Electrical Conductivity Detector Research Articles

Noticeably enhanced photosensing properties of Fe-doped Bi2S3 thin films developed by nebulizer spray pyrolysis technique for photosensor applications

The current study uses the nebulized spray pyrolysis (NSP) approach to study the effect on crystalline, morphological, electrical conductivity, and photo detector properties of Bi2S3 thin films through Fe doping produced on amorphous glass substrates. The orthorhombic structure of Bi2S3 thin films for the pristine and Fe doped Bi2S3 thin films was confirmed by X-ray diffraction studies. The XRD data of the samples were used to calculate crystallite size value and maximum crystallite size value of 38 nm was observed for 2% Fe-doped Bi2S3 film. FESEM image of 2% Fe-doped film shows the distribution of uniform grains. With the increase in concentration of the Fe dopants from 0% to 5%, the energy gap value changes from 2.2 to 2.47 eV. The 2% Fe-doped Bi2S3 film possesses highest responsivity (9.60 × 10-2 AW-1), external quantum efficiency (22.4%), and detectivity (1.34 × 1010 Jones) properties suggests that the sample might be better suited for the application of the photo detectors.

Lactic Acid production from Tomato Pomace Fermentable Sugars using Innovative Biological Treatments

The organic residues from agro-food sector can be transformed into valuable economic resources rather than representing an unmanageable waste, whose disposal in landfills contributes to increase both soil pollution and the greenhouse effect. With this in mind, the aim of the investigation is to design eco-friendly compatible innovative biological processes for producing lactic acid (LA) from fermentable sugars using as substrate tomato pomace. In the first part of the investigation, we show the physico-chemical characterization of tomato pomace produced in the 2017 season with or without thermal pre-treatment. pH, total and volatile solids content, sugars and cellulose are measured. The microorganism consortia suitable for lactic acid production are selected from buffalo dung, and compared with commercial strains of lactic acid producing bacteria. Both bacteria consortia are used as inoculum for the anaerobic fermentation of tomato pomace as sole substrate for producing fermentable sugars and convert them in LA. Sugars are measured by a spectrophotometric- coupled enzyme assay and LA by HPLC with electrical conductivity detector. The molecular analysis of the isolated bacteria is performed by using the denaturing gradient gel electrophoresis (DGGE). Anaerobic fermentation of tomato pomace is also performed using different initial pH values of the substrate. The final goal is to design biological processes aimed at achieving the highest LA recovery yields.

Nutrient Sensing Using Chip Scale Electrophoresis and <italic>In Situ</italic> Soil Solution Extraction

This paper reports an electrophoresis-based microfluidic ion nutrient sensor for the detection of anions in soil solution samples. The sensor is able to analyze the concentration of various anions in extracted soil solutions with high sensitivity as well as high specificity, while it is an approach requiring no labels. The electrophoretic microchip integrates a pair of in-plane conductivity detection microelectrodes. A programmable high voltage power supply unit was designed to achieve precise control over voltage potentials needed for sample and buffer injection and ion separation. An electrical conductivity detector was designed to extract and process the changes in conductivity due to the arrivals of separated anions at the electrodes at various times. An arrival time serves to identify an anionic species, while the peak height indicates the concentration. A soil water extraction device was also designed to extract the soil solution analyte from the bulk soil, by applying vacuum suction. Only a minute amount of solution (on the order of $\mu$ L) is needed for the electrophoretic measurement. Extracted soil solutions were analyzed for ionic concentrations to demonstrate the feasibility of using this microfluidic sensor, showing a limit of detection of about $\mu$ M.

The effect of pH and amino acids on the formation of methylglyoxal in a glucose-amino acid model system.

Methylglyoxal (MGO) as a α-dicarbonyl compound not only affects food flavor and color but also contributes to the loss of nutrition and the generation of toxic compounds. The study was carried out using a glucose-amino acid model system with incubation at 120 °C to investigate the effect of amino acids and pH on the formation of MGO. MGO derivative (2-methylquinoxaline) was detected by high-performance liquid chromatography with a diode array detector. Changes in glucose, amino acids and products such as acetic acid were tested using high-performance anion exchange chromatography with an electrochemical detector or an electrical conductivity detector. Lysine and glycine had higher reactivity to form MGO and melanoidins than arginine and proline. More acetic acid was produced and a higher consumption of arginine was observed in glucose-arginine solution. Moreover, higher pH significantly accelerated the formation of MGO. Amino reactivity and pH were two important factors affecting the formation of MGO in the Maillard reaction. © 2016 Society of Chemical Industry.

Determination a variety of acidic gas in air of workplace by Ion Chromatography

To establish a method for determination of a variety of acid gas in the workplace air by Ion Chromatography. (hydrofluoric acid, hydrogen chloride or hydrochloric acid, sulfur anhydride or sulfuric acid, phosphoric acid, oxalic acid). The sample in workplace air was collected by the porous glass plate absorption tube containing 5 ml leacheate. (Sulfuric acid fog, phosphoric acid aerosol microporous membrane after collection, eluted with 5 ml of eluent.) To separated by AS14+AG14 chromatography column, by carbonate (2.0+1.0) mmol/L (Na(2)CO(3)-NaHCO(3)) as eluent, flow rate of 1 ml/min, then analyzed by electrical conductivity detector. The retain time was used for qualitative and the peak area was used for quantitation. The each ion of a variety of acid gas in the air of workplace were excellent in carbonate eluent separation. The linear range of working curve of 0∼20 mg/L. The correlation coefficient r>0.999; lower detection limit of 3.6∼115 µg/L; quantitative limit of 0.012∼0.53 mg/L; acquisition of 15L air were measured, the minimum detection concentration is 0.004 0∼0.13 mg/m(3). The recovery rate is 99.7%∼101.1%. In the sample without mutual interference ions. Samples stored at room temperature for 7 days. The same analysis method, the detection of various acidic gases in the air of workplace, simple operation, good separation effect, high sensitivity, high detection efficiency, easy popularization and application.

Reduction of acrylamide formation by selected agents in fried potato crisps on industrial scale

Great interest and rapid research efforts on acrylamide in foods followed an announcement in April 2002 by the Swedish National Food Authority and the University of Stockholm. Reduction of acrylamide in high-temperature processing foods, including selection of the raw material and variation of processing parameters, etc. were extensive reported. In this research, effect of some agents on acrylamide formation was investigated. A glucose-asparagines reaction model system was used to test the effect of ferulic acid, catechin, CaCl2, NaHSO3, and l-cysteine on inhibition of acrylamide formation and three efficient inhibitors, NaHSO3, CaCl2 and l-cysteine were screened. The results showed that immersing of the fresh potato chips using different concentration of the agents greatly inhibited acrylamide formation in fried potato crisps, and the efficiency increased as their concentrations increased; among them, l-cysteine is the most efficient agent but CaCl2 is most potential. Effects of these food additives on the texture of fried potato crisps were also studied. It was found that l-cysteine showed little effect on the texture of the crisps and CaCl2 is regarded as the suitable choice because of its low price and the acceptable mouth feel of fried crisps treated by CaCl2, although it increased the brittleness. Moreover, the application of CaCl2 in industrial production of fried potato crisps was also studied. In the blanching process (deactivation process of enzymes at 85 °C), a computerized electrical conductivity detector was used to keep the concentration of CaCl2 at constant and the result showed that immersion of potato slices in CaCl2 solution at 5 g/L reduced acrylamide formation by more than 85% in fried crisps. This research presents a technology to inhibit acrylamide formation in fried potato chips by immersion of fresh potato chips with some food additives. The approach suggested that cysteine and calcium chloride significantly decreased the content of acrylamide in fried potato chips and their concentrations could be kept constant by using a conductor as a detector.

DEVELOPMENT AND PERFORMANCE TEST OF A PORTABLE SOIL EC DETECTOR

A portable soil electrical conductivity (EC) detector was developed and its performance was tested. The ECdetector adopts a four-electrode method and consists of three parts: a probe with four electrodes, a control and display unit,and the data processing software. The probe injects a constant electrical current into soil and detects the voltage drop betweentwo output electrodes. The voltage drop is then used to estimate the soil EC. The control and display unit consists of severalsections including the microprocessor, power, the constant current source sections, the A/D conversion section, the displaysection, and the communication section. All sections were designed in a circuit board to measure, display, and record signalsfrom the probe. The performance test showed that the measured voltage drop had high correlation with soil ECs obtained fromsoil extract solution. The highest correlation coefficient was obtained when the distance between an inputting electrode anda detecting in the same side was 15 cm and the distance between two detecting electrodes was 30 cm. Three nonlinearregressions were attempted to describe the correlation: the power function regression, the polynomial regression, and theexponential function regression. The best estimation was observed with the power function model (R2 = 0.994) with two modelparameters: intercept and power. These model parameters had little variation and hence the model was reliable. All resultsshowed that the developed detector was practical.

Resonance light scattering (RLS) detection of nanoparticle separations in a microelectrical field-flow fractionation system

In this study, resonance light scattering (RLS) is demonstrated as a detection methodology for real-time visualization of the electrical field-flow fractionation process. On-column RLS was used to monitor the fractionation of a bolus sample containing 40-, 60-, and 80-nm-diameter RLS Particles into individual particles and bands of particles. Optical detection using the RLS system was correlated to an on-chip electrical conductivity detector. Particle concentrations as low as 1.08/spl times/10/sup -12/ M (1 RLS Particle/1.54 pL) were detected using both the optical and electrical detection systems.

Development of ion chromatography methods for the determination of trace anions in ultra pure water from power plants

A suppressed ion chromatography (IC) technique, using a carbonate/hydrogen carbonate or a hydroxide eluent, has been evaluated as a monitoring tool for the detection of major anions (F-, Cl-, NO3-, PO43- and SO42-) in ultra pure water and condensed steam from thermal power plants. An electrical conductivity detector with an anion-exchange column (IonPac AS14), an auto self-regenerating suppressor (ASRS), and an isocratic high-pressure pump system were used for the detection of low concentrations of inorganic anions. It was shown that the suppressed IC technique provides a suitable means for preventing possible damage to generating equipment in power plants. The detection limits of the method for the anions of interest were < 0.3 ?g/L.

Improving the Selectivity of Semiconductor Gas Sensors Using the Pulse Adsorption Mode

A procedure is proposed for improving the selectivity of semiconductor gas sensors by the pulsed supply of the test gas mixture, with the use of transient spectroscopy for the separation and assessment of component contributions to the response of an electrical conductivity detector. The experimental verification of the procedure showed that the selective determination of several compounds and their mixtures can be performed using the same SnO2 detector. The simulation of the detector response as the sum of simplest relaxations revealed three types of surface sites on SnO2 films, with energy levels of 0.97, 1.38, and 1.50 eV. This means that the number of gas components that can be selectively determined with a single detector is limited to three.

Suppressed ion chromatography for monitoring chemical impurities in steam for geothermal power plants

A suppressed ion chromatography (IC) technique has been evaluated as a chemical monitoring tool for detecting major anions (F −, Cl −, NO 3 − and SO 4 2−) of condensed steam in geothermal power plants. It is shown that the suppressed IC technique provides a suitable means for preventing possible damage to generating equipment in the geothermal industry. An electrical conductivity detector (0.1 μS sensitivity) with an anion-exchange column (IonPac AS4A-SC), a micro-membrane suppressor (AMMS II), and an isocratic high-pressure pump system were successfully used for detecting low concentrations of inorganic anions. Method detection limits for the anions of interest were <0.184 mg/L. Details of the IC methodology as well as some experimental results obtained during its application for the chemical monitoring of geothermal steam pipes are also described.

Continuous measurement of hydrogen chloride evolved during thermal degradation of poly vinyl chloride.

Poly vinyl chloride (PVC) is easily degraded and colored by heating through dehydrochlorination and formation of a polyene structure. The measurement of evolved hydrogen chloride is the most suitable method for evaluation of the early stage of degradation. An apparatus is described for the accurate, safe and reproducible measurement of hydrogen chloride evolved during the degradation of PVC. The reaction vessel is set in a GC oven. PVC is loaded into the reaction vessel using a special tool. The evolved hydrogen chloride is absorbed in distilled water. The water is pumped from the absorber to the electrical conductivity detector and returns to the absorber. Measurements of the dehydrochlorination rate showed a standard deviation of 2.3% of the mean value.

Determination of the specific surface area of silica gel by on-column titration with hydrochloric acid

Specific surface areas of silica gel packings could be determined by an on-column acid—base titration method. Silica gel materials packed in microcolumns were equilibrated with sodium hydrogencarbonate, followed by titration with hydrocloric acid. The effluents from the columns were monitored by an electrical conductivity detector and the end-points were determined from the breakthrough curves. The breakthrough volume was linearly dependent on the surface area per unit volume of the packings or on the total surface area of the column.

Microcolumn ion chromatography with conductimetric detection

A miniaturized flow cell for an electrical conductivity detector has been made and applied to the ion chromatography of inorganic anions. It consisted of stainless steel tubes (0.13 mm ID×0.31 mm OD) and PTFE tubes (0.25 mm ID×2 mm OD). The detection limit for chloride at S/N=3 was 36 pg or 0.33 ppm for a 0.11 μl injection.

Determination of nitrogen oxides and sulfur oxides in nitrate melts by ion chromatography.

A method for determining nitrogen oxides and sulfur oxides by ion chromatography was investigated in order to develop a method for eliminating nitrogen oxides and sulfuric oxides in stack gas using nitrate melts. A Toyo Soda IC-Anion-PW column, an electrical conductivity detector and a UV detector were used. The effect of pH and concentrations of phosphoric acid and gluconic-Borax complex on retention times were investigated for nitrite, nitrate, sulfite and sulfate ions in an aqueous solution. A solution containing 0.7mM potassium gluconate, 0.7mM Borax, 0.1mM potassium dihydrogen phosphate and EDTA (1.5mM/l) adjusted to pH 7.4 with boric acid was found to be an optimum eluent. Nitrous acid, sulfurous acid and sulfuric acid in nitrate melts containing abundant ions of nitric acid were determined by this method.

Complementary analytical methods for cyanide, sulphide, certain transition metals and lanthanides in ion chromatography

Conventional ion chromatography excludes the analyses of anionic species with pK > 7, and transition metals that can form hydroxide precipitates at neutral pH. These limitations come from the combined characteristics of the suppressor column and the electrical conductivity detector. By suitable selection of the detection system, an extension of analytical limits can be achieved. For fast and accurate analyses of cyanide and sulphide ions, with an electrochemical method involving a silver sulphide based ion-selective electrode and a high pH buffered eluent, the detection limit can reach the p.p.b. level. For determinations of transition and rare earth metal ions, a spectrophotometric detection system is proposed. By post-column mixing with the colour-forming reagents PAR and Arsenazo I, respectively, transition metal and rare earth metal ions can be monitored by measuring the absorbance at 498 and 600 nm. The detection limit can reach the 0.1 p.p.m. level with good precision. The working principle and reaction mechanism of the proposed methods are also discussed in detail.

Capillary column gas chromatography with sulphur- and nitrogen-specific Hall detectors for determination of kinetics of hydroprocessing reactions of individual compounds in coal-liquid fractions

Fractions of a coal-derived liquid were prepared by preparative liquid chromatography and used as feeds to a high-pressure flow reactor, where they underwent hydroprocessing reactions catalysed by sulphided Ni Mo/ γ Al 2 O 3 . The feeds and products were characterized by capillary-column gas chromatography with a flame ionization detector and a Hall electrical conductivity detector, the latter being sulphur- or nitrogen-specific. The results were used to determine quantitative kinetics of the hydroprocessing reactions of individual compounds in the coal-derived liquids under the conditions of potential industrial processes.

Single-column ion chromatography for the determination of chloride and sulfate in steam condensate and boiler feed water

An effective analytical method is described for determination of parts-per-billion concentrations of chloride and sulfate in very pure water such as steam condensates. Sample anions are concentrated on a short precolumn, separated on an anion-exchange column of very low capacity, and detected by an electrical conductivity detector placed immediately after the separation column. No suppressor column is employed. Chloride and sulfate can be determined at concentrations as low as 1 to 2 ppB in the water samples. Several real water samples have been analyzed successfully by the new procedure.

An electrical conductivity detector for paper, thin-layer and column chromatography

An electrical conductivity detector has been developed for application to the paper, thin-layer and column chromatography of ionic substances.Two arms of an a.c. Wheatstone bridge comprise two pairs of electrodes applied directly on to the separating layer so that a signal ensues from the bridge when a chromatographic spot passes one electrode pair while the other pair is traversed by the eluting agent. The sensitivity is about 1 µg and the precision is about 2 to 3 per cent.