Showing papers by "Purnendu K. Dasgupta published in 1988"

Comparison of techniques for measurement of ambient levels of hydrogen peroxide.

Abstract: A study was conducted to measure hydrogen peroxide from three sources: (1) zero air in the presence and absence of common interferences, (2) steady-state irradiations of hydrocarbon/NO/sub x/ mixtures, and (3) ambient air. The techniques employed for measuring H/sub 2/O/sub 2/ included infrared absorption from a diode laser, fluorescence from an enzymatically produced complex, and chemiluminescence from reaction with luminol. The measurements were conducted simultaneously from a common manifold. Four systems, each of which utilized one of the above techniques, were compared with respect to sensitivity, selectivity, and dynamic range in measuring H/sub 2/O/sub 2/ concentrations ranging from 0.062 to 128 ppbv. For pure samples measured in zero air, agreement of 14-23% was achieved when compared to standard values. In these examples, there was no indication of interferences for an H/sub 2/O/sub 2/ level of 6 ppbv except in the luminol technique where a negative interference was caused by SO/sub 2/. Agreement among techniques was much worse for measurement of H/sub 2/O/sub 2/ produced in the photochemical mixtures. In these mixtures, significant concentrations of organic peroxide were also measured by the enzymatic techniques.

Apparatus and method for automated microbatch reaction

Abstract: Apparatus and method for automatic microbatch reaction including a reactor having a reaction chamber, such as a 1.5 milliliter plastic centrifuge tube having a conical bottom. An automatically actuated injection valve is used to inject less than 1 milliliter of a sample into the reaction chamber. One or more automatically actuated reagent valves are used to introduce respective pressurized reagents into the reaction chamber to process the sample. The volume of the reagent(s) introduced into the reaction chamber is less than 1 milliliter and controlled by the on time of the respective reagent valve. The automatically actuated valves are controlled by a computer based timer. A sensor positioned in the chamber, such as a pH electrode, can be used to analyze the processed sample in place or the processed sample can be analyzed by flowing it from the reaction chamber through a flow-through detector, such as a flow-through spectrophotometer.

Novel automated micro batch analyzer

Abstract: An automated micro batch analyzer (AMBA) system is described. The sample is introduced into an air‐tight reaction chamber (a polypropylene microcentrifuge tube) by a loop injector made from two three‐way valves by flowing gas. Reagents/diluents are introduced into the chamber from pneumatically pressurized reservoirs provided with on‐off valves. A microprocessor‐controlled timer controls valve status and thus provides control of delivered volumes. Gas bubbles are introduced through the bottom of the chamber to perform mixing; the mixed liquid is then discharged into an optical detector via a bubble gate by superincumbent pressure. The bubble gate allows the data‐acquisition system to collect data only when liquid is actually in the detection cell. For simple fast reactions, throughput rates of 210 samples/h could be obtained.

Apparatus for preventing undissolved alloying ingredient from entering continuous casting mold

Abstract: Molten steel containing an undissolved alloying ingredient denser than molten steel (e.g. Pb and/or Bi) flows from a tundish to a continuous casting mold. Various expedients are employed to prevent large globules of undissolved alloying ingredient from flowing out of the tundish into the mold. Another expedient prevents large quantities of undissolved alloying ingredient from accumulating on the bottom of the tundish.

Chelating Fluorogenic Surfactants For The Trace Detection Of Metals

Abstract: Four 7-alkyl-8-hydroxyquinoline-5 sulfonates were synthesized with the alkyl chain containing 6 to 12 carbon atoms. These compounds behave as Zwitterionic surfactants in neutral solution and as anionic surfactants in alkaline solution. More importantly, the o-hydroxyquinoline functionality is a versatile chelating group. Of the many metal complexes that it forms, several are fluorescent. Micellar media frequently have great effects on fluorescence properties; this is the first time fluorescence properties of such systems have been studied in conjunction with surfactant properties such as critical micelle concentration, etc. for systematically engineered lengths of the hydrocarbon tail.