title: Phenylalanine analyses of blood-spot control materials: preparation of samples and evaluation of interlaboratory performance.
abstract: Aliquots (0.1 mL) of whole-blood pools prepared to contain various concentrations of phenylalanine were applied to filter-paper collection cards, dried, and stored in sealed bags. We measured the phenylalanine content of the dried blood spots by bioassay, fluorometry, and "high-performance" liquid chromatography, and found that the concentrations remained constant for two years when samples were kept at -20 degrees C or lower. Intra- and interlaboratory studies showed that results for phenylalanine were greater for laboratories using bioassay procedures than for those using fluorometric procedures. Further, CVs (both among- and within-laboratory) obtained with fluorometric procedures were nearly half as great as the CVs obtained by laboratories using bioassay techniques.
mesh_terms: D001681:Biological Assay; D001800:Blood Specimen Collection / Q000379:methods; D002851:Chromatography, High Pressure Liquid; D004912:Erythrocytes / Q000032:analysis; D005374:Filtration; D006801:Humans; D007753:Laboratories / Q000592:standards; D010649:Phenylalanine / Q000097:blood*; D011786:Quality Control; D013048:Specimen Handling; D013050:Spectrometry, Fluorescence
chemical_list: D010649:Phenylalanine