Effect of specimen storage and preservation on toxicological analyses of urine

1. The stability of nineteen classes of drugs or their metabolites in urine specimens, for the purpose of toxicological screening has been studied for periods of up to thirty-six weeks. 2. The effect of specimen preservation by refrigation and by the addition of boric acid, chloroform, sodium fluoride, mercuric chloride, and buffers, has been assessed. 3. With the exception of flurazepam, glutethimide, and secobarbital, specimens may be retained at room temperature for periods in excess of six weeks without deterioration. 4. Preservation by the addition of sodium fluoride (5 g/l) followed by freezing, thawing, and filtration significantly prevents specimen deterioration, and may be used as the method of choice.