Sensitivity and selectivity of switchable reagent ion soft chemical ionization mass spectrometry for the detection of picric acid.

We have investigated the reactions of NO(+), H3O(+), O2(+), and Kr(+) with picric acid (2,4,6 trinitrophenol, C6H3N3O7, PiA) using a time-of-flight mass spectrometer with a switchable reagent ion source. NO(+) forms a simple adduct ion PiA·NO(+), while H3O(+) reacts with PiA via nondissociative proton transfer to form PiAH(+). In contrast, both O2(+) and Kr(+) react with PiA by nondissociative charge transfer to produce PiA(+). For Kr(+), we also observe dissociation of PiA, producing NO2(+) with a branching percentage of approximately 40%. For the reagent ions H3O(+) and O2(+) (and operating the drift tube with normal laboratory air), we find that the intensities of the PiAH(+) and PiA(+) ions both exhibit a peak at a given drift-tube voltage (which is humidity dependent). This unusual behavior implies a peak in the detection sensitivity of PiA as a function of the drift-tube voltage (and hence E/N). Aided by electronic-structure calculations and our previous studies of trinitrotoluene and trinitrobenzene, we provide a possible explanation for the observed peak in the detection sensitivity of PiA.

Headspace analysis of new psychoactive substances using a Selective Reagent Ionisation-Time of Flight-Mass Spectrometer.

The rapid expansion in the number and use of new psychoactive substances presents a significant analytical challenge because highly sensitive instrumentation capable of detecting a broad range of chemical compounds in real-time with a low rate of false positives is required. A Selective Reagent Ionisation-Time of Flight-Mass Spectrometry (SRI-ToF-MS) instrument is capable of meeting all of these requirements. With its high mass resolution (up to m/Δm of 8000), the application of variations in reduced electric field strength (E/N) and use of different reagent ions, the ambiguity of a nominal (monoisotopic) m/z is reduced and hence the identification of chemicals in a complex chemical environment with a high level of confidence is enabled. In this study we report the use of a SRI-ToF-MS instrument to investigate the reactions of H3O+, O2+, NO+ and Kr+ with 10 readily available (at the time of purchase) new psychoactive substances, namely 4-fluoroamphetamine, methiopropamine, ethcathinone, 4-methylethcathinone, N-ethylbuphedrone, ethylphenidate, 5-MeO-DALT, dimethocaine, 5-(2-aminopropyl)benzofuran and nitracaine. In particular, the dependence of product ion branching ratios on the reduced electric field strength for all reagent ions was investigated and is reported here. The results reported represent a significant amount of new data which will be of use for the development of drug detection techniques suitable for real world scenarios.

Rapid and facile detection of four date rape drugs in different beverages utilizing proton transfer reaction mass spectrometry (PTR-MS).

In this work, we illustrate the application of proton transfer reaction mass spectrometry (PTR-MS) in the field of food and drink safety. We present proof-of-principle measurements of four different drinks (water, tea, red wine and white wine) each spiked separately with four different date rape drugs (chloral hydrate, tricholorethanol, γ-butyrolactone and butanediol). At first, the ideal PTR-MS operating conditions (reduced electric field strength and monitoring the most abundant [fragment] ion) for detection of the drugs were determined utilizing a time-of-flight-based PTR-MS instrument. We then dissolved small quantities of the drugs (below the activation threshold for effects on humans) into the various types of drinks and detected them using a quadrupole-based PTR-MS instrument via two different sampling methods: (1) dynamic headspace sampling and (2) direct liquid injection. Both methods have their advantages and drawbacks. Only with dynamic headspace sampling can rape drug contaminations be detected within a timeframe of seconds, and therefore, this method is the most promising use of PTR-MS as a fast, sensitive and selective monitor for the detection of food and drink contamination.

Proton transfer reaction mass spectrometry and the unambiguous real-time detection of 2,4,6 trinitrotoluene.

Fears of terrorist attacks have led to the development of various technologies for the real-time detection of explosives, but all suffer from potential ambiguities in the assignment of threat agents. Using proton transfer reaction mass spectrometry (PTR-MS), an unusual bias dependence in the detection sensitivity of 2,4,6 trinitrotoluene (TNT) on the reduced electric field (E/N) has been observed. For protonated TNT, rather than decreasing signal intensity with increasing E/N, which is the more usual sensitivity pattern observed in PTR-MS studies, an anomalous behavior is first observed, whereby the signal intensity initially rises with increasing E/N. We relate this to unexpected ion-molecule chemistry based upon comparisons of measurements taken with related nitroaromatic compounds (1,3,5 trinitrobenzene, 1,3 dinitrobenzene, and 2,4 dinitrotoluene) and electronic structure calculations. This dependence provides an easily measurable signature that can be used to provide a rapid highly selective analytical procedure to minimize false positives for the detection of TNT. This has major implications for Homeland Security and, in addition, has the potential of making instrumentation cost-effective for use in security areas. This study shows that an understanding of fundamental ion-molecule chemistry occurring in low-pressure drift tubes is needed to exploit selectivity and sensitivity for analytical purposes.