Electronic Pressure Control Research Articles

Portable light weight open tubular ion chromatograph for field determination of environmental anions

We report a battery powered non-suppressed open tubular ion chromatograph (NSOTIC) that weighs less than 3 kg with on-board rechargeable lithium-ion batteries that provide power for 18 h of operation. It is contained in an aluminum case measuring 30 × 25 × 16 cm. Separation relies on open tubular (OT) chromatographic columns which eliminate the need for high pressure pumps, drastically reducing weight and complexity. Eluent consumption is less than 100 µL per separation. Eluent is supplied from a pressurized vessel via a voltage-controlled electronic pressure controller. Flow rates are typically <200 nL/min which allows a single 16–20 g gas cartridge to perform hundreds of separations. Two anions, chloride and nitrate, in Atacama soil samples were field determined by running the portable NSOTIC. More samples were lab analyzed by commercial IC and IC/MS-MS (only perchlorate due to its low concentration level). To demonstrate the feasibility of running NSOTIC on sample analysis, samples were tested by both non-portable and portable NSOTIC.

METHOD DEVELOPMENT AND VALIDATION OF DIMETHYL SULPHATE CONTENT IN ESOMEPRAZOLE MAGNESIUM DRUG SUBSTANCE BY GC-MS

Dimethyl sulfate is universally used as an alkylating, sulfating and sulfonating agent in organic synthesis; hence it is one of the probable impurities during the synthesis of the esomeprazole magnesium. As per ICH M7, it is genotoxic and mutagenic, so it needs to be controlled as per the acceptable intake of dimethyl sulfate and daily sample dosage. This method validation can be achieved by the hyphenated technique of gas chromatography with mass spectroscopy, which is used to develop the dimethyl sulfate impurity in esomeprazole magnesium drug substance containing salt. The method is achieved with a DB-1 column with electron impact ionization source in sim mode ion under electronic pneumatic pressure control and deliberate oven ramp programming temperature was used. A dissolved, extracted and auto-injection sample was implemented for sample introduction in a splitless mode. Dichloromethane and 2N NaOH was used as a diluent. The calibration curve showed good linearity over the 1.69 to 8.40 ppm (limit: 5.56 ppm) and its correlation coefficient was &gt;0.999. A limit of detection 0.50 ppm and limit of quantitation 1.69 ppm was achieved when the samples were prepared at 50 mg/mL. While recovery proved to be 106.8 to 113.5%, hence it signified the matrix effect.

Microminiature Pressure Sensors Based on Diode Structures

The paper analyzes modern microminiature pressure sensors made on various diode structures, in particular on organic light-emitting diodes, field-effect transistors, photovoltaic elements and multi-circuit piezoresistive sensors. The possible areas of application of such sensors, their main advantages and disadvantages are shown. The study of 4 groups of samples of diode heterostructures based on CdS / ZnS / CuS / CdTe was carried out and the perspective of using pressure sensors based on these materials as an analogue of existing semiconductor devices was shown. On the basis of experimental studies with the application of pressure, twisting and illumination, it is substantiated that these structures are piezoelectric. The complete technological process of the step-by-step creation of these structures is presented. The obtained structures were analyzed: structural diagrams, current-voltage and piezoelectric characteristics in comparison with the characteristics of other piezoelectric materials are given. Possible areas of application of such structures are described. The provided design schemes and parameters of the obtained diode structures may be of interest to a wide range of specialists in the field of sensor technology and automation of various technological processes of microelectronic equipment manufacturing. It is shown that by changing the sensor manufacturing technologies and the concentration of chemical elements in the obtained films, it is possible to change the sensitivity of the sensor and the dynamic range of its operation, adapting the sensor parameters to the field of its application in the relevant measuring electronic equipment and pressure control systems.

Conceptual design of the MGI system for JT-60SA

Disruption mitigation is of high priority for future tokamaks like ITER and DEMO. Massive gas injection (MGI) has proven to be an effective method in medium size machines and will likely be part of future disruption mitigation systems. For further research, the large superconducting tokamak JT-60SA will be equipped with a MGI system as an experimental equipment. This system will consist of two in-vessel MGI valves, which are mounted in opposite segments of the machine, vacuum feed throughs, a gas preparation system and an industrial PLC for control. The MGI valves are a scaled version of the spring-driven valve used in ADSEX Upgrade with an internal gas reservoir of 815 cm³, a maximum mitigation gas pressure of 6.5 MPa, a closing pressure of about 2 MPa, a nozzle diameter of 28 mm and an opening time below 2 ms. CFD simulations with common gas mixtures indicate a peak flow rate of 3.8 kg/s after 1.6 ms. The valve has a size of 140 mm x 110 mm x 292 mm. The gas preparation system allows easy and reproducible mixing of two gases by using an electronic pressure controller.

Built-in Chamber-Coupled Electronic Pressure Control of Ambient Air as the Carrier Gas for a Cylinder-Free Portable Gas Chromatograph

Built-in Chamber-Coupled Electronic Pressure Control of Ambient Air as the Carrier Gas for a Cylinder-Free Portable Gas Chromatograph

A portable gas chromatograph for real-time monitoring of aromatic volatile organic compounds in air samples

We describe the design and performance evaluation of a portable gas chromatograph suitable for the analysis of volatile organic and odorous compounds at trace levels. The system comprises a carbon nanotube sponge preconcentrator, an electronic pressure control (EPC) unit, a temperature-programmable column module, and a fast-response photoionization detector. A built-in tablet computer controls instrumental parameters and chromatogram display functions. The compact GC with dimensions of 35 cm (l) × 26 cm (w) × 15 cm (h) is self-contained, weighing less than 5 kg without a battery pack, and uses no auxiliary compressed gases. Our design has three main advantages over conventional portable GCs: recharging configuration of ambient air as the carrier gas using a miniature diaphragm pump, precise control of column flow by the built-in canister and EPC system, and rapid thermal desorption of the preconcentrator facilitated by intrinsic resistivity of the carbon nanotube sponge. A 30 m, 0.28 mm I.D. capillary column operated at a head pressure of 14 psi provided a peak capacity of 55 for a 10 min isothermal analysis. The temperature-programmability feature could decrease the analysis time of less than 5 min for vapor mixture of benzene, toluene, ethylbenzene, and o-xylene. More than a 100-fold increase in sensitivity by preconcentrating a sample adsorption volume of 90 mL resulted in improved detection limits of 0.13 (benzene), 0.20 (toluene), 0.23 (ethylbenzene), and 0.28 (o-xylene) ppb (v/v). Our instrument displayed good stability and reproducibility of retention times (< 0.14% RSD) and intensities (< 4.5% RSD) for continuous measurements using the preconcentrator over 10 h. Thus, continuous and on-site determinations of trace volatile organic compounds in air samples with this instrument appear feasible.

Comparison of Ventilator’s Work of Breath Cased on Constant Flow Nasal CPAP Through Pressure Limited and Electronic Feedback Pressure Control Mechanisms in the Treatment of RDS in Neonates Weighing About 1000 Grams

Background: Continuous distending pressure (CDP) is considered as standard care in neonates with decreased pulmonary compliance. Concerns regarding the implementation of non-invasive CDP in a respiratory cycle in order to establish an optimal level of functional residual capacity (FRC) abound in the related literature. Examples include how to manage gas leakage in the interface, no imposed increased work of breath (WOB) on patients and prevention of applying trans-pulmonary pressure levels leading to metabolic acidosis. Following the development of autoflow hardware, pressure control (PC) respiratory pattern was defined in the field of mechanical ventilation (MV) in order to compensate for gas leakage in interface or compensate for pressure drop and increased CDP pressure level in respiratory phases of inspiration and expiration. Objectives: The study aimed at decreasing WOB in neonates with RDS using pressure control-nCPAP. Methods: This study was a retrospective clinical trial performed on 70 neonates weighing about 1000 grams with RDS. Participants were randomly assigned into two respiratory support groups based on the use of pressure limited nCPAP (PL-nCPAP) and pressure control nCPAP (PC-nCPAP). Each group consisted of 35 infants compared in terms of their demographic characteristics, duration of non-invasive respiratory support, rapid shallow breathing (RSB) index, ventilator’s WOB, need for MV, need for surfactant administration, chronic lung diseases, pneumothorax, intra-ventricular hemorrhage (IVH) and death. Results: No significant difference was observed between the mean time of non-invasive respiratory support and the need for MV, between the incidence of pneumothorax and IVH and also between the mortality rate and degree of involvement in chronic lung diseases in the two groups. The mean respiratory ventilation rate of ventilator’s WOB in PC-nCPAP group was significantly higher than that of PL-nCPAP group. The mean RSB index was also significantly higher in PL-nCPAP group than in PC-nCPAP group. Finally, the mean of surfactant administration in PL-nCPAP group was significantly higher than that in PC-nCPAP group. Conclusions: In this study, ventilator’s WOB in PC-nCPAP group, which was significantly higher than that of PL-nCPAP group, can be explained by significantly higher RSB index in PL-nCPAP group and significantly lower mean surfactant prescription in PC-nCPAP group.

Back-flushing and heart cut capillary gas chromatography using planar microfluidic Deans’ switching for the separation of benzene and alkylbenzenes in industrial samples

Planar microfluidic devices coupled with modern electronic pressure control have allowed gas chromatography (GC) practitioners to easily manipulate chromatographic systems to achieve heart cut and back-flushing configurations. These planar microfluidic devices have enhanced the connectivity between different components of GC instrumentation and have improved the inertness and minimised system dead volumes compared to classical chromatographic unions and valves. In the present contribution the setup and configuration of two multidimensional GC (MDGC) platforms is described for achieving the separation and quantification of trace level target C6–C8 alkylbenzenes in styrene monomer and Isoparaffin™ solvents, using flame ionisation detection (FID). The performance of these MDGC platforms indicated excellent retention time (0.2% relative standard deviation, RSD) and peak area repeatability (1% RSD) for all analytes of interest. The limit of detection (LOD) was 0.8mgkg−1 for benzene in styrene monomer, and 2.4–2.8mgkg−1 for C6–C8 alkylbenzenes such as benzene, toluene, ethylbenzene and xylene in Isoparaffin™ solvent.

Intelligent controls for electro-hydraulic poppet valves

This paper describes an intelligent controller that combines an auto-calibration state-trajectory-based control method with a simple algorithm that enables fault detection. The application of the controller to achieve intelligent electronic pressure control in a fluid power system is included. More specifically, the proposed control algorithm is designed to learn the inverse input-state map of an Electro-Hydraulic Poppet Valve (EHPV) with the aid of a Nodal Link Perceptron Network (NLPN). While in operation, the controller enforces the tracking of a desired hydraulic supply pressure profile at the same time that it learns the inverse input-state calibration map and monitors the latter for deviations from prescribed bounds. The tracking performance of the auto-calibration scheme is validated experimentally and the fault detection algorithm is explored via a computer simulation.

Auto-calibration Based Control and Its Application to a Kind of Electrohydraulic Poppet Valves

Abstract This paper describes a novel learning/adaptive state trajectory control method and its application to electronic hydraulic pressure control. The control algorithm presented herein learns the inverse input-state mapping of the plant at the same time this map is employed in the feedforward loop to force the state of the plant to asymptotically converge to a prescribed state trajectory. The algorithm accomplishes this task without requiring prior exact information about the state transition map of the plant. The novel controller is applied to an electrohydraulic poppet valve with the objective of tracking a desired supply pressure signal. In this application, the controller learns the inverse conductance characteristics of the valve. The supply pressure tracking performance subject to the proposed controller is validated through experimental data.

Electronic Health Record Components and the Quality of Care

Electronic health records (EHRs) have been promoted as an important tool to improve quality of care. We examined the association between EHR components, a complete EHR, and the quality of care. Using data from the 2005 National Ambulatory Medical Care Survey and the National Hospital Ambulatory Medical Care Survey, we conducted a cross-sectional analysis of all visits with an established primary care provider and examined the association between presence of EHR components and: (1) blood pressure control; and (2) receipt of appropriate therapy for chronic conditions. We examined similar associations for complete EHRs which we defined as one that includes physician and nursing notes, electronic reminder system, computerized prescription order entry, test results, and computerized test order entry. We constructed multivariate models to examine the association between EHR components and each outcome controlling for patient sociodemographic, health, physician practice, and geographic factors. We found no association between electronic physician notes and blood pressure control or receipt of appropriate therapies, with the exception of inhaled steroids among asthmatics (adjusted odds ratio 2.86; 95% confidence interval, 1.12-7.32). We found no association between electronic reminder systems and blood pressure control or receipt of appropriate therapies, with the exception of angiotensin converting enzyme inhibitors or angiotensin receptor blockers in patients with diabetes with hypertension (odds ratio 2.58; 95% confidence interval, 1.22-5.42). We found no association between electronic physician notes and any measure of quality. We found no relationship between having a complete EHR and any of the quality measures investigated. We found no consistent association between blood pressure control, management of chronic conditions, and specific EHR components. Future research focusing on how an EHR is implemented and used and how care is integrated through an EHR will improve our understanding of the impact of EHRs on the quality of care.

Multidimensional gas chromatography with capillary flow technology and LTM‐GC

2-D GC is a logical and cost effective extension to 1-D GC for improving the separation resolution, selectivity, and peak capacity of an analytical system. The advent of electronic pressure control systems that are accurate to the third decimal place, combined with recently innovated chromatographic devices such as capillary flow technology, has eliminated many deficiencies encountered in current conventional 2-D GC by making the technique reliable and simple to implement in both production and research analytical facilities. Low thermal mass GC (LTM-GC) was successfully integrated with capillary flow technology to further enhance overall 2-D GC chromatographic system performance by providing not only faster throughput via rapid heating and cooling, but independent temperature control for each dimension to maximize separation power. As an example, despite the enhanced peak capacity obtained from conventional 2-D GC, alkyl naphthalene isomers such as 2,3-dimethyl and 1,4-dimethyl naphthalene coeluted. These two critical compounds were well resolved (R = 5.2) using 2-D GC with LTM-GC with a similar analytical time. This paper demonstrates the benefits of combining capillary flow technology with LTM-GC to provide major enhancements to conventional 2-D GC. The synergy of these techniques is highlighted with practical industrial applications.

Rapid analysis of food products by means of high speed gas chromatography

Since the invention of GC, there has been an ever increasing interest within the chromatographic community for faster GC methods. This is obviously related to the fact that the number of samples subjected to GC analysis has risen greatly. Nowadays, in routine analytical applications, sample throughput is often the most important aspect considered when choosing an analytical method. Gas chromatographic instrumentation, especially in the last decade, has been subjected to continuous and considerable improvement. High-speed injection systems, electronic gas pressure control, rapid oven heating/cooling and fast detection are currently available in a variety of commercial gas chromatographs. The main consequence of this favourable aspect is that high-speed GC is being increasingly employed for routine analysis in different fields. Furthermore, the employment of dedicated software makes the passage from a conventional to a fast GC method a rather simple step. The present review provides an overview of the employment of fast GC techniques for the analysis of food constituents and contaminants. A brief historical and theoretical background is also provided for the approaches described.

High-speed peak matching algorithm for retention time alignment of gas chromatographic data for chemometric analysis

A rapid retention time alignment algorithm was developed as a preprocessing utility to be used prior to chemometric analysis of large datasets of diesel fuel profiles obtained using gas chromatography (GC). Retention time variation from chromatogram-to-chromatogram has been a significant impediment against the use of chemometric techniques in the analysis of chromatographic data due to the inability of current chemometric techniques to correctly model information that shifts from variable to variable within a dataset. The alignment algorithm developed is shown to increase the efficacy of pattern recognition methods applied to diesel fuel chromatograms by retaining chemical selectivity while reducing chromatogram-to-chromatogram retention time variations and to do so on a time scale that makes analysis of large sets of chromatographic data practical. Two sets of diesel fuel gas chromatograms were studied using the novel alignment algorithm followed by principal component analysis (PCA). In the first study, retention times for corresponding chromatographic peaks in 60 chromatograms varied by as much as 300 ms between chromatograms before alignment. In the second study of 42 chromatograms, the retention time shifting exhibited was on the order of 10 s between corresponding chromatographic peaks, and required a coarse retention time correction prior to alignment with the algorithm. In both cases, an increase in retention time precision afforded by the algorithm was clearly visible in plots of overlaid chromatograms before and then after applying the retention time alignment algorithm. Using the alignment algorithm, the standard deviation for corresponding peak retention times following alignment was 17 ms throughout a given chromatogram, corresponding to a relative standard deviation of 0.003% at an average retention time of 8 min. This level of retention time precision is a 5-fold improvement over the retention time precision initially provided by a state-of-the-art GC instrument equipped with electronic pressure control and was critical to the performance of the chemometric analysis. This increase in retention time precision does not come at the expense of chemical selectivity, since the PCA results suggest that essentially all of the chemical selectivity is preserved. Cluster resolution between dissimilar groups of diesel fuel chromatograms in a two-dimensional scores space generated with PCA is shown to substantially increase after alignment. The alignment method is robust against missing or extra peaks relative to a target chromatogram used in the alignment, and operates at high speed, requiring roughly 1 s of computation time per GC chromatogram.

Pressure-tunable column selectivity for high-speed vacuum-outlet GC.

A pressure-tunable ensemble of two series-coupled capillary columns operated at subambient outlet pressure is described. The ensemble consists of a 4.5-m length of nonpolar dimethyl polysiloxane column followed by a 7.5-m length of polar trifluoropropylmethyl polysiloxane column. Air at an inlet pressure of 1.0 atm is used as carrier gas, and a vacuum pump is used to pull the carrier gas and injected samples through the column ensemble. Detection is provided by a photoionization detector operated at a pressure of 0.3 psia. Ensemble selectivity is controlled by means of an electronic pressure controller located at the junction point between the columns. The minimum pressure step size is 0.1 psi, and 50 different set-point pressures can be used, each one producing a different pattern of peaks eluting from the column ensemble. Measured ensemble retention factors for a set of target compounds produce straight lines when plotted versus the ratio of the calculated holdup time of the first column in the ensemble to the total ensemble holdup time. A component band trajectory model is used to describe the effects of ensemble junction-point pressure on the elution patterns generated by the ensemble. Ensemble retention times predicted by the model are in good agreement with values obtained from chromatograms. The use of on-the-fly set-point pressure changes during a separation (selectivity programming) is demonstrated and used to improve the quality of the separation of a 19-component test mixture.

Pressure-Tunable Dual-Column Ensembles for High-Speed GC and GC/MS

A series-coupled ensemble of two capillary GC columns of different selectivity with an adjustable pressure at the column junction point is used to obtain tunable selectivity for high-speed GC and GC/ TOFMS. An electronic pressure controller with a 0.1-psi step size is used to obtain numerous computer-selected unique selectivities. System configurations for conventional, atmospheric-pressure outlet operation with flame ionization detection and for vacuum-outlet operation with photoionization detection are described for GC-only experiments. Polydimethylsiloxane is used as the non-polar column and polyethylene glycol (atmospheric outlet) or triflouropropylpolysiloxane (vacuum outlet) is used as the polar column. For GC/ TOFMS experiments, 5% phenyl polydimethylsiloxane was used as the non-polar column, and polyethylene glycol was used as the polar column. The time-of-flight mass spectrometer can acquire up to 500 complete mass spectra per second. Since spectral continuity is achieved across the entire chromatographic peak profile, severely overlapping peaks can be spectrally deconvoluted for high-speed characterization of completely unknown mixtures. For mixture components with significantly different fragmentation patterns, spectral deconvolution can be achieved for chromatographic peak separations of as little as 6.0 ms. This can result is very large peak capacity for time compressed (not completely resolved) chromatograms. The use of columns with tunable selectivity allows for precise peak-position control, which can result in more efficient utilization of available peak capacity and thus further time compression of chromatograms. The limits of tunability and deconvolution are tested for near co-elutions of different classes of hydrocarbon compounds as well as for more multi-functional mixtures.

Tunable-Column Selectivity and Time-of-Flight Detection for High-Speed GC/MS

A pressure-tunable ensemble of two capillary separation columns is combined with time-of-flight mass spectral detection for the high-speed characterization and analysis of volatile organic compounds. The detector can record up to 500 complete mass spectra per second and can obtain spectral deconvolution and thus characterization of severely overlapping and unknown chromatographic peaks. The tunable capillary column ensemble consists of the series combination of a nonpolar 5% phenyl poly(dimethylsiloxane) column and a polar poly(ethylene glycol) column. Adjustment of the pressure at the column junction point is achieved by the use of an electronic pressure controller. Changes in the junction pressure result in changes in the relative contribution that each of the columns makes to overall retention. This causes changes in the retention patterns, which can be used to enhance the utility of the TOFMS detector. The use of high spectral acquisition rates allows for the deconvolution of very closely spaced peaks...

Analysis of Underivatizated Patulin by a GC-MS Technique

An alternative approach based on the use of gas chromatography-mass spectrometry (GC-MS) is used to confirm the presence of patulin in apple juice. In the gas chromatography (GC) methods previously described, derivatization of patulin was always necessary in order to achieve good chromatographic detection. The use of electronic pressure control (EPC) and on-column injection avoids the need for patulin derivatization and allows a sensitive analysis of patulin. A detection limit of 4 μg/liter in apple juice can be attributed to the method.

Pressure-Tunable GC Columns with Electronic Pressure Control

High-precision selectivity tuning is achieved by the use of a series-coupled (tandem) ensemble of a nonpolar and a polar capillary GC column with adjustable pressure at the junction point between the columns. Changing the junction pressure results in a differential change in the holdup times for the two columns. This results in a change in the fractional contribution that each column makes to the overall separation selectivity. An electronic pressure controller is used to obtain greater control and improved tuning precision. With an available tuning range extending from less than 0.60 to greater than 0.85 for the fractional contribution of the nonpolar column, 37 unique, digitally selectable elution patterns are obtained. High-precision tuning is required since fractional contribution changes as small as 0.5% can significantly degrade resolution. With this system, resolution increments of 0.2 or less are achieved for typical critical component pairs.

Rapid and simultaneous analysis of protein and non-protein amino acids as N(O,S)-isobutoxycarbonyl methyl ester derivatives by capillary gas chromatography

A simple and rapid gas chromatographic method is described for the simultaneous determination of protein and non-protein amino acids present in aqueous samples. The amino acids were converted into their N(O,S)-isobutoxycarbonyl methyl ester derivatives and measured by gas chromatography7 equipped with a split inlet mode, an electronic pressure control system and a hydrogen flame ionization detector using a DB-17ht capillary column. Using this method, the 21 protein amino acids and the 33 non-protein amino acids were quantitatively and reproducibly resolved within 25 min. The calibration curves were linear in the range 0.2–20 μg of each amino acid, with correlation coefficients being above 0.998, and the relative standard deviations in each point ranged from 0.2 to 9.2%. The detection limits of amino acids were 0.09–1.15 ng per injection.