Efficacy of 1% sodium fluoride as a preservative in urine samples containing glucose and Candida albicans

Abstract

Whether urine samples used in forensic science DUI testing can be compromised by endogenous ethanol production is a recurrent and yet unresolved issue. This study first assessed unpreserved urine samples that were collected, processed, and analyzed repeatedly over 13 to 41 days using a standard gas chromatographic procedure for ethanol analysis. Despite extensive microbial growth, ethanol was not detected in any test sample. The extent of ethanol production in samples supplemented with glucose, Candida albicans, or both was determined to evaluate the potential for ethanol production in urine samples associated with pathological conditions such as urinary tract yeast infections and diabetes mellitus. Ethanol production under each of the above treatment conditions was assessed in the presence and absence of 1% sodium fluoride as a microbial suppressant. Mean ethanol concentrations were determined for unpreserved samples containing urine only (0.003 +/- 0.005 g%), urine plus yeast (0.006 +/- 0.009 g%) and urine plus glucose (0.067 +/- 0.070 g%). Unpreserved samples supplemented with both yeast and glucose attained mean ethanol concentrations of 0.164 +/- 0.057 g% (P < 0.01). Ethanol could not be detected in any corresponding duplicate samples, which were preserved with 1% sodium fluoride. A lack of ethanol production in any of the unpreserved urine samples indicates that false DUI convictions due to endogenous ethanol production are very unlikely. And while endogenous ethanol production is possible in the presence of both glucose and contaminating C. albicans, 1% sodium fluoride completely eliminated microbial fermentation.