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Biomedical subjects

P K Dasgupta

Publications and source records attributed to P K Dasgupta.

At least 19 recordsLinked to original sources
PubMed2001

Fluorometric field instrument for continuous measurement of atmospheric hydrogen sulfide.

A sensitive (limit of detection approximately <100 pptv at S/N = 3), fully automated, portable (32 x 25 x 38 cm, 4.5 kg) instrument has been designed for continuous field measurement of atmospheric hydrogen sulfide. Air is sampled by a PTFE membrane-based diffusion scrubber and collected into an aLkaline fluorescein mercuric acetate (FMA) solution flowing under a controlled and constant pneumatic pressure. The collected sulfide quenches the fluorescence that is measured with a miniature blue LED photodiode-based fluorescence detector. Acquisition and interpretation of signal and all flow control are carried out via a mininotebook personal computer (PC) using custom software written in HP-VEE. The instrument provides for self-calibration and zero functions using an on-board permeation tube enclosed in a thermostated block, at any preprogrammed desired interval. During sampling, the computed H2S concentration is stored every 2 min. The complete system, including the PC, is operated in the field by a 12-V marine battery. The system was field tested near oil field operations in West Texas and showed good correlations with a concurrently operated lead acetate tape-based commercial sampler, with a response speed and time resolution much better than that of the latter instrument.

Air Pollutants↗
PubMed2001

Two-Dimensional detection in ion chromatography: sequential conductometry after suppression and passive hydroxide introduction.

An improved method that uses sequential suppressed and nonsuppressed IC for the sensitive detection of both common anions and very weak acid anions is described. After suppressed conductometric detection of an electrolytically generated hydroxide eluent and an electrolytic suppressor, the eluent is passed into a membrane device where KOH is passively introduced into the eluent stream using Donnan forbidden leakage. A second conductivity detector then measures the conductivity of the stream. The background conductance of the second detector is typically maintained at a relatively low level of 20-30 microS/ cm. The weak acids are converted to potassium salts that are fully ionized and are detected against a low KOH background as negative peaks. The applicability of different commercially available cation exchange membranes was studied. Device configurations investigated include planar, tubular, and a filament-filled annular helical (FFAH) device. The FFAH device provided more effective mixing of the penetrated hydroxide with the eluent stream, resulting in a noise level of < or = 7 nS/cm and a band dispersion value of less than 82 microL. Optimal design and performance data are presented.

Journal Article↗
PubMed2001

Continuous automated measurement of hexavalent chromium in airborne particulate matter.

An automated continuous instrument for the collection and measurement of aerosol Cr(VI) is described. The system alternately collects the sample on one of two glass fiber filters. After 15-min sample collection on one filter, the sampling switches over to the second filter. The freshly sampled filter is washed for 8.5 min, and the washings are preconcentrated on a minicolumn packed with anion exchange resin. The washed filter is dried with filtered hot air for the next 6.5 min so that it is ready for sampling at the end of the 15-min cycle. The preconcentrated Cr(VI) on the column is eluted with 0.1 M sodium perchlorate and then reacted with sym-1,5-diphenylcarbazide prior to absorbance detection with a light emitting diode-based dedicated flow-through absorbance detector. The detection limit (S/N = 3) is 5 ng of Cr(VI)/m3, orders of magnitude lower than current regulatory requirements. The instrument operates unattended over long periods. In continuous round-the-clock operation, filter replacement frequency is every 24-72 h, depending on dust loading. The system is portable for facile field deployment and permits fully automated rapid determinations at a very low analysis cost per sample.

Aerosols↗
PubMed2000

Ion chromatographic determination of acidity.

The practice of determining acid concentrations by titrations has remained unchanged for more than a century. We introduce a new approach to the determination of acid concentrations based on cation exchange chromatography. We demonstrate the ability of sulfonated styrene-divinylbenzene based stationary phases to separate the hydrogen ion from other monovalent cations. The eluent is a dilute solution of a neutral salt, sometimes containing a small concentration of the corresponding acid, e.g., sodium ethanesulfonate, pH adjusted with ethanesulfonic acid. The high equivalent conductance (approximately 350 S.cm2/equiv) of H+ and relatively low eluent concentration allows sensitive conductometric detection of H+, down to the 50 microM level under favorable conditions. The conductometric response to H+ can be linear over a wide range of H+ concentrations, from sub-millimolar to several molar concentrations. The system allows the rapid quantitation of strong acids; weak acids can also be determined depending on pKa and injected concentration. The determinations of several strong and weak acids are presented along with factors that govern their chromatographic analysis.

Carboxylic Acids↗
PubMed2000

A study of cardio-pulmonary efficiency in different categories of runners.

Selected short distance runners, middle distance runners and long distance runners were subjected to graded exercise on a treadmill. The maximum aerobic power (VO2 max) and other indices related to oxygen transport system viz. heart rate, ventilation volume, breathing reserve, dyspnoeic index, O2 pulse and RQ were recorded at respective VO2 max work loads, and the values were compared. Long distance runners and middle distance runners showed a significantly higher VO2 max than the short distance runners when VO2 max was expressed per unit of body weight. Among the endurance runners, long distance runners had a significantly lower resting pulse rate as well as the maximum heart rate during work than the middle distance runners. On comparison, Ventilation Volume, Breathing reserve, Dyspnoeic index, O2 pulse and RQ at VO2 max work loads do not differ significantly among different categories of runners.

Adult↗
PubMed1996

Measurement of phenols on a loop-supported liquid film by micellar electrokinetic chromatography and direct UV detection.

This paper describes a direct measurement of phenolic substances in the gas phase at levels relevant to occupational health by micellar electrokinetic chromatography (MEKC) using direct ultraviolet detection. A small circular loop (2 mm O.D.) is formed with 100 mm Pt-wire at the sampling end of a fused-silica capillary. The capillary tip of the sampling end is present at the center of the loop and in the same plane. A thin film of 0.50 mM NaOH is formed on the loop by immersion and withdrawal. The film is in fluid communication with the capillary and acts as an absorber for gaseous phenols. Gas sampling is performed by transferring the film-bearing loop into a chamber through which air is aspirated for a preset time at a preselected flow-rate (typically 1 min at 100 cm3/min). A part of the film content is then introduced into the capillary by gravity injection and then MEKC is performed. A total of twelve chloro- and nitrophenols were selected for this study. Under the above sampling conditions, limits of detection (LODs) for various phenols range from high-single-digit to low-double-digit ppbv levels. The effect of several critical parameters, such as the composition of the liquid film and the MEKC running electrolyte, sampling period and film evaporation on the collection efficiency, separation efficiency and calibration behaviour are described.

Adsorption↗
PubMed1992

Hematin as a peroxidase substitute in hydrogen peroxide determinations.

Hematin can substitute for horseradish peroxidase (HRP) as the catalyst in the determination of hydrogen peroxide using phenolic substrates such as p-hydroxyphenylacetate or p-cresol. Although the peroxidatic activity of hematin from bovine blood is not as great as HRP in terms of unit iron content, the activity per unit weight is substantially greater. Hematin is 500 times less expensive than HRP per unit peroxidatic activity. In hematin-catalyzed systems, reaction development and fluorescence measurement can both be conducted optimally in the same ammoniacal buffer. Hydroxyalkyl hydroperoxides are rapidly hydrolyzed to H2O2 at this pH and are also determined. On the other hand, for methyl hydroperoxide, hematin exhibits only approximately 10% of the sensitivity exhibited by HRP. Hematin is significantly more stable in solution than HRP. The use of hematin as catalyst and p-cresol as the substrate leads to a particularly inexpensive and sensitive system, permitting a limit of detection (LOD) of 7 nM H2O2 in a flow-injection configuration.

Buffers↗
PubMed1992

Nitroprusside and methylene blue methods for silicone membrane differentiated flow injection determination of sulfide in water and wastewater.

Hydrogen sulfide evolved from an acidified sample is pre-concentrated by permeation in a stationary alkaline acceptor solution enclosed in a silicone rubber sample loop. Depending on the sample volume pre-concentrated, the applicable analytical range spans low micrograms/L to tens of mg/L for both methods. The methylene blue method is more sensitive by a factor of approximately 30 and actually permits practical determinations in the sub-micrograms/L levels. The limit of detection (LOD) for the nitroprusside method ranges from 20 micrograms/L for a 20 microL sample by conventional flow-injection determination (no membrane, throughput 30 samples/h) to less than 2 micrograms/L for 12 mL sample pre-concentrated in the membrane system (throughput 5 samples/h). The membrane is highly resistant to fouling and permits analysis of untreated wastewater samples bearing suspended solids, oil, grease, etc. without any pretreatment. No significant interference is observed with either chemistry. Although the nitroprusside chemistry is less sensitive, it does not involve the use of concentrated aggressive reagents and is recommended unless ultratrace determinations are essential. Viable reaction mechanisms are proposed for both of these chemistries.

Hydrogen-Ion Concentration↗
PubMed1989

Determination of total mercury in water and urine by a gold film sensor following Fenton's reagent digestion.

Fenton's reagent (Fe(II) + H2O2) is utilized for the digestion of environmental water samples and urine. Following the digestion, which converts organic forms of Hg to inorganic Hg(II), Hg(0) is liberated by borohydride reduction and measured by a conductometric gold film sensor. Quantitative recovery of Hg from samples spiked with mercuric chloride, methylmercury(II) chloride, and phenylmercury(II) acetate was attainable in the presence of naturally occurring suspended matter and humic and fulvic acids as well as 3% NaCl. The digestion is performed at moderate pH (3-4) and temperature (less than or equal to 50 degrees C) and does not use large amounts of any reagent. Excellent agreement is shown for reference water, wastewater, and urine standards. The limit of detection, facilitated by the low blank value, is 500 pg of Hg or 10 ng/L for a 50-mL sample.

Gold↗
PubMed1989

Role of plasminogen activators and leukocytes in IUD-induced inflammation: effect of some anti-inflammatory agents.

Insertion of an IUD causes a persistent inflammatory reaction, evident from an increase in the vascular dilatation and permeability of IUD-exposed endometrium. IUD-induced inflammatory changes can be checked by using anti-inflammatory drugs. In this study in rats, we report that IUD-induced inflammatory changes were partially checked by the use of anti-inflammatory drugs, in order of effectiveness, indomethacin greater than naproxen greater than ibuprofen. Histologically, IUDs provoke mild degeneration of uterine epithelium and necrotic changes in the endometrial glands. Heavy infiltration of polymorphonuclear leukocytes (PMNs) in the uterine lumen was also noticed. IUD-induced degenerative changes in the histoarchitecture of uterine epithelium were partially repaired following treatment with anti-inflammatory drugs.

Animals↗
PubMed1984

A multi-centre study of sulindac versus naproxen in the treatment of elderly osteoarthritic patients.

Ninety-five geriatric patients with osteoarthritis of the hip and/or knee were entered into an open parallel group study of sulindac (400 mg/day) and naproxen (500 mg/day), both given in twice-daily regimens. Patients received the drugs for 12 weeks. Both drugs produced improvements in the patients' overall condition. There were no statistically significant differences between the effects of the two drugs. Overall, both drugs proved beneficial and well tolerated.

Aged↗
PubMed1982

Physical efficiency tests on Indian male "Kabaddi" inter-university players.

The participants of inter-university "Kabaddi" competition showed higher values of height, weight and surface area than average Indian population, indicating better attainment of growth in them. Further, the values of respiratory efficiency tests like, FEV1, MEFR and PEFR were also observed to be more in these players, probably due to training effect. The grip strength values were high in comparison to those of Indian football goalkeepers and hockey players.

Anthropometry↗
PubMed1980

Generatation and characterization of sodium sulfite aerosols for applications in inhalation toxicologic research.

A method has been developed for generation of submicrometer aerosols of sodium sulfite suitable for use in inhalation toxicologic research. Concentrations ranging up to about 30 mg/m3 Na2SO3 were achieved in a 0.44 m3 exposure chamber with an air flow rate of 0.20 m3/min for periods up to 16 days. The coefficient of variation of the sulfite aerosol mass concentration was about 4% during a typical exposure period. The measured mass median aerodynamic diameters (MMADar) of the generated aerosols were 1.2 (+/- 0.2SD) microns with a geometric standard deviation (sigma g) of 1.9 (+/- 0.3SD). The chamber was sampled for gas phase SO2 concentration, and aerosol samples were analyzed for particulate sulfite and sulfate. The fraction of sulfur qas sulfite in the aerosol was usually 95% and was always greater than 90%. Gas phase SO2 amounted to less than 2% of the total S(IV) present in the chamber.

Aerosols↗