Showing papers by "Purnendu K. Dasgupta published in 1994"

Electroosmosis: A reliable fluid propulsion system for flow injection analysis

Abstract: An electroosmosis based fluid propulsion system is described. The electroosmotic pump, operating in a high electric field, is isolated from other components by a grounding joint that is electrically conductive and permits the pumped fluid to be hydrodynamically coupled to contents downstream without leakage. The pump was used in single- and double-line flow injection analysis (FIA) systems. The determinations of chloride and iron(III) are discussed as representative examples. The experimental results shows excellent reproducibilities (relative standard deviation 0.4-0.8%), reflecting the stability and the reliability of the pump. The system can also be operated in a hybrid manner

Continuous automated determination of atmospheric formaldehyde at the parts per trillion level

Abstract: 1,3-Cyclohexanedione was used for automated near real-time fluorometric determination of atmospheric formaldehyde. Although previous literature reports indicate this reagent to be nonselective, adaptation of a fast flow injection technique that does not rely on the completion of the reaction provided a method with a selectivity factor of >300 for HCHO over its nearest congener, CH 3 CHO. The system was optimized with respect to the reagent and scrubber liquid composition, reaction temperature, and pH. The limit of detection (LOD) in the aqueous phase is ∼6 nM (180 ng/L) HCHO for a 45-μL sample (270 fmol) with the linear dynamic range spanning >3 orders of magnitude, up to at least 14 μM

Computer-Interfaced Bipolar Pulse Conductivity Detector for Capillary Systems

Abstract: Conductivity detectors sufficiently small for deployment in capillary analytical systems can be fabricated very simply and reproducibly from commonly available micro assemblies of multiconductor ribbons. It results in a unique geometry for the conductivity detection cell where the fluid does not flow between the electrodes. Interface circuitry for a personal computer (PC)-based bipolar pulse conductance detector is described. The cell can be used with this or commercial detectors. Results obtained with the new cell and electronic design in a suppressed conductometric capillary electrophoresis separation system are presented

Indoor Nitrous Acid Levels. Production of Nitrous Acid from Open-Flame Sources

Abstract: The concentrations of HONO in indoor atmospheres are clearly correlated with open flame sources (e.g., hydrocarbon fuel fired heaters, stoves, etc.). Relatively high levels, 20–90 ppbv, were encountered in a number of sampling sites. The half-life of HONO in a typical indoor environment appears to range from 2 to 8 h.

Auxiliary electroosmotic pumping in capillary electrophoresis

Abstract: Following a conventional capillary electrophoresis system with an optical detector, a conductive membrane can be used to connect a second capillary, the terminal end of which is connected to a second power supply, the membrane serving as the common ground for both high-voltage sources. The direction and magnitude of the field applied to the second capillary govern in the bulk flow in the first capillary is augmented, inhibited, or unaffected by the pumping action exerted by the second capillary. The majority of CE applications involve samples of ionic strength lower than that of the running electrolyte and optimum sample stacking is desirable

Measurement of Carbonyl Compounds as the 2,4-Dinitrophenylhydrazonate Anion. Reaction Mechanism and an Automated Measurement System

Abstract: The standard procedure for determining carbonyl compounds involves the addition of strong caustic alkali to 2,4-dinitrophenylhydrazones formed upon the reaction of carbonyl compounds with 2,4-dinitrophenylhydrazine (DNPH) 1 In strong base, the hydrazones form a dark red anion of quinonoid structure, 2 while the corresponding product from the unreacted DNPH decomposes rapidly, resulting in a low blank The mechanism of this decomposition has never been clearly understood In this work, we describe a photometric flow injection analyzer for the automated measurement of the carbonyl content of alcohol ethoxylate samples A detailed study of the mechanism of the alkatine decomposition is reported

Methods for chromatography analysis.

Abstract: A method for normalizing variabilities between chromatograms (electropherograms) of standard and sample chromatography (capillary electrophoresis) runs, where the detection method utilized results in a change in the detector output as a result of a difference between the sample diluent and the system running buffer (water dip), said method comprises using the relationship between the area (migration time) of the water dips of the standard run and the sample runs to correlate the sample concentration (electrophoretic mobility) with the standard concentration (electrophoretic mobility).

Sequential ion chromatography and conversion system

Abstract: Apparatus and method for ion chromatography having a chromatography column (10) followed by a suppressor (11) for converting the eluent electrolyte to weakly ionized form and converting analyte ions to acid or base form. First detection of analyte ions occurs in a first conductivity detector (12) followed by conversion of the analyte ions in acid or base form to salt form in a salt converter and subsequent detection in a second conductivity detector (32). Comparison of signals from the two detectors (12, 32) provides additional information about the analytes.

Method and apparatus for chromatography analysis

Abstract: not available for EP0646239Abstract of corresponding document: US5316630A method is described for the normalization and standardization of variabilities of electropherograms obtained with conductometric capillary electrophoresis. The variabilities may be associated with differences in the sample injection volume between two or more runs. Alternatively, the variabilities may be associated with alterations in the electroosmotic flow velocity of two or more runs.