Evaluation of fused-core and monolithic versus porous silica-based C18 columns and porous graphitic carbon for ion-pairing liquid chromatography analysis of catecholamines and related compounds

Analysis of human biological samples using porous graphitic carbon columns and liquid chromatography-mass spectrometry: a review

Liquid chromatography-mass spectrometry (LC-MS) has emerged as a powerful analytical technique for analyzing complex biological samples. Among various chromatographic stationary phases, porous graphitic carbon (PGC) columns have attracted significant attention due to their unique properties-such as the ability to separate both polar and non-polar compounds and their stability through all pH ranges and to high temperatures-besides the compatibility with LC-MS. This review discusses the applicability of PGC for SPE and separation in LC-MS-based analyses of human biological samples, highlighting the diverse applications of PGC-LC-MS in analyzing endogenous metabolites, pharmaceuticals, and biomarkers, such as glycans, proteins, oligosaccharides, sugar phosphates, and nucleotides. Additionally, the fundamental principles underlying PGC column chemistry and its advantages, challenges, and advances in method development are explored. This comprehensive review aims to provide researchers and practitioners with a valuable resource for understanding the capabilities and limitations of PGC columns in LC-MS-based analysis of human biological samples, thereby facilitating advancements in analytical methodologies and biomedical research.

Single-particle-frit-based packed columns for microchip chromatographic analysis of neurotransmitters

The fabrication of effective microchip liquid chromatography (LC) systems tends to be limited by the availability of suitable chromatographic columns. Herein, we developed a glass microchip LC system in which porous single-particle silica was adopted as frits and a freeze-thaw valve was utilized to achieve sample injection without interfering with sampling. The fabrication of single-particle-frit-based packed columns did not require an additional packing channel, thus avoiding dead volumes within the channel interface that can influence chromatographic separation. Further, the length of the packed column could be adjusted using the location of single-particle frits within the column channel. The fabricated frits exhibited high mechanical strength, good permeability, and tolerance for high pressures during chromatographic separation. In particular, the developed microchip LC system was able to withstand high separation pressures of more than 5000 psi. The microchip LC system was applied to the separation of neurotransmitters. Three different monoamine neurotransmitters were completely separated within 5 min with theoretical plate numbers on the order of 100,000 plates m^-1. The microchip LC system has a potential for application in a variety of fields including environmental analysis, food safety, drug analysis, and biomedicine.

Development and validation of a liquid chromatography tandem mass spectrometry method for the measurement of urinary catecholamines in diagnosis of pheochromocytoma

The measurement of catecholamines in human body fluids is requested frequently for the differential diagnosis and monitoring of pheochromocytoma. The methods in most clinical laboratories focus on high-performance liquid chromatography coupled with electrochemical detection, which suffers from high background noise, low sensitivity, and poor separation. We reported and developed a robust high-throughput liquid chromatography tandem mass spectrometry method in routine clinical laboratories for the measurement of urinary catecholamines for diagnosis of pheochromocytoma. The method was validated for consistent linearity, good recovery (88-112%), excellent stability and low carryover. Intra- and inter-assay precision values for catecholamines were all below 3.35 and 4.83% respectively. Dilution linearity was investigated with satisfactory linearly dependent coefficients (r > 0.9988). The reference intervals were obtained from 310 results derived from patients in which the diagnosis of pheochromocytoma was excluded. This method was successfully used in our laboratory. The clinical characteristics of patients have been explored with satisfactory sensitivity and specificity. Therefore, we have developed a reliable assay for the liquid chromatography tandem mass spectrometry measurement of catecholamines in a routine clinical laboratory. The assay requires a small volume of urine, and all analytes are measured simultaneously. The assay is rapid and reliable to be executed, offering the potential for routine clinical laboratories.

Sensitive determination of norepinephrine, epinephrine, dopamine and 5-hydroxytryptamine by coupling HPLC with [Ag(HIO6 )2 ](5-) -luminol chemiluminescence detection

Based on the enhancing effects of norepinephrine (NE), epinephrine (EP), dopamine (DA) and 5-hydroxytryptamine (5-HT) on the chemiluminescence (CL) reaction between [Ag(HIO6 )2 ](5-) and luminol in alkaline solution, a high-performance liquid chromatography (HPLC) method with CL detection was explored for the sensitive determination of monoamine neurotransmitters for the first time. The UV-visible absorption spectra were recorded to study the enhancement mechanism of monoamine neurotransmitters on the CL of [Ag(HIO6 )2 ](5-) and luminol reaction. The HPLC separation of NE, EP, DA and 5-HT was achieved with isocratic elution using a mixture of aqueous 0.2% phosphoric acid and methanol (5:95, v/v) within 11.0 min. Under the optimized conditions, the detection limits of NE, EP, DA, and 5-HT were 4.8, 0.9, 1.9 and 2.3 ng/mL, respectively, corresponding to 17.6-96.0 pg for 20 μL sample injection. The recoveries of monoamine neurotransmitters in rat brain were >95.6% with the precisions expressed by RSD <5.0%. The validated HPLC-CL method was successfully applied for the quantification of NE, EP, DA and 5-HT in rat brain. This method has promising potential for some biological and clinical investigations focusing on the levels of monoamine neurotransmitters. Copyright © 2016 John Wiley & Sons, Ltd.

Effective and reusable monolith capillary trap of nitrosamine extraction by superheated water from frankfurter sausage

A novel, simple, rapid, and inexpensive method of extraction and cleanup of nitrosamines from frankfurter sausage was achieved with a capillary filled with monolith of either polystyrene-co-divinylbenzene (PS-DVB), Polydivinylbenzene (P-DVB), or silica that had been fabricated. The study of capability in trapping nonpolar matrix and monolith capillaries with varied lengths revealed that a silica monolith gave the best result for nitrosamine determination. With an online coupling between superheated water extraction (SWE) and silica monolith capillary connected to a 5% phenyl-methylpolysiloxane column, factors affecting the extraction and determination, namely, sensitivity with and without the monolith, reusability, injection-injection repeatability, capillary-capillary precision, and chromatographic separation, were investigated. This confirmed the feasibility of the method. The optimal length of silica monolith capillary was 30 mm, offering reuse more than 20 times. Separation and quantification of selected volatile nitrosamines were carried out using gas chromatography (GC) coupled with either a flame ionization detector (FID) or mass spectrometer (MS). The overall extraction and determination method determined by GC-MS allowed for a recovery of 75-88% with a <5% relative standard deviation (RSD) and detection limit of 2-5 ng of injected nitrosamine.

LC–MS/MS in endocrinology: what is the profit of the last 5 years?

Currently, chromatography (GC but more commonly HPLC) is the analytical method of choice for several hormones, either because the immunoassays suffer from extensive crossreactivity or because chromatography permits simultaneous measurements of hormones. However, sometimes the conventional detection systems with HPLC methods do not meet desired specificity. With the increase of robust and affordable LC–MS/MS systems, the next step forward in specificity was taken. LC–MS/MS is rapidly being incorporated in the endocrine laboratories. To be useful in the clinical diagnostic practice, it is of utmost importance that methods are both analytically and clinically vaidated, as until now, the majority of applications of LC–MS/MS in the clinical laboratories are ‘home-made’ methods, therefore special case must be taken. This review aims to focus on Clinical and Laboratory Standards Institute or comparable validated LC–MS/MS methods for targeted hormone analysis used for diagnostic purposes in human samples, published in the last 5 years.