Showing papers by "Purnendu K. Dasgupta published in 1991"
TL;DR: In this article, four designs of a wet denuder are described, and performance data for one design coupled to an ion chromatograph are presented, which permits efficient removal of soluble gases for their determination at sub-ppbv levels.
Abstract: Four designs of a wet denuder are described, and performance data for one design coupled to an ion chromatograph are presented. The system permits efficient removal of soluble gases for their determination at sub-ppbv levels
78 citations
TL;DR: In this paper, a diffusion scrubber based automated instrument was used to measure HONO utilizing ion chromatography and UV detection with time resolutions of 7-15 min and a detection limit of ca. 20 pptv.
Abstract: A diffusion scrubber based automated instrument measures HONO utilizing ion chromatography and UV detection with time resolutions of 7-15 min and a detection limit of ca. 20 pptv. The thermodynamic equilibrium of NH{sub 3}(g) and HONO(g) over NH{sub 4}NO{sub 2}(s) can be described by ln (p{sub HONO}, atm) = {minus}8,018 {plus minus} 84/T + 16.81 {plus minus} 0.30 and provides a convenient and reliable source for HONO(g) free from major contamination with NO{sub x}. Ambient measurement data for Lubbock, TX, are presented. Persistent daytime concentrations of HONO in the 100-500 pptv range, weekday morning peak concentrations up to 1 ppbv following peak traffic hours, and typical nighttime peak concentrations between 1 and 2 ppbv are observed.
70 citations
67 citations
TL;DR: A membrane-based electrochemical approach for the in situ production of ultrapure ionic substances has been developed with specific reference to the production of NaOH solutions and their use in ion chromatography.
Abstract: A membrane-based electrochemical approach for the in situ production of ultrapure ionic substances has been developed. This is illustrated with specific reference to the production of NaOH solutions and their use in ion chromatography. Two basic types of generators are described. In the first, a current-efficient single-membrane device generates a stream of NaOH and H 2 . This stream is degassed by a membrane-degasser en route to the chromatographic pump. In the second type, multiple membranes are used and the product NaOH channel does not contain gas. The product purity is excellent ― an electrodialytic membrane suppressor (EMS) produces a typical exchanged conductance of 340±40 nS/cm for 0-175 mM NaOH
63 citations
TL;DR: In this article, chemical reactivities, ptta differences, and differing volatilities of S-containing acids permit selective determinations in four conjoined but independant FIA schemes.
Abstract: Chemical reactivities, ptta differences, and differing volatilities of S-containing acids permit selective determinations in four conjoined but independant FIA schemes
58 citations
TL;DR: In this paper, a mechanism for the photomediated reaction involving an aryloxy radical derived from the substrate is suggested, which is the same as that formed in the peroxidase enzyme-mediated H2O2 oxidation of HPA.
44 citations
TL;DR: In this article, an approach to generating high purity NaOH solutions in a continuous flow system by electrodialytic means is described, and the generated product is at least an order of magnitude purer in terms of carbonate contamination relative to the feed NaOH solution.
25 citations
Patent•
04 Oct 1991TL;DR: In this article, a miniature ion chromatography membrane suppressor was added to the outlet end of the capillary tube to reduce the electrical conductivity of the buffer to produce a suppressed buffer.
Abstract: Improved capillary electrophoresis apparatus of the type that generally includes a capillary tube, the capillary tube having a sample inlet end and an outlet end, a first electrode in electrical communication with the inlet end of the capillary tube, a second electrode in electrical communication with the outlet end of the capillary tube and a high voltage power supply in electrical communication with the first and second electrodes. The improvement is to connect a miniature Ion Chromatography membrane suppressor to the outlet end of the capillary tube, to connect a conductivity detector to the membrane suppressor and to place the second electrode in the regenerant compartment of the membrane suppressor. The method embodiment of the invention for anion analysis includes the steps of: (a) separating anions of interest by capillary electrophoresis in a buffer solution; (b) exchanging cations of the buffer for regenerant cations using an ion chromatography membrane suppressor to reduce the electrical conductivity of the buffer to produce a suppressed buffer; and (c) measuring the electrical conductivity of the suppressed buffer to determine the separated anions. Similarly, the method embodiment of the invention for cation analysis includes the steps of: (a) separating cations of interest by capillary electrophoresis in a buffer solution; (b) exchanging anions of the buffer for regenerant anions using a stationary means for exchanging anions thereby reducing the electrical conductivity of the buffer to produce a suppressed buffer; and (c) measuring the electrical conductivity of the suppressed buffer to determine the separated cations.
24 citations
TL;DR: In this paper, a simultaneous cation/anion exchange scheme is proposed where the effluent eluite acids from a suppressed anion chromatography system proceed through the annular channel of a dual membrane converter device composed of an anion and a cation-exchange membrane tube.
Abstract: A simultaneous cation/anion-exchange scheme is proposed where the effluent eluite acids from a suppressed anion chromatography system proceed through the annular channel of a dual membrane converter device composed of an anion and a cation-exchange membrane tube. The optimum regenerants consist of LiF doped with LiOH for the cation side and LiF doped with HF (or NH[sub 4]HF[sub 2]) for the anion side. Sensitivity to very weak acids is far better than detection in the suppressed mode and is also improved markedly over a previously described system involving sequential ion exchange to NaOH. A model is presented for the process, and qualitative agreement to the experimental data is established. The two-dimensional information permits the estimation of the pK[sub a] of unknown eluites. 15 refs., 7 figs., 1 tab.
22 citations
TL;DR: Particle deposition characteristics of several diffusion scrubber (DS) designs of annular geometry were studied and a straight inlet geometry was selected for further performance evaluation as mentioned in this paper, and extensive performance tests were made with the new geometry DS; Nafion® membrane based DS devices are recommended for the measurement of H2O2 and HCHO.
22 citations
TL;DR: Good agreements with ASTM procedures are shown for a variety of test compounds, lake water, wastewater and urine samples, and the method is tolerant of variations in salinity of the sample.
TL;DR: An increase in effective ion exchange capacity also appears to occur in the presence of the field, and this effects are ascribed to the greater kinetic energy of the ions exposed to the alternating field and thus to the higher effective thermodynamic temperature the ions experience.
Abstract: Transport of permitted and Donnas-forbidden ions as well as neutral solutes through ion exchange membranes have been investigated in continuous flow-through configurations in the presence and absence of an alternating electrical field (0.05–100 kHz, 0–40 V p-p). There is no discernible effect on the transport rate of forbidden ions and neutral solutes but very significant increases in steady state transmembrane transport occur for permitted ions. At least for cation exchangers, an increase in effective ion exchange capacity also appears to occur in the presence of the field. These effects are ascribed to the greater kinetic energy of the ions exposed to the alternating field and thus to the higher effective thermodynamic temperature the ions experience.