Test samples from Norchem Drug Testing were prepared in 1:4 dilutions of pooled urine with deionized water.
Results and Discussion
The LC gradient for this analysis results in a retention time of 4.6 minutes for the THCC analyte and the IS peak. Chromatograms for the 1 ng/mL sample and 25 ng/mL IS (20 pg and 500 pg on column, respectively) are shown in Figure 1. This level is 50 times below the proposed drug cutoff level for the initial immunoassay screen published by the Substance Abuse and Mental Health Services Administration (SAMHSA)1 and 15 times below the proposed cutoff level for the GC/MS confirmatory test.
The LC/MS/MS method described here is linear from 1 ppb to 1000 ppb as shown in Figure 2. Each calibration standard was run in triplicate and the three data points were averaged.
A series of test samples ranging from 1 ng/mL to 800 ng/mL were run on the 1200L LC/MS/MS. The calculated and actual values are shown in Table 1.
A representative chromatogram for the Norchem Drug Testing samples is shown in Figure 3. At the 1 ng/mL LOQ level, no interference is observed, demonstrating the specificity of the LC/MS/MS method.
The LC/MS/MS method presented in this application note is very simple and sensitive. The method eliminates the need for a time-consuming derivatization step which can take an hour or more. The Varian 1200L LC/MS/MS can be a powerful tool in forensic, clinical, and toxicology laboratories offering significant cost and time savings.
The authors would like thank Dr. A. Fischinger, Norchem Drug Test