Quantification of acylglycines in human urine by HPLC electrospray ionization-tandem mass spectrometry and the establishment of pediatric reference interval in local Chinese

Acylglycine Analysis by Ultra-Performance Liquid Chromatography-Tandem Mass Spectrometry (UPLC-MS/MS)

Quantitative analysis of urine acylglycines has shown to be a highly sensitive and specific method with proven clinical utility for the diagnosis of several inherited metabolic disorders including: medium chain acyl-CoA dehydrogenase deficiency, multiple acyl-CoA dehydrogenase deficiency, short chain acyl-CoA dehydrogenase deficiency, 3-methylcrotonyl-CoA carboxylase deficiency, 2-methylbutyryl-CoA dehydrogenase deficiency, isovaleric acidemia, propionic academia, and isobutyryl-CoA dehydrogenase deficiency. Here, a method that is currently performed using ultra-performance liquid chromatography/tandem mass spectrometry (UPLC-MS/MS) is described. © 2023 Wiley Periodicals LLC. Basic Protocol: Urinary acylglycine analysis by UPLC-MS/MS Support Protocol 1: Quality control preparation Support Protocol 2: Internal standard (ISTD) preparation Support Protocol 3: Standard (STD)/calibrator preparation.

Derivatization of N-Acyl Glycines by 3-Nitrophenylhydrazine for Targeted Metabolomics Analysis and Their Application to the Study of Diabetes Progression in Mice

N-Acyl glycines (NAGlys) are an important class of metabolites in the detoxification system of the human body. They have been used in the diagnosis of several metabolic diseases. Liquid chromatography-mass spectrometry (LC-MS) is the most frequently used NAGlys detection platform. Here, we describe a simple and sensitive method of NAGlys detection by LC-MS in plasma and urine samples. This approach is based on the use of a derivatization reagent, 3-nitrophenylhydrazine. The reaction is quick in aqueous solution, and no quenching step is needed. To expand the coverage of NAGlys when standards are not available, NAGlys were first identified based on high-resolution LC-MS. Quantification was subsequently carried out on triple quadrupole LC-MS. This approach allowed a much broader measurement of NAGlys (41 NAGlys in total), especially when authentic standards are unavailable. Comprehensive analysis of NAGlys with this new method was applied in plasma and urine samples of db/db diabetic and non-diabetic db/m+ control mice. The majority of detected NAGlys were altered with high differentiation ability in plasma and urine samples from diabetic and non-diabetic mice. These identified NAGlys hold the potential to be diagnostic biomarkers for type II diabetes and diabetic complications.

Quantitative analysis of urine acylglycines by ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS): Reference intervals and disease specific patterns in individuals with organic acidemias and fatty acid oxidation disorders

BACKGROUND

Acylglycine species accumulate in specific disorders of branched-chain amino acid metabolism and fatty acid β-oxidation. These species are excreted in urine and their analysis can facilitate diagnosis. Previous studies evaluated reference ranges and increases in metabolic patients, but these involved small numbers of individuals. We have conducted an analysis encompassing large numbers of individuals to better characterize the reference ranges of these analytes and additionally describe our findings from patients with confirmed metabolic disorders.

METHODS

We conducted a retrospective analysis of approximately 9 y of urine acylglycine data from our clinical laboratory. Acylglycines were extracted from urine, derivatized and analyzed using UPLC-MS/MS. Reference ranges were determined from the non-diseased population. Data from confirmed patients were used to document the range of increases observed in these conditions and to generate multiple of the median graphs.

RESULTS

In total, 6162 urine specimens from 5633 patients with and without metabolic disorders were analyzed. Magnitude and pattern of acylglycine elevations in patients with confirmed metabolic disorders were documented.

CONCLUSION

This manuscript extends our previously published method by providing the reference ranges and disease specific elevations and patterns of urine acylglycine species using the largest data set published to date.

Ion suppression; a critical review on causes, evaluation, prevention and applications

The consequences of matrix effects in mass spectrometry analysis are a major issue of concern to analytical chemists. The identification of any ion suppressing (or enhancing) agents caused by sample matrix, solvent or LC-MS system components should be quantified and measures should be taken to eliminate or reduce the problem. Taking account of ion suppression should form part of the optimisation and validation of any quantitative LC-MS method. For example the US Food and Drug Administration has included the evaluation of matrix effects in its "Guidance for Industry on Bioanalytical Method Validation" (F.D.A. Department of Health and Human Services, Guidance for industry on bioanalytical method validation, Fed. Regist. 66 (100) 2001). If ion suppression is not assessed and corrected in an analytical method, the sensitivity of the LC-MS method can be seriously undermined, and it is possible that the target analyte may be undetected even when using very sensitive instrumentation. Sample analysis may be further complicated in cases where there are large sample-to-sample matrix variations (e.g. blood samples from different people can sometimes vary in certain matrix components, shellfish tissue samples sourced from different regions where different phytoplankton food sources are present, etc) and therefore exhibit varying ion-suppression effects. Although it is widely agreed that there is no generic method to overcome ion suppression, the purpose of this review is to: provide an overview of how ion suppression occurs, outline the methodologies used to assess and quantify the impact of ion suppression, discuss the various corrective actions that have been used to eliminate ion suppression in sample analysis, that is to say the deployment of techniques that eliminate or reduce the components in the sample matrix that cause ion suppression. This review article aims to collect together the latest information on the causes of ion suppression in LC-MS analysis and to consider the efficacy of common approaches to eliminate or reduce the problem using relevant examples published in the literature.