Electronic Pressure Control Research Articles

Electronic pressure control of gas chromatography-mass spectrometry for the confirmation of pesticide residues in cereals and related products

An analytical method for the confirmation of 30 pesticide residues in cereals and related products has been developed. Splitless injection with electronic pressure control using constant carrier gas flow gives higher sensitivity and better resolution than electronic pressure control and isobaric analysis. The use of electronic pressure control assures consistent retention times enabling selected ions to be collected in short time windows. Mass spectrometric detection in the selected ion monitoring mode using three ions for each pesticide ensured good sensitivity and accurate pesticide confirmation.

Gas chromatographic determination of midazolam in low-volume plasma samples

A gas chromatographic method for the sensitive determination of midazolam in plasma volumes as low as 40 μl was developed, utilizing clinazolam as the internal standard. After liquid-liquid extraction at basic pH into 1-chlorobutane-dichloromethane (96:4) a 2- to 4-μl portion of the reconstituted extract was injected under electronic pressure control onto a 12 m × 0.2 mm I.D. methyl silicone capillary column, and was exposed to a three-step temperature program from 120 to 310°C, to separate the analytes from the plasma constituents. The compound of interest was identified and quantified by means of a mass-selective detector. The assay was linear from 10 to 500 ng/ml using 40 μl of plasma (limit of quantification: 10 ng/ml) and was linear from 0.25 to 100 ng/ml using 500 μl of plasma (limit of quantification: 0.25 ng/ml). The intra-day precision for the 40-μl aliquots varied from 2.2 to 6.6%, the corresponding accuracy from −7.4 to −4.4%; the inter-day precision ranged from 5 to 7.2% and the corresponding accuracy from −7.2 to −5.1%.

Capillary Gas Chromatography–Atomic Emission Detection Method for the Determination of Pentylated Organotin Compounds: Interlaboratory Study

Abstract A capillary gas chromatography-atomic emission detection (GC–AED) method was developed for the U.S. Environmental Protection Agency’s Environmental Monitoring Systems Laboratory in Las Vegas, NV, for determination of selected organotin compounds. Here we report on an interlaboratory study to establish whether these compounds can reliably be detected and quantitated by this method and to establish the interlaboratory precision and accuracy with currently available instrumentation. A blind, balanced-replicate design was selected for this study, based on a recommendation of AOAC INTERNATIONAL. Ten laboratories volunteered for this study. Each laboratory received 5 calibration standards (pentylated organotin compounds), 3 pentylated soil or sediment extracts (prepared in our laboratory by an in situ complexation/supercritical fluid extraction method), and 1 pentylation blank. The participating laboratories analyzed the extracts according to our instructions and submitted the data to us for statistical analysis. Of 720 individual sample results, the number of outliers identified with the Cochran test was 60 (8.3%). Two laboratories accounted for most of the outliers. Results indicate that good chromatographic performance was achieved regardless of the type of injection inlet; however, electronic pressure control was needed to achieve acceptable chromatography for tetracyclohexyltin and tetraphenyltin. The intralaboratory precisions of the GC-AED method ranged from 1.3 to 22% relative standard deviation (RSD), depending on the compound. The interlaboratory method precisions ranged from 11 to 40% RSD over the concentration range tested.

Optimizing the gas chromatographic separation and detection of polychlorinated biphenyls by use of electronic pressure programming and experimental design

AbstractThe applicability of electronic pressure control and Taguchi L27 experimental design to the optimization of the gas chromatographic separation and detection of polychlorinated biphenyls has been evaluated. The influence of several experimental variables, column temperature program, carrier gas pressure program, on‐column injector temperature program, and make‐up gas pressure program, was studied using analysis of variance. Simultaneous optimization of sample introduction, column efficiency, and detector performance could be achieved without compromising system performance. The relationships between system performance and experimental variables were established using regression analysis. Agreement between the simulated and experimental results obtained using suggested optimum conditions demonstrated the applicability of the technique developed in this study. The improvement achieved in the chromatographic separation of PCBs is presented.

Real-time controlled multidimensional gas chromatography with electronic pressure control: application to chlorobiphenyl analysis

Multidimensional gas chromatography was applied to the quantitative determination of planar chlorobiphenyls (PCBs) in commercial PCB mixtures. The instrumental setup is based on real-time controlled column switching in which the heartcuts are elucidated through retention indices calculated by linear extrapolation from the retention times of n-alkanes as reference compounds. Electronic pressure control providing pressure programming was used to adjust the pressure at the injector and at the mid-point of the column tandem.

Increasing GC separation efficiency by electronic pressure control?

Journal of High Resolution ChromatographyVolume 17, Issue 7 p. 556-556 Forum Increasing GC separation efficiency by electronic pressure control? Konrad Grob, Konrad Grob Kantonales Labor, P.O. Box CH-8030, Zürich, SwitzerlandSearch for more papers by this author Konrad Grob, Konrad Grob Kantonales Labor, P.O. Box CH-8030, Zürich, SwitzerlandSearch for more papers by this author First published: July 1994 https://doi.org/10.1002/jhrc.1240170710Citations: 4AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article.Citing Literature Volume17, Issue7July 1994Pages 556-556 RelatedInformation

Optimization of GC detector parameters using electronic pressure control

AbstractHP 5890 Series II Gas Chromatographs are equipped with prototype hardware enabling electronic pressure programming of all detector and carrier gases. A method of using electronic pressure control (EPC) to optimize detector performance (sensitivity, selectivity, and baseline stability) is demonstrated. With EPC, sample introduction, column separation, and detector performance can be optimized simultaneously without the classical trade‐offs in performance. An example is also presented of the use of a new automated system which enables cool on‐column injection into 250 or 320 μm columns without the need for a retention gap.

Improving splitless injection with electronic pressure programming

AbstractAn experimental injection port has been designed for split or splitless sample introduction in capillary gas chromatography; the inlet uses electronic pressure control, in order that the column head pressure may be set from the GC keyboard, and the inlet may be used in the constant flow or constant pressure modes. Alternatively, the column head pressure may be programmed up or down during a GC run in a manner analogous to even temperature programming. Using electronic pressure control, a method was developed which used high column head pressures (high column flow rates) at the time of injection, followed by rapid reduction of the pressure to that required for optimum GC separation. In this way, high flow rates could be used at the time of splitless injection to reduce sample discrimination, while lower flow rates could be used for the separation. Using this method, up to 5 μl of a test sample could be injected in the splitless mode with no discrimination; in another experiment, 2.3 times as much sample was introduced into the column by using electronic pressure programming. Some GC peak broadening was observed in the first experiment.

CGC using a programmable electronic pressure controller

AbstractCapillary gas chromatographic separations were performed with an electronic pressure control system developed to provide precise closed‐loop control of inlet pressure through the use of a solid state micro‐machined pressure sensor and electronically controlled proportional valve. The closed‐loop control of the electronic system provided better precision than the open‐loop control achieved by manual pressure regulation. Closed‐loop control can perform pressure programming, which can be combined with temperature programming to optimize separations. The pressure sensor monitors the integrity of the flow system and singals the controller to reduce flow in the presence of a sudden loss of system pressure.

Fluidic Cabin Pressure Control Systems for Military and Civil Aircraft

In common with other pneumatic and electronic cabin pressure control installations the two new pneumatic systems discussed in this paper have been designed to control cabin pressure automatically by throttling the out-flow of the cabin conditioning air. For those unfamiliar with the subject Fig. 1 shows diagrammatically a typical modern military aircraft installation. Both the systems discussed should however be of particular technical interest warranting general description, as for the first time with this type of equipment low cost and robust integrated fluidic circuits have been extensively used in their design. Patents covering these have now been granted in the United Kingdom, the United States and other countries.

Design and Use of Electronic Pressure Controller

Design and Use of Electronic Pressure Controller