Showing papers by "Purnendu K. Dasgupta published in 2009"
TL;DR: This work demonstrates the use of bare and hydroxypropylcellulose coated open tubular nanocapillaries for protein separations and achieves baseline resolution for a protein mixture consisting of transferrin, alpha-lactalbumin, insulin, and alpha-2-macroglobulin.
Abstract: We have recently examined the potential of bare nanocapillaries for free solution DNA separations and demonstrated efficiencies exceeding 106 theoretical plates/m. In the present work, we demonstrate the use of bare and hydroxypropylcellulose (HPC) coated open tubular nanocapillaries for protein separations. Using 1.5 μm inner diameter (i.d.) capillary columns, hydrodynamically injecting femto- to picoliter volumes of fluorescent or fluorescent dye labeled protein samples, utilizing a pneumatically pressurized chamber containing 1.0 mM sodium tetraborate solution eluent (typically 200 psi) as the pump, and performing on-column detection using a simple laser-induced fluorescence detector, we demonstrate efficiencies of close to a million theoretical plates/m while generating single digit microliter volumes of waste for a complete chromatographic run. We achieve baseline resolution for a protein mixture consisting of transferrin, α-lactalbumin, insulin, and α-2-macroglobulin.
48 citations
TL;DR: While it is found that the removal of the developed color can be accelerated by simultaneous heating and suction, permitting the reuse of the same sensing area multiple times, it is also observed that the sensitivity gradually decreased.
44 citations
TL;DR: Under operating conditions, arsenobetaine (AsB), until now regarded to be inert, also generates a hydride (albeit the response is only approximately 7% of others), and the limit of detection (LOD) based on three times the standard deviation of the blank with this technique for AsB, DMA, As(III), MMA, and As(V) is 90, 66, 63, 63 and 63 pg As, respectively.
Abstract: An automated hydride generation (AHG) interface to inductive coupled plasma mass spectroscopy (ICPMS) was developed for measuring arsenic in environmental samples. This technique provides statistically indistinguishable response slopes (within about 3%) for hydride generation-ICPMS (HG-ICPMS) analysis of all major As species, inorganic As(III), dimethylarsinic acid (DMA), monomethylarsonic acid (MMA), and inorganic As(V); this has not previously been achieved. Previously, sample pretreatment to convert all forms of As into As(V) has been a prerequisite for measuring total arsenic in complex matrices. Under our operating conditions, arsenobetaine (AsB), until now regarded to be inert, also generates a hydride (albeit the response is only approximately 7% of others). The limit of detection (LOD) based on three times the standard deviation of the blank with this technique for AsB, DMA, As(III), MMA, and As(V) is 90, 66, 63, 63, and 63 pg As, respectively. This AHG-ICPMS technique was compared with a flow injection-UV photolysis-HG-ICPMS (FI-UV-ICPMS) and liquid chromatography-UV-HG-ICPMS analysis of arsenic content in National Institute of Standards & Technology (NIST) standard rice flour (standard reference material: SRM 1568a) and rice samples collected from West Bengal, India. Both oxidative acid digestion and methanol:water (1:1) extraction were used. The analytical results for total As in the SRM 1568a digest were 99.2 +/- 0.6 and 100.2 +/- 0.8% of the certified value (290 +/- 3 microg As/kg) by the AHG-ICPMS and the FI-UV-HG-ICPMS techniques, respectively. For rice extracts and the digests, the two techniques provided results that were correlated with linear r2 values of 0.9988 and 0.9987 with intercepts statistically indistinguishable from zero. Chromatographic analysis indicated that As in these rice samples were 75-90% inorganic.
41 citations
TL;DR: The developed system allows rapid, simple, cost-effective, and robust creatinine analysis and is suitable for the analysis of large numbers of urine samples.
41 citations
TL;DR: Live HeLa cells immobilized on Sephadex G-50 beads were used as a medium for the preconcentration and speciation of inorganic arsenic and the procedure was validated by arsenic speciation in certified reference river water.
Abstract: Live HeLa cells immobilized on Sephadex G-50 beads were used as a medium for the preconcentration and speciation of inorganic arsenic. The sorption of arsenic species by live HeLa cells involves both surface uptake and bioaccumulation within the cells. At pH 3.0, the cells accumulate arsenate with high specificity over arsenite: 83.0 ± 1.3% of the arsenate was sorbed while the retention of arsenite was negligible at 2.1 ± 0.6%. The speciation of inorganic arsenic could thus be performed by direct determination of arsenate followed by quantifying total inorganic arsenic after conversion of arsenite to arsenate. We formed a disposable live cell preconcentration microcolumn with the live HeLa cells immobilized on Sephadex G-50 beads. After the sample was passed through the column for sorption to occur, the cells and any retained arsenate were stripped with 2 M HNO3. The arsenic in the 30 μL eluate was directly measured by graphite furnace atomic absorption spectrometry. A new microcolumn was used for each sa...
37 citations
TL;DR: A novel optical sensor for the simultaneous measurement of atmospheric nitrogen dioxide, ozone, and relative humidity, using a transparent backing thin layer silica gel chromatographic plate impregnated with 8-amino-1-naphthol-5-sulfonic acid as the collection/sensor element is described.
Abstract: We describe a novel optical sensor for the simultaneous measurement of atmospheric nitrogen dioxide (NO2), ozone (O3), and relative humidity (RH). A transparent backing thin layer silica gel chromatographic plate impregnated with 8-amino-1-naphthol-5-sulfonic acid (ANS) is used as the collection/sensor element. The plate transmittance is probed by three discrete light emitting diodes (LEDs) centered, respectively, at 442, 525, and 850 nm. The transmission of the plate changes reversibly across visible to NIR wavelengths as the RH around the plate changes; this is the basis for a limited-resolution RH sensor. The ANS on the plate reacts to form brown and pink colored products, respectively, when it reacts with NO2 and O3. The sample air impinges on the plate via an entrance nozzle. The LEDs are alternately turned on in a preprogrammed manner and the light is brought to the impregnated face of the plate by a three-legged fiber optic. The transmitted light is detected on the obverse side of the plate. The 85...
35 citations
TL;DR: A simple method for the rapid fabrication of nanoporous materials from colloidal dispersions of Polymethyl Silsesquioxane nanoparticles is described and the entropic gain experienced by the nanoparticles in this rubric is harnessed to fabricate novel highly porous films composed of nanoparticles.
Abstract: Nanoporous materials have become indispensable in many fields ranging from photonics, catalysis and semiconductor processing to biosensor infrastructure. Rapid and energy efficient process fabrication of these materials is, however, nontrivial. In this communication, we describe a simple method for the rapid fabrication of these materials from colloidal dispersions of Polymethyl Silsesquioxane nanoparticles. Nanoparticle–polymer composites above the decomposition temperature of the polymer are examined and the entropic gain experienced by the nanoparticles in this rubric is harnessed to fabricate novel highly porous films composed of nanoparticles. Optically smooth, hydrophobic films with low refractive indices (as low as 1.048) and high surface areas (as high as 1325 m2 g−1) have been achieved with this approach. In this communication we address the behavior of such systems that are both temperature and substrate surface energy dependent. The method is applicable, in principle, to a variety of nanoparticle–polymer systems to fabricate custom nanoporous materials.
32 citations
TL;DR: The results showed that 12 of 13 infants did not have an adequate intake of iodine as defined by the Institute of Medicine and 9 out of13 infants were likely ingesting perchlorate at a level exceeding the reference dose suggested by the National Academy of Science panel.
Abstract: Perchlorate, thiocyanate, and iodine excretion in urine and milk of 13 breastfeeding women was investigated and the results were interpreted by a model of parallel/competitive transport of these species bythe sodium iodide symporter. For each species i, we assumed physiological homeostasis, where i(T,in) equals the corresponding total excretion in urine and milk (i(e,u) + i(e,m)). The fraction of the total excretion that appeared in milk f(I,m) was measured and ranged from 0.394-0.781, 0.018-0.144, and 0.086-0.464 for perchlorate,thiocyanate, and iodine, respectively. The corresponding median values were 0.541, 0.053, and 0.177, respectively. The selectivity factors of perchlorate over iodide transport, and thiocyanate over iodide transport, defined as f(PC,m)/ f(I,m), and f(SCN,m)/ f(I,m), respectively, were 3.14 +/- 1.20 and 0.27 +/- 0.26 while PC(T,in), SCN(T,in), and I(T,in) among individuals varied 4.9, 5.0, and 8.4x, respectively. These transport selectivities are an order of magnitude lower than those indicated by in vitro studies, suggesting that the impact of both these anions on inhibiting iodide transport in milk may have been overestimated in the extant literature. On the other hand, our results showed that 12 of 13 infants did not have an adequate intake of iodine as defined by the Institute of Medicine and 9 out of 13 infants were likely ingesting perchlorate at a level exceeding the reference dose suggested bythe National Academy of Science panel.
28 citations
TL;DR: Recovery of iodine was found to be markedly low when IC-MS/MS was used without an internal standard, and recovery was similarly low using (35)Cl(18)O(4) as aninternal standard for milk and unpredictable when used for urine.
27 citations
Patent•
17 Feb 2009TL;DR: In this paper, the authors present an ion transfer device with a signal detector in communication with the electrodes of the transfer device, and a combination ion transfer devices/electrolyte generator.
Abstract: Apparatus and method for detecting current or potential generated in a liquid sample suitable for use in a chromatography or other liquid sample analytical system. One embodiment is an electrolytic ion transfer device with a signal detector in communication with the electrodes of the transfer device. Another is a combination ion transfer device/electrolyte generator. Another substitutes a detector for the ion transfer device in the combination.
26 citations
TL;DR: A multifunctional electrodialytic generator for capillary ion chromatography (CIC) is described, which ensures the production of gas-free eluent, obviating the need of a gas removal device used with single ion exchanger EDG's.
TL;DR: The sensor combines the dual functions of gas collection and measurement, thus permitting a simple miniature economic device to be applied to the determination of TOC in water samples where the analyte carbon was oxidized to CO(2) by UV/persulfate.
TL;DR: An electroosmotic pump that utilizes a cation exchange resin bead as the electric field decoupler is described, which serves as a electrical grounding joint without fluid leakage, thus eliminating electrolytic gas interference from the flow channels.
Abstract: We describe an electroosmotic pump (EOP) that utilizes a cation exchange resin bead as the electric field decoupler. The resin bead serves as a electrical grounding joint without fluid leakage, thus eliminating electrolytic gas interference from the flow channels. The arrangement is easy to practice from readily available components, displays a very low electrical resistance, and is capable of bearing high backpressure (at least 3200 psi). We use a silica xerogel column as the EOP element to pump water and demonstrate a complete capillary ion chromatograph (CIC), which uses a similar bead based microelectrodialytic generator (μ-EDG) to generate a KOH eluent from the pumped water. We observed good operational stability of the complete arrangement over long periods.
TL;DR: There is little consciousness that even many developed nations are putting future generations in peril with vulnerable populations that are barely iodine sufficient, whether or not there is any excessive perchlorate intake.
Abstract: Environmental context. Depending on its severity, inadequate iodine nutrition can lead from minor developmental disorders all the way to cretinism. In recent years, the omnipresence of environmental perchlorate, a potent iodine transport inhibitor, has been much in the news but the ultimate issue of iodine nutrition has largely been ignored. There is little consciousness that even many developed nations are putting future generations in peril with vulnerable populations that are barely iodine sufficient, whether or not there is any excessive perchlorate intake.