Direct detection of trace level illicit drugs in human body fluids by probe electrospray ionization mass spectrometry (PESI-MS)

Detection of illicit drugs by ambient mass spectrometry has been gaining attention due to the unique advantage of detecting trace levels of chemicals from complex matrices without or with minimal sample pretreatment. This paper reports the application, characteristics and advantages of probe electrospray ionization mass spectrometry (PESI-MS) for rapid, sensitive and direct detection of methamphetamine, morphine, cocaine and codeine from human urine, oral fluid and plasma. The limits of detection (LODs) of various illicit drug standards were found to be 2–5 ppb and the trace levels of drugs were confirmed by their exact masses obtained using an ‘Exactive Orbitrap’ mass spectrometer. Here, for the first time, we evaluate the quantitative capabilities of PESI-MS from urine, oral fluid and plasma using methamphetamine as a representative illicit drug and N-benzylmethylamine as an internal standard. The LODs for illicit drugs in body fluids were one to two orders of magnitude higher compared to the standard samples and the relative standard deviations for the quantitative analysis were found to be less than 20%. As PESI is a solid needle based ambient electrospray system and free from clogging problems, it can easily be used as a spraying and direct ionization source for complex liquid mixtures.