title: Quantitation of total folate in whole blood using LC-MS/MS.
abstract: An accurate method for measuring whole blood total folate using liquid chromatography with tandem mass spectrometry is described and compared to GC/MS and a chemiluminescence assay. Whole blood from normal adults (n = 15) was fortified with a [(13)C(6)]para-aminobenzoic acid (pABA) internal standard and treated with 12.1 N hydrochloric acid at 110 degrees C for 4 h to hydrolyze all folates to pABA. Contaminants in the hydrolysate were adsorbed onto a C18 SPE cartridge. The eluate containing the folate catabolite pABA was partitioned into ethyl acetate and methylesterified with trimethylsilyldiazomethane. The methyl-pABA derivatives were quantified by positive-ion atmospheric pressure chemical ionization (APCI)LC-MS/MS. An isocratic mobile phase of acetonitrile-water (70:30) (v/v) on a C18 analytical column was used with a postcolumn reagent of 0.025% formic acid. The limit of quantitation for folate was 56.6 nmol/L RBC, and the limit of detection was 22.6 nmol/L RBC. Folate levels as determined by LC-MS/MS correlated well with the chemiluminescence assay and a GC/MS method. This new LC-MS/MS method provides enhanced sample throughput (n = 36 per day) as compared to GC/MS methods. LC-MS/MS will enable accurate measurements of red blood cell (RBC) folate in nutrition surveys and clinical trials.
authors.affiliation: Department of Nutrition and Division of Agricultural and Natural Resources Analytical Laboratory, University of California, Davis, 95616, USA.
authors.forename: Janel E
authors.initials: JE
authors.lastname: Owens
authors.forename: Dirk M
authors.initials: DM
authors.lastname: Holstege
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Clifford
mesh_terms: D010129:4-Aminobenzoic Acid; D000328:Adult; D002851:Chromatography, High Pressure Liquid / Q000379:methods*; D005492:Folic Acid / Q000097:blood*; D008401:Gas Chromatography-Mass Spectrometry; D006801:Humans; D008163:Luminescent Measurements; D013058:Mass Spectrometry / Q000379:methods*; D012680:Sensitivity and Specificity
chemical_list: D005492:Folic Acid; D010129:4-Aminobenzoic Acid