[Asymmetric control method for ion shutter and the resolution improvement of ion mobility spectrum].

In order to change the driving mode of ion shutter, simplify the design of ion shutter driving power and improve the resolution of ion mobility spectrometry, a series of resistors were added to achieve asymmetric power supply of ion shutter, and the low voltage part was controlled to realize the function of ion shutter. Two conditions in this mode, the effect of electric field in drift tube and the resolution and signal-to-noise ratio of ion mobility spectrum were analyzed. Aided by SIMION 7.0, the electric field distribution at both sides of ion shutter was simulated and compared. Electric field data of drift tube axis was calculated through the method of numerical solution of Laplace equation. Experiment has proved that: compared with floating ground driving power used in conventional ion mobility spectrometry, the driving mode was low cost, and the design of ion shutter driving power supply was simple, and the resolution of ion mobility spectrometry was enhanced significantly. The method can be used in measurement instrument or experimental device of ion mobility spectrometry.

[Photoionization ion mobility spectrometry (UV-IMS) for the isomeric volatile organic compounds].

The construction and performance study is reported for a newly developed ultraviolet photoionization ion mobility spectrometry (UV-IMS). In the present paper, an UV-IMS technique was firstly developed to detect eleven isomeric volatile organic compounds including the differences in the structure of carbon chain, the style of function group and the position of function group. Their reduced mobility values were determined and increased in this order: linears < branches < cycles, primary < secondary < tertiary, para- < meta- < ortho- and alcohols < acetones < aromas. The concentrations of analytes were obtained by means of exponential dilution method, and the experiments show that the limit of detection of the homemade UV-IMS was around ppb-ppm.

[Rapid detection of residual cyclohexanone in disposable medical devices by ultraviolet photoionization ion mobility spectrometry (UV-IMS)].

In the manufacture of disposable PVC medical devices, cyclohexanone is frequently used as an adhesive reagent, which can be released into the tube airspace or stored solution and thus may cause some adverse effects on patients in therapy. In this paper, an ultraviolet photoionization ion mobility spectrometry (UV-IMS) technique has been developed to detect cyclohexanone through monitoring the gas composition within a package of infusion sets. The concentrations of cyclohexanone were prepared by means of exponential dilution method, and the experiments show that the UV-IMS has a limit of detection at 15 ppb and its measurable linear dynamics range is over three orders of magnitude. The concentrations of cyclohexanone in three brands of infusion sets packages were determined to be 16.78, 17.59 and 46.69 ppm respectively. The UV-IMS is proposed as a tool for the quality control of medical devices to monitor illegal uses of chemical solvents like cyclohexanone.

[Determination of metal by liquid electrode discharge atomic emission spectrometry with a new design].

A liquid electrode discharge atomic emission spectrometry has been developed with a new design. Plasma fluctuation from the variations in the gap between the W anode and liquid cathode was eliminated by providing a sawtooth-shaped drainage structure. The sawtooth was placed at a distance of 2 mm from the glass capillary top. When a solution is pumped through a glass capillary, the liquid drop forms and rises and on reaching the maximum size collapses while the next drop forms. This results in a continuous change in the interelectrode distance which will cause the discharge current to change, plasma flickers and is extinguished. With the new design, the surface tension of the drop was destroyed before its growing up, and the solution was flowing along the drainage groove. The discharge can last for 3 hours at least with such arrangement. The analytical response curves for lead, chromium, cadmium, zinc, vanadium, nickel, copper, silver and cobalt demonstrated good linearity. The limit of detections of lead, chromium, cadmium, zinc, vanadium nickel, copper, silver and cobalt were determined to be 0.08, 0.61, 0.48, 1.60, 10.88, 0.48, 0.084, 0.048 and 0.27 mg x L(-1) respectively.

[Detection of metal residue in aqueous solutions by electrolyte cathode atmospheric glow discharge emission spectroscopy].

Toxic metal elements in waters and wastewaters contaminate the environment and greatly threaten the health of human beings, therefore developing a rapid monitor for metal residues in aqueous solutions is urgently required. In the present work, a new homemade apparatus of electrolyte cathode atmospheric glow discharge emission spectroscopy was developed and described. It can detect and discriminate many kinds of trace mental elements by atomic emission spectrum from atmospheric pressure liquid cathode glow discharge. In order to estimate the analytical performance of the present atmospheric pressure electrolyte cathode glow discharge emission spectroscopy system, the detection limit values for Na, Li, Cu, Pb and Mn were obtained based on 3sigma of the background signal, and the current limits of detection were 0.008, 0.005, 1.1, 2.06 and 1.95 mg L(-1), respectively. It demonstrates that the atmospheric pressure electrolyte cathode glow discharge emission spectroscopy has a promising application in real time measurements of metal residues in aqueous solutions.

[Characterization of an atmospheric pressure DC microplasma jet].

In the present work, a simply designed and easy made micrometer plasma jet device operating under atmospheric pressure was characterized. The microplasma jet operates in many kinds of working gas at atmospheric pressure, such as Ar, He, N2 etc, and is powered by a direct current power source. It can generate high current density glow discharge. In order to identify various excited species generated by the direct current microplasma jet device, the optical emission spectra of the jet with argon or nitrogen as working gas were studied. Based on the optical emission spectroscopy analysis of argon microplasma jet, the electron excitation temperature was determined to be about 3 000 K by the intensity ratio of two spectral lines. It is much lower than the electron excitation temperature of atmospheric pressure plasma torch, and hints that the atmospheric pressure direct current microplasma jet is cold compared with the atmospheric pressure plasma torch. The emission spectra of the N2 second positive band system were used to determine the vibrational temperature of the atmospheric pressure direct current microplasma jet. The experimental result shows that the molecular vibrational temperature of N2 is about 2 500 K. The electron density of the microplasma jet is about 10(13) cm(-3), which can be estimated from the electrical parameters of the discharge in the microplasma jet. A simple example of application of the microplasma jet is given. General print paper surface was modified with the microplasma jet and afterwards a droplet test was carried out. It was shown that the microplasma jet is more efficient in changing the hydrophilicity of general print paper.

[Spectroscopic study of atmospheric pressure argon DC microdischarge].

Microhollow cathode discharge or microdischarge is an efficient method to generate plasma in a high pressure gas. In the present work, the emission spectra were observed in an atmospheric pressure argon direct current microdischarge apparatus, using a stainless steel capillary as the cathode, and a stainless steel mesh as the anode. It was shown that all of the seventeen argon spectral lines arose from electronically excited argon atom 4p-4s transition in the wavelength range of 690-860 nm. The dependences of emission intensity on the discharge current, gas pressure and argon flow rate were investigated. The experimental results show that the emission intensity increased with discharge current from 1 to 6 mA and argon flow rate from 100 to 700 mL x min(-1). The dependence of emission intensity on gas pressure exhibited different characteristics, i.e., spectral signal increased with the gas pressure, but reached the intensity maximum at 13.3 kPa, and decreased afterwards. The argon atom spectral lines 763.51 and 772.42 nm were chosen to measure the electron excitation temperature by the intensity ratio of two spectral lines. The electron excitation temperature was determined to be in the range of 2000 to 2800 K in the atmospheric pressure argon microdischarge. The changes in electron excitation temperature with discharge current, gas pressure and argon flow rate were explored, indicating that the electron excited temperature increased with the discharge current, but decreased when gas flow rate or argon pressure increased.

Determination of alcohol compounds using corona discharge ion mobility spectrometry.

Ion mobility spectrometry (IMS) is a very fast, highly sensitive, and inexpensive technique, it permits efficient monitoring of volatile organic compounds like alcohols. In this article, positive ion mobility spectra for six alcohol organic compounds have been systematically studied for the first time using a high-resolution IMS apparatus equipped with a discharge ionization source. Utilizing protonated water cluster ions (H2O)n H+ as the reactant ions and clean air as the drift gas, alcohol organic compounds, ethanol, 1-propanol, 2-propanol, 1-butanol, 1-pentanol and 2-octanol, all exhibit product ion characteristic peaks in their respective ion mobility spectrometry, that is a result of proton transfer reactions between the alcohols and reaction ions (H2O)n H+. The mixture of these alcohols, including two isomers, has been detected, and the results showed that they could be distinguished effectively in the ion mobility spectrum. The reduced mobility values have been determined, which are in very well agreement with the traditional 63Ni-IMS experimental values. The exponential dilution method was used to calibrate the alcohol concentrations, and a detection limit available for the alcohols is in order of magnitude of a few ng/L.

[Discharge ion mobility spectrometry of ketonic organic compounds].

Ion mobility spectrometry (IMS) is a sensitive technique for fast on-line monitoring trace volatile organic compounds based upon the mobilities of gas phase ions at ambient pressure in weak electric field. In the present work, protonated water reactant ions were successfully prepared, and eight ketones were studied on a homemade high-resolution IMS apparatus using a discharge ionization source. The reduced mobility values of all ions were derived from the observed ion mobility spectra. The experimentally determined reduced mobilities for acetone, 2-butone, 1-methyl-2-pyrrolidinone acetophenone, cyclohexanone and product ions were compared with the previously reported values in the Ni-IMS, indicating that they are in good agreement. The reduced mobilities of methyl isopropyl ketone, 4-methyl-2-pentanone and cyclopentanone ions were given for the first time. The ionization process for organic compounds in the authors' discharge ion mobility spectrometer is suggested to be similar to Ni-IMS system, i.e., the proton transfer reactions produce protonated ketone ions. In addition, a linear correlation was found between the reduced mobilities of the ketone ions and their molecular masses. Qualitative measurements show that the limit of detection is in the ng x L(-1) order of magnitude in the authors' discharge ion mobility spectrometer.

[Ion mobility spectrometry for the isomeric volatile organic compounds].

Ion mobility spectrometry (IMS) is based on determining the drift velocities, which the ionized sample molecules attain in the weak electric field of a drift tube at atmospheric pressure. The drift behavior can be affected by structural differences of the analytes, so that ion mobility spectrometry has the ability to separated isomeric compounds. In the present article, an introduction to IMS is given, followed by a description of the instrument used for the experiments to differentiate isomeric compounds. Positive ion mobility spectras of three kinds of isomeric volatile organic compounds were studied in a homemade high-resolution IMS apparatus with a discharge ionization source. The study includes the differences in the structure of carbon chain, the style of function group, and the position of function group. The reduced mobility values were determined, which are in very good agreement with the previously reported theoretical values using neural network theory. The influence of the structural features of the substances and including the size and shape of the molecule has been investigated. The reduced mobility values increases in the order: alcohols < acetones < aromas, linears < branches < cycles, and para- < meta- < ortho-. The deviating ion mobility spectra of the constitutional isomers studied reflect the influence of structural features. In order to calibrate or determine the detection limits and the sensitivity of the ion mobility spectrometry, the exponential dilution flask (EDF) was used. Using this method, the detection limit of the analytes can reach the order of magnitude of ng x L(-1).