Journal Article Quantification of phenylalanine in serum with a centrifugal analyzer. Get access C L Welch, C L Welch Search for other works by this author on: Oxford Academic Google Scholar S E Boon S E Boon Search for other works by this author on: Oxford Academic Google Scholar Clinical Chemistry, Volume 31, Issue 5, 1 May 1985, Pages 785–786, https://doi.org/10.1093/clinchem/31.5.785 Published: 01 May 1985

This method for measuring fecal occult blood is based on the heme-catalyzed oxidation of tetramethylbenzidine by H2O2. An aliquot of heated stool homogenate is mixed with acetic acid to chemically separate heme from globin. The heme is extracted into ethyl acetate and reacted with the reagent and H2O2 to produce a green oxidation product. The reaction is followed kinetically for 30 to 60 s at 660 nm. A660 is linearly related to the amount of hemoglobin. The lower limit of detection is 1 to 2 mg of hemoglobin per gram (wet weight) of feces. Within-day precision (CV) of the analysis for hemoglobin added to stool specimens (4 to 30 mg/g) ranged from 2.3 to 7.6%, between-day CV from 2.1 to 8.1%. Analytical recovery of hemoglobin added to fecal specimens (4 to 30 mg/g) ranged from 86.7 to 106.2%. Of the substances known to interfere with conventional dye-oxidation tests for fecal occult blood, only myoglobin and ascorbic acid interfere with hemoglobin quantification by our procedure. The test is fast, inexpensive, and easy to perform, and involves equipment available in hospital laboratories.

We describe a determination of zomepirac concentration in plasma and serum by reversed-phase "high-performance" liquid chromatography. The assay requires 1.0 mL of sample and involves diethyl ether extraction of zomepirac from an acidified sample, followed by concentration and injection into a liquid chromatograph. The column effluent is monitored at 330 nm. Retention times of zomepirac and the internal standard (tolmetin) are 3.8 and 2.7 min, respectively. The lower limit of detection for zomepirac in serum or plasma is 0.05 mg/L. Within-day precision (CV) of analysis in plasma or serum with zomepirac added (0.1-10.0 mg/L) ranged from 1.4 to 6.7%; between-day CV varied from 1.4 to 7.5%. Analytical recovery of zomepirac (1.0 mg/L) from serum and plasma was 77.6 (SD 3.5)% and 80.4 (SD 5.2)%, respectively. Numerous commonly coadministered drugs did not interfere. The elimination half-life of the drug was 1.8 h, and the peak plasma concentration ranged from 1.1 to 2.4 mg/L. Peak and trough concentrations measured throughout five days of therapy imply no accumulation.