Photolysis by UVA-Visible Light of TNT in Ethanolic, Aqueous-Ethanolic, and Aqueous Solutions According to Electrospray and Aerodynamic Thermal Breakup Droplet Ionization Mass Spectrometry.

The mechanism of photolytic degradation of 2-4-6-trinitrotoluene (TNT) by UVA−visible light (>320 nm) in ethanolic, aqueous-ethanolic, and aqueous solutions was investigated by electrospray and aerodynamic thermal breakup droplet ionization mass-spectrometric analyses. For the photolysis, a DRK-120 mercury-quartz lamp was used. Products of the photolysis reaction were compared with known products of TNT transformation in the environment. Because the photochemistry of some compounds in alcohols (in contrast to aqueous solutions) features a transfer of electrons from the solvent to the light-excited compound, we believe that the efficiency of photolysis (polymerization) of TNT in ethanol and aqueous-ethanolic solutions is based on this mechanism.

Acceleration of the thermal degradation of PETN in the microdroplets flow reactor.

Thermal degradation of pentaerythritol tetranitrate (PETN) was investigated in microdroplets within a heated capillary used as a flow reactor. The thermal degradation was monitored by aerodynamic thermal breakup droplet ionization mass spectrometry. It was shown that the PETN degradation in microdroplets occurs much faster than the bulk reaction (by 4-5 orders of magnitude). The effect of the capillary material [stainless steel (Fe, Cr), copper (Cu), or fused quartz (SiO2)] on the thermal PETN degradation in microdroplets of water or acetonitrile was studied next. The capillary material affected the rate of thermal PETN degradation much more weakly than did the use of microdroplets (pure Cu was most conducive to the degradation). Kinetic parameters (activation energy and the frequency factor) of the PETN degradation for all the studied materials of the flow-through reactor and the solvents were estimated under the assumption that the thermal degradation is a first-order reaction. Implications of the acceleration of PETN degradation in microdroplets are discussed.

Aerodynamic Thermal Breakup Droplet Ionization in Mass Spectrometric Drug Analysis.

Aerodynamic thermal breakup droplet ionization (ATBDI) in mass spectrometric drug analysis is considered. Cocaine, heroin, and the main alkaloids of opium (morphine, codeine, papaverine) were chosen as the test compounds. The principles of ATBDI ionization are discussed. The dependences of the intensities of the peaks of the target compounds on temperature during ATBDI ionization are also considered. In some cases, a comparison of ATBDI ionization with electrospray ionization (ESI) was performed. In addition, a comparison of methods is demonstrated by the analysis of confiscated opium that was provided by the local police department. Five major alkaloids are found in opium: morphine, codeine, thebaine, papaverine, and narcotine.

Analysis of trinitrotoluene in solutions using Aerodynamic Thermal Breakup Droplet Ionization (ATBDI) mass spectrometry.

The droplets breakup and compounds ionization in the heated capillary were investigated; the ionization method was named Aerodynamic Thermal Breakup Droplet Ionization (ATBDI). The mass spectrometric analysis was performed for solutions of trinitrotoluene (TNT) in water, ethanol, and acetonitrile. Considering the total current and the target analyte peaks, the ionization efficiency in the heated capillary was correlated with the physical properties of the solvents. For aqueous and ethanol solutions of TNT, the limit of detection (LOD) was obtained when using the ATBDI mass spectrometry. It was estimated to be 10-7 g mL-1 and 10-6 g mL-1 for water and ethanol solutions, respectively.

Semi-quantitative analysis of samples in solutions using Aerodynamic Breakup Droplet ionization (ABDI) mass spectrometry.

In Aerodynamic Breakup Droplet ionization (ABDI) mass spectrometry the dimer/monomer (I2/I1) and trimer/dimer (I3/I2) ratios are considered for compounds ionized in various ways. The following test compounds were selected: morphine (gives protonated ion, (M+H)+); hexogen, RDX (forms adducts with anion of chlorine or nitrate ion); and trinitrotoluene, TNT (gives deprotonated ion, (M-H)-). The test compounds were dissolved in water, acetonitrile or ethanol. It is shown that in the ABDI mass spectra of a number of compounds (protonated morphine ions in water and RDX adducts with chlorine in acetonitrile), the ratios I2/I1 and I3/I2 linearly depend on the analyte concentration in the solution. This is evident throughout the range of measured concentrations, when monomers and dimers are simultaneously visible in the mass spectrum. The phenomenon can be roughly explained by the dimerization of analyte molecules in singly charged parent drops during ABDI ionization. The linearity of the I2/I1 and I3/I2 on the concentration can be used for estimation of the analyte concentration in a sample without using an internal or external standard. This can be useful for routine analysis when standards are not commercially available or very expensive.

Using of aerodynamic droplet breakup for mass-spectrometric analysis.

The method of ionization by aerodynamic droplet breakup is considered for applications in mass spectrometric analysis. It is assumed that Aerodynamic Breakup Droplet Ionization (ABDI) occurs in a tube linking the region of atmospheric pressure to the area of weak vacuum. The possibility of ionization of solutions of organic compounds and organometallic complexes is shown. As test compounds were chosen: heroin (as an example of organic compounds) and organometallic complexes of ruthenium and copper, dissolved in water or acetonitrile. The quality of the ABDI spectra depends on the analyte. In general, the analytes ionized by the ABDI method show a great propensity to form dimers and trimers. ABDI system can be easily installed on any mass spectrometer with inlet at atmospheric pressure and used as an additional method. Since compounds prone to degradation in ESI analysis are better suited for ABDI analysis, this seems useful.

Ionization of solutions using mechanical spray in collison nebulizer: a new simple ion source for mass-spectrometric analysis.

Ionization methods for mass-spectrometric analysis based on mechanical liquid spray by a high-speed gas flow (like Sonic Spray Ionization (SSI)) offer some advantages over other ionization methods. Among these one should mention the absence of electric voltage, radioactive sources and heaters. In this paper we suggest using the Collison nebulizer for solution ionization via mechanical spray. Research results into the efficiency of the Collison spray ionization of different solvents used in chemical synthesis are submitted. It is shown that an increase in dipole moment of the solvent molecules leads to increased ionization efficiency for all solvents tested, except water. This seems to result from anomaly high surface tension and vaporization enthalpy for water. High concentrations (>10(-4) g/ml) of both inorganic salts (NaCl, K2SO4) and organic additive (morphine) give a decrease in the total ion current at the Collison nebulizer outlet. This is assumed to be due both to an increased droplet size of aerosol produced upon spraying and a low dipole moment of an ion-solvation shell complex. Mass-spectra of aqueous K2SO4 and morphine (C17H19NO3) were obtained with the Collison nebulizer. These spectra contained non-identified background peaks along with the peaks of K(+) and H(+)C17H19NO3 that were likely to result from the water ionization and presence of uncontrolled impurities. A relationship between the intensity of mass-spectroscopic peaks of the ions of potassium and morphine and the concentration of appropriate aqueous solution was determined. Mass-spectrometric analysis using the Collison spray ionization gave a detection limit for morphine ∼10(-8) g/ml and a linear response range for protonated molecular ion (H(+)C17H19NO3 with m/z=286 from 10(-8) g/ml to 2×10(-7) g/ml.

Vortex focusing of ions produced in corona discharge.

Completeness of the ion transportation into an analytical path defines the efficiency of ionization analysis techniques. This is of particular importance for atmospheric pressure ionization sources like corona discharge, electrospray, ionization with radioactive ((3)H, (63)Ni) isotopes that produce nonuniform spatial distribution of sample ions. The available methods of sample ion focusing are either efficient at reduced pressure (~1Torr) or feature high sample losses. This paper deals with experimental research into atmospheric pressure focusing of unipolar (positive) ions using a highly swirled air stream with a well-defined vortex core. Effects of electrical fields from corona needle and inlet capillary of mass spectrometer on collection efficiency is considered. We used a corona discharge to produce an ionized unipolar sample. It is shown experimentally that with an electrical field barrier efficient transportation and focusing of an ionized sample are possible only when a metal plate restricting the stream and provided with an opening covered with a grid is used. This gives a five-fold increase of the transportation efficiency. It is shown that the electric field barrier in the vortex sampling region reduces the efficiency of remote ionized sample transportation two times. The difference in the efficiency of light ion focusing observed may be explained by a high mobility and a significant effect of the electric field barrier upon them. It is possible to conclude based on the experimental data that the presence of the field barrier narrows considerably (more than by one and half) the region of the vortex sample ion focusing.

Atmospheric pressure ion focusing with a vortex stream.

For successful operation of ionization analysis techniques an efficient sampling and sample ion transportation into an analytical path are required. This is of particular importance for atmospheric pressure ionization sources like corona discharge, electrospray, MALDI, ionization with radioactive isotopes ((3)H, (63)Ni) that produce nonuniform spatial distribution of sample ions. The available methods of sample ion focusing with electric fields are either efficient at reduced pressure (to 1 Torr) or feature high sample losses. In this paper we suggest to use a highly whirled gas stream for atmospheric pressure ion focusing. We use a (63)Ni radioactive source to produce an ionized bipolar sample at atmospheric pressure. It is shown by experiments that compared to an aspiration method a forced highly whirled vortex stream allows one to enhance the efficiency of remote ionized sample collection at distances equal to the vortex sampler diameter by an order of magnitude. With a vortex stream, a sixfold increase in the efficiency of the radial ionized sample collection has been obtained. It may be deduced that with the vortex stream remote sampling obtains a new feature which is characterized by a considerable enhancement of the efficiency of the ionized sample collection and can be called as a "gas-dynamic" ionized sample focusing. Considered is the effect of recombination losses of the ionized sample during the remote sampling thereof with the vortex sampler. Prospects for a practical implementation of the vortex sampler for solving the problems of the customs control over the smuggling of radioactive α and ß sources are made based on the research results.

Remote gas sampling with a swirl air stream.

One of the promising techniques of remote gas sampling from the surface or from the inside of an object involves the use of a swirl air stream. The case in which a swirl sampling stream produces a vortex core of a composite swirl is of most interest. But a practical implementation of a vortex sampling faces major problems due to the fact that the majority of the available gas analyzers feature a low analytical flow. This offers limitations on sampling distance and reduced pressure created at the object surface. This paper deals with the problem of adjusting vortex and sampling flows for a mass-spectrometer with atmospheric pressure ionization used for remote sampling of diethylanyline vapors. It is shown experimentally that additional sampling flow (Q(add)) that coaxially envelops an analytical channel allows one to achieve conditions required for the formation of a vortex core, which is characterized by an increased tangential component of the flow velocity at its boundary and abnormally low pressure on the core axis. A satisfactory agreement between the calculations by the composite vortex model and the experiment is obtained. The studies performed have shown that the optimal relationship between vortex (Q(vortex)) and additional flows is Q(vortex)/Q(add)=1.3 and is symbate in terms of both gas dynamic parameters (minimal diameter of a backflow core) and sampling efficiency. It is shown that both the sampling distance and sampling area depend mainly on geometric sampler parameters. The experiments performed have revealed the unique ability of a vortex sampling flow in the form of a composite vortex to focus the sample inside the vortex core, thus preventing its dilution over the backflow.

Ion peak narrowing by applying additional AC voltage (ripple voltage) to FAIMS extractor electrode.

The use of a non-uniform electric field in a high-field asymmetric waveform ion mobility spectrometry (FAIMS) analyzer increases sensitivity but decreases resolution. The application of an additional AC voltage to the extractor electrode ("ripple" voltage, U(ripple)) can overcome this effect, which decreases the FAIMS peak width. In this approach, the diffusion ion loss remains minimal in the non-uniform electric field in the cylindrical part of the device, and all ion losses under U(ripple) occur in a short portion of their path. Application of the ripple voltage to the extractor electrode is twice as efficient as the applying of U(ripple) along the total length of the device.

Effect of UV irradiation on detection of cocaine hydrochloride and crack vapors by IMIS and API-MS methods.

Detection of drug vapors and volatile products of their decomposition is an important, and sometimes the only way to determine the presence of illegal drug traces at the surface of mail items, documents, hands and banknotes. This paper gives the results of experimental studies on the effect of UV irradiation on the sensitivity of a vapor phase detection of cocaine of different origin by a technology of ion mobility increment spectrometry (IMIS). It is shown that the influence of UV irradiation on the surface of cocaine hydrochloride and crack increases the amplitude of IMIS signals by about eight times. We analyzed ions emerged by photolysis of tested cocaine samples using mass-spectrometry with atmospheric pressure ionization (API-MS). The assumption is made about structural formula of volatile products of photolysis of crack and cocaine hydrochloride. By the results of API-MS and IMIS studies on photolysis of cocaine samples it is assumed that compound C(10)H(15)NO(3) with a molecular weight of 197 amu and ecgonidine methyl ester with a molecular weight of 181 amu are responsible for the increase of an amplitude of IMIS signals upon UV irradiation of samples of crack and cocaine hydrochloride.