Koon, Teoh Way
(2022)
Laboratory-based simultaneous detection of residual xylazine and sedative-hypnotics from drugs-spiked beverages for forensic investigation.
PhD thesis, Universiti Sains Malaysia.
Abstract
Drug Facilitated Crimes (DFCs) involve the incapacitation of a victim due to
the administration of a single drug or a combination of drugs. Xylazine, ketamine and
benzodiazepines such as diazepam and nimetazepam are also the frequently used drugs
in DFCs. Conventionally, biological samples are collected from a victim and analysed
to provide evidence of drug administration. However, the rapid metabolism of many
such drugs together with delays in analysis can compromise the detection of such drugs.
Therefore, drugs-spiked beverages were suggested as evidence during DFC
investigation. The present study was aimed to establish the analytical strategies for
simultaneous detection of xylazine and sedative-hypnotics (diazepam, ketamine and
nimetazepam) in drugs-spiked beverages appearing in liquid, droplet, and dry forms.
In this study, chemical tests, attenuated total reflectance-Fourier transform infrared
(ATR-FTIR) spectroscopy, gas chromatography (GC) and high-performance liquid
chromatography (HPLC) detection were used and applied for the detection of the target
substances from drugs-spiked beverage samples. Janovsky test allowed for the
detection of diazepam ( 5 μg), ketamine ( 1 mg) and nimetazepam ( 5 μg).
Xylazine could not be detected using the chemical tests. ATR-FTIR in couple with
chemometric analyses enabled the discrimination of xylazine and sedative-hypnotics
(diazepam, ketamine and nimetazepam), including those samples recovered from the
dry beverage remains. GC method was established [limit of detection (LOD) (xylazine; 80 ng/mL; ketamine: 80 ng/mL; nimetazepam: 160 ng/mL); linearity (R2>0.99),
precision (%RSD <7.20); accuracy (% recovery: 92.84 – 103.48%)] to detect target
substances in spiked beverages remains. Satisfactory recoveries were achieved from
drugs-spiked liquid (51.03% – 97.13%), droplet (48.27% – 95.91%) and dry (44.38%
– 92.71%) samples through the application of developed GC method upon dispersive
liquid-liquid microextraction (DLLME) procedure. A HPLC method was also
established [LOD (xylazine: 39.1 ng/mL; diazepam: 78.1 ng/mL; ketamine: 156.3
ng/mL; nimetazepam: 78.1 ng/mL); linearity (R2>0.99), precision (%RSD <7.82);
accuracy (% recovery: 95.31% - 106.56%)] and applied to detect target substances in
spiked beverage remains. Good recoveries were achieved from the drug-spiked
samples in liquid (64.21% – 105.43%), droplet (49.45% – 81.67%) and dry (47.24%
– 88.27%) forms. However, only 13.33% of ketamine was able to be recovered from
mineral water appearing in dry form. To conclude, analytical methods were
successfully developed to simultaneously detect residual xylazine and other drugs of
abuse (diazepam, ketamine, and nimetazepam) from spiked beverages. This study is
beneficial to the law enforcement authorities during DFCs investigation, especially the
determination of whether a sedative-hypnotic drug had been used.
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