National Medical Services Inc., 3701 Welsh Road Willow Grove, PA 19090, USA

The objective of this study was to determine what concentration of nitrite was present in urine specimens adulterated with Klear® and secondly to determine what concentrations of nitrite were required to prevent the GC/MS confirmation of 9-carboxy THC and opiates in urine. The concentration of nitrite in 50 urine specimens suspected of being adulterated was determined by ion chromatography (IC). To determine the effects of increasing nitrite concentrations on EMIT screening techniques and GC/MS confirmations, urine spiked with either 6 or 30 ng/mL 9-carboxy THC and 75 or 750 ng/mL of dihydrocodeine, codeine, hydrocodone, oxycodone, hydromorphone, morphine and oxymorphone were spiked with concentrations of potassium nitrite from 0 mcg/mL to 40,000 mcg/mL. These were then analyzed by both EMIT using Syva reagents for THC and opiates and by GC/MS. Nitrite concentrations were confirmed by ion-chromatography (IC).

In urine specimens presumed to have been adulterated the mean nitrite concentration was 3600 mcg/mL with a range of 0 mcg/mL to 11,300 mcg/mL. In all cases the EMIT screen for THC was positive and the GC/MS confirmation was unsuccessful. In the urine specimens spiked with various concentrations of nitrite, all were positive for THC and opiates by EMIT with no detectable inhibition of response. There was however a concentration dependant decrease in peak heights when analyzed by GC/MS which was found to be analyte specific. 9-carboxy THC and its deuterated internal standard were suppressed by 80% at 5000 mcg/mL with no recovery of either 9-carboxy THC or the internal standard at 10,000 mcg/mL. When analyzing the opiates, only hydromorphone, morphine and oxymorphone were effected by nitrite. The peak height of morphine was reduced by 70% at a nitrite concentration of 3000 mcg/mL, however no peaks were detected for either hydromorphone, morphine or oxymorphone when the nitrite concentration was 10,000 mcg/mL. This study shows that Klear®, when added to urine prevents the confirmation of 9-carboxy THC but has no effect on the EMIT analysis and supports the findings of other authors. This study also shows that nitrite, at concentrations equivalent to those found in urine specimens adulterated with Klear®, can not only prevent the confirmation of 9-carboxy THC, but also hydromorphone, morphine and oxymorphone.