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Biomedical subjects

Purnendu K Dasgupta

Publications and source records attributed to Purnendu K Dasgupta.

6 recordsLinked to original sources
PubMed2003

Pulsed excitation source multiplexed fluorometry for the simultaneous measurement of multiple analytes. Continuous measurement of atmospheric hydrogen peroxide and methyl hydroperoxide.

Presently, solid-state sources such as light-emitting diodes (LEDs) provide for intense, nearly monochromatic light. They are available over a broad range of emission wavelengths. Unlike incandescent and discharge lamps, LEDs can be turned on and off at high speeds. The resulting light pulses are highly reproducible. This allows the use of a single photomultiplier tube (PMT), often the most expensive component in a high-sensitivity measurement system, as a multiplexed detector with multiple, fiber-optic-coupled, fluorescence-detection cells excited by solid-state sources. A time resolution of 1 min is adequate in many continuous detection schemes. This enables multiple-channel single-detector multiplexed measurement without any loss of S/N. On the basis of this principle, we describe a new automated continuous instrument for the simultaneous measurement of atmospheric hydrogen peroxide and methyl hydroperoxide (MHP). A Nafion membrane diffusion scrubber (DS) is used with hematin-catalyzed oxidation of thiamine to thiochrome for the measurement of H2O2, and an expanded poly(tetrafluoroethylene) (ePTFE) DS is used with a H2O2 destruction catalyst and horseradish peroxidase-catalyzed oxidation of thiamine to thiochrome for the measurement of MHP. The respective limits of detection are 25 pptv and 15 pptv. Design, performance details, and illustrative results from a field campaign (Philadelphia NEO3PS study, 2001) are presented.

Journal Article↗
PubMed2003

Determination of trace perchlorate in high-salinity water samples by ion chromatography with on-line preconcentration and preelution.

A simple, automated system for the determination of trace perchlorate by ion chromatography (IC) with an online preconcentration technique is reported. The sample is preconcentrated, and less strongly held ions preeluted before the analyte is transferred to the principal separation system. This approach provides low limits of detection (LOD) and is particularly robust toward the effect of high concentrations of common anions, such as those present in groundwater samples. It compares favorably with currently promulgated EPA method 314.0. The LOD (S/N = 3) is 0.77 microg/L for a 2-mL reagent water sample and decreases more-or-less proportionately with increasing sample volume, at least up to 20 mL. Even with a sample of conductivity 14.7 mS/cm (approximately that of 0.1 M Na2SO4), the recovery of added perchlorate at the 25.0 microg/L level was still 92%. The concentration of added perchlorate in the range of 1-400 microg/L was linearly correlated to the peak area, with an r2 value of 0.9997. The recovery of perchlorate from artificial samples with different conductivity by the present method compares favorably with those from the currently recommended EPA Method. The ability of this approach to remove matrix interferences suggests that it would be also promising for perchlorate analysis in other challenging samples.

Fresh Water↗
PubMed2003

Selective measurement of gaseous hydrogen peroxide with light emitting diode-based liquid-core waveguide absorbance detector.

Atmospheric H2O2 is typically determined by enzymatically mediated fluorogenic reactions that do not discriminate between H2O2 and organic peroxides. Reactions of Ti(IV) with H2O2 has also been the basis of colorimetric measurements of H2O2 but is too insensitive. A more sensitive determination is possible with the Ti(IV)-4-(2-pyridylazo)resorcinol (PAR) complex, however, unreacted PAR must be chromatographically separated. A titanium(IV)porphyrin complex, oxo[5,10,15,20-tetra(4-pyridyl)porphyrinato]titanium(IV) [TiO(tpypH4)4+], (TiTPyP) was introduced for the measurement of aqueous H2O2. In this paper, we show that TiTPyP can be used for measuring H2O2(g)), it does not respond to CH3HO2. With a proper membrane collector, practically there is no interference from concurrently present gaseous SO2 and O3. The approach permits a S/N = 3 limit of detection (LOD) of 26 pptv with a 50 mm path liquid core waveguide (LCW) absorbance detector and a light emitting diode based light source. This is adequate for real atmospheric measurements.

Journal Article↗
PubMed2002

Microscale continuous ion exchanger.

A microscale continuous ion exchanger based on two liquid streams flowing in parallel is presented. The ion exchange reaction occurs through diffusional transfer of molecules between the ion exchanger phase and the eluent phase and is applied for conductivity suppression. Two approaches are demonstrated. In the first approach, a liquid ion exchanger (i.e. a strongly basic compound, e.g., tetraoctylammonium hydroxide, or a secondary amine, e.g., Amberlite IA-2) is dissolved in an organic solvent immiscible with the aqueous eluent. The system allows for sensitive suppressed conductivity detection of various inorganic cations. When the weakly basic secondary amine is used, conductometric detection of heavy metals is possible. In the second approach, a suspension of finely ground ion-exchange resin is used as the ion exchanger phase. In this case, the suspension need not involve an organic solvent. Theoretical models and computations are presented along with experimental results. The potential of such a system as a chip-scale post-separation suppressor/reactor is evident.

Cations↗
PubMed2002

Oxygen-independent poly(dimethylsiloxane)-based carbon-paste glucose biosensors.

Several silicone oils have been assessed and compared as an internal source of oxygen in connection to their use as binders for carbon-paste glucose biosensors. All four poly(dimethylsiloxane) (PDMS) oils tested a dramatic increase in the oxygen capacity of carbon-paste enzyme electrodes to allow convenient biosensing under severe oxygen-deficit conditions. The resulting oxygen independence is better than that exerted by perfluorocarbon binders or that displayed by mediator-based bioelectrodes. The resistance to oxygen effects is indicated from the identical response (observed in the presence and absence of oxygen) up to 2 x 10(-2) M glucose and the slight (12%) sensitivity loss at 4 x 10(-2) M. The influence of the viscosity of the PDMS binder upon the internal oxygen supply is examined. The PDMS carbon-paste enzyme electrode displays a stable glucose response over prolonged (15 h) operation in an oxygen-free solution. On-line continuous testing indicates favorable dynamic properties with no carry-over effects over the physiological and pathophysiological range (3-12 mM glucose).

Biosensing Techniques↗