G. Madhavi

Application of phytogenic zerovalent iron nanoparticles in the adsorption of hexavalent chromium

Zerovalent iron nanoparticles (ZVNI) were synthesized using a rapid, single step and completely green synthetic method from the leaf extracts of Eucalyptus globules and were characterized using the techniques Scanning Electron Microscopy (SEM), UV-Vis Spectroscopy, Fourier Transform-Infrared Spectroscopy (FT-IR), X-ray Diffraction (XRD) and Zeta potential measurement. The FT-IR analysis reveals that the polyphenolic compounds present in the leaf extract may be responsible for the reduction and stabilization of the ZVNI. These nanoparticles were utilized for the adsorption of hexavalent chromium (Cr (VI)) and the concentration of Cr (VI) was determined using UV-Vis spectrometer after treating with ZVNI. Response and surface contour plots were drawn with the help of Mini-tab software to explain the adsorption of Cr (VI). The adsorption efficiency of Cr (VI) reaches to the highest value (98.1%) when the reaction time was about 30 min. and the ZVNI dosage was 0.8 g/L. The effective parameters such as adsorbent (ZVNI) dosage, initial Cr (VI) concentration and the kinetics were also examined.

Determination of dopamine in presence of ascorbic acid and uric acid using poly (Spands Reagent) modified carbon paste electrode

In this paper, we have fabricated a modified carbon paste electrode (CPE) by electropolymerisation of spands reagent (SR) onto surface of CPE using cyclic voltammetry (CV). The developed electrode was abbreviated as poly(SR)/CPE and the surface morphology of the modified electrode was studied by using scanning electron microscopy (SEM). The developed electrode showed higher electrocatalytic properties towards the detection of dopamine (DA) in 0.1M phosphate buffer solution (PBS) at pH7.0. The effect of pH, scan rate, accumulation time and concentration of dopamine was studied at poly(SR)/CPE. The poly(SR)/CPE was successfully used as a sensor for the selective determination of DA in presence of ascorbic acid (AA) and uric acid (UA) without any interference. The poly(SR)/CPE showed a good detection limit of 0.7 μM over the linear dynamic range of 1.6 μM to 16 μM, which is extremely lower than the reported methods. The prepared poly(SR)/CPE exhibited good stability, high sensitivity, better reproducibility, low detection limit towards the determination of DA. The developed method was also applied for the determination of DA in real samples.

A selective and sensitive UPLC–MS/MS approach for trace level quantification of four potential genotoxic impurities in zolmitriptan drug substance

The pivotal task of pharmaceutical industry is to separate and quantify the potential genotoxic impurities (PGIs) rising from the process of drug production. For trace level quantification of these PGIs we need to develop sensitive and selective analytical methods. APP, NPA, NPP and MNA have been highlighted as PGIs in zolmitriptan. A sensitive and selective UPLC-MS/MS method has developed for identification and quantification of four PGIs viz. APP, NPA, NPP and MNA in zolmitriptan. The method utilizes Hypersil BDS C8 column (50 mm × 4.6 mm, 3.0 μm) with electrospray ionization in selected ion recording (SIR) mode for quantitation of four PGIs. The method was validated as per International Conference on Harmonization (ICH) guidelines and is able to quantitate APP at 0.1 ppm and NPA, NPP and MNA at 0.15 ppm with respect to 5.0mg/mL of zolmitriptan. The proposed method is specific, linear, accurate and precise. The method is linear in the range of 0.1-2.0 ppm for APP and 0.15-2.0 ppm for NPA, NPP and MNA, which matches the range of LOQ-200% of estimated permitted level (1.0 ppm). The correlation coefficient obtained was >0.999 in each case. The impurities were not present in the studied three pure and formulation batches of zolmitriptan. The accuracy of the method was ranged between 98.1 and 102.8% for four PGIs. This method is a good quality control tool for quantitation of four APP, NPA, NPP and MNA PGIs at very low levels in zolmitriptan.

Remediation of Chlorpyrifos-Contaminated Soils by Laboratory-Synthesized Zero-Valent Nano Iron Particles: Effect of pH and Aluminium Salts

Degradation of the insecticide chlorpyrifos in contaminated soils was investigated using laboratory synthesized zero-valent nano iron (ZVNI) particles. The synthesized ZVNI particles were characterized as nanoscale sized by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The zero-valent state (Fe0) of iron was confirmed by EDAX analysis and the morphology of the ZVNI particles was studied by XRD. Batch experiments were conducted by treating the chlorpyrifos contaminated soil with ZVNI, our results indicate that 90% of chlorpyrifos was degraded after 10 days of incubation. Only 32% degradation was observed with micro zero-valent iron (mZVI) and no considerable degradation was attained without ZVNI. The degradation of chlorpyrifos followed the first-order kinetics with a rate constant and a half-life of 0.245 day−1 and 2.82 days, respectively. Degradation was monitored at two different pH values, that is, pH 10 and pH 4. Chlorpyrifos degradation rate constant increased as the pH decreases from 10 to 4. The corresponding rate constant and half-lives were 0.43 day−1 and 1.57days for pH 4, 0.18 day−1 and 3.65 days for pH 10. In addition, an attempt was made by augmenting Al2(SO4)3 with ZVNI and it was found that the degradation rate of chlorpyrifos was greatly enhanced and the rate constant was rapidly increased from 0.245 day−1 to 0.60 day−1. Hydrolysis and stepwise dechlorination pathway of chlorpyrifos with ZVNI was the dominant reaction.

Development and validation of a systematic UPLC-MS/MS method for simultaneous determination of three phenol impurities in ritonavir.

A stability indicating gradient reverse phase UPLC-MS/MS method was developed and validated for the simultaneous determination of three phenol impurities in ritonavir drug substance. The chromatographic separation was performed on Acquity UPLC BEH C18 column (100 mm × 2.1 mm, 1.7 μm) using gradient elution of 0.05% ammonia in methanol and 5.0 mM ammonium acetate buffer (30:70, v/v) at a flow rate of 0.2 mL/min. Both negative and positive electrospray ionization (ESI) modes were operated simultaneously for the quantification of three phenol impurities. The total run time was 11 min, within which ritonavir and its three impurities were well separated. The developed method was validated as per ICH guidelines with respect to specificity, linearity, limit of detection, limit of quantification, accuracy, precision and robustness. The calibration curves showed a good linearity over the concentration range of 0.3-1.5 ppm for phenol and 0.1-1.5 ppm for both 4-nitrophenol and N-phenoxycarbonyl-L-valine (NPV). The determination coefficient obtained was >0.9998 in each case. The method had very low limit of detection (LOD) and limit of quantification (LOQ) and the accuracy lies between 97.8% and 103.2% for all the three phenol impurities. The developed method was successfully applied for five formulation batches of ritonavir to determine its phenol impurities.

Simultaneous determination of asenapine and valproic acid in human plasma using LC–MS/MS: Application of the method to support pharmacokinetic study

Combination of asenapine with valproic acid received regulatory approval for acute treatment of schizophrenia and maniac episodes of bipolar disorders. A simple LC–MS/MS method was developed and validated for simultaneous quantification of asenapine and valproic acid in human plasma. Internal standards were added to 300 μL of plasma sample prior to liquid–liquid extraction using methyl tertiary butyl ether (MTBE). Chromatographic separation was achieved on Phenomenex C18 column (50 mm×4.6 mm, 5 μm) in isocratic mode at 40 °C. The mobile phase used was 10 mM ammonium formate–acetonitrile (5:95, v/v) at a constant flow rate of 0.8 mL/min monitored on triple quadrupole mass spectrometer, operating in the multiple reaction monitoring (MRM) mode. The injection volume used for LC–MS/MS analysis was 15 μL and the run time was 2.5 min. These low run time and small injection volume suggest the high efficiency of the proposed method. The method was validated over the concentration range of 0.1–10.02 ng/mL and 10–20,000 ng/mL for asenapine and valproic acid respectively. The method recoveries of asenapine (81.33%), valproic acid (81.70%), gliclazide (78.45%) and benzoic acid (79.73) from spiked plasma samples were consistent and reproducible. The application of this method was demonstrated by a pharmacokinetic study in 8 healthy male volunteers with 5 mg asenapine and 250 mg valproic acid administration.

Method development and validation study for quantitative determination of 2-chloromethyl-3,4-dimethoxy pyridine hydrochloride a genotoxic impurity in pantoprazole active pharmaceutical ingredient (API) by LC/MS/MS.

A sensitive and selective liquid chromatographic-tandem mass spectrometric (LC/MS/MS) method was developed and validated for the trace analysis (>1 ppm level) of 2-chloromethyl-3,4-dimethoxy pyridine hydrochloride a genotoxic impurity in pantoprazole sodium drug substances. LC/MS/MS analysis of 2-chloromethyl-3,4-dimethoxy pyridine hydrochloride was done on Hypersil BDS C18 (50 mm × 4.6 mm) 3 μm column and 10 mM ammonium acetate in 1000 mL of water was used as buffer. The mobile phase used was in the ratio of buffer-acetonitrile (79:21, v/v). The flow rate was 1.0 mL/min and elution was monitored at 210 nm. The method was validated as per International Conference on Harmonization (ICH) guidelines. LC/MS/MS is able to quantitate up to 0.3 ppm of 2-chloromethyl-3,4-dimethoxy pyridine hydrochloride.

Development and validation of a rapid ultra high performance liquid chromatography with tandem mass spectrometry method for the simultaneous determination of darunavir, ritonavir, and tenofovir in human plasma: Application to human pharmacokinetics

A sensitive ultra high performance liquid chromatography with tandem mass spectrometry method was developed for the simultaneous determination of darunavir, ritonavir and tenofovir in human plasma. Sample preparation involved a simple liquid-liquid extraction using 200 μL of human plasma extracted with methyl tert-butyl ether for three analytes and internal standard. The separation was accomplished on an Acquity UPLC BEH C18 (50 mm x 2.1 mm, 1.7 μm) analytical column using gradient elution of acetonitrile/methanol (80:20, v/v) and 5.0 mM ammonium acetate containing 0.01% formic acid at a flow rate of 0.4 mL/min. The linearity of the method ranged between 20.0 and 12 000 ng/mL for darunavir, 2.0 and 2280 ng/mL for ritonavir, and 14.0 and 1600 ng/mL for tenofovir using 200 μL of plasma. The method was completely validated for its selectivity, sensitivity, linearity, precision and accuracy, recovery, matrix effect, stability, and dilution integrity. The extraction recoveries were consistent and ranged between 79.91 and 90.04% for all three analytes and internal standard. The method exhibited good intra-day and inter-day precision between 1.78 and 6.27%. Finally the method was successfully applied for human pharmacokinetic study in eight healthy male volunteers after the oral administration of 600 mg darunavir along with 100 mg ritonavir and 100 mg tenofovir as boosters.

Systematic approach for trace level quantification of 2-n-butyl-4-spirocyclopentane-2-imidazole-5-one genotoxic impurity in irbesartan using lc-ms/ms

2-N-butyl-4-spirocyclopentane-2-imidazoline-5-one has been highlighted as a potential genotoxic impurity in irbesartan. A sensitive LC-MS/MS method was developed and validated for the determination of 2-N-butyl-4-spirocyclopentane-2-imidazoline-5-one in irbesartan. Good separation between 2-N-butyl-4-spirocyclopentane-2-imidazoline-5-one and irbesartan was achieved with Symmetry C18 (100×4.6 mm, 3.5 μm) column using 65:35 v/v mixture of 0.1% formic acid and acetonitrile as mobile phase with a flow rate of 0.7 ml/min. The proposed method was specific, linear, accurate, and precise. The calibration curve shows good linearity over the concentration range of 0.1-2.0 μg/ml, which matches the range of limit of quantitation-20×limit of quantitation of estimated permitted level (1.0 μg/ml) of 2-N-butyl-4-spirocyclopentane-2-imidazoline-5-one. The method was validated as per International Conference on Harmonization guidelines and was able to quantitate 2-N-butyl-4-spirocyclopentane-2-imidazoline-5-one impurity at 1.0 μg/ml with respect to 2 mg/ml of irbesartan. 2-N-butyl-4-spirocyclopentane-2-imidazoline-5-one was not present in the three studied pure and formulation batches of irbesartan and the developed method was a good quality control tool for quantitation of 2-N-butyl-4-spirocyclopentane-2-imidazole-5-one at very low levels in irbesartan.

Ultrafine Pt–Ni bimetallic nanoparticles anchored on reduced graphene oxide nanocomposites for boosting electrochemical detection of dopamine in biological samples

Pt–Ni bimetallic nanoparticles on the surface of reduced graphene oxide (rGO) nanosheets were prepared by using a wet–reflux strategy and characterized by transmission electron microscopy (TEM), field emission scanning electron microscopy (FE-SEM), Xray diffraction (XRD) and Raman spectroscopy. The glassy carbon electrode modified with Pt–Ni/rGO demonstrated excellent electrochemical activity towards dopamine (DA) in the presence of acetaminophen (APAP) and etilefrine hydrochloride (ET). From the differential pulse voltammetry (DPV) results obtained for the ternary mixture of DA, APAP and ET, the limit of detection (LOD) and limit of quantification (LOQ) of DA were calculated to be 0.0026 μM and 0.00876 μM, respectively. The proposed sensor was successfully employed for the sensing of DA in aqueous solution, pharmaceutical drugs and human serum samples in a mixture with APAP and ET.