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Figure 1 – Recovered residues of spike recovery by three sample preparation methods. Five residues were quantified within 10 different sample types.


monitoring procedures are also vital to maintain this sensitivity. Fresh mobile phase was purged through the autosampler and pumps daily, and matrix-matched QC samples were injected every 25 samples to track performance. A five-point matrix-matched calibration curve was gener- ated weekly and used for quantification. The curtain plate and orifice were cleaned weekly according to the manufacturer’s protocols, and a new guard column was installed.


Results and discussion


With over 5000 samples run, the finished method has proven robust and dependable. Daily tracking of the QC has permitted continual updates to method performance, with very little change in sensitivity, as shown in Figure 2. The instrumental response to these ions has remained within 15% of the average throughout the use of the instrument, indicating that maintenance protocols are effective. These results illustrate the reliabil- ity of an instrument and method in constant use with minimal sample preparation. By limiting costs from sample preparation and maximizing run time, the method allows for high throughput with lower operating costs for the laboratory.


Several of the analytes on the target list have yet to be detected on the samples tested, although many appear to be in common use (Figure 3). Powdery mildew (caused by fungi of the order Erysiphales) and vari- ous insects (mites, aphids, whiteflies, thrips and worms) are the most common targets of a chemical treatment on Cannabis. This explains the


Instrumentation Pump


Figure 2 – Performance of the QC sample as shown by stability of quantifi- cation ion transitions over time.


AMERICAN LABORATORY 33 JANUARY/FEBRUARY 2017


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