title: Reference measurement procedure for total glycerides by isotope dilution GC-MS.
abstract: BACKGROUND
  The CDC's Lipid Standardization Program established the chromotropic acid (CA) reference measurement procedure (RMP) as the accuracy base for standardization and metrological traceability for triglyceride testing. The CA RMP has several disadvantages, including lack of ruggedness. It uses obsolete instrumentation and hazardous reagents. To overcome these problems the CDC developed an isotope dilution GC-MS (ID-GC-MS) RMP for total glycerides in serum.
  
  
  METHODS
  We diluted serum samples with Tris-HCl buffer solution and spiked 200-μL aliquots with [(13)C(3)]-glycerol. These samples were incubated and hydrolyzed under basic conditions. The samples were dried, derivatized with acetic anhydride and pyridine, extracted with ethyl acetate, and analyzed by ID-GC-MS. Linearity, imprecision, and accuracy were evaluated by analyzing calibrator solutions, 10 serum pools, and a standard reference material (SRM 1951b).
  
  
  RESULTS
  The calibration response was linear for the range of calibrator concentrations examined (0-1.24 mmol/L) with a slope and intercept of 0.717 (95% CI, 0.7123-0.7225) and 0.3122 (95% CI, 0.3096-0.3140), respectively. The limit of detection was 14.8 μmol/L. The mean %CV for the sample set (serum pools and SRM) was 1.2%. The mean %bias from NIST isotope dilution MS values for SRM 1951b was 0.7%.
  
  
  CONCLUSIONS
  This ID-GC-MS RMP has the specificity and ruggedness to accurately quantify total glycerides in the serum pools used in the CDC's Lipid Standardization Program and demonstrates sufficiently acceptable agreement with the NIST primary RMP for total glyceride measurement.
authors.affiliation: Centers for Disease Control and Prevention, National Center for Environmental Health, Division of Laboratory Sciences, Clinical Chemistry Branch, Atlanta, Georgia 30341, USA. sedwards@cdc.gov
authors.forename: Selvin H
authors.initials: SH
authors.lastname: Edwards
authors.forename: Shelton L
authors.initials: SL
authors.lastname: Stribling
authors.forename: Susan D
authors.initials: SD
authors.lastname: Pyatt
authors.forename: Mary M
authors.initials: MM
authors.lastname: Kimberly
mesh_terms: D002138:Calibration; D002247:Carbon Isotopes; D008401:Gas Chromatography-Mass Spectrometry / Q000592:standards; D005990:Glycerol / Q000097:blood / Q000592:standards; D006801:Humans; D007201:Indicator Dilution Techniques; D012015:Reference Standards; D014215:Triacetin / Q000097:blood* / Q000592:standards
chemical_list: D002247:Carbon Isotopes; D005990:Glycerol; D014215:Triacetin