Sensitive liquid chromatography-tandem mass spectrometry method for quantification of hydrochlorothiazide in human plasma

A simple, rapid, sensitive and specific liquid chromatography-tandem mass spectrometry method was developed and validated for quantification of hydrochlorothiazide (I), a common diuretic and anti-hypertensive agent. The analyte and internal standard, tamsulosin (II) were extracted by liquid-liquid extraction with diethyl ether-dichloromethane (70:30, v/v) using a Glas-Col Multi-Pulse Vortexer. The chromatographic separation was performed on a reversed-phase column (Waters symmetry C18) with a mobile phase of 10 mm ammonium acetate-methanol (15:85, v/v). The protonated analyte was quantitated in negative ionization by multiple reaction monitoring with a mass spectrometer. The mass transitions m/z 296.1 solidus in circle 205.0 and m/z 407.2 solidus in circle 184.9 were used to measure I and II, respectively. The assay exhibited a linear dynamic range of 0.5-200 ng/mL for hydrochlorothiazide in human plasma. The lower limit of quantitation was 500 pg/mL, with a relative standard deviation of less than 9%. Acceptable precision and accuracy were obtained for concentrations over the standard curve ranges. A run time of 2.5 min for each sample made it possible to analyze a throughput of more than 400 human plasma samples per day. The validated method has been successfully used to analyze human plasma samples for application in pharmacokinetic, bioavailability or bioequivalence studies.

Liquid chromatography/electrospray ionization mass spectrometry method for the quantification of valproic acid in human plasma

A simple, sensitive and rapid liquid chromatography/electrospray ionization mass spectrometry (LC/ESI-MS) method was developed and validated for the quantification of valproic acid, an antiepileptic drug, in human plasma using benzoic acid as internal standard (IS). Following solid-phase extraction, the analytes were separated using an isocratic mobile phase on a reversed-phase C18 column and analyzed by MS in the single ion monitoring mode using the respective [M-H]- ions, m/z 143 for valproic acid and m/z 121 for the IS. The assay exhibited a linear dynamic range of 0.5-60 microg/mL for valproic acid in human plasma. The lower limit of quantification was 500 ng/mL with a relative standard deviation of less than 10%. Acceptable precision and accuracy were obtained for concentrations over the standard curve range. The average absolute recoveries of valproic acid and the IS from spiked plasma samples were 96.1+/-4.2 and 95.6+/-2.7%, respectively. A run time of 4.5 min for each sample made it possible to analyze more than 250 human plasma samples per day. The validated method has been successfully used to analyze human plasma samples for application in pharmacokinetic, bioavailability and bioequivalence studies.

Liquid chromatography–negative ion electrospray tandem mass spectrometry method for the quantification of tacrolimus in human plasma and its bioanalytical applications

A simple, rapid, novel and sensitive liquid chromatography-tandem mass spectrometry method was developed and validated for quantification of tacrolimus (I) in human plasma, a narrow therapeutic index, potent macrolide immunosuppressive drug. The analyte and internal standard (tamsulosin (II)) were extracted by liquid-liquid extraction with t-butylmethylether using a Glas-Col Multi-Pulse Vortexer. The chromatographic separation was performed on reverse phase Xterra ODS column with a mobile phase of 99% methanol and 1% 10mM ammonium acetate buffer. The deprotonate of analyte was quantitated in negative ionization by multiple reaction monitoring (MRM) with a mass spectrometer. The mass transitions m/z 802.5-->560.3 and m/z 407.2-->151.9 were used to measure I and II, respectively. The assay exhibited a linear dynamic range of 0.05-25ng/ml for tacrolimus in human plasma. The lower limit of quantitation was 50pg/ml with a relative standard deviation of less than 20%. Acceptable precision and accuracy were obtained for concentrations over the standard curve ranges. Run time of 2min for each sample made it possible to analyze a throughput of more than 400 human plasma samples per day. The validated method has been successfully used to analyze human plasma samples for application in comparative bioavailability studies. The tacrolimus plasma concentration profile could be obtained for pharmacokinetic study. The observed maximum plasma concentration (C(max)) of tacrolimus (5mg oral dose) is 440pg/ml, time to observed maximum plasma concentration (T(max)) is 2.5h and elimination half-life (T(1/2)) is 21h.

Rapid quantification of nebivolol in human plasma by liquid chromatography coupled with electrospray ionization tandem mass spectrometry

A simple, sensitive and rapid liquid chromatographic/electrospray ionization tandem mass spectrometric method was developed and validated for the quantitation of nebivolol in human plasma. The method involved a simple single-step liquid-liquid extraction with diethyl ether/dichloromethane (70/30). The analyte was chromatographed on Waters symmetry C18 reversed-phase chromatographic column by isocratic elution with water:acetonitrile:formic acid (30:70:0.03, v/v) and analyzed by mass spectrometry in the multiple reaction monitoring mode. The precursor to product ion transitions of m/z 406.4-151.5 and m/z 409.1-228.1 were used to measure the analyte and the internal standard (I.S.), respectively. The chromatographic runtime was 2 min and the weighted (1/x2) calibration curves were linear over the range 50-10,000 pg/mL. The method was validated in terms of accuracy, precision, absolute recovery, freeze-thaw stability, bench-top stability and re-injection reproducibility. The limit of detection and lower limit of quantification in human plasma were 10 and 50 pg/mL, respectively. The within- and between-batch accuracy and precision were found to be well within acceptable limits (<10%). The analyte was stable after three freeze-thaw cycles (deviation <10%). The average absolute recoveries of nebivolol and tamsulosin, used as an internal standard, from spiked plasma samples were 73.4+/-3.7 and 72.1+/-2.0%, respectively. The assay method described here was applied to study the pharmacokinetics of nebivolol.

Simple, sensitive and rapid liquid chromatographic/electrospray ionization tandem mass spectrometric method for the quantification of lacidipine in human plasma

A simple, sensitive and rapid liquid chromatographic/electrospray ionization tandem mass spectrometric method was developed and validated for the quantification of lacidipine in human plasma using its structural analogue, amlodipine, as internal standard (IS). The method involves a simple single-step liquid-liquid extraction with tert-butyl methyl ether. The analyte was chromatographed on an Xterra MS C(18) reversed-phase chromatographic column by isocratic elution with 20 mM ammonium acetate buffer-acetonitrile (10:90, v/v; pH 6) and analyzed by mass spectrometry in the multiple reaction monitoring mode. The precursor to product ion transitions of m/z 456.4 --> 354.4 and m/z 409.3 --> 238.3 were used to measure the analyte and the I.S., respectively. The chromatographic run time was 1.5 min and the weighted (1/x(2)) calibration curves were linear over the range 0.1-25 ng ml(-1). Lacidipine was sensitive to temperature in addition to light. The method was validated in terms of accuracy, precision, absolute recovery, freeze-thaw stability, bench-top stability and re-injection reproducibility. The limit of detection and lower limit of quantification in human plasma were 50 and 100 pg ml(-1), respectively. The within- and between-batch accuracy and precision were found to be well within acceptable limits (<15%). The analyte was stable after three freeze-thaw cycles (deviation <15%). The average absolute recoveries of lacidipine and amlodipine (IS) from spiked plasma samples were 51.1 +/- 1.3 and 50.3 +/- 4.9%, respectively. The assay method described here could be applied to study the pharmacokinetics of lacidipine.

Selective and rapid liquid chromatography–tandem mass spectrometry assay of dutasteride in human plasma

A simple, rapid, sensitive and specific liquid chromatography-tandem mass spectrometry method was developed and validated for quantification of dutasteride (I), a potent and the first specific dual inhibitor of 5alpha-reductase, in human plasma. The analyte and internal standard (finasteride (II)) were extracted by liquid-liquid extraction with diethyl ether/dichloromethane (70/30, v/v) using a Glas-Col Multi-Pulse Vortexer. The chromatographic separation was performed on a reverse phase Xterra MS C18 column with a mobile phase of 10 mM ammonium formate/acetonitrile (15/85, v/v, pH adjusted to 3.0 with formic acid). The protonated analyte was quantitated in positive ionization by multiple reaction monitoring with a mass spectrometer. The mass transitions m/z 529.5 --> 461.5 and m/z 373.3 --> 317.4 were used to measure I and II, respectively. The assay exhibited a linear dynamic range of 0.1-25.0 ng/mL for dutasteride in human plasma. The lower limit of quantitation was 100 pg/mL with a relative standard deviation of less than 15%. Acceptable precision and accuracy were obtained for concentrations over the standard curve ranges. A run time of 1.2 min for each sample made it possible to analyze a throughput of more than 400 human plasma samples/day. The validated method has been successfully used to analyze human plasma samples for application in pharmacokinetic, bioavailability or bioequivalence studies.

Rapid, simple and highly sensitive LC-ESI-MS/MS method for the quantification of tamsulosin in human plasma

A simple, rapid, sensitive and specific liquid chromatography-tandem mass spectrometry method was developed and validated for quantification of tamsulosin (I), a highly selective alpha1-adrenoceptor antagonist used for the treatment of patients with symptomatic benign prostatic hyperplasia. The analyte and internal standard, mosapride (II) were extracted by liquid-liquid extraction with diethyl ether-dichloromethane (70:30, v/v) using a Glas-Col Multi-Pulse Vortexer. The chromatographic separation was performed on a reverse phase Waters symmetry C18 column with a mobile phase of 0.03% formic acid-acetonitrile (30:70, v/v). The protonated analyte was quantitated in positive ionization by multiple reaction monitoring with a mass spectrometer. The mass transitions m/z 409.1 solidus in circle 228.1 and m/z 422.3 solidus in circle 198.3 were used to measure I and II, respectively. The assay exhibited a linear dynamic range of 0.1-50.0 ng/mL for tamsulosin in human plasma. The lower limit of quantitation was 100 pg/mL with a relative standard deviation of less than 10%. Acceptable precision and accuracy were obtained for concentrations over the standard curve ranges. A run time of 2.0 min for each sample made it possible to analyze a throughput of more than 400 human plasma samples per day. The validated method has been successfully used to analyze human plasma samples for application in pharmacokinetic, bioavailability or bioequivalence studies.

Rapid quantification of gabapentin in human plasma by liquid chromatography/tandem mass spectrometry

A simple, sensitive and rapid liquid chromatography/tandem mass spectrometry (LC-MS/MS) method was developed and validated for the quantification of gabapentin, a new antiepileptic drug, in human plasma using its structural analogue, 1,1-cyclohexane diacetic acid monoamide (CAM) as internal standard. The method involved a simple protein precipitation by means of acetonitrile followed by a rapid isocratic elution with 10mM ammonium formate buffer/acetonitrile (20/80, v/v, pH 3.0) on Waters Symmetry C(18 reversed phase chromatographic column and analyzed by mass spectrometry in the multiple reaction monitoring mode. The precursor to product ion transitions of m/z 172-->154 and m/z 200-->182 were used to measure the analyte and the IS, respectively. The assay exhibited a linear dynamic range of 40-10000 ng/mL for gabapentin in human plasma. The limit of detection and lower limit of quantification in human plasma were 10 and 40 ng/mL, respectively. Acceptable precision and accuracy were obtained for concentrations over the standard curve ranges. A run time of 2 min for each sample made it possible to analyze a throughput of more than 400 human plasma samples per day. The validated method has been successfully used to analyze human plasma samples for application in pharmacokinetic, bioavailability or bioequivalence studies.

Simple, sensitive and rapid LC–MS/MS method for the quantitation of cerivastatin in human plasma — application to pharmacokinetic studies

A simple and sensitive liquid chromatography-tandem mass spectrometry method was developed and validated for estimation of cerivastatin (I) in human plasma, a potent hydroxy-methylglutaryl-coenzyme A reductase inhibitor. The analyte and internal standard (atorvastatin, II) were extracted by liquid/liquid extraction with diethyl ether/dichloromethane (70/30, v/v). The chromatographic separation was performed on reverse phase Xterra ODS column with a mobile phase of water/acetonitrile (30/70, v/v) with 0.03% formic acid. The protonated analyte was quantitated in positive ionization by multiple reaction monitoring with a mass spectrometer. The mass transitions m/z 460.4 --> 356.3 and 559.2 --> 440.3 were used to measure I and II, respectively. The lower limit of quantitation was 10pg/mL with a relative standard deviation of less than 15%. Acceptable precision and accuracy were obtained for concentrations over the calibration curve ranges (0.01-10ng/mL). Sample analysis time of 2min for each sample made it possible to analyze a throughput of more than 400 human plasma samples per day. The assay can be used to analyze human plasma samples to support phase I and II clinical studies.

Quantitation of tadalafil in human plasma by liquid chromatography-tandem mass spectrometry with electrospray ionization

A simple, rapid, sensitive and specific liquid chromatography-tandem mass spectrometry method was developed and validated for quantitation of tadalafil (I) in human plasma, a new selective, reversible phosphodiesterase 5 inhibitor. The analyte and internal standard (sildenafil, II) were extracted by liquid-liquid extraction with diethyl ether/dichloromethane (70/30, v/v) using a Glas-Col Multi-Pulse Vortexer. The chromatographic separation was performed on reverse phase Xterra MS C18 column with a mobile phase of 10mM ammonium formate/acetonitrile (10/90, v/v, pH adjusted to 3.0 with formic acid). The protonate of analyte was quantitated in positive ionization by multiple reaction monitoring with a mass spectrometer. The mass transitions m/z 390.4 --> 268.0 and m/z 475.5 --> 58.3 were used to measure I and II, respectively. The assay exhibited a linear dynamic range of 10-1000 ng/mL for tadalafil in human plasma. The lower limit of quantitation was 10 ng/mL with a relative standard deviation of less than 15%. Acceptable precision and accuracy were obtained for concentrations over the standard curve ranges. Run time of 1.2 min for each sample made it possible to analyze a throughput of more than 400 human plasma samples per day. The validated method has been successfully used to analyze human plasma samples for application in pharmacokinetic, bioavailability or bioequivalence studies.

Validation and application of a high-performance liquid chromatography-tandem mass spectrometry assay for mosapride in human plasma

A simple, rapid, sensitive and specific liquid chromatography-tandem mass spectrometry method was developed and validated for quantification of mosapride (I), a novel and potent gastroprokinetic agent that enhances the upper gastrointestinal motility by stimulating 5-HT(4) receptor. The analyte and internal standard, tamsulosin (II), were extracted by liquid-liquid extraction with diethyl ether-dichloromethane (70:30, v/v) using a Glas-Col Multi-Pulse Vortexer. The chromatographic separation was performed on a reversed-phase Waters symmetry C(18) column with a mobile phase of 0.03% formic acid-acetonitrile (10:90, v/v). The protonated analyte was quantitated in positive ionization by multiple reaction monitoring with a mass spectrometer. The mass transitions m/z 422.3 -->198.3 and m/z 409.1 -->228.1 were used to measure I and II, respectively. The assay exhibited a linear dynamic range of 0.5-100.0 ng/mL for mosapride in human plasma. The lower limit of quantitation was 500 pg/mL with a relative standard deviation of less than 15%. Acceptable precision and accuracy were obtained for concentrations over the standard curve ranges. A run time of 2.0 min for each sample made it possible to analyze a throughput of more than 400 human plasma samples per day. The validated method has been successfully used to analyze human plasma samples for application in pharmacokinetic, bioavailability or bioequivalence studies.

Long-term exposure to chromium contaminated waters and the associated human health risk in a highly contaminated industrialised region

Disposal of industrial waste is of great concern because it releases toxic metals resulting into the degradation of environments and consequently causes health effects on humans. The present study was carried out with the objectives of identifying the possible source and migration of contaminants in the surface water and groundwater and the associated health risks in the industrial region of Ranipet, Tamil Nadu, India. A total of 22 water samples were collected and analysed for the concentration of major ions and trace elements. Chemical speciation of chromium and lead in surface and groundwater was calculated using the geochemical code, PHREEQC. The concentration of total dissolved solids, chromium and lead was high in the surface water than groundwater in this region. The chromium in most of the sampled water is dominated with Cr(OH)²⁺ and Cr(OH)₃ species and the dominant species of lead was PbCO₃. The major source of contamination is the waste dumped in this region and also the improper disposal of effluents from the small-scale industries in this region. Use of groundwater with the present level of chromium and lead in this region will cause several health effects through oral and dermal pathways. Hence, stringent monitoring of quality of water sources of this region, enforcement of regulation of the disposal of wastes from the industries, recover and treat the dumped solid waste are very much necessary to prevent the spread of contamination.

Recovery from rabies, a universally fatal disease

BACKGROUND

Rabies is a zoonosis transmitted via the bites of various mammals, primarily dogs and bats. Known since antiquity, this disease may have the deadliest human fatality rates and is responsible for approximately 65,000 deaths worldwide per year.

CASE PRESENTATION

We report the case details of a 13-year-old boy from India belonging to a South Asian ethnicity, who presented with altered sensorium one month following a dog bite. He did not receive the active rabies immunization and was managed with supportive therapy. The patient had extensive T2W (T2 weighted)/fluid attenuation and inversion recovery (FLAIR) hyper intensities involving the deep gray matter of the cerebral hemispheres, hippocampus, brainstem, and cerebellum. The diagnosis was confirmed by the demonstration of the rabies antigen from a nuchal skin biopsy and a corneal smear. The patient had a slow but significant recovery over four months and was discharged from the hospital in stable condition with severe neurological sequelae.

CONCLUSION

We report a unique case of survival after infection with a universally fatal disease.

Rhenium Sulfide Incorporated in Molybdenum Sulfide Nanosheets for High-Performance Symmetric Supercapacitors with Enhanced Capacitance

Supercapacitors are considered potential energy storage devices and have drawn significant attention due to their superior intrinsic advantages. Herein, we report the synthesis of ReS₂ embedded in MoS₂ nanosheets (RMS-31) by a hydrothermal technique. The prepared RMS-31 electrode material demonstrated superior pseudocapacitive behavior in 1 M KOH electrolyte solution, which is confirmed by the heterostructure of RMS-31 nanosheet architectures. RMS-31 has a specific capacitance of 244 F g^-1 at a current density of 1 A g^-1 and a greater areal capacitance of 540 mF cm^-2 at a current density of 5 mA cm^-2. The symmetric supercapacitor device with the RMS-31 electrode delivers an energy density of 28 W h cm^-2 with a power density of 1 W cm^-2 and reveals long-term stability at a constant current density of 5 mA cm^-2 for 10,000 cycles while accomplishing a retention of 66.5%. The high performance of this symmetric device is attributed to the synergistic effect of ReS₂ and MoS₂ and the presence of the metallic 1T-MoS₂ phase in the RMS-31 electrode. To the best of our knowledge, this is the first report of increasing the interlayer spacing of 2H-MoS₂ by incorporating ReS₂ for symmetric supercapacitor applications.

Determination of distribution coefficient of uranium from physical and chemical properties of soil

Uranium is a long lived radioactive element which is naturally present in minute concentrations in igneous, sedimentary and metamorphic rocks. These rocks when subjected to weathering results in the formation of soil which also has traces of uranium. Distribution coefficient (K_d) is a crucial parameter in environmental assessment which is used to predict the interaction and transport of uranium in groundwater. The objective of the study is to estimate the K_d of uranium in soils and to develop a relation between this and the soil parameters. Seven rock samples and twenty three soil samples were collected during this study. The K_d of rock samples of different grain sizes where determined and the soil samples were analysed for electrical conductivity, pH, grain size, bulk density, particle density, porosity, calcium carbonate, cation exchange capacity and K_d. The K_d of the soil increases with increase in soil pH up to 6, after which it gradually decreases. Multiple regression analysis was performed to quantify the effect of various soil parameters on soil K_d and equations were statistically significant. Thus, soil K_d in a region could be predicted using limited soil properties with such statistically significant equations.

Facile ultrasonic preparation of a polypyrrole membrane as an absorbent for efficient oil-water separation and as an antimicrobial agent

Polypyrrole (PPY) spherical particles synthesized using carbon dots as an efficient catalyst were strongly embedded on fluorinated nonwoven fabric by ultrasonication to form a membrane with high hydrophilicity. An optimal amount of PPY adhered to the membrane after 30 min of sonication enhanced the overall membrane area with high hydrophilicity. Oil with high hydrophobicity was repelled by the resulting membrane, whereas water was freely penetrated and diffused from the membrane. The membrane exhibited good reusability and efficiency for the recovery of oil from a cooking oil-water mixture within 30 s. The incorporation of PPY in the fluorinated fabric imparts significant antibacterial properties against two common pathogens, Escherichia coli (Gram-negative) and Staphylococcus aureus (Gram-positive). The anti-biofouling membrane could pave the way for its potential application to separate spilled oil from contaminated waters, comprising different microorganisms and living species. The novelty of this manuscript is described in a new system, the fabrication of PPY membranes with two important properties: biocidal and oil/water separation.

Simulation of ground water quality for noyyal river basin of Coimbatore city, Tamilnadu using MODFLOW

In recent years groundwater modelling has become a major part of many projects dealing with groundwater exploitation, protection and remediation. Coimbatore city is located along the Noyyal River which is grown in size and population on either side of the river and the dumping of wastes very close to the river banks, leads to pollution of both surface and groundwater. Study on the quality of groundwater along the Noyyal River in Coimbatore city of Tamilnadu, is necessary to safeguard the interest of the people with respect to quality and quantity of water. The objective of the research is to develop Groundwater quality models to suggest ways and means to contain and remediate the polluted groundwater under various conditions. Data related to the groundwater quality, rainfall and well log were collected from the reputed government departments and fifteen sample well locations are identified near the noyyal river basin. The quality parameters such as pH, TDS, EC, TH, chlorides, alkalinity, sodium, calcium, magnesium, sulphates and nitrates are considered for the study. Groundwater quality modelling is attempted by using MODFLOW/MT3DMS with different scenarios. This study revealed that in all the scenarios the center portion of study area is more affected i.e. from P·N.Palayam to Kalangal. The groundwater flow is moving towards and along the river flow. Hence the pollutants are moving easily from upstream to the downstream side. necessary measures has to be taken to control the groundwater contamination.