Confiscation by field investigations of items that have the potential to alter performance is an integral part of enforcing drug prohibition in horse racing. Analysis of the confiscated items by a previously established approach of flow injection analysis coupled to high-resolution mass spectrometry (MS) is high throughput, inclusive, and comprehensive. However, labeled drugs for the contents were not detected initially in two confiscation samples due to the presence of high concentrations of Polyethylene glycols (PEGs) in them, which is named as the PEGs’ masking effect on drug detection. To eliminate this masking effect, an analytical method was developed, and then the labeled drugs were identified.
In a confiscated bottle labeled with trichloromethanide and dexamethasone acetate, the latter was not detected in the initial analysis. In the full scan mass spectrum acquired in positive ion mode for this sample, there was a series of highly intense PEGs peaks, but the mass spectral peak for dexamethasone acetate was absent. To detect dexamethasone acetate, the sample was extracted with methyl tert-butyl ether (MTBE), and the extract was analyzed. Dexamethasone acetate was detected and identified in the extract, even though intense PEGs peaks were still present in the MS spectrum. In another confiscation sample, the labeled substance toltrazuril was not detected in positive ion mode in the initial experiments, but an envelope of strong PEGs peaks was observed in the MS spectrum acquired for this sample. The sample was extracted with MTBE and then analyzed. Toltrazuril was detected and identified in this sample.
Given the masking effect of PEGs on the detection of substances in positive ion mode, when intense PEGs peaks are observed in the MS spectrum acquired for a confiscation sample, it should be extracted with MTBE to minimize the PEGs’ masking effect, and the extracted sample should be reanalyzed for drugs.