Liquid chromatography/tandem mass spectrometry methods for quantitation of mevalonic acid in human plasma and urine: method validation, demonstration of using a surrogate analyte, and demonstration of unacceptable matrix effect in spite of use of a stable isotope analog internal standard

2003 ◽  
Vol 17 (15) ◽  
pp. 1723-1734 ◽  
Author(s):  
Mohammed Jemal ◽  
Alan Schuster ◽  
Daisy B. Whigan
2004 ◽  
Vol 50 (8) ◽  
pp. 1391-1395 ◽  
Author(s):  
Eduard A Struys ◽  
Erwin E W Jansen ◽  
Nanda M Verhoeven ◽  
Cornelis Jakobs

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.


Author(s):  
C A Chadwick ◽  
L J Owen ◽  
B G Keevil

Background: Dehydroepiandrosterone sulphate (DHEAS) is a steroid that is increasingly being recognized as a potential drug of abuse in many countries. This is due to its reputation as a hormone that may be able to retard the ageing process. The measurement of DHEAS is useful in the diagnosis of medical conditions such as congenital adrenal hyperplasia and polycystic ovary syndrome. Thus, a liquid chromatography-tandem mass spectrometry method has been developed to determine DHEAS concentrations in human serum. Method: The chromatography was performed using a WatersTM 2795 Alliance HT LC system coupled to a Mercury Fusion-RP column fitted with a SecurityGuardTM column. Results: DHEAS and the internal standard, deuterated DHEAS, both had a retention time of 1.5 min. The transition determined by the Micromass QuattroTM tandem mass spectrometer for DHEAS was m/z 367.3>96.7 and for the internal standard m/z 369.3>96.6. The method was linear up to 20 µmol/L; the lower limit of detection and the lower limit of quantitation were both 1 µmol/L. The intra- and interassay imprecision were <11% over a concentration range of 1-18 µmol/L for the in-house quality control and <12% for the intra- and interassay imprecision for the Bio-Rad Lyphocheck QC. Conclusion: The measurement of DHEAS by liquid chromatography-tandem mass spectrometry is robust and has a simple sample preparation procedure with a rapid cycle time of only 4 min.


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