title: Developing a reference measurement procedure for free glycerol in human serum by two-step gas chromatography-isotope dilution mass spectrometry.
abstract: BACKGROUND
  Free glycerol in human serum is measured in clinical laboratories using enzymatic methods, which can be affected by interferences from biological samples. These methods are not applicable when stable isotopic tracers are used to determine lipid kinetics. Hence, a reference measurement procedure for free glycerol in human serum is needed.
  
  
  METHODS
  A reference measurement procedure based on two-step gas chromatography-isotope dilution mass spectrometry (GC-IDMS) was developed for the measurement of free glycerol in human serum. This procedure involved spiking with (13)C3-glycerol, protein precipitation and cation exchange SPE, followed by two-step derivatization with 1-butylboronic acid and N-methyl-N-trimethylsilyltrifluoroacetamide. Tripalmitin certified reference material (CRM) was used as the calibration standard to ensure metrological traceability.
  
  
  RESULTS
  Good precision and accuracy were obtained as demonstrated by relative standard deviation (RSD) of 1.51%-3.33%, with average recoveries over 98%. The relative measurement uncertainty was below 3% with major contributions from the concentration of glycerol calibration solution, choice of ion pair, linear regression, and measurement precision.
  
  
  CONCLUSIONS
  With good accuracy and precision, as well as clear metrological traceability, the developed GC-IDMS procedure is useful in producing traceable and accurate measurement of free glycerol in human serum.
authors.affiliation: Chemical Metrology Division, Applied Sciences Group, Health Sciences Authority, Singapore.
authors.forename: Yizhao
authors.initials: Y
authors.lastname: Chen
authors.affiliation: Chemical Metrology Division, Applied Sciences Group, Health Sciences Authority, Singapore.
authors.forename: Hui Ling
authors.initials: HL
authors.lastname: Teo
authors.affiliation: Chemical Metrology Division, Applied Sciences Group, Health Sciences Authority, Singapore. Electronic address: liu_qinde@hsa.gov.sg.
authors.forename: Qinde
authors.initials: Q
authors.lastname: Liu
authors.affiliation: Chemical Metrology Division, Applied Sciences Group, Health Sciences Authority, Singapore.
authors.forename: Tong Kooi
authors.initials: TK
authors.lastname: Lee
mesh_terms: D002138:Calibration; D008401:Gas Chromatography-Mass Spectrometry / Q000379:methods*; D005990:Glycerol / Q000097:blood*; D006801:Humans; D007201:Indicator Dilution Techniques; D012015:Reference Standards; D012996:Solutions; D035501:Uncertainty
chemical_list: D012996:Solutions; D005990:Glycerol
keywords: Free glycerol; Gas chromatography–mass spectrometry; Human serum; Isotope dilution mass spectrometry; Reference measurement procedure