanol and purified with the QuEChERS method employing C18 sorbent. The aliquot was dried under a nitrogen stream, reconstituted with methanol-water solvent, and analyzed by HPLC-MS/MS. The developed method exhibited good linearity (r2 > 0.995) over a wide concentration range (1-100 μg/L) and a low limit of detection (1 µg/kg). Average recoveries ranged between 70 and 110% at spiked concentrations of 1, 50, and 100 μg/kg, with associated intra- and inter-day relative standard deviations of 1.25 to 7.32% (n = 6) and 2.91 to 10.08% (n = 3), for different representative aquatic animal production, respectively. To the best of our knowledge, this is the first reported HPLC-MS/MS method for the quantification of moenomycin A in aquatic animal products. The new approach was effectively employed in the analysis of moenomycin A across various aquatic samples.

Comparison of calibration strategies for accurate quantitation by isotope dilution mass spectrometry: a case study of ochratoxin A in flour

Analysis of low-level organic contaminants in complex matrices is essential for monitoring global food safety. However, balancing sample throughput with complex experimental designs and/or sample clean-up to best reduce matrix effects is a constant challenge. Multiple strategies exist to mitigate these effects, with internal standard-based methods such as isotope dilution mass spectrometry (IDMS) being the most advantageous. Here, multiple internal calibration strategies were investigated for the quantification of ochratoxin A (OTA) in wheat samples by liquid chromatography-mass spectrometry (LC-MS). Internal standard-based quantitation methods such as single (ID1MS), double (ID2MS), and quintuple (ID5MS) isotope dilution mass spectrometry, as well as external standard calibration, were explored and compared. A certified reference material (CRM) of OTA in flour, MYCO-1, was used to evaluate the accuracy of each method. External calibration generated results 18-38% lower than the certified value for MYCO-1, largely due to matrix suppression effects. Concurrently, consistently lower OTA mass fractions were obtained for the wheat samples upon quantitation by external calibration as opposed to ID1MS, ID2MS, and ID5MS. All isotope dilution methods produced results that fell within the expected range for MYCO-1 (3.17-4.93 µg/kg), validating their accuracy. However, an average 6% decrease in the OTA mass fraction was observed from results obtained by ID1MS compared to those by ID2MS and ID5MS. Upon scrutiny, these differences were attributed to an isotopic enrichment bias in the isotopically labelled internal standard [13C6]-OTA that was used for ID1MS, the OTAL-1 CRM. The advantages and limitations of each isotopic method are illustrated.

Validation of UHPLC-ESI-MS/MS Method for Determining Steviol Glycoside and Its Derivatives in Foods and Beverages

The aim of this study was to validate a method for determining nine types of steviol glycoside and its derivatives in food and beverage products, using ultrahigh-performance liquid chromatography tandem mass spectrometry with electrospray ionization (UHPLC ESI MS/MS). The performance characteristics of the analysis method were determined along with their suitability for the intended use. Coefficient of determination (R2) calibration curves from 0.2 to 1.0 mg L-1 were in the ranges of 0.9911-0.9990, 0.9939-1.0000 and 0.9973-0.9999 for a beverage, yogurt and snack, respectively. Intra-day precisions in terms of percent relative standard deviation (% RSD) of concentration, at 0.2, 0.5 and 1.0 mg L-1, for the beverage, yogurt and snack were lower than 15% (1.1-9.3%). At all concentrations, percentage recoveries were in the accepted range of 70-120%. For the matrix effect study, matrix-matched calibration was used for all compounds, obtaining a linear concentration range from 0.2 mg L-1 to 1.0 mg L-1. Almost all matrix-matched results presented as percentage recoveries were within the accepted range of 80-120%. The limit of detection (LOD) for steviol glycosides ranged from 0.003 to 0.078 μg g-1, while the limit of quantitation (LOQ) ranged from 0.011 to 0.261 μg g-1. These results indicate that the modified test method can be applied to determine the presence of steviol glycoside and its derivatives in a wide range of sample matrices.

Development and validation of a sensitive ultra-high-performance liquid chromatography-tandem mass spectrometry method for quantitative analysis of bambermycin in livestock and aquatic products: Implications for food safety control and regulatory enforcement

A sensitive and accurate analytical method was developed and validated to detect bambermycin, a commonly used antibiotic in animal feed and livestock. The presence of bambermycin residues in food products can pose health risks to consumers, emphasizing the need for a sensitive and accurate analytical method. A reversed-phase analytical column was utilized with a mobile phase comprising 0.005 mol/L ammonium acetate in 5% acetonitrile (A) and 0.005 mol/L ammonium acetate in 95% acetonitrile (B) to achieve effective chromatographic separation. Quantitative determination of bambermycin in various samples, including beef, pork, chicken, milk, eggs, flatfish, eel, and shrimp, was performed using ultra-high-performance liquid chromatography-tandem mass spectrometry. Sample extraction involved a mixture of methanol and a 25% ammonium hydroxide solution, followed by low-temperature purification and phospholipid removal utilizing a Phree cartridge. The method exhibited a satisfactory recovery rate ranging from 69% to 100%. Validation results demonstrated the reliability, robustness, and accuracy of the method, exhibiting good linearity, precision, and recovery. This validated method can be applied for routine analysis of bambermycin residues, assisting in the development of effective monitoring and control measures to ensure the safety of livestock and aquatic products.

An effective pretreatment technique based on multi-walled carbon nanotubes to reduce the matrix effect in plasma samples analyzed by a new type probe electrospray ionization method

The quantitative analysis of drug plasma samples plays an important role in the drug development and drug clinical use. Our research team developed a new electrospray ion source-Micro probe electrospray ionization (μPESI) in the early stage, which was combined with mass spectrometry (μPESI-MS/MS) showing good qualitative and quantitative analysis performance. However, matrix effect severely interfered the sensitivity in μPESI-MS/MS analysis. To solve this problem, we recently developed a Solid-phase purification method based on multi-walled carbon nanotubes (MWCNTs), which was used for removing matrix interfering substances (especially phospholipid compounds) in the preparation of plasma samples, so as to reduce the matrix effect. In this study, aripiprazole (APZ), carbamazepine (CBZ) and omeprazole (OME) were used as representative analytes, the quantitative analysis related to the plasma samples spiked with the analytes above and the mechanism of the MWCNTs to reduce matrix effect were both investigated. Compared with the ordinary protein precipitation, MWCNTs could reduced the matrix effect for several to dozens of times, which resulting from the removement of phospholipid compounds from the plasma samples by MWCNTs in the selective adsorption manner. We further validated the linearity, precision and accuracy of this pretreatment technique by the μPESI-MS/MS method. These parameters all met the requirements of FDA guidelines. It was showed that MWCNTs have a good application prospect in the drug quantitative analysis of plasma samples using the μPESI-ESI-MS/MS method.

A new sample preparation approach for the analysis of 98 current-use pesticides in soil and herbaceous vegetation using HPLC-MS/MS in combination with an acetonitrile-based extraction

A simple acetonitrile-based extraction method for the determination of 98 current-use pesticides (CUPs) in soil and herbaceous vegetation using HPLC-ESI-MS/MS is reported. The method was optimized in terms of extraction time, buffer (ammonium formate) ratio, and graphitized carbon black (GCB) ratio for the clean-up of vegetation. The validated method yielded accuracy in terms of percentage recovery of 71-125% (soil) and 70-117% (vegetation) for the majority of 98 CUPs. The precision in terms of relative standard deviation was at 1-14% (soil), and 1-13% (vegetation). Matrix-matched calibration curves exhibited good linearities (R² > 0.99). The limits of quantitation ranged between 0.008 and 21.5 μg kg^-1 in soil and vegetation. The reported method was applied to soils and vegetation from 13 agricultural sites across Germany. Overall, 44 of the 98 common CUPs were detected in our samples and the qualitative load is well above the average for arable soils in the EU.

An analytical method for the determination of glyphosate and aminomethylphosphoric acid using an anionic polar pesticide column and the application in urine and serum from glyphosate poisoning patients

An analytical method for the determination of glyphosate (GLY) and aminomethylphosphoric acid (AMPA) in biological fluid samples (serum and urine) from poisoning patients using liquid chromatography-tandem mass spectrometry (LC-MS/MS) is established. After the sample pretreatment, including protein precipitation and a modified liquid-liquid extraction method, the chromatographic separation was conducted on a trifunctional modified hydrophilic column. The mobile phases in the gradient program were 2.5% formic acid aqueous solution and acetonitrile. The multiple reaction monitoring (MRM) models and the isotope-labeled internal standards were used in the acquisition process. Good linearities and satisfying recovery rates were obtained in two sample matrices with good RSDs. The detection limits of GLY and AMPA were <2 μg L^-1, which were close to those obtained in our previous research. The established method was applied to biological samples from five patients with glyphosate intoxication. The analysis of the trend for the concentration of GLY and AMPA in two biological samples was investigated, and the difference in the downward trend of AMPA in urine was found in patients with a relatively higher concentration of GLY in serum.

Electrochemical Organophosphorus Pesticide Detection Using Nanostructured Gold-Modified Electrodes

In this study, nanostructured gold was successfully prepared on a bare Au electrode using the electrochemical deposition method. Nanostructured gold provided more exposed active sites to facilitate the ion and electron transfer during the electrocatalytic reaction of organophosphorus pesticide (methyl parathion). The morphological and structural characterization of nanostructured gold was conducted using field-emission scanning electron microscopy (FESEM), X-ray photoelectron spectroscopy (XPS), and X-ray diffraction (XRD), which was further carried out to evaluate the electrocatalytic activity towards methyl parathion sensing. The electrochemical performance of nanostructured gold was investigated by electrochemical measurements (cyclic voltammetry (CV) and differential pulse voltammetry (DPV)). The proposed nanostructured gold-modified electrode exhibited prominent electrochemical methyl parathion sensing performance (including two linear concentration ranges from 0.01 to 0.5 ppm (R² = 0.993) and from 0.5 to 4 ppm (R² = 0.996), limit of detection of 5.9 ppb, excellent selectivity and stability), and excellent capability in determination of pesticide residue in real fruit and vegetable samples (bok choy and strawberry). The study demonstrated that the presented approach to fabricate a nanostructured gold-modified electrode could be practically applied to detect pesticide residue in agricultural products via integrating the electrochemical and gas chromatography coupled with mass spectrometry (GC/MS-MS) analysis.

Mass Spectrometric Methods for Non-Targeted Screening of Metabolites: A Future Perspective for the Identification of Unknown Compounds in Plant Extracts

Phyto products are widely used in natural products, such as medicines, cosmetics or as so-called “superfoods”. However, the exact metabolite composition of these products is still unknown, due to the time-consuming process of metabolite identification. Non-target screening by LC-HRMS/MS could be a technique to overcome these problems with its capacity to identify compounds based on their retention time, accurate mass and fragmentation pattern. In particular, the use of computational tools, such as deconvolution algorithms, retention time prediction, in silico fragmentation and sophisticated search algorithms, for comparison of spectra similarity with mass spectral databases facilitate researchers to conduct a more exhaustive profiling of metabolic contents. This review aims to provide an overview of various techniques and tools for non-target screening of phyto samples using LC-HRMS/MS.

Simultaneous Determination of Pyrethroid Insecticides in Foods of Animal Origins Using the Modified QuEChERS Method and Gas Chromatography-Mass Spectrometry

Pyrethroid insecticides are used in agriculture to treat parasites in livestock. This study developed a simultaneous residue analysis method to measure seventeen pyrethroid insecticides in foods of animal origin, including beef, pork, chicken, milk, and eggs. The method, which comprises instrumental analysis using gas chromatography-tandem mass spectrometry and a modified QuEChERS (quick, easy, cheap, effective, rugged, and safe) method for pretreatment, was optimized to verify the applicability of the method. A mixture of acetonitrile, ethyl acetate, and original salt (MgSO4 4 g, NaCl 1 g) was used as the extraction solvent and salt. MgSO4 (150 mg) primary secondary amine (25 mg) and graphitized carbon black (25 mg) were selected for dispersive solid phase extraction (d-SPE). The method limit of quantitation was 0.01 mg/L, and the linearity of the matrix-matched calibration curves was reasonable (R2 > 0.99). Recovery tests were performed at three concentrations (LOQ, 10 LOQ, and 50 LOQ). Good recoveries (75.2109.8%) and reproducibility (coefficient of variation <10%) were obtained. The matrix effects were in the range of −35.8 to 56.0%. The established method was fully validated and can be used as an official analytical method for quantifying pyrethroid insecticides in animal commodities.

Validation of a Multi-Residue Analysis Method for 287 Pesticides in Citrus Fruits Mandarin Orange and Grapefruit Using Liquid Chromatography-Tandem Mass Spectrometry

Since the introduction of the positive list system (PLS) for agricultural products in the Republic of Korea, the demand for a quick, easy multi-residue analysis method increased continuously. Herein, the quick, easy, cheap, effective, rugged, and safe (QuEChERS) technique combined with liquid chromatography−tandem mass spectrometry was employed to optimize a method for the multi-residue analysis of 287 pesticide residues in mandarin orange and grapefruit. Method validation was conducted in terms of selectivity, limit of quantitation (LOQ), linearity, accuracy, precision, and matrix effect. All the compounds at low spiking levels (1, 2.5, 5, or 10 mg/kg) could be quantified at LOQs lower than 0.01 mg/kg (PLS level). The linearity of the matrix-matched calibration curve for each compound is in the range 0.5−50 μg/L, and its coefficient of determination (R2) is >0.990. Satisfactory recovery values of 70−120% with a relative standard deviation of ≤20% are obtained for all compounds in the mandarin orange and grapefruit samples. A negligible matrix effect (−20−20%) is observed for more than 94.8% and 85.4% of the pesticides in mandarin orange and grapefruit, respectively. Therefore, this analytical method can contribute to pesticide residue analyses of citrus fruits for routine laboratory testing.

Determination of Cyclaniliprole in Fruits and Vegetables Using Disposable Pipette Extraction Cleanup and Ultrahigh-Performance Liquid Chromatography-Tandem Mass Spectrometry

Despite an outstanding agent for control of Lepidoptera, the diamide insecticide cyclaniliprole (CYCP) is a suspected carcinogen. In the present study, an analytical method was developed for the determination of CYCP in six fruits and vegetables (apple, grape, peach, bell pepper, lettuce, and tomato) using ultrahigh-performance liquid chromatography coupled with tandem mass spectrometry. Sample preparation was carried out by the acetonitrile-salting-out extraction followed by simple and fast cleanup of disposable pipette extraction tip containing styrene divinyl benzene and/or graphitized carbon black. Satisfactory linearity (r > 0.99) was obtained in the calibration range of 0.001−1 µg mL−1. Matrix effects decreased from −9.9−−17.9% to −1.0−−7.6% after the cleanup. The recoveries of CYCP at three spike levels (0.01, 0.1, and 1 mg kg−1) from different matrices were between 75.7% and 111.5%, with the intra-day (n = 5) and inter-day (n = 15) relative standard deviations lower than 12.1%. The limit of quantification was 0.01 mg kg−1. The developed method provides a good reference for routine monitoring of CYCP in these fruits and vegetables.

Analysis of Near 400 Pesticides in Tea via LC–MS/MS: Simple Sample Preparation and APCI to Improve Analyte Coverage

As regulatory laboratories search for and implement consolidated methods for multiple matrix and analyte classes, compound lists increase to hundreds or thousands of targets. Multi-instrument approaches are often relied upon to analyze all pesticide targets, with the workload split between liquid chromatography–mass spectrometry (LC–MS) and gas chromatography–mass spectrometry (GC–MS) instrumentation. In this work, a simple solvent extraction approach was coupled with dual source electrospray ionization (ESI) and atmospheric pressure chemical ionization (APCI) modes on an LC–tandem mass spectrometry (MS/MS) instrument to analyze 395 analytes extracted from black tea (345 compounds via ESI and 50 compounds via APCI, along with the internal standards). Excellent method performance (defined as an accuracy of 70–120% and a precision of <20% at one of two validation levels) was achieved for over 93% of analytes, including compounds normally analyzed by GC–MS, such as trifluralin, chlorfenson, chlormephos, fenchlorphos, etridiazole, and others. This approach can allow the consolidation of a pesticide method to a single instrument or significantly reduce the workload of a complementary GC–MS method.

Optimization and validation of liquid-liquid extraction with low-temperature purification (LLE-LTP) for determining fluopyram fungicide in water samples using HPLC-DAD

Fluopyram is a fungicide and nematicide that belongs to the chemical group of benzamides, which act as succinate dehydrogenase inhibitors (SDHIs) on the mitochondrial respiratory chain of fungi. Despite being well known in several countries, there are few studies involving the optimization and validation of extraction methods for determining fluopyram in water samples. Therefore, this study aimed to optimize and validate liquid-liquid extraction with low-temperature purification (LLE-LTP) to determine fluopyram fungicide in water samples using high-performance liquid chromatography with diode array detection (HPLC-DAD). A two-level full factorial design was employed to optimize LLE-LTP which enabled achieving a recovery rate close to 100% and relative standard deviations (RSD) < 10.0%. The validation showed that the extraction method may be considered selective, precise, accurate, and linear in the range of 6.0 to 200 μg L^-1. The LOD and LOQ were 4.0 and 6.0 μg L^-1, respectively, proving the efficiency of this method for trace level determination of this fungicide in water samples. LLE-LTP coupled to HLPC-DAD analysis showed a matrix effect of less than 8% and it was applied in monitoring 20 environmental water samples, but no fluopyram residue was detected in the samples.

Trace determination of imidacloprid and its major metabolites in wheat-soil system

Trace analysis method is a reliable basis for studying the translocation and metabolism of imidacloprid used as an insecticide in wheat, and it clarifies whether biologically active metabolites including residual imidacloprid, have long-lasting insecticidal potency against wheat aphids under seed treatment during the entire growth period. In this study, a highly sensitive analytical method was established to determine the residues of imidacloprid and its six metabolites (5-hydroxy imidacloprid, imidacloprid olefin, imidacloprid guanidine, imidacloprid urea, 6-chloronicotinic acid and imidacloprid nitrosimine) in wheat-soil systems, such as in wheat leaves, wheat ears, wheat grains, roots and soil. All the compounds were extracted using an ACN:water (8:2, v/v) mixture and purified by dispersive solid-phase extraction. The average recoveries ranged from 74.4 to 109.5% for all matrices, with intra- and inter-day variations of less than 14.9%. The limit of quantitation was in the range of 0.001 to 0.005 mg/kg. The method is demonstrated to be sensitive and accurate for monitoring imidacloprid and its metabolites at trace levels during the entire growth period under field conditions. This article is protected by copyright. All rights reserved.

Development of cVSSI-APCI for the Improvement of Ion Suppression and Matrix Effects in Complex Mixtures

The new ionization technique termed vibrating sharp-edge spray ionization (cVSSI) has been coupled with corona discharge to investigate atmospheric pressure chemical ionization (APCI) capabilities. The optimized source was evaluated for its ability to enhance ion signal intensity, overcome matrix effects, and limit ion suppression. The results have been compared with state-of-the-art ESI source performance as well as a new APCI-like source. In methanol, the ion signal intensity increased 10-fold and >10-fold for cocaine and the suppressed analytes, respectively. The ability to overcome ion suppression was improved from 2-fold to 16-fold for theophylline and vitamin D2, respectively. For aqueous samples, ion signal levels increased by two orders of magnitude for all analytes. In both solvent systems, the signal-to-noise ratios also increased for all suppressed analytes. One example of the characterization of low-ionizing (by ESI or cVSSI alone) species in the presence of high-ionizing species by direct analysis from a cotton swab is presented. The work is discussed with respect to the advantages of cVSSI-APCI for direct, in situ, and field analyses.

A novel calibration strategy based on isotopic distribution for high-throughput quantitative analysis of pesticides and veterinary drugs using LC-HRMS

Preparation of calibration curves is a critical step for large-scale quantification. However, this procedure is time-consuming, labor intensive. Herein, a novel isotopologue multipoint calibration (IMC) strategy, was proposed and demonstrated for the simultaneous quantitation of 120 pesticides and 83 veterinary drugs in surface water samples using Liquid Chromatography-High Resolution Mass Spectrometry (LC-HRMS). In this strategy, the natural isotopic distribution was used to generate external calibration curves, eliminating the need of analyst's adjustment and many sets of chemical standard solutions required in external calibration curves. Additionally, this strategy was comprehensively validated, and the results indicated this strategy had better performance in both accuracy and precision, fully meeting the requirements for the quantitative analysis. Interestingly, for the samples with high concentration beyond the upper limit of quantitation, the IMC strategy could avoid samples dilution by monitoring the less abundant isotopic channels. Furthermore, the IMC method was successfully applied in the surface water samples collected from Anhui province, China. Among which, sulfamethoxazole and imidacoprid were the main contributors. In conclusion, we present a promising LC-HRMS strategy for the accurate quantitation of small molecules, which has a potential application in food and environmental analysis.

Zeolite H-Beta as a Dispersive Solid-Phase Extraction Sorbent for the Determination of Eight Neonicotinoid Insecticides Using Ultra-High-Performance Liquid Chromatography—Tandem Mass Spectrometry

In this study, a dispersive solid-phase extraction (DSPE) pretreatment procedure using zeolite H-Beta as a sorbent was exploited for the determination of eight neonicotinoids in bottled water and honey products based on ultra-high-performance liquid chromatography–tandem mass spectrometry analysis. The zeolite H-Beta was demonstrated to be a suitable sorbent for neonicotinoid insecticides, even after 10 recycles of reuse. The method performance was evaluated by the linearity (R2 ≥ 0.998), recovery (71–108%), precision (0.1–7.8%), limit of detection (0.05–0.1 ng/mL) and limit of quantification (0.1–0.2 ng/mL), which suggested excellent stability and high sensitivity with the use of the DSPE procedure. The method was further successfully applied in the test of neonicotinoid insecticides in 34 samples. Zeolite H-Beta shows promise as an efficient and practical material for monitoring neonicotinoid insecticides in bottled water and multiplex honey matrices.

Development of an isotope dilution liquid chromatography/tandem mass spectrometry method for the accurate determination of neonicotinoid pesticides, imidacloprid, clothianidin, and thiamethoxam in kimchi cabbage reference materials

A method based on isotope dilution liquid chromatography/tandem mass spectrometry (ID-LC/MS/MS) was established as a candidate reference method for accurate determination of neonicotinoid pesticides, imidacloprid, clothianidin, and thiamethoxam in kimchi cabbage. Their deuterated isotopes, imidacloprid-d4, chlothianidin-d3, and thiamethoxam-d4 were used as internal standards. The combination of HLB and Carb solid-phase extraction (SPE) cartridges was used to clean-up kimchi cabbage extracts. The ID-LC/MS/MS conditions were optimized with fortified kimchi cabbage samples for validation. Imidacloprid in the ERM-BC403 cucumber sample (0.627 ± 0.026) mg/kg was analyzed with the developed method, and the measured value (0.604 ± 0.028) mg/kg agreed within their uncertainties. The developed method was employed for the certification of kimchi cabbage reference materials prepared in this laboratory. The measured values of imidacloprid, clothianidin, and thiamethoxam are (0.860 ± 0.020) mg/kg, (0.524 ± 0.012) mg/kg, (0.787 ± 0.014) mg/kg, respectively. The standard deviation of the measured values for ten bottles was < 1%, and the measured values after one year agreed with their first measurements indicating reliable repeatability and reproducibility of the developed method.

Impact of pesticide formulation excipients and employed analytical approach on relative matrix effects of pesticide determination in strawberries

Relative matrix effects between an ambient mass spectrometric technique known as coated blade spray (CBS) and liquid chromatographic separation approach when applied to multiresidue pesticide analysis in strawberry samples are explored. Acceptable slope relative standard deviations (RSD <15 %) were observed for the 9 compounds under study for both CBS-MS/MS (2.2-12.6 %) and LC-MS/MS (2.8-12.9 %) approaches. The findings signify both the elimination of relative matrix effects with the sample preparation and matrix match calibration with internal standard correction methods employed along with no matrix effect compromise made when using the direct-to-MS approach. Similarly, slopes of pesticides spiked from commercially available formulations (containing one or two pesticides) were found to not differ significantly from slopes generated with multiresidue pesticide standards (containing 24 additional pesticides besides the target 9 analytes) with either technique, highlighting the resistance of the employed methods to the excipients present in pesticide formulations in large amounts.

A Comparison between a Two-Dimensional Liquid Chromatography System and a Traditional QuEChERS-LC Method with Regard to Matrix Removal and Matrix Effects in Pesticide Analysis Using Time-of-Flight Mass Spectrometry

In this study, a fully automated two-dimensional liquid chromatography (2D-LC) system was used for the investigation of the clean-up effect and was compared with a traditional Quick Easy Cheap Effective Rugged and Safe (QuEChERS) liquid chromatography (LC) method. The focus of those investigations was on negative electrospray ionization (ESI) mode. For that purpose, matrix fingerprinting profiles were created. The results allowed a comparison of both methods regarding the estimation of the number and the polarity of detected compounds. Moreover, the results of the present study were compared with the results generated in positive ESI mode (presented in a previous study). Furthermore, the two methods were compared with regard to matrix effects (ME) of 321 analytes in positive ESI mode and 96 analytes in negative ESI mode. In general, fewer compounds could be detected when 2D-LC and/or the negative ESI mode was used. Especially, very polar compounds with m/z values >1000 could be separated and could not be detected anymore when 2D-LC was applied. Furthermore, the best results were obtained for most analytes when 2D-LC was used, although the extent of ME seemed to be higher with 2D-LC.

Development of an LC-MS-based method to study the fate of nanoencapsulated pesticides in soils and strawberry plant

The increased production and use of nanopesticides will increase the likelihood of their exposure to humans and the environment. In order to properly evaluate their risk, it will be necessary to rigorously quantify their concentrations in major environmental compartments including water, soil and food. Due to major differences in the characteristics of their formulation, it is unclear whether analytical techniques that have been developed for conventional pesticides will allow quantification of the nano-forms. Therefore, it is necessary to develop and validate analytical techniques for the quantification of nanopesticides in foods and the environment. The goal of this study was to validate a method for analyzing the active ingredients of two pesticides with different physicochemical properties: azoxystrobin (AZOX, a fungicide, log K_ow 3.7) and bifenthrin (BFT, an insecticide, log K_ow 6.6) that were applied to agricultural soils, either as a conventional formulation or encapsulated in nanoparticles (either Allosperse® or porous hollow nSiO₂). Pesticide-free strawberry plants (Fragaria × ananassa) and three different agricultural soils were spiked with the active ingredients (azoxystrobin and bifenthrin), in either conventional or nano formulations. A modified QuEChERS approach was used to extract the pesticides from the strawberry plants (roots, leaves and fruits) and a solvent extraction (1:2 acetonitrile) was employed for the soils. Samples were analyzed by liquid chromatography-hybrid quadrupole time-of-flight mass spectrometry in order to determine method detection limits, recoveries, precision and matrix effects for both the "conventional" and nanoencapsulated pesticides. Results for the modified method indicated good recoveries and precision for the analysis of the nanoencapsulated pesticides from strawberries and agricultural soils, with recoveries ranging from 85 to 127% (AZOX) and 68-138% (BFT). The results indicated that the presence of the nanoencapsulants had significant effects on the efficiency of extraction and the quantification of the active ingredients. The modified analytical methods were successfully used to measure strawberry and soil samples from a field experiment, providing the means to explore the fate of nanoencapsulated pesticides in food and environmental matrices.

Evaluation of identification accuracy using AIQS for GC-MS for measuring heavily contaminated samples

Automated identification and quantification systems with gas chromatography-mass spectrometry (GC-MS) (i.e., AIQS-GC) are used as a simple and comprehensive method for screening chemicals existing in the environment and are expected to be useful for emergency surveys in the event of a disaster. However, reports on the potential of AIQS-GC in heavily contaminated samples (HCSs) are limited. In this study, the identification performance of AIQS-GC was confirmed by comparing the exact mass of the targets identified by AIQS-GC with the measured accurate mass using GC-quadrupole-time-of-flight MS (GC-QTofMS) and by employing firefighting wastewater as HCS. In HCS, the mass spectrum interference was determined to cause false positives. The GC-QTofMS method revealed the presence of false positives and the false rate of AIQS-GC in HCS. Herein, AIQS-GC showed high identification accuracy in a normal sample such as river water. Conversely, in HCS, AIQS-GC may lead to incorrect evaluations. The combination of AIQS-GC and support method using GC-QTofMS, which can avoid the false positive is extremely useful for the rapid and easy analysis of HCS.

Multiple heart-cutting two dimensional liquid chromatography and isotope dilution tandem mass spectrometry for the absolute quantification of proteins in human serum

We evaluate here the combination of two-dimensional liquid chromatography (2D-LC) in the multiple heart cutting mode and isotope dilution tandem mass spectrometry for the direct analysis of tryptic digests of serum samples. As a proof of concept, we attempt the quantification of proteotypic peptides of Apolipoprotein AIV (APOA4), Complement C3 (C3) and Vitronectin (VTN) which have been previously identified as potential candidate biomarkers of glaucoma. Using this 2D-LC strategy, analyte enrichment steps are avoided and the sample preparation involved after enzymatic digestion amounted to a simple centrifugation, evaporation of the supernatant and reconstitution in the 1D mobile phase. A mobile phase not compatible with the ESI source (10 mM KH₂PO₄ at pH 2.7) was used in the first dimension as it provided a satisfactory chromatographic resolution of the peptides and a high buffering capacity avoiding changes in retention times when analyzing complex matrices like human serum. We also demonstrate that using coeluting labelled analogues of the target peptides, protein concentrations were not affected by slight retention time shifts affecting the amount of target peptides transferred to the second dimension. Satisfactory results were obtained when analyzing fortified serum samples (recoveries from 98 to 113%). Precisions in the range of 1-9% RSD were obtained when replicating the analysis of a pooled serum sample. The comparative analysis of serum samples from n = 94 control subjects and n = 91 patients diagnosed with primary open-angle glaucoma did not show significant differences in the APOA4, VTN and C3 concentrations in contrast with previous studies using immunoassays.

Fast Determination of Carbamates in Environmental Water Based on Magnetic Molecularly Imprinted Polymers as Adsorbent

Magnetic molecularly imprinted polymers (MMIPs) were prepared with isoprocarb as template molecule and applied to extraction of carbamates pesticides in different water samples. This method based on magnetic solid-phase extraction (SPE) avoided the time-consuming column-passing process of loading large volume samples in conventional SPE. In the study, only 0.1 g MMIPs could be used to obtain satisfactory recoveries, due to the high-surface area and excellent adsorption capacity of these nano-magnetic adsorbents. Owing to the excellent selectivity of MMIPs, in high-performance liquid chromatography-mass spectrometry analysis, the matrix effects of this technique were obviously lower than the conventional SPE method. Under the optimal conditions, the detection limits of carbamates were in the range of 2.7-11.7 ng L-1. The relative standard deviations of intra-day and inter-day were 2.5-7.4% and 3.6-8.4%, respectively. At all the spiked level, the recoveries of four analyzed carbamates in environmental water samples were in the range of 74.2-94.2%. The significant positive results were achieved in the proposed method for the determination of four carbamates in water samples from different lakes and rivers. In the three samples we tested, the carbaryl was found in the lake water obtained from Yitong River, and the content was 2.4 ng L-1.

Determination of DDT in honey samples by liquid-liquid extraction with low-temperature purification (LLE-LTP) combined to HPLC-DAD

Honey is widely consumed worldwide, however, this food can be contaminated by chemical contaminants, such as the insecticide dichlorodiphenyltrichloroethane (DDT). Despite legal restrictions on DDT use, this organochlorine pesticide has been detected in honey collected in several developed and developing countries, representing risks to human health, animals, and the environment due to its high environmental persistence, potential carcinogenicity, and ecotoxicological effects. Thus, the development of an analytical method for DDT monitoring in this matrix is important to ensure food security. Therefore, this study aimed to optimize and validate a simple, low-cost, and efficient method using the liquid-liquid extraction with low-temperature purification (LLE-LTP) to determine DDT in honey samples by high-performance liquid chromatography with diode array detector (HPLC-DAD). The proposed method was validated according to SANTE guidelines, being considered selective, precise, accurate, and linear in the range of 8.0-160 μg kg^-1. The limits of detection (LOD) and quantification (LOQ) achieved were 4.0 and 8.0 μg kg^-1, respectively. This LOQ value is lower than the maximum residue limit established by the Brazilian and European Union legislation. Therefore, the LLE-LTP combined to HPLC-DAD allows the routine analysis of DDT in honey samples and can be widely applied in studies to monitor this pesticide, especially in developing countries, where DDT use is still allowed.

Determination of the Novel Insecticide Flupyradifurone and Its Two Metabolites in Traditional Chinese Herbal Medicines Using Modified QuEChERS and High-Performance Liquid Chromatography-Tandem Mass Spectrometry

In this study, an analytical method for the simultaneous determination of the novel insecticide flupyradifurone and its two metabolites in a variety of traditional Chinese herbal medicines was developed for the first time using high-performance liquid chromatography-tandem mass spectrometry. A simple and efficient method using dispersive solid-phase extraction was employed for the pretreatment of the samples. Several extractions and cleanup strategies were evaluated. The recoveries (n = 15) of flupyradifurone and its metabolites at three spiking levels were in the range 71.3%-101.7%, with corresponding intraday and interday relative standard deviations of 1.1%-14.8%. The limits of quantitation were 0.01 mg/kg for flupyradifurone and 0.1 mg/kg for its two metabolites. Overall, our developed method was sensitive and reliable for the fast screening of flupyradifurone and its two metabolites in traditional Chinese herbal medicine samples.

Benchmarking of the quantification approaches for the non-targeted screening of micropollutants and their transformation products in groundwater

A wide range of micropollutants can be monitored with non-targeted screening; however, the quantification of the newly discovered compounds is challenging. Transformation products (TPs) are especially problematic because analytical standards are rarely available. Here, we compared three quantification approaches for non-target compounds that do not require the availability of analytical standards. The comparison is based on a unique set of concentration data for 341 compounds, mainly pesticides, pharmaceuticals, and their TPs in 31 groundwater samples from Switzerland. The best accuracy was observed with the predicted ionization efficiency-based quantification, the mean error of concentration prediction for the groundwater samples was a factor of 1.8, and all of the 74 micropollutants detected in the groundwater were quantified with an error less than a factor of 10. The quantification of TPs with the parent compounds had significantly lower accuracy (mean error of a factor of 3.8) and could only be applied to a fraction of the detected compounds, while the mean performance (mean error of a factor of 3.2) of the closest eluting standard approach was similar to the parent compound approach.

STRATEGIES AND CHALLENGES IN METHOD DEVELOPMENT AND VALIDATION FOR THE ABSOLUTE QUANTIFICATION OF ENDOGENOUS BIOMARKER METABOLITES USING LIQUID CHROMATOGRAPHY-TANDEM MASS SPECTROMETRY

Metabolomics is a dynamically evolving field, with a major application in identifying biomarkers for drug development and personalized medicine. Numerous metabolomic studies have identified endogenous metabolites that, in principle, are eligible for translation to clinical practice. However, few metabolomic-derived biomarker candidates have been qualified by regulatory bodies for clinical applications. Such interruption in the biomarker qualification process can be largely attributed to various reasons including inappropriate study design and inadequate data to support the clinical utility of the biomarkers. In addition, the lack of robust assays for the routine quantification of candidate biomarkers has been suggested as a potential bottleneck in the biomarker qualification process. In fact, the nature of the endogenous metabolites precludes the application of the current validation guidelines for bioanalytical methods. As a result, there have been individual efforts in modifying existing guidelines and/or developing alternative approaches to facilitate method validation. In this review, three main challenges for method development and validation for endogenous metabolites are discussed, namely matrix effects evaluation, alternative analyte-free matrices, and the choice of internal standards (ISs). Some studies have modified the equations described by the European Medicines Agency for the evaluation of matrix effects. However, alternative strategies were also described; for instance, calibration curves can be generated in solvents and in biological samples and the slopes can be compared through ratios, relative standard deviation, or a modified Stufour suggested approaches while quantifying mainly endogenous metabolitesdent t-test. ISs, on the contrary, are diverse; in which seven different possible types, used in metabolomics-based studies, were identified in the literature. Each type has its advantages and limitations; however, isotope-labeled ISs and ISs created through isotope derivatization show superior performance. Finally, alternative matrices have been described and tested during method development and validation for the quantification of endogenous entities. These alternatives are discussed in detail, highlighting their advantages and shortcomings. The goal of this review is to compare, apprise, and debate current knowledge and practices in order to aid researchers and clinical scientists in developing robust assays needed during the qualification process of candidate metabolite biomarkers. © 2019 John Wiley & Sons Ltd. Mass Spec Rev.

Sustainable polypyrrole-based magnetic-microextraction of phthalates from jellies and apple-based beverages prior to tandem mass spectrometry analysis

Synthesised polypyrrole-coated Fe₃O₄ magnetic nanoparticles have been successfully characterised and applied as sorbent for the magnetic-micro-dispersive solid-phase extraction of eleven phthalic acid esters from jelly and apple-based beverage matrices widely consumed by the population and, especially, by children. Sorbent was synthesised through chemical coprecipitation and subsequently characterised by different techniques. The influence of several parameters on the extraction efficiency was exhaustively evaluated using a step-by-step strategy. The separation and quantification of the selected phthalates were performed by ultra-high performance liquid chromatography coupled to tandem mass spectrometry. The validation of the methodology was carried out for jellies and apple-based beverages, employing dihexyl phthalate-3,4,5,6-d₄ as the surrogate standard. Relative recovery values were in the range 70-114% for both matrices and relative standard deviations below 20% were obtained. The limits of quantification of the method were found in the range 0.147-0.416 µg/L. Feasibility of the developed methodology was proved by the analysis of commercialised jelly and apple-based beverage products.

LC-MS/MS Quantification of Nevirapine and Its Metabolites in Hair for Assessing Long-Term Adherence

The adherence assessment based on the combination of nevirapine (NVP) and its two metabolites (2-hydroxynevirapine and 3-hydroxynevirapine) would more comprehensively and accurately reflect long-term adherence than that of a single prototype. This study aimed to develop a specific, sensitive and selective method for simultaneous detection of the three compounds in hair and explore whether there was consistency among the three compounds in assessing long-term adherence. Furthermore, 75 HIV-positive patients who were taking the NVP drug were randomly recruited and divided into two groups (high-and low-adherence group). All participants self-reported their days of oral drug administration per month and provided their hair strands closest to the scalp at the region of posterior vertex. The concentrations of three compounds in the hair were determined using a developed LC-MS/MS method in multiple reaction monitoring. This method showed good performances in limit of quantification and accuracy with the recoveries from 85 to 115% and in precision with the intra-day and inter-day coefficients of variation within 15% for the three compounds. The population analysis revealed that patients with high-adherence showed significantly higher concentrations than those with low-adherence for all three compounds. There were significantly moderate correlations of nevirapine with 2-hydroxynevirapine and 3-hydroxynevirapin and high correlation between 2-hydroxynevirapine and 3-hydroxynevirapin. The two NVP’s metabolites showed high consistency with NVP in evaluating long-term adherence.

Determination of estrogens by solid-phase quadruplex stable isotope dansylation coupled with liquid chromatography-high resolution mass spectrometry in environmental samples

Estrogens distribute widely in the environment as endocrine-disrupting chemicals (EDCs), which have to be monitored to evaluate their environmental impact. Aim to improve the analytical throughput of liquid chromatography-high resolution mass spectrometry (LC-HRMS), a quadruplex stable isotope dansylation method was developed, with which three real samples could be quantitatively analyzed in one injection. As the estrogens were at trace level in complex matrices, magnetic solid-phase extraction (MSPE) was applied to enrich these analytes and remove the interfaces. By integrating MSPE and quadruplex stable isotope dansylation, a solid-phase quadruplex labeling method was developed for the LC-HRMS analysis of estrogen analogues. For the tested seven estrogens, the developed method showed low detection limits (0.1-0.5 ng/L for pond water and 0.01-0.05 μg/kg for poultry manure), good precision (RSD < 5.5%) and accuracy (96.8-108.3%). The method was applied in the determination of estrogens in environmental samples, and the results revealed that all the tested estrogens were present in the estuary water (unquantifiable to 71.2 ng/L) and chicken manure (undetectable to 25.43 μg/kg).

Optimized multimatrix calibration concept for liquid chromatography mass spectrometry-based bioanalysis methods

In this paper, a calibration procedure for LC/MS-based bioanalysis methods, termed "A/B fortification", is proposed. The concept relies on the post-extraction fortification (B-spike) of an aliquot of the injection-ready sample extract for the determination and compensation of specific signal suppression or enhancement effects compared to matrix-free extract prepared in buffer or mobile phase. Conventional analyte recovery, observed due to the incomplete extraction of analytes from the sample or losses during a cleanup, is determined by the conventional pre-extraction fortification (A-spike) of a blank sample that belongs to the same type of matrix as the sample with the unknown analyte concentration. This approach permits a higher throughput than conventional sample fortification strategies. The results obtained by utilizing the A/B fortification concept were extensively compared against conventional methods (representative bank matrix fortification, sample fortification and internal standard). The proposed concept (based on the pre-fortification of a reference matrix and post-fortification of the sample) was found to be significantly less biased than internal standard-based techniques. The A/B fortification indicated a better accuracy than the sample fortification or representative blank matrix fortification approach and, most importantly, produced significantly fewer outliers. This was linked to the fact that in the case of the A/B fortification, the uncertainty of the subtraction of two peak areas (fortified minus unfortified sample) is reduced, because fortifications are not made prior to the extraction step but are made into the final injection-ready sample extract. Fortification into an injection-ready aliquot eliminates all sample processing-related differences (procedural errors), which can affect conventional sample fortification-based quantifications.

Investigating the Association of the Biogenic Amine Profile in Urine with Therapeutic Response to Neoadjuvant Chemotherapy in Breast Cancer Patients

Neoadjuvant treatment (NAT) can downstage breast cancer and can be utilized for different clinical applications. However, the response to NAT varies among individuals. Having effective biomarkers is important to optimize the treatment of breast cancer. Concentrations of biogenic amines have been found to show an association with cancer cell proliferation, but their clinical utility remains unclear. This study developed a postcolumn-infused internal standard (PCI-IS)-assisted liquid chromatography combined with tandem mass spectrometry (LC-MS/MS) method for profiling biogenic amines in human urine. Putrescine-d₈ was selected as the PCI-IS to calibrate the errors caused by matrix effects in the urine sample. The optimized method was applied to investigate the association between changes in 14 amines and the therapeutic response to NAT in breast cancer patients. Urine samples were collected before initiation of chemotherapy (n = 60). Our results indicated that the levels of N¹-acetylspermine, spermidine, norepinephrine, and dopamine were significantly higher in the responder group than the nonresponder group. These metabolites were incorporated with clinical factors to identify NAT responders, and the prediction model showed an area under the curve value of 0.949. These observations provide remarkable insights for future studies in elucidating the roles of biogenic amines in breast cancer. Additionally, the PCI-IS-assisted amine profiling method can facilitate these studies.