Quantitation of Cocaine and Its Principal Metabolite, Benzoylecgonine, by GLC-Mass Spectrometry Using Stable Isotope Labeled Analogs as Internal Standards

1978 ◽  
Vol 67 (6) ◽  
pp. 811-814 ◽  
Author(s):  
Satya P. Jindal ◽  
Per Vestergaard
Keyword(s):  
Mass Spectrometry ◽  
Stable Isotope ◽  
Internal Standards

scholarly journals Measurement of Urinary d- and l-2-Hydroxyglutarate Enantiomers by Stable-Isotope-Dilution Liquid Chromatography–Tandem Mass Spectrometry after Derivatization with Diacetyl-l-Tartaric Anhydride

2004 ◽  
Vol 50 (8) ◽  
pp. 1391-1395 ◽  
Author(s):  
Eduard A Struys ◽  
Erwin E W Jansen ◽  
Nanda M Verhoeven ◽  
Cornelis Jakobs
Keyword(s):  
Mass Spectrometry ◽  
Differential Diagnosis ◽  
Liquid Chromatography ◽  
Stable Isotope ◽  
Tandem Mass Spectrometry ◽  
Tandem Mass ◽  
Internal Standards ◽  
Chromatography Tandem Mass Spectrometry ◽  
Liquid Chromatography Tandem Mass

Abstract Background: The differential diagnosis of d-2-hydroxyglutaric aciduria (d-2-HGA), l-2-hydroxyglutaric aciduria (l-2-HGA), and the combined d/l-2-hydroxyglutaric aciduria (d/l-2-HGA) can be accomplished only by the measurement of the corresponding 2-hydroxyglutarate (2-HG). Available methods for the determination of d- and l-2-HG in urine are either time-consuming and expensive or have not been extensively validated. We aimed to develop a method for their rapid and sensitive measurement. Methods: We used liquid chromatography–tandem mass spectrometry (LC-MS/MS) for the determination of d- and l-2-HG with stable-isotope-labeled internal standards. Urine samples of 20 μL were mixed with 250 μL of methanol containing the internal standards and subsequently dried under nitrogen. The analytes were derivatized by use of diacetyl-l-tartaric anhydride (DATAN) to obtain diastereomers, which were separated on an achiral C18 HPLC column and detected by MS/MS in multiple-reaction-monitoring mode. Results: The use of DATAN as chiral derivatization reagent provided very well separated peaks of the formed diastereomers of d- and l-2-HG, with a total runtime of 5 min. The inter- and intraassay CVs for d- and l-2-HG ranged from 3.4% to 6.2%. Mean recoveries of d- and l-2-HG, evaluated on two concentrations, were 94%. Detection limit of the presented method was 20 pmol for a sample volume of 20 μL. Method comparison of the LC-MS/MS method with a gas chromatography–mass spectrometry method, in which d- and l-2-HG were derivatized with R-(−)-butanol, showed good agreement between the two methods. Conclusions: Urinary d- and l-2-HG can be analyzed by MS/MS after derivatization with DATAN. The presented method may be suitable for the differential diagnosis of 2-HGA.

scholarly journals Measurement of Nε-(Carboxymethyl)lysine and Nε-(Carboxyethyl)lysine in Human Plasma Protein by Stable-Isotope-Dilution Tandem Mass Spectrometry

2004 ◽  
Vol 50 (7) ◽  
pp. 1222-1228 ◽  
Author(s):  
Tom Teerlink ◽  
Rob Barto ◽  
Herman J ten Brink ◽  
Casper G Schalkwijk
Keyword(s):  
Mass Spectrometry ◽  
Stable Isotope ◽  
Tandem Mass Spectrometry ◽  
Isotope Dilution ◽  
Plasma Proteins ◽  
Plasma Concentrations ◽  
Tandem Mass ◽  
Internal Standards ◽  
Stable Isotope Dilution ◽  
Carboxymethyl Lysine

Abstract Background: N ε-(Carboxymethyl)lysine (CML) and Nε-(carboxyethyl)lysine (CEL) are two stable, nonenzymatic chemical modifications of protein lysine residues resulting from glycation and oxidation reactions. We developed a tandem mass spectrometric method for their simultaneous measurement in hydrolysates of plasma proteins. Methods: CML and CEL were liberated from plasma proteins by acid hydrolysis after addition of deuterated CML and CEL as internal standards. Chromatographic separation was performed by gradient-elution reversed-phase chromatography with a mobile phase containing 5 mmol/L nonafluoropentanoic acid as ion-pairing agent. Mass transitions of 205.1→84.1 and 219.1→84.1 for CML and CEL, respectively, and 209.1→88.1 and 223.1→88.1 for their respective internal standards were monitored in positive-ion mode. Results: CML and CEL were separated with baseline resolution with a total analysis time of 21 min. The lower limit of quantification was 0.02 μmol/L for both compounds. Mean recoveries from plasma samples to which CML and CEL had been added were 92% for CML and 98% for CEL. Within-day CVs were <7.2% for CML and <8.2% for CEL, and between-day CVs were <8.5% for CML and <9.0% for CEL. In healthy individuals (n = 10), mean (SD) plasma concentrations of CML and CEL were 2.80 (0.40) μmol/L (range, 2.1–3.4 μmol/L) and 0.82 (0.21) μmol/L (range, 0.5–1.2 μmol/L), respectively. In hemodialysis (n = 17) and peritoneal dialysis (n = 9) patients, plasma concentrations of CML and CEL were increased two- to threefold compared with controls, without significant differences between dialysis modes [7.26 (1.36) vs 8.01 (3.80) μmol/L (P = 0.89) for CML, and 1.84 (0.39) vs 1.71 (0.42) μmol/L (P = 0.53) for CEL]. Conclusions: This stable-isotope-dilution tandem mass spectrometry method is suitable for simultaneous analysis of CML and CEL in hydrolysates of plasma proteins. Its robustness makes it suitable for assessing the value of these compounds as biomarkers of oxidative stress resulting from sugar and lipid oxidation.

scholarly journals Light contamination in stable isotope-labelled internal peptide standards is frequent and a potential source of false discovery and quantitation error in proteomics

2021 ◽  
Author(s):  
Mogjiborahman Salek ◽  
Jonas D Foerster ◽  
Wolf-Dieter Lehmann ◽  
Angelika B Riemer
Keyword(s):  
Mass Spectrometry ◽  
Stable Isotope ◽  
Biological Samples ◽  
Synthetic Peptides ◽  
Isotopic Enrichment ◽  
Internal Standards ◽  
False Discovery ◽  
Potential Source ◽  
Internal Peptide ◽  
Detection And Quantification

In mass spectrometry-based proteomics, heavy internal standards are used to validate target peptide detections and to calibrate peptide quantification. Here we report light contamination present in heavy labelled synthetic peptides of high isotopic enrichment. Application of such peptides as assay-internal standards potentially compromises the detection and quantification especially of low abundant cellular peptides. Therefore, it is important to adopt guidelines to prevent false-positive identifications of endogenous light peptides as well as errors in their quantification from biological samples.

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