Nonenzymatic elimination of ascorbic acid in clinical samples.
OBJECTIVE
Ascorbic acid interferes significantly in the oxidative reaction of chromogenic reagents by peroxidase and hydrogen peroxide. Currently, ascorbate oxidase is commonly utilized for eliminating the interference of ascorbic acid in the oxidative colorimetric reaction. This enzyme, however, displays several disadvantages, such as high cost, variation from lot to lot, and low stability. We applied a series of commercially available and stable radicals (ascorbic acid quenchers [AAQs]) for nonenzymatic quenching of ascorbic acid in the uricase-based uric acid determination in serum and urine.


METHODS
In order to evaluate the quenching activity of AAQs, a commercially available uric acid detection kit was used. TBA-80FR.NEO biochemical analyzer was utilized for the assay.


RESULTS
4-Hydroxy-2,2,6,6-tetramethyl-1-piperidinyloxy free radical (AAQ-2) was the most effective ascorbic acid quencher among the four stable radicals, and the uric acid assay suffered no interference by AAQ-2. The ascorbic acid quenching ability of 2 mmol/L of AAQ-2 in reagent solution (reagent-I) was > or = 2 U/ml ascorbate oxidase in reagent solution.


CONCLUSIONS
AAQ-2 was proven to be a suitable quencher of ascorbic acid in clinical samples.
Kayamori
Y
Y
Department of Clinical Chemistry, National Cardiovascular Center, Osaka, Japan. ykayamor@hsp.ncvc.go.jp
Katayama
Y
Y
Urata
T
T
D001204:Ascorbate Oxidase / Q000378:metabolism / Q000494:pharmacology; D001205:Ascorbic Acid / Q000097:blood / Q000592:standards* / Q000652:urine; D002138:Calibration; D002863:Chromogenic Compounds; D019963:Clinical Chemistry Tests / Q000379:methods*; D003497:Cyclic N-Oxides / Q000378:metabolism / Q000494:pharmacology; D016166:Free Radical Scavengers; D006801:Humans; D016014:Linear Models; D012016:Reference Values; D015203:Reproducibility of Results; D013056:Spectrophotometry, Ultraviolet; D013113:Spin Labels; D014527:Uric Acid / Q000097:blood / Q000592:standards* / Q000652:urine
D002863:Chromogenic Compounds; D003497:Cyclic N-Oxides; D016166:Free Radical Scavengers; D013113:Spin Labels; D014527:Uric Acid; D001204:Ascorbate Oxidase; D001205:Ascorbic Acid; C001803:tempol