Calibrant Solutions for Continuous-Flow Urate Analysis: Interference by Formaldehyde

Abstract

The use of formaldehyde to preserve aqueous urate calibration solutions has been recommended since 1913, but it interferes in some commonly used methods. At a pH below 8·5 formaldehyde affects the rate of dialysis of urate in Technicon AutoAnalyzer systems. This effect has been studied by variation of the pH at which dialysis takes place. The interference is attributed to the formation of pH-dependent addition products between uric acid and formaldehyde, which have been examined by thin-layer chromatography and mass spectrometry. Recovery experiments on protein-containing solutions show that a purely aqueous urate calibrant solution is satisfactory for use in AutoAnalyzer systems.

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