title: Simultaneous Determination of Underivatized Vitamin B1 and B6 in Whole Blood by Reversed Phase Ultra High Performance Liquid Chromatography Tandem Mass Spectrometry.
abstract: BACKGROUND
  Vitamin B1 (thiamine-diphosphate) and B6 (pyridoxal-5'phosphate) are micronutrients. Analysis of these micronutrients is important to diagnose potential deficiency which often occurs in elderly people due to malnutrition, in severe alcoholism and in gastrointestinal compromise due to bypass surgery or disease. Existing High Performance Liquid Chromatography (HPLC) based methods include the need for derivatization and long analysis time. We developed an Ultra High Performance Liquid Chromatography Tandem Mass spectrometry (UHPLC-MS/MS) assay with internal standards for simultaneous measurement of underivatized thiamine-diphosphate and pyridoxal-5'phosphate without use of ion pairing reagent.
  
  
  METHODS
  Whole blood, deproteinized with perchloric acid, containing deuterium labelled internal standards thiamine-diphosphate(thiazole-methyl-D3) and pyridoxal-5'phosphate(methyl-D3), was analyzed by UHPLC-MS/MS. The method was validated for imprecision, linearity, recovery and limit of quantification. Alternate (quantitative) method comparisons of the new versus currently used routine HPLC methods were established with Deming regression.
  
  
  RESULTS
  Thiamine-diphosphate and pyridoxal-5'phosphate were measured within 2.5 minutes instrumental run time. Limits of detection were 2.8 nmol/L and 7.8 nmol/L for thiamine-diphosphate and pyridoxal-5'phosphate respectively. Limit of quantification was 9.4 nmol/L for thiamine-diphosphate and 25.9 nmol/L for pyridoxal-5'phosphate. The total imprecision ranged from 3.5-7.7% for thiamine-diphosphate (44-157 nmol/L) and 6.0-10.4% for pyridoxal-5'phosphate (30-130 nmol/L). Extraction recoveries were 101-102% ± 2.5% (thiamine-diphosphate) and 98-100% ± 5% (pyridoxal-5'phosphate). Deming regression yielded slopes of 0.926 and 0.990 in patient samples (n = 282) and national proficiency testing samples (n = 12) respectively, intercepts of +3.5 and +3 for thiamine-diphosphate (n = 282 and n = 12) and slopes of 1.04 and 0.84, intercepts of -2.9 and +20 for pyridoxal-5'phosphate (n = 376 and n = 12).
  
  
  CONCLUSIONS
  The described UHPLC-MS/MS method allows simultaneous determination of underivatized thiamine-diphosphate and pyridoxal-5'phosphate in whole blood without intensive sample preparation.
authors.affiliation: Department of Clinical Chemistry and Haematology, Elisabeth-TweeSteden Hospital, Tilburg, The Netherlands.
authors.forename: Johan
authors.initials: J
authors.lastname: Puts
authors.affiliation: Department of Clinical Chemistry and Haematology, Elisabeth-TweeSteden Hospital, Tilburg, The Netherlands.
authors.forename: Monique
authors.initials: M
authors.lastname: de Groot
authors.affiliation: Life Science group, Agilent Technologies, Amstelveen, The Netherlands.
authors.forename: Martin
authors.initials: M
authors.lastname: Haex
authors.affiliation: Department of Clinical Chemistry and Haematology, Elisabeth-TweeSteden Hospital, Tilburg, The Netherlands.
authors.forename: Bernadette
authors.initials: B
authors.lastname: Jakobs
mesh_terms: D001800:Blood Specimen Collection; D002138:Calibration; D002851:Chromatography, High Pressure Liquid / Q000379:methods*; D006801:Humans; D012015:Reference Standards; D012680:Sensitivity and Specificity; D053719:Tandem Mass Spectrometry / Q000379:methods*; D013831:Thiamine / Q000097:blood*; D013997:Time Factors; D025101:Vitamin B 6 / Q000097:blood*
chemical_list: D025101:Vitamin B 6; D013831:Thiamine