We purchased the following compounds from Sigma: adenine, adenosine, 2-deoxyadenosine, 2-deoxyguanosine, inosine, 2-deoxyinosine, xanthine, hypoxanthine, orotic acid, uric acid, thymine, uracil, dihydrothymine, dihydrouracil, N-carbamyl-[beta]-aminoisobutyric acid, N-carbamyl-[beta]-alanine, thymidine, uridine, pseudouracil, 5-hydroxymethyluracil, and 2-deoxyuridine.
Optimal peak shapes were achieved for all analytes except for dihydrouracil and N-carbamyl-[beta]-alanine, which were characterized by broader and split peaks.
For xanthine, adenosine, 2,8-dihydroxyadenine, uracil, thymine, dihydrouracil, dihydrothymine, N-carbamyl-[beta]-amino-isobutyric acid, N-carbamyl-[beta]-alanine, uridine, and pseudouridine, the detection limit was between 1 and 10 [micro]mol/L.
Dihydrouracil was an exception; its CV was higher, at 42%.
For 2-deoxyinosine, adenosine, 2-deoxyadenosine, guanosine, 2-deoxyguanosine, succinyladenosine, orotic acid, thymine, dihydrouracil, dihydrothymine, uridine, 2-deoxyuridine, and 5-hydroxymethyluracil, sample concentrations were below the lower limits of quantification, as were the concentrations of inosine and N-carbamyl-[beta]-aminoisobutyric acid for children older than 1 year and N-carbamyl-[beta]-alanine for children older than 4 years of age.
The interference of 5,6-dihydrouridine could be eliminated by use of the transition m/z 132 [right arrow] 115 for the detection of dihydrouracil (see Fig.
Correlation between uracil and dihydrouracil plasma ratio, fluorouracil (5-FU) pharmacokinetic parameters, and tolerance in patients with advanced colorectal cancer: a potential interest for predicting 5-FU toxicity and determining optimal 5-FU dosage.
Simple liquid chromatographic method for the determination of uracil and dihydrouracil plasma levels: a potential pretreatment predictor of 5-fluorouracil toxicity.