Determination of ocfentanil and W-18 in a suspicious heroin-like powder in Belgium

Purpose Since the early 2010s, synthetic opioids have been on the rise in the illicit drug markets of North America and Europe, often as adulterants or substitutes for heroin. Ocfentanil, an early-onset fentanyl analogue, has been implicated in several fatalities, predominantly in Europe. W-18 is more prevalent in Canada and the United States. We present the findings for an unknown brown powder, advertised and purchased as heroin, which was sent to our laboratory for analysis in the framework of the Belgian Early Warning System on Drugs.