The atmospheric oxidation of chemicals has produced many new unpredicted pollutants. A microwave plasma torch-based ion/molecular reactor (MPTIR) interfacing an online mass spectrometer has been developed for creating and monitoring rapid oxidation reactions. Oxygen in the air is activated by the plasma into highly reactive oxygen radicals, thereby achieving oxidation of thioethers, alcohols, and various environmental pollutants on a millisecond scale without the addition of external oxidants or catalysts (6 orders of magnitude faster than bulk). The direct and real-time oxidation products of polycyclic aromatic hydrocarbons and p-phenylenediamines from the MPTIR match those of the long-term multistep environmental oxidative process. Meanwhile, two unreported environmental compounds were identified with an MPTIR and measured in the actual water samples, which demonstrates the considerable significance of the proposed device for both predicting the environmental pollutants (non-target screening) and studying the mechanism of atmospheric oxidative processes.

In mass spectrometry (MS), nonvolatile salts contaminate the transmission system and cause ion suppression, hampering MS analysis. When MS is combined with liquid chromatography (LC) that uses a salty mobile phase, the problems become more intractable due to long analysis time. Here, a novel heat-assisted dual neutral spray ionization (HADSI) method was developed, which projected sample solution spray and solvent spray onto a heated plate to achieve online desalting and high ionization. The experimental parameters of HADSI were optimized, which indicated that the plate temperature was crucial for ionization and desalination. Eight drug compounds dissolved in various commonly used buffers were directly analyzed using HADSI-MS, even though the concentration of PBS buffer reached 500 mmol/L. The established method showed considerable sensitivity in the positive ion mode with the limits of detection at the level of nmol/L, and good linearity (R 2 > 0.99) was achieved for all the analyzed compounds. The repeatability and intra-and interday precisions of the method were evaluated, demonstrating the feasibility and reliability of the analysis of salty samples by HADSI-MS. Further, the method was demonstrated to tolerate the long-time analysis of high-salt LC eluates and the device was easy to maintain. Finally, a crude roxithromycin product was separated by LC and then analyzed by HADSI-MS, and seven unknown impurities and nine known impurities were successfully detected. Our results indicated that HADSI-MS may have potential applications in academic and industrial fields.

This study presents the rapid surface detection of explosives by employing atmospheric pressure arc desorption/ionization mass spectrometry (APADI-MS) using point-to-plane arc discharge. In APADI, neutral explosives readily bind to the gas-phase nitrate ion, NO3 –, induced by arc discharge to form anionic adducts [M+NO3]−. This avoids the need for inorganic anionic additives such as NO3 –, NO2 –, Cl–, acetate, and trifluoroacetate for unique explosive ionization pathways and simplifies mass spectra. The analytical performance of APADI was thoroughly evaluated for the rapid detection of 10 explosives at levels in the range of 800 fg–1 μg. Arc-induced nitrogen oxide anions promoted the formation of characteristic adducts, such as [M+NO3]−, and improved the instrument response for all the explosives tested. APADI showed considerable sensitivity in the negative ion mode with limits of detection in the low picogram range, particularly when explosives were analyzed on a copper or aluminum foil substrate. APADI coupled with an Orbitrap mass spectrometer displayed a good linear response for the studied explosives. The linearity and intraday and interday precisions were evaluated, demonstrating the feasibility and robustness of APADI-MS for the detection of trace explosives on solid surfaces. The mechanisms of APADI for explosive ionization and desorption were examined and verified by performing density functional theory calculations.

A direct analytical method based on dual ambient plasma ion source tandem mass spectrometry was used for the simultaneous determination of four sterols in the environment. This technology has very high sensitivity and the method detects the four sterols in methanol–water (1:3) solutions with limits of detection (LOD) and limits of quantification (LOQ) ranging from 1.2 ng/L to 6.9 ng/L and 7.6 ng/L to 10.0 ng/L, respectively. The method was also used to test water quality at three locations within the city and successfully detected all four sterols at very low concentrations. The dual plasma source tandem mass spectrometry technique is extremely simple, rapid, sensitive and highly efficient compared to other traditional methods, providing a useful screening tool for sterols in water.

Recent worldwide interest in the development of miniaturized, array--based, multianalyte binding assay methods suggests that the ligand assay field is on the brink of a technological revolution. Our own collaborative studies in this area have centered largely (but not exclusively) on antibody spot "immunoarrays" localized on "microchips" which are potentially capable of determining the amounts of hundreds of different analytes in a small sample (such as a single drop of blood). Analogous technology for genetic testing using oligonucleotide arrays is under active development both in the US and Europe. Array-based immunoassay methods are clearly likely to prove of particular importance in areas such as environmental monitoring where the concentrations of many different analytes in test samples are required to be simultaneously determined. In this presentation we review the general principles underlying this emerging technology. Immunoassay"Binding" or "ligand" assay methods have, in the past 35 years, been applied to the assay of a wide range of substances of biological importance. Because antibodies can be raised against many such analytes, antibody-based "immunoassay" techniques have achieved particular prominence, but the principles on which these techniques rest can be exploited using many other classes of binding agent. Of particular and increasing importance is the use -in methods relying on identical analytical concepts -of oligonucleotide probes, which bind to single chain fragments of DNA with affinities and specificities of the same order as, or greater than, those characterizing antibody-antigen and other binding reactions.Such "binding assay" techniques were originally developed to determine the minute concentrations of hormones in biological fluids, but were subsequently exploited in many other areas of medicine in which the estimation of small amounts of biologically-important substances is required. More recently still, they have been increasingly adopted in fields such as environmental monitoring in which similar needs arise.During the period 1960-80 the "competitive" or "saturation" assay approachrelying on the use of radiolabeled analyte markers, and typified by radioimmunoassay (RIA) -dominated the field. Radiolabeled antibody methods, usually referred to as

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