Adulteration of Urine with Nitrite Containing Agents

The product "Klear" comes in two microtubes containing 500 mg of white crystalline material. This product readily dissolves in urine without affecting color or temperature.

Klear may cause a false-negative GC/MS confirmation for marijuana. ElSohly et al. first reported this product as potassium nitrite and provided evidence that nitrite leads to decomposition of ions of 9-THC and its internal standard. The authors reported that using a bisulfite step at the beginning of sample preparation could eliminate such interference (30). Tsai et al. further investigated the effect of nitrite on immunoassay screening of other drugs. These drugs include cocaine metabolites, morphine, THC metabolites (THC-COOH), amphetamine and phencyclidine. Nitrite at a concentration of 1.0 M had no effect on the Abuscreen assay. At a higher nitrite concentration, the amphetamine assay becomes more sensitive and the THC metabolite assay becomes less sensitive. The GC/MS analyses of BE, morphine, amphetamine and phencyclidine were not affected while recovery of the THC metabolite was significantly reduced. Again, this interference could be eliminated by bisulfite treatment (31). Both duration of nitrite exposure and the urine matrix affect the THC-COOH assay. In an in vitro study, 40 clinical urine specimens confirmed positive for THC-COOH were supplemented with 1.15 or 0.30 M nitrite. The results indicated that the pH of the urine and the original drug concentrations play major roles in dictating the effectiveness of nitrite in causing false-negative THC metabolite tests. With acidic pH significant decreases in the immunoassay screening, results can be observed in all urine specimens within 4 h of adulteration with nitrite regardless of original concentrations of THC-COOH (range of concentrations 33-488 ng/mL as determined by GC/MS). All specimens were negative for THC-COOH after 1 day. In contrast, the immunoassay results of urine specimens with basic or neutral pH were less affected by nitrite exposure. Approximately two-thirds of the samples with pH values greater than 7.0 were immunoassay positive even 3 days after supplementing with nitrite (32).

Nitrite in urine may arise in vivo and is found in urine in low concentration. Patients receiving medications such as nitroglycerine, isosorbide dinitrate, nitro-prusside and ranitidine may have increased nitrite levels in their blood. However, concentrations of nitrite were below 36 ^g/mL in specimens cultured positive for microorganisms, and nitrite concentrations were below 6 ^g/mL in patients receiving medications that are metabolized to nitrite. On the other hand, nitrite concentrations were 1910-12,200 ^g/mL in urine specimens adulterated with nitrite (33). Whizzies is another urine adulterant available from the Internet. This adulterant also contains potassium nitrite.

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