The effects of urine adulteration with oxidants before drug analysis with LC-HRMS and CEDIA

In drug analysis, different kinds of immunoassays are often used as an initial screening for urine samples. The positive screening results are then followed by a confirmatory test, which consists of mass spectrometry methods to detect the drugs. The confirmatory tests are considered to be more resistant to manipulation than the screening tests. If the tested person wants to obtain a false negative result in the drug analysis, there are a lot of different manipulation strategies available today. Manipulation of urine with oxidants before the drug analysis, oxidizes the drugs, and obtains negative results. The aim of this study was to investigate how the results of the drug analysis with the screening test; cloned enzyme donor immunoassay (CEDIA) and the confirmatory test; liquid chromatography- high resolution mass spectrometry (LC-HRMS), were affected when the urine was manipulated with oxidants before the analysis. Four different oxidants (pyridinium chlorochromate, hypochlorite, sodium nitrite and povidone iodine) in three different concentrations, were investigated and evaluated on 37 different drugs with LC-HRMS. The most effective oxidant and the most adulterated drugs were then further investigated with LC-HRMS, CEDIA and with urine adulteration test strips. The results of the drug analysis were affected by the oxidants with both the CEDIA, and LC-HRMS analysis. All samples containing pyridinium chlorochromate and hypochlorite obtained negative results with CEDIA. With LC-HRMS, the tested samples containing 1 % hypochlorite effectively lowered the drug concentrations under the cut-off. Adulteration tests can be used to identify urine samples, manipulated with oxidants.