Plasma Detector Research Articles

Element-selective gas chromatographic detection and determination of organoboron compounds

Element-selective gas chromatographic detection using a microwave-induced plasma detector has been evaluated for the detection of borated molecules. Boron-selective detection offers low detection limits (3 pg s–1), a wide linear dynamic range (≈104) and high selectivity over interference from carbon (20 000). Motor oils containing 3–200 ppm of boron were analysed for total boron content. Results from the analyses compare favourably with values obtained using a standard industrial method.

Determination of Sulfur-Containing Polycyclic Aromatic Compounds in Coal Extracts using Capillary Column Gas Chromatography with Radio Frequency Plasma Detection

Abstract Detailed identification of sulfur-containing polycyclic aromatic compounds (S-PAC) was accomplished for solvent extracts of five different coals. The S-PAC were isolated by ligand-exchange chromatography. Due to the great complexities of these samples, capillary gas chromatography (GC) was employed for their analysis. An element selective radio frequency plasma detector was used to provide sulfur selective detection. Gas chromatography-mass spectrometry was used to identify individual compounds in isolated sulfur fractions. Condensed thiophenic compounds were found to be the major constituents in all five S-PAC fractions. Diaryl sulfides were also detected in the high volatile bituminous Illinois #6 coal. The prevalence of various S-PAC in different coal extracts was observed as a function of their rank.

ChemInform Abstract: Recent Developments in Analytical Chromatography

Capillary gas chromatography (GC) is rapidly reaching a state of maturity. Recent advances in GC include new highly selective and stable open-tubular columns, capillary sampling techniques, and element-sensitive (plasma) detectors. An impressive growth of modern liquid chromatography continues with an emphasis on the separations of biopolymers, new silica-based and stable polymeric packings, microcolumn techniques, electroosmotically driven separations, and ultrasensitive detection. Supercritical fluid chromatography has gained considerable attention primarily because of its distinctive detection capabilities. Novel combinations of chromatographic techniques with each other, or with spectroscopic methods, continue to be explored.

Evaluation of an alternating current plasma emission detector for high-performance liquid chromatography

The details of construction and operation of an alternating current plasma (ACP) detector supported with helium gas for reversed-phase high-performance liquid chromatography is described. The system is evaluated as a selective detector for the determination of organomercury compounds. The chromatographic eluent is introduced into the plasma by means of a frit nebulizer and the plasma can tolerate the nebulization of 100% methanol without extinguishment. Detection limits of methylmercury chloride and ethylmercury chloride were found to be 4.5 and 2.2 ng Hg/sec, respectively. In the nanogram to microgram mass range studied the precision was found to be less than 10% (relative standard deviation). The deduction of organomercurials in complex sample matrices elustrates the selectivity of the ACP detector.

Improvement of the semiautomated headspace analysis method for the determination of methylmercury in biological samples

An improvement in the extraction step in the method of Decadt et al. for determining methylmercury in biological tissues is described. The methylmercury is released from the tissue by use of sulphuric acid as the cleaving agent and immediately converted to the iodide form by iodoacetic acid. These reaction steps take place in a closed headspace vial. The methylmercury iodide is then headspace-injected into a gas-chromatograph and detected with a microwave-induced plasma detector. Quantitation is accomplished by standard addition. Analysis of one sample takes less than 15 min. The detection limit of the method is 20 ng methylmercury per gram biological tissue when 50 mg of tissue are taken.

Solvent venting interface for capillary gas chromatography and a microwave-induced plasma

A solvent venting system for capillary gas chromatography coupled with a microwave-induced plasma detector was constructed and evaluated. The solvent vent is based on a fluid logic system within the plasma containment tube. During solvent elution, the column effluent is routed to waste and does not pass through the plasma. During analyte elution, the fluid logic system is used to direct the analytes through the plasma for detection. Because the system has no transfer line, problems associated with interface dead volume and analyte degradation reaction due to reactive sites in the transfer line are eliminated. Switching from the vent-on to the vent-off mode is rapid and does not affect plasma stability or flow through the chromatographic column. The baseline shift during switching is negligible. The solvent venting system is simple and easily constructed. Design details are presented and chromatographic results are evaluated.

Packed microcolumn SFC coupled with photodiode array UV detector and inductively coupled plasma detector (SFC‐photodiode array UV‐ICP)

AbstractHyphenation of packed microcolumn SFC, a photodiode array UV detector, and an inductively coupled plasma spectrometer has been developed in order to evaluate the stability of acetylacetone complexes under supercritical conditions.

Radio frequency plasma detector for sulfur selective capillary gas chromatographic analysis of fossil fuels

Due to the relatively low abundances of sulfur compounds in extremely complex fossil fuels, capillary gas chromatography coupled with element selective radio frequency plasma detection was used to provide sulfur selective (>10 3 ) analysis of petroleum distillates and coal extracts

Element-selective detection after supercritical fluid chromatography using a radio frequency plasma detector

Evaluation des avantages et des inconvenients de l'utilisation d'un plasma helium comme detecteur selectif en chromatographie SFC capillaire. Description des spectres de background pour CO 2 et NO 2 et demonstration de la detection selective de S et Cl pour plusieurs pesticides

Gas chromatographic determination of organolead compounds with an alternating current plasma detector

AbstractThe performance of the gas chromatography/alternating current plasma detector as a selective detector for organolead compounds is investigated. The helium make‐up flow rate and the spatial position from which the lead emission is viewed, have an effect on the detector response. The detection limit for tetrabutyl lead was established as 130 pg/s and the lead selectivity ratio was found to exceed 13,800. Some applications of organolead determination in complex matrices were also studied in order to demonstrate the selectivity and sensitivity of the alternating current plasma detector.

Characterization and Purity Determination of Trans (±) 1,2-Diaminocyclohexane Platinum (Iv) Tetrachloride Using Liquid Chromatography With A Platinum Selective Detector

Abstract An important aspect of drug development is the reliable determination of the purity of a bulk drug substance. In the case of Trans (±) 1,2-Diaminocvclohexane Platinum (IV) Tetrachloride, classical techniques such as differential scanning calorimetry and phase solubility analysis cannot be used because of the compound's poor tabulation of the fractions (percent) of platinum contained in each peak as measured with d.c. plasma and a corresponding response factor for the UV detector. the power of the d.c. plasma detector in producing unequivocal information on the platinum-containing species and its application in elucidating the data obtained with the UV detector is well demonstrated in this case.

Determination of impurities in argon by gas chromatography with a microwave-induced plasma detector

A helium microwave-induced plasma at atmospheric pressure is used as a detector for the gas chromatographic determination of gaseous impurities in argon. Either a Porapak N or a 5 A molecular sieve stationary phase is used to separate H2, CH4 and CO2 from argon. Atomic emission from carbon or hydrogen is monitored at 247.8 or 656.2 nm, respectively. Retention times and elemental contents serve to characterise the gas mixtures qualitatively and peak area is used for mass calibration. At higher concentrations of H2, CH4 and CO2, either stationary phase is adequate. However, the use of the Porapak N column provides a significantly lower background at the carbon emission line, thereby yielding superior sensitivity for CO2 and CH4. For the Porapak N stationary phase, linear calibration ranges are observed from approximately 100 p.p.b. to 100 p.p.m. for H2(defined as mole fractions assuming ideal gases) at 656.2 nm, and from 100 p.p.b. to 300–1000 p.p.m. for CO2 and CH4 at 247.8 nm. At the H l emission line, the absolute detection limits for H2 and CH4 are 2 and 40 pg, respectively. At the C l line, these limits are 10 and 30 pg for CH4 and CO2, respectively.

Sulfur selective detection in gas chromatography with a microwave-induced plasma detector

Sulfur selective detection in gas chromatography with a microwave-induced plasma detector

Capacitively coupled plasma detector for gas chromatography

A radiofrequency, atmospheric pressure capacitively coupled plasma torch which can be used as an element specific, spectroscopic detector for gas chromatography is described.

Gas chromatographic detection of selected organochlorine species using an alternating current plasma detector

The alternating current plasma detector for gas chromatography is shown to be a useful detector for selective organochlorine detection. The detector incorporates a simple design and a power source that produces a stable discharge which does not extinguish under high solvent concentration conditions. The plasma discharge produces diatomic emission of CCl species, with few atomic chlorine emission lines. Detection limits for various organochlorine compounds are approximately 1.0 ng/s. The detector exhibits a complex response dependent on molecular structure and environment. Detector selectivity towards CCl versus C 2 emission is presented, along with various selective chlorine detection applications in complex matrices.

Detection of thiophenes in the offgas condensate of an oil shale retort by a GC-microwave induced helium plasma detector

A series of alkylthiophenes and dimethyl disulfide were tentatively identified in an oil shale retort gas condensate from a 6-kg bench-scale retort using gas chromatography with a microwave-induced helium plasma detector (GC-MIP). The sulfur species were present in concentrations ranging from 1.5 to 10.7 mol ppm in the undiluted offgas. The GC-MIP technique was successful in selectively detecting the sulfur components in the complex mixture. Quantitation was simplified relative to GC with flame-photometric detection because of the absence of quenching or other interference problems at the concentrations studied. Attempts to determine stoichiometry of the sulfur components by comparison of carbon, hydrogen, and sulfur ratios with those of standards were unsuccessful because of the complexity of the carbon and hydrogen chromatograms.

Simplex Optimization of the Alternating-Current Plasma Detector for Gas Chromatography

Several operating parameters for the alternating-current plasma detector for gas chromatography were optimized on the basis of maximization of the peak area response of the detector towards ethylmerctiry (II) chloride by the modified simplex algorithm. The parameters included in the study were the ac power output, helium make-up flow rate, column flow rate, PMT voltage, and slit width. Univariant values of the optimum were equivalent to most simplex optimum values in this study. Detector evaluation was based on the new optimized response and a new detector interface design and is compared to previous values obtained for this detector. Lower detection limits of 1.10 pg/s were realized, coupled with a relative standard deviation between 1 and 5%. Detector linearity extended over three orders of magnitude.

Solar and interplanetary observations of the mass ejection on 7 May, 1979

We present observations of a mass ejection that was observed by five different instruments along its way from the solar surface to more than 100 solar radii. The instruments involved are the ground-based Hα coronagraph at Wroclaw, the white-light SOLWIND coronagraph on board the P78-1 satellite, zodiacal light photometers of the HELIOS B spacecraft, in situ plasma detectors and magnetometers on board the HELIOS B spacecraft, and interplanetary scintillation measurements on the ground. By using a CAT-scan analysis of the images obtained by the SOLWIND coronagraph near the Earth and HELIOS B photometers placed at 0.3 AU perpendicular to the Earth-Sun line, we have been able to get a three-dimensional density reconstruction of the mass ejection and fit the best velocity curve for its propagation. Although problems exist in smoothly joining the height-time curves (for instance, we had to reduce the brightness of the SOLWIND data by more than a factor of two to make the data sets agree photometrically), both this analysis and direct measurements by the other experiments clearly indicate higher speeds at greater distances from the Sun. The plasma acceleration in this case was obviously not limited only to distances within 3 R 0 , as is usually the case, but continued beyond the outer limit of the coronagraph view at ∼ 8 R 0 .

Selective determination of organofluorine compounds by capillary column gas chromatography with an atmospheric pressure helium microwave‐induced plasma detector

AbstractFluorinated analogs of compounds typical of those found in metabolic and other biological studies are detected with high selectivity using a gas chromatograph/microwave‐induced plasma detector (GC‐MIPD), which permits fluorine‐selective detection by monitoring the emission at 685.6 nm. Using the described atmospheric pressure helium‐sustained plasma detector, the minimum detectable level, fluorine selectivity (relative to carbon), and linear dynamic range of this GC‐MIPD system were determined to be 4.8 pg‐F/s, 1060, and 5000, respectively. The utility of this GC‐MIPD system for the selective detection of organofluorine compounds is demonstrated by its application in the analysis of the metabolic fate of a fluorinated substrate administered to a mixture of wheat germ phosphatase and potato apyrase, as well as by analysis of synthetic mixtures.

Oxygen-selective microwave-induced plasma gas chromatography detector for petroleum-related samples

An atmospheric-pressure, microwave-induced, helium plasma system for oxygen-selective gas chromatographic detection of petroleum-related samples is presented. Extensive purification of the helium plasma gas, exclusion, of atmospheric oxygen, and use of an appropriate plasma containment tube were crucial to minimize oxygen spectral emission produced by impurities in the plasma gas, air leaks, back diffusion of air into the plasma, and the plasma containment tube itself. With these precautions, the oxygen-to-carbon selectivity is 10/sup 3/. This is the best oxygen selectivity reported in the literature to date for a microwave-induced plasma detector system. The system is sensitive down to 2 ppm/sub w/ (parts per million by weight) oxygen for narrow-boiling range distillates and simple mixtures and 500 ppm/sub w/ oxygen for wide-boiling range, complex samples. The detector is linear over 3 orders of magnitude and has uniform response to different types of oxygenates. Examples illustrate the feasibility of gas chromatography/microwave-induced plasma for detecting organic oxygenated compounds in simple mixtures and in petroleum and synfuel distillates boiling up to ca. 500/sup 0/F.