Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0033036 (APC)
 10,214 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Benzo[a]pyrene (BaP), a well-known carcinogen, is frequently measured as an "indicator" of the potential dermal tumorigenicity of a sample. The present sequential high-performance liquid chromatography--high-performance liquid chromatography method overcomes problems in trace-level sample enrichment and recovery corrections encountered earlier. An amount of 5 g of naphtha or fuel oil is diluted to 10 ml with dichloromethane and spiked with a small quantity (ca. 0.25 micrograms) of 14C-labeled BaP tracer. A BaP-enriched fraction is obtained from a 1-ml aliquot of this sample by semipreparative chromatography on a Partisil PAC 10 column with dichloromethane-hexane (10:90) as the eluent, and concentrated to exactly 0.3, 0.5, or 1.0 ml in acetonitrile. Quantitation is performed using a reversed-phase Vydac 201 TP 5415 column with acetonitrile-water (75:25) as eluent and a Waters Model 420 E/420 AC fluorescence detector, employing an excitation/emission filter pair of 360/425 nm. The recovery of the radiolabeled tracer is evaluated by combustion of 50 microliter of the final isolate in pure oxygen, collection of the liberated 14CO2 in an alkaline desorber, and liquid scintillation counting. The recovery of BaP normally exceeded 90%, but values as low as ca. 50% were occasionally observed. Potential matrix interferences in the recovery determination were eliminated by sample combustion. The nominal precision of the overall method is approximately +/- 30% relative standard deviation at a BaP concentration of 30 ppb. The nominal analysis time for a single sample is approximately 4 h.
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PMID:Liquid chromatographic determination of benzo[a]pyrene at part-per-billion concentrations in highly refined coal- and petroleum-derived fuels. 355 98

Vitamin D3 was determined in commercially fortified instant nonfat dried milk by using normal phase high pressure liquid chromatography (HPLC). The sample was extracted with dichloromethane with sodium phosphate tribasic solution added. The sample was cleaned up by using a Sep-Pak silica cartridge and then a microparticulate column containing 10 micrometer Partisil-10 PAC packing material. The final analysis was performed by using a normal phase HPLC system with 10 micrometer LiChrosorb NH2 column. Recovery of vitamin D3 at levels as low as 10000 IU/kg was 97.7% with a standard deviation of 3.9%.
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PMID:High pressure liquid chromatographic determination of vitamin D3 in instant nonfat dried milk. 625 Oct 24

A simple and rapid quantitative method for the determination of vitamin E in animal feeds is described. The method involves direct extraction with a mixture of isooctane--1,4-dioxane (80 + 20) followed by saponification. Additional purification was achieved by using a silica gel Sep-Pak. Elution time for vitamin E alcohol was 7.98 min (standard deviation (SD) 0.06) using a Partisil-10 PAC column and an isocratic mobile phase of hexane--dichloromethane--isopropanol (70 + 30 + 0.2) with a flow rate of 1 mL/min, and detection at 292 nm and 0.01 AUFS by a variable UV monitor. The average recovery of vitamin E was 96.64% (SD 5.19) in 4 different animal feeds. The method compared favorably with the official AOAC method. The minimum detectable amount of vitamin E in an animal feed is 10 IU/kg.
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PMID:Determination of vitamin E in animal feeds by normal phase high pressure liquid chromatography. 745 86