Showing papers by "Purnendu K. Dasgupta published in 2017"
TL;DR: The ITD separation was effective for matrix isolation and reduction of interferences, and potential cationic interferences were not transferred into the anionic Cr(VI) acceptor stream.
22 citations
TL;DR: In this article, a permeative amine/acid introduction device (PAID) is placed after a conventional KOH eluent suppressed conductometric anion chromatography (SCAC) system, which converts the suppressed eluites from the acid form to the corresponding salt.
Abstract: A permeative amine/acid introduction device (PAID) is placed after a conventional KOH eluent suppressed conductometric anion chromatography (SCAC) system. The PAID converts the suppressed eluites from the acid form to the corresponding salt. For example, when the analytes are acids, they are converted to the corresponding ammonium salt (NR 2 H + Hex → NR 2 H 2 + + X - ) and allows very weak acids HX (pK a ≥ 7.0) that cannot normally be detected by SCAC to be measured by a second conductivity detector following the PAID. Permeative reagent introduction is dilutionless, can be operated without pumps and provides good mixing with low band dispersion (as small as 30 µL). An exemplary amine is diethylamine (DEA), which was chosen as the amine source due to its low pK b value (pK b 3.0), high vapor pressure, and low toxicity and low odor.
15 citations
TL;DR: A width-based quantitation (WBQ) paradigm complementing height or area based approaches can offer superior overall performance compared to area- or height-based linear regression methods, rivaling weighted linear regression, provided that response is uniform near the height used for width measurement.
Abstract: Height- and area-based quantitation reduce two-dimensional data to a single value. For a calibration set, there is a single height- or area-based quantitation equation. High-speed high-resolution data acquisition now permits rapid measurement of the width of a peak (Wh), at any height h (a fixed height, not a fixed fraction of the peak maximum) leading to any number of calibration curves. We propose a width-based quantitation (WBQ) paradigm complementing height or area based approaches. When the analyte response across the measurement range is not strictly linear, WBQ can offer superior overall performance (lower root-mean-square relative error over the entire range) compared to area- or height-based linear regression methods, rivaling weighted linear regression, provided that response is uniform near the height used for width measurement. To express concentration as an explicit function of width, chromatographic peaks are modeled as two different independent generalized Gaussian distribution functions, r...
12 citations
TL;DR: A novel carbonate-bicarbonate eluent generation system in which CO2 is introduced using programmable CO2 pressures across a membrane into a flowing solution of electrodialytically generated high purity KOH, which allows particular latitude in controlling elution order/time of polyprotic acid analytes.
Abstract: We introduce a novel carbonate–bicarbonate eluent generation system in which CO2 is introduced using programmable CO2 pressures across a membrane into a flowing solution of electrodialytically generated high purity KOH. Many different gradient types are possible, including situations where gradients are run both on the [KOH] and the CO2 pressure. The system is more versatile than current electrodialytic carbonate eluent generators and can easily generate significantly higher eluent concentrations (at least to 40 mM carbonate), paving the way for future higher capacity columns. Demonstrably purer carbonate–bicarbonate eluent systems are possible compared to manually prepared carbonate–bicarbonate eluents and with considerable savings in time. Performance in different modes is examined. The dissolved CO2 is removed by a carbon dioxide removal device prior to detection. Best case noise levels are within a factor of 2–3 of best case suppressed hydroxide eluent operation. The eluent system allows particular la...
10 citations
TL;DR: In this paper, the authors focus on situations where WBQ is effective while height/area-based linear calibrations fail, e.g., when the detector is in a nonlinear response region, the data system is saturated, causing clipping/truncation of the signal, or the detector signal is not a single-valued function of concentration, as when a fluorescence signal goes into the self-quenched domain.
Abstract: The preceding paper (Anal. Chem. 2017, 10.1021/acs.analchem.6b04857) introduced width-based quantitation (WBQ). The present paper focuses on (1) situations where WBQ is effective while height/area-based linear calibrations fail, e.g., when (a) the detector is in a nonlinear response region, (b) the detector/data system is saturated, causing clipping/truncation of the signal, or (c) the detector signal is not a single-valued function of concentration, as when a fluorescence signal goes into the self-quenched domain. (2) Utilization of WBQ in postcolumn reagent addition methods where the reagent produces a significant detector background. WBQ can minimize added reagent without sacrificing the upper determination limit; a limited reagent amount truncates peaks from high analyte concentrations but does not hamper WBQ at a low height. (3) A description of peak asymmetry via leading/trailing half-widths vs relative height (fraction of maximum height) plots. (4) A holistic description of chromatographic peaks th...
10 citations
TL;DR: The automated preparation of carbonic acid eluents at concentrations exceeding 0.15M is introduced by introducing CO2 into a flowing water stream through the walls of a Teflon AF® capillary tube under pressure and the resulting eluent concentration is controlled by varying the CO2 pressure in a programmed manner.
8 citations
TL;DR: Electromechanically scanned admittance imaging is proposed and applied to open tubular (OT) chromatography, demonstrating its applicability with both OT and commercial packed columns and exploring uniformity of retention along a column, increasing S/N by stopped-flow repeat scans, etc. as unique applications.
Abstract: Whole column detection (WCD) is as old as chromatography itself WCD requires an ability to interrogate column contents from the outside Other than the obvious case of optical detection through a transparent column, admittance (often termed contactless conductance) measurements can also sense changes in the column contents (especially ionic content) from the outside without galvanic contact with the solution We propose here electromechanically scanned admittance imaging and apply this to open tubular (OT) chromatography The detector scans across the column; the length resolution depends on the scanning velocity and the data acquisition frequency, ultimately limited by the physical step resolution (40 μm in the present setup) Precision equal to this step resolution was observed for locating an interface between two immiscible liquids inside a 21 μm capillary Mechanically, the maximum scanning speed was 100 mm/s, but at 1 kHz sampling rate and a time constant of 25 ms, the highest practical scan speed
6 citations
TL;DR: An inline system that reliably and quantitatively measures the CSF flow rate is reported, using a single thermistor to both heat the surrounding and to sense the temperature.
Abstract: In hydrocephalus, cerebrospinal fluid (CSF) builds up in the cranial cavity causing swelling of the head and potentially brain damage. A shunt to drain the fluid into a body cavity is now universally used, but failure is all too common. Techniques for ascertaining shunt failure are time-consuming, expertise-dependent, and often inconclusive. We report here an inline system that reliably and quantitatively measures the CSF flow rate. The system uses a single thermistor to both heat the surrounding and to sense the temperature. In the heating mode, the thermistor is subjected to a 5 s voltage pulse. In the sensing mode, it is part of a Wheatstone’s bridge, the output being proportional to temperature. The signal, Vi – Vf, which is the net change ΔV in the bridge output immediately before and after the heat pulse, depends both on the flow rate and the surrounding temperature. In vitro, a single equation, flow rate = 3.75 × 10–6 × ΔV(−9.568+1.088 Vi) provided good prediction for the flow rate, with 6.3% RMS r...
4 citations
Patent•
28 Nov 2017TL;DR: In this article, the authors presented a method for quantifying chromatographic peaks based on a width measurement of a peak trace at a selected height as a quantitation element, which is used for the detection of impurities in peak trace outputs.
Abstract: Systems, methods and devices are taught for providing analytical methods for peak-shaped responses separated in time or space, including quantitation of chromatographic peaks based on a width measurement of a peak trace at a selected height as a quantitation element. Methods of treating a peak trace as a composition of exponential functions representing a leading and a trailing end are included. Methods that facilitate the detection of impurities in peak trace outputs are also included.