INFLUENCE OF POLYSTYRENE LATEX CARRYOVER ON PYROLYSIS MASS SPECTRAL RESPONSE

Carryover from preceding qualification procedures can interfere with subsequent analysis in sequential mass-spectrometric testing. During quality-assurance testing of a military biological detector, one of six systems showed an unexpected biological-simulant classification accompanied by a mass-spectral pattern different from the expected response after prior collection efficiency qualification using polystyrene latex (PSL) particles. The investigation examined whether residual PSL contributed to the interference. The incident spectrum showed prominent responses at nominal m/z 51, 78, and 104, similar to the PSL-only response, and particulate material was observed within the incident filter structure. Four controlled verification tests examined complementary aspects of the proposed carryover pathway. Direct co-loading of PSL and biological simulant produced incident-like spectral interference and altered classification. When cleaning after PSL qualification was deliberately omitted, visible residue and subsequent PSL-associated spectral responses were observed, and biological-simulant testing under these conditions again produced altered spectral relationships and classification. A separate repeat verification produced a similar outcome. Following the incident, the cleaning procedure was strengthened by additional mechanical removal, ultrasonic cleaning, and residue inspection, after which the expected detection result was documented.