Showing papers by "Tyge Greibrokk published in 1997"

Microconcentric Nebulizer for the Coupling of Micro Liquid Chromatography and Capillary Zone Electrophoresis With Inductively Coupled Plasma Mass Spectrometry

Abstract: A concentric nebulizer designed to deliver less than 10 µl min -1 directly into an ICP-MS system is described. The influence of the liquid flow rate, the nebulizer gas flow rate and the distance from the nebulizer tip to the plasma was evaluated with regard to sensitivity and precision. The nebulizer was tested at liquid flow rates of 3–7 µl min -1 . Samples of tetramethyllead and tetraethyllead dissolved in dimethylformamide were used for the evaluation of the nebulizer. The detection limit for Pb ( m =208) with a direct injection system was found to be 0.3 pg (S/N=3) or 5 µg l -1 , based on an injection volume of 60 nl, a liquid flow rate of 5 µl min -1 and a dwell time of 10 ms. The precision was found to be 1.9% ( n =10) based on peak area measurements. The responses of tetramethyllead and tetraethyllead were not significantly different ( p =0.05). The time needed for one determination was less than 15 s, owing to the quick rinse out of the nebulizer. The nebulizer can be used as part of a direct injection instrumental set-up. An application of the nebulizer to the coupling of packed capillary liquid chromatography with ICP-MS detection is demonstrated.

Separation and Quantification of Components of Edible Fat Utilizing Open Tubular Columns in SFC. Sample Introduction by Direct Injection and SFE Coupled On-Line to SFC

Abstract: Geometric isomers of fatty acids were separated by open tubular columns in SFC. The concentration of the analytes varied between 9 and 16 μg mL−1. Quantification of triglycerides with repeatability better than 20% were obtained in a home made SFE-SFC unit. A four point calibration curve for both trimyristin and tripalmitin was developed with correlation coefficients of 0.998 and 0.9998, respectively. The limit of quantification was approximately 3 ng for both components. Supercritical CO2 as extraction solvent in matrix containing lipids increased the recovery of cholesterol by a factor of three. Using immobilized lipase in on-line SFE-SFC quantification of cholesterol in spray dried egg yolk was possible.

Simultaneous determination of trace amounts of sulphur hexafluoride and cyclic perfluorocarbons in reservoir samples by gas chromatography

Abstract: Both sulphur hexafluoride and a group of compounds among the perfluorinated cyclic hydrocarbons: perfluorodimethyl cyclobutane, perfluoromethyl cyclopentane, perfluoromethyl cyclohexane and the 1,2- and 1,3-isomers of perfluordimethyl cyclohexane are well known to be good gas tracers, in various applications. Unfortunately different methods have been used for the analysis of SF6 and the perfluorocarbons. Therefore, in many cases, the analytical costs may have hindered the use of both SF6 and the perfluorocarbons in the same tracer experiments. The analytical method described in this paper enables the determination of both types of gas tracer in one single run. The new method has already replaced two former methods and was used to run the gas tracer analysis routinely, proving the reliability of the method.

Determination of chlorinated and brominated micropollutants by capillary gas chromatography coupled with on‐column radio frequency plasma atomic emission detection

Abstract: Capillary gas chromatography (GC) combined with on-column radio frequency plasma atomic emission detection was evaluated for the determination of polychlorinated and polybrominated biphenyls (PCBs and PBBs). Quantitation was possible utilizing a single chlorine or bromine calibration curve based on a randomly selected reference compound, because the signal per ng of halogen ranged within 17 % for 29 congeners. Combined with an internal standard to correct for potential plasma quenching from matrix components, this type of universal quantitation represented a sub-stantial simplification of current calibration procedures. In combi-nation with relatively low detection limits (1–5 pg/s of halogen), the present work suggested that GC, coupled with on-column atomic emission detection is a promising technique for the determination of halogenated micropollutants.

Determination of extractable organic chlorine and bromine by probe injection dual-microplasma atomic emission spectrometry.

Abstract: A probe injection dual-microplasma spectrometer is evaluated as a low-cost alternative for the determination of extractable organic chlorine and bromine (EOCl and EOBr). The system consists of two 350 kHz plasmas sustained in the same stream of helium and a probe for sample application in the interplasma region. The sample was applied with a microsyringe into a small cup on the sample probe. Subsequently, the extraction solvent was gently evaporated, and the sample cup was pushed into the interplasma region. The first plasma was in direct contact with the sample probe and served to rapidly vaporize the sample material. The vaporized sample was then transferred to the second plasma, where atomic emission was measured for the determination of EOCl and EOBr. For both Cl and Br, 120 pg detection limits and 1000:1 halogen-to-carbon selectivities were obtained, and responses were linear over 3 orders of magnitude.

Determination of brominated alkylbenzenes in nickel industry sludge by capillary gas chromatography

Abstract: Capillary gas chromatography coupled to both mass spectrometry (GCMS) and atomic emission spectroscopy (GC-AED) was studied for the analysis of bromine-containing alkylbenzenes present in sludge from a nickel refinery. Owing to the high abundance of chlorinated compounds, location of the brominated species was difficult based on GC-MS with electron ionization. In contrast, GC-MS with negative chemical ionization (GC-NCIMS) and GC-AED enabled bromine-selective detection and were utilized for an effective location of the brominated compounds. Bromine-selective detection by GC-NCIMS relied on the monitoring of Br− (m/z 79/81) with CH4 as ionization gas, while atomic emission (827.2 nm) from a helium plasma was utilized in the case of GC-AED. While GC-NCIMS was 30–500 times more sensitive than GC-AED, the latter technique was superior for quantitative purposes. Because the bromine response of the AED was independent of molecular structure, quantification was possible without reference material.