Quantification of isotope-labelled and unlabelled folates in plasma, ileostomy and food samples.
New stable isotope dilution assays were developed for the simultaneous quantitation of [(13)C(5)]-labelled and unlabelled 5-methyltetrahydrofolic acid, 5-formyltetrahydrofolic acid, folic acid along with unlabelled tetrahydrofolic acid and 10-formylfolic acid in clinical samples deriving from human bioavailability studies, i.e. plasma, ileostomy samples, and food. The methods were based on clean-up by strong anion exchange followed by LC-MS/MS detection. Deuterated analogues of the folates were applied as the internal standards in the stable isotope dilution assays. Assay sensitivity was sufficient to detect all relevant folates in the respective samples as their limits of detection were below 0.62 nmol/L in plasma and below 0.73 μg/100 g in food or ileostomy samples. Quantification of the [(13)C(5)]-label in clinical samples offers the possibility to differentiate between folate from endogenous body pools and the administered dose when executing bioavailability trials.
Division BIOANALYTIK Weihenstephan, Research Center for Nutrition and Food Sciences (Z I E L), Technische Universität München, 85350 Freising-Weihenstephan, Germany.
Barbara E
BE
Büttner
Veronica E
VE
Öhrvik
Cornelia M
CM
Witthöft
Michael
M
Rychlik
D002247:Carbon Isotopes / Q000032:analysis; D005492:Folic Acid / Q000032:analysis*; D005504:Food Analysis; D006801:Humans; D007081:Ileostomy; D007082:Ileum / Q000737:chemistry* / Q000601:surgery; D007553:Isotope Labeling / Q000379:methods*; D010949:Plasma / Q000737:chemistry*
D002247:Carbon Isotopes; D005492:Folic Acid