High-performance liquid chromatographic–nuclear magnetic resonance investigation of the isomerization of alachlor–ethanesulfonic acid

A highly efficient and selective rapid detection method applied to the detection of amide herbicides in fish serum

Misuse of amide herbicides in the fisheries environment can pose unpredictable harm to aquatic products and ultimately human health. Thus, the development of a real-time, rapid on-site detection method is crucial. This study proposes for the first time, a paper-based visual detection method for amide herbicides in fish serum, by coating the molecularly imprinted polymer layer onto quantum dots, prepared fluorescent sensing materials (QDs@MIPs) for the detection of amide herbicides in aquatic products. These materials specifically cause fluorescence quenching in the presence of amide herbicides resulting in a color change. For practical application, this research designed a rapid test strip based on QDs@MIPs, meanwhile, incorporate a smartphone or a fluorescence spectrophotometer for qualitative and quantitative measurements, the limit of detection ranges of 0.061-0.500 μM. The method can be used for on-site evaluation of aquatic products, providing new technology for monitoring the safety of aquatic products.

Development and validation of an LC-MS/MS assay with multiple stage fragmentation for the quantification of alachlor in McF-7 cells

Alachlor is one of the most widely used herbicides and can also be a carcinogenic compound. It is of great significance to establish a sensitive analytical method for the determination of alachlor in the environment and organisms. In this study, a high-performance liquid chromatography tandem mass spectrometry cubed (LC/MS³) method was developed and validated to quantify alachlor in human breast cancer cells (McF-7 cells). The cell samples were processed by simple protein precipitation with acetonitrile, then the analytes were separated on a Waters AcQuity® UPLC BEH (2.1 × 50 mm I.D, 1.7 μm) column using the gradient elution with solvent A (0.1 % formic acid) and solvent B (acetonitrile) at a flow rate of 0.5 mL/min. MS³ detection in positive ion mode was used to detect the analytes. The MRM³ transitions at m/z 270.1 → 238.0 → 162.1 and 312.2 → 238.1 → 147.2 were used to determine alachlor and butachlor, respectively. The run time for each sample was only 4 min. This method was validated for various parameters including accuracy, precision, selectivity, linearity, lower limit of quantitation (LLOQ), etc. The LC/MS³ assay was linear in the concentration range 0.5-50 ng/mL (R² ≥ 0.995). For all concentrations, the precision is < 9.49 %, and the intra-day and intra-day accuracy is < 13.05 %. Cytotoxic potential of alachlor against McF-7 cell lines was measured by MTT method after 48 h of incubation. For alachlor, half maximal inhibitory concentration (IC₅₀) on McF-7 cells was 87.95 µg/mL. This method was successfully applied to cellular pharmacokinetic study of alachlor in McF-7 cells after administration with a dose of 20 μg/mL.

Peak distortion in reversed-phase liquid chromatography separation of active carbonyl-containing compounds: Mechanism and solution for this overlooked phenomenon

Peak distortion is frequently encountered for compounds containing active carbonyl groups during reversed-phase (RP) LC separation. However, as being commonly overlooked or misdiagnosed, this problem is rarely reported in the literature and lacks an effective solution. In the present study, six pharmaceutical-related compounds containing keto or aldehyde groups, that exhibited severe peak distortion in early method development, were selected as the model compounds for further investigation. Systematic pH-screening experiments and a series of LC quadrupole-time of flight (Q-TOF) MS and NMR experiments were conducted on each model compound. The underlying chemical behavior of this type of compound during RP-LC separation was explicitly revealed. The formation of gem-diol/hemiketal/hemiacetal species via nucleophilic addition with H₂O/MeOH will occur in a low pH eluent, but will be completely suppressed when the pH is higher than an analyte-specific value. As further validated by twelve other pharmaceutical-related compounds belonging to this type, we confirmed that increasing the eluent pH using buffers without nucleophilicity is a simple and effective method to solve this peak distortion problem.

Metabolomic by 1H NMR spectroscopy differentiates "Fiano di Avellino" white wines obtained with different yeast strains

We employed (1)H NMR spectroscopy to examine the molecular profile of a white "Fiano di Avellino" wine obtained through fermentation by either a commercial or a selected autochthonous Saccharomyces cerevisiae yeast starter. The latter was isolated from the same grape variety used in the wine-making process in order to strengthen the relationship between wine molecular quality and its geographical origin. (1)H NMR spectra, where water and ethanol signals were suppressed by a presaturated T1-edited NMR pulse sequence, allowed for definition of the metabolic content of the two differently treated wines. Elaboration of NMR spectral data by multivariate statistical analyses showed that the two different yeasts led to significant diversity in the wine metabolomes. Our results indicate that metabolomics by (1)H NMR spectroscopy combined with multivariate statistical analysis enables wine differentiation as a function of yeast species and other wine-making factors, thereby contributing to objectively relate wine quality to the terroir.

Pesticides analysis by liquid chromatography and capillary electrophoresis

Nowadays, a wide range of pesticides are used in agricultural production, and their monitoring in samples of environmental and alimentary interest is of extreme importance to ensure, among others, the safety of consumption of foods. The aim of this work is to provide updated information about the major developments in CE and HPLC in pesticide analysis, covering relevant publications between 2004 and early 2006. The use of different sample pretreatment steps to provide a suitable extraction of these compounds from the different matrices as well as to increase the sensitivity of the determination is also discussed.

Degradation of alachlor in natural and sludge-amended soils, studied by gas and liquid chromatography coupled to mass spectrometry (GC-MS and HPLC-MS)

Alachlor [2-chloro-N-(2,6-diethylphenyl)-N-(methoxymethyl)acetamide] is an herbicide used worldwide. The relative rates of disappearance of alachlor, the formation kinetics of alachlor ethane sulfonic acid (ESA), and the formation of other degradation products in two different soils (a soil with natural organic matter and a sludge-amended soil) has been studied. For such a purpose, soil samples were spiked with alachlor at 2.5 mg kg(-1), concentration generally applied in agricultural soils, and were submitted to sunlight, simulating natural field conditions. Extracts were analyzed by GC-MS and HPLC-MS in scan mode. A good correlation was observed between both techniques, and HPLC-MS allowed the determination of two eluting peaks corresponding to the two stereoisomeric forms of alachlor ESA. Degradation of alachlor in the two soils followed first-order kinetics. Half-life in the natural soil was 4.2 +/- 0.1 days, and half-life in the sludge-amended soil was 5.8 +/- 0.8 days. The higher half-life observed in the sludge-amended soil was attributed to the higher sorption of alachlor to this soil compared to the natural soil. The degradation of alachlor in both soils gave rise to the production of alachlor ESA. Its concentration increased during the incubation period, and after 27 days, its concentration was about 0.59 mg kg(-1) in the natural soil and 0.37 mg kg(-1) in the sludge-amended soil. The other two alachlor transformation products were identified using GC-MS, and the abundance of these degradation products increased while alachlor was degraded.