Chemistry

Adsorption of lead (II) ions onto cassava starch 5-choloromethyl-8-hydroxyquinoline polymer (CSCMQ) was investigated with the variation in the parameters of pH, contact time, lead (II) ions concentration, temperature and the adsorbent dose. The Langmuir and Freundlich models have been applied. CSCMQ was characterized by Fourier transform infrared spectroscopy and scanning electron microscopy. Results showed that the adsorption process was better described by the Langmuir model. Adsorption kinetics data obtained for the metal ions sorption were investigated using pseudo-first-order, pseudo-second-order and intraparticle diffusion model. The maximum adsorption capacities (qm) were 46.512, 43.859 and 42.735 mg/g at 25, 35 and 45 °C, respectively. The dynamical data fit well with the second-order kinetics model. The results indicate that CSCMQ could be employed as low-cost material for the adsorption of Pb(II) ions from aqueous medium.

The new “upper-rim” functionalized 11,23-disemicarbazono-26,28-n-dipropoxy-25,27-dihydroxy calix[4]arene has been synthesized by condensing 11,23-diformyl-26,28-n-dipropoxy-25,27-dihydroxy calix[4]arene with semicarbazide hydrochloride. This calix[4]arene-semicarbazone derivative was then covalently linked with commercially available Merrifield’s peptide resin at the “lower-rim” to obtain polymeric chelating resin and its analytical properties were investigated. The resin was then used successfully for the separation and preconcentration of lanthanum(III), cerium(III), thorium(IV) and uranium(VI) prior to their determination by spectrophotometry and inductively coupled plasma atomic emission spectroscopy. The resin exhibits good separating ability with maximum sorption between pH 2.5–4.5 for Th(IV) and between pH 5.5–7.0 for U(VI) whereas La(III) and Ce(III) were found to have maximum sorption between pH 6.5–8.5. The elution studies were carried out with 0.01 M HCl for La(III) and Ce(III), 2.0 M HCl for Th(IV) and 0.25 M HCl for U(VI). The preconcentration factors for La(III), Ce(III), Th(IV) and U(VI) were 125, 130, 102 and 108, respectively. The resin shows good stability along with faster rate of equilibrium for all the metal ions. The influence of several ions (cations and anions) on the resin performance is also discussed. The relative standard deviation was between 96 and 98% with good analytical reliability. The proposed method was applied for the determination of metal ions in monazite sand and some standard geological materials.

A method for the determination of sertraline, a new antidepressant drug and a selective serotonin reuptake inhibitor (SSRI), in human plasma is described. Therapeutic drug monitoring (TDM) necessitates efficient, fast and reliable analytical methods validated by external quality control. We therefore devised a simple, rapid and sensitive isocratic reversed-phase liquid chromatographic-tandem mass spectrometric method equipped with Turbo Ion spray (TIS) source, operating in the positive ion and selective reaction monitoring (SRM) acquisition mode to quantify sertraline in human plasma. A new and superior procedure of solid-phase extraction (SPE) (compared to liquid–liquid extraction) was followed to extract sertraline and imipramine as internal standard (IS) from the human plasma. Sample preparation was performed using waters hydrophilic–lipophilic balance (HLB) cartridge and this method yielded extremely clean extracts with very good recovery, 81.47 and 85.79% for sertraline and IS, respectively. Both were analyzed by combined reverse phase liquid chromatography and tandem mass spectrometry (LC–MS/MS) with positive ion TIS ionization using SRM acquisition mode. The response of the LC–MS/MS method for sertraline was linear over the dynamic range of 0.5–60.0 ng/ml with correlation coefficient r ≥ 0.9996. The coefficient of variance (%CV) was 8.53% at 0.5 ng/ml and the accuracy was well within the accepted limit of ±20% at lower limit of quantification (LLOQ) and ±15% at all the other concentrations in the linear range. This method was fully validated for the accuracy, precision and stability studies. The above findings indicate that the method is very much accurate and precise and can be successfully applied for bioequivalence studies in human subjects.

A very stable chelating resin matrix was synthesized by covalently linking o-vanillinthiosemicarbazone (oVTSC) with the benzene ring of the polystyrene-divinylbenzene resin Amberlite XAD-2 through a -NN- group. The resin was used successfully for the separation and preconcentration of copper(II), zinc(II) and lead(II) prior to their determination by atomic absorption spectrophotometry. The total sorption capacity of the resin was 850, 1500 and 2000 μg g−1 of the resin for Cu(II), Zn(II) and Pb(II), respectively. For the quantitative sorption and recovery of Cu(II), Zn(II) and Pb(II), the optimum pH and eluants were pH 2.5–4.0 and 4 M HCl or 2 M HNO3 for Cu(II), pH 5.5–6.5 and 1.0–2.0 M HCl for Zn(II) and pH 6.0–7.5 and 3 M HCl or 1 M HNO3 for Pb(II). Both, the uptake and stripping of these metal ions were fairly rapid, indicating a better accessibility of the chelating sites. The values for Cu(II), Zn(II) and Pb(II) were also determined. Limit of tolerance of some electrolytes like NaCl, NaF, NaNO3, Na2SO4 and Na3PO4 have been reported. The preconcentration factor for Cu(II), Zn(II) and Pb(II) was 90, 140 and 100 respectively. The method was applied for the determination of Cu(II), Zn(II) and Pb(II) in the water samples collected from Sabarmati river, Ahmedabad, India.

A new chelating polymeric sorbent is developed using Merrifield chloromethylated resin anchored with calix[4]arene-o-vanillinsemicarbazone for simultaneous separation and solid phase extractive preconcentration of U(VI) and Th(IV). The “upper-rim” functionalized calix[4]arene-o-vanillinsemicarbazone was covalently linked to Merrifield resin and characterized by FT-IR and elemental analysis. The synthesized chelating polymeric sorbent shows superior binding affinity towards U(VI) and Th(IV) under selective pH conditions. Various physico-chemical parameters that influence the quantitative extraction of metal ions were optimized. The optimum pH range and flow rates for U(VI) and Th(IV) were 6.0–7.0 and 1.0–4.0 ml min−1 and 3.5–4.5 and 1.5–4.0 ml min−1, respectively. The total sorption capacity found for U(VI) and Th(IV) was 48734 and 41175 μg g−1, respectively. Interference studies carried out in the presence of diverse ions and electrolyte species showed quantitative analyte recovery (98–98.5%) with lower limits of detection, 6.14 and 4.29 μg l−1 and high preconcentration factors, 143 and 153 for U(VI) and Th(IV), respectively. The uptake and stripping of these metal ions on the resin were fast, indicating a better accessibility of the metal ions towards the chelating sites. The analytical applicability of the synthesized polymeric sorbent was tested with some synthetic mixtures for the separation of U(VI) and Th(IV) from each other and also from La(III), Cu(II) and Pb(II) by varying the pH and sequential acidic elution. The validity of the proposed method was checked by analyzing these metal ions in natural water samples, monazite sand and standard geological materials.

The first liquid chromatography/tandem mass spectrometry (LC/MS/MS) method for the determination of levetiracetam, an antiepileptic drug, in human plasma is described. The plasma filtrate obtained after solid-phase extraction (SPE), using a polymer-based, hydrophilic-lipophilic balanced (HLB) cartridge, was submitted directly to a short column LC/MS/MS assay. There was no significant matrix effect on the analysis. For validation of the method, the recovery of the free analytes was compared to that from an optimized extraction method, and the analyte stability was examined under conditions mimicking sample storage, handling, and analytical procedures. The extraction procedure yielded extremely clean extracts with a recovery of 79.95% and 89.02% for levetiracetam and the internal standard (IS), respectively. The intra-assay and inter-assay precision for the samples at the lower limit of quantitation (LLOQ) were 6.33 and 6.82%, respectively. The calibration curves were linear for the dynamic range of 0.5 to 50 µg/mL with a correlation coefficient r ≥ 0.9971. The intra-assay accuracy at LLOQ, LQC, MQC, and HQC levels ranged from 81.60 to 95.40, 93.00 to 103.47, 95.97 to 104.09, and 91.15 to 95.18%, respectively, while the inter-assay accuracy at LLOQ, LQC, MQC and HQC levels varied from 80.20 to 95.40, 88.53 to 107.53, 95.97 to 108.45, and 91.15 to 112.70%, respectively. The method is rugged and fast with a total instrumental run time of 2 min. The method was successfully applied for bioequivalence studies in human subject samples after oral administration of 1000 mg immediate release (IR) formulations. Copyright © 2006 John Wiley & Sons, Ltd.

A selective and high throughput liquid chromatography/tandem mass spectrometry (LC–MS/MS) method has been developed and validated to separate, detect and simultaneously quantify lamivudine (3TC), stavudine (d4T) and nevirapine (NVP) in human plasma using metaxalone as internal standard (IS). After solid phase extraction (SPE), the analytes and the IS were chromatographed on a Symmetry C18 (150 mm × 3.9 mm i.d., 5 μm particle size) column using 5 μL injection volume with a run time of 4.5 min. An isocratic mobile phase consisting of 0.5% glacial acetic acid in water:acetonitrile (20:80, v/v) was used to separate all these drugs. The precursor and product ions of these drugs were monitored on a triple quadrupole mass spectrometer, operating in the multiple reaction monitoring mode (MRM) without polarity switch. The method was validated over the range of 25–3000 ng/mL for 3TC, 20–2000 ng/mL for d4T and 50–5000 ng/mL for NVP. The absolute recoveries for analytes (≥86%) and IS (98.12%) achieved from spiked plasma samples were consistent and reproducible. Inter-batch and intra-batch precision (%CV) across four validation runs (LLOQ, LQC, MQC and HQC) was less than 10. The accuracy determined at these levels was within ±8% in terms of relative error. The method was successfully applied to a pivotal bioequivalence study of [60 (3TC) + 12 (d4T) + 100 (NVP)] mg dispersible tablets in 60 healthy human subjects under fasting condition.

A rapid, specific and sensitive LC-MS/MS assay using solid-phase extraction (SPE) for the determination of pravastatin, in human plasma is described. The plasma filtrate obtained after SPE, using a polymer base, a hydrophilic–lipophilic balance (HLB) cartridge, was submitted directly to short-column liquid chromatography–tandem mass spectrometric (LC-MS/MS) assay, with negligible matrix effect on the analysis. For validation of the method, the recovery of the free analytes was compared with that from an optimized extraction method, and the analyte stability was examined under conditions mimicking the sample storage, handling, and analysis procedures. The extraction procedure yielded extremely clean extracts with a recovery of 107.44 and 98.93% for pravastatin and IS, respectively. The intra-assay and inter-assay precisions for the samples at the LLOQ were 3.30 and 7.31% respectively. The calibration curves were linear for the dynamic range 0.5–200 ng/mL with correlation coefficient r ≥ 0.9988. The intra- and inter-assay accuracy ranged from 95.87 to 112.40%. The method is simple and reliable with a total run time of 3 min. This novel validated method was applied to the pharmacokinetic (PK) study in human volunteers receiving a single oral dose of 40 mg immediate release (IR) formulation. Copyright © 2006 John Wiley & Sons, Ltd.

The present study was an attempt to investigate the hepatoprotective and antioxidative property of Phyllanthus amarus (P. amarus) extract and phyllanthin. Phyllanthin, one of the active lignin present in this plant species was isolated from the aerial parts, by silica gel column chromatography employing gradient elution with hexane–ethyl acetate solvent mixture. It was obtained in high yields (1.23%), compared to reported procedures and the purity was ascertained by HPTLC and reversed-phase HPLC analysis. Characterization of phyllanthin was done by mp, UV–Visible spectrophotometry, elemental analysis, FT-IR, 1H NMR, 13C NMR and mass spectral analysis. Free radical scavenging activity of P. amarus extract and phyllanthin was also examined using DPPH assay. The protective effect of P. amarus extract and phyllanthin was studied on CCl4-induced toxicity in human hepatoma HepG2 cell line. The results indicated that CCl4 treatment caused a significant decrease in cell viability. In addition, the toxin treatment initiated lipid peroxidation (LPO), caused leakage of enzymes like alanine transaminase (ALT) and lactate dehydrogenase (LDH) with a significant decrease in glutathione (GSH) levels. It was observed that phyllanthin effectively alleviated the changes induced by CCl4 in a concentration-dependent manner, with much smaller strengths as compared to P. amarus extract.

A high throughput bioanalytical method based on solid phase extraction and liquid chromatography–tandem mass spectrometry (LC–MS/MS), has been developed for the estimation of perindopril and its metabolite perindoprilat, an angiotensin-converting enzyme inhibitor in human plasma. Ramipril was used as internal standard (IS). The extraction of perindopril, perindoprilat and ramipril from the plasma involved treatment with phosphoric acid followed by solid phase extraction (SPE) using hydrophilic lipophilic balance HLB cartridge. The SPE eluate without drying were analyzed by LC–MS/MS, equipped with turbo ion spray (TIS) source, operating in the negative ion and selective reaction monitoring (SRM) acquisition mode to quantify perindopril and perindoprilat in human plasma. The total chromatographic run time was 1.5 min with retention time for perindopril, perindoprilat and ramipril at 0.33, 0.35 and 0.30 min. The developed method was validated in human plasma matrix, with a sensitivity of 0.5 ng/ml (CV, 7.67%) for perindopril and 0.3 ng/ml (CV, 4.94%) for perindoprilat. This method was extensively validated for its accuracy, precision, recovery, stability studies and matrix effect especially because the pattern of elution of all the analytes appears as flow injection elution. Sample preparation by this method yielded extremely clean extracts with very good and consistent mean recoveries; 78.29% for perindopril, 76.32% for perindoprilat and 77.72% for IS. The response of the LC–MS/MS method for perindopril and perindoprilat was linear over the range 0.5–350.0 ng/ml for perindopril and 0.3–40 ng/ml for perindoprilat with correlation coefficient, r ≥ 0.9998 and 0.9996, respectively. The method was successfully applied for bioequivalence studies in human subjects samples with 4 mg immediate release (IR) formulations.

New chromogenic supramolecular vanadophiles were designed and synthesized by incorporating hydroxamic acid chains on a 1,3-alternate thiacalix[4]arene scaffold and were found to show high affinity toward vanadate ions. The article describes a comprehensive design process to devise a tailor-made co-ordination cavity for vanadate ions by pre-organization of hydroxamic acid chelating moieties on a 1,3-alternate thiacalix[4]arene scaffold. These receptors simultaneously co-ordinate two vanadate ions giving a highly ‘staggered’ geometry with almost D2d symmetry. Proposed structures and complexation behavior of the receptors were explained by critical examination of FTIR, UV–visible, mass, and 1H NMR data.

A new crown hydroxamic acid, 5,14-N,N′-hydroxyphenyl-4,15-dioxo-1,5,14,18-tetraaza hexacosane (NHDTAHA) for the extraction and spectrophotometric determination of lanthanum(III) is described. Lanthanum(III) forms a yellow coloured complex with NHDTAHA, which is extracted with chloroform, having molar absorptivity 7.7 × 103 1 mol−1 per cm at 372 nm. The system obeys Beer's law in the range 1.2–20 ppm of lanthanum. The extract is directly aspirated for ICP-AES measurements, the limits for estimation are 5–140 ppb of lanthanum. Lanthanum has been determined in monazite sand and standard samples.

A solvent extraction separation of uranium with a new crown hydroxamic acid 5, 14-N, N′-hydroxyphenyl-4, 15-dioxo-1,5,14,18-tetraaza hexacosane (NHDTAHA) in the presence of cerium, thorium and lanthanides is described. The uranium is extracted with chloroform solution of NHDTAHA and the extract is directly used for GS-AAS measurements. The detection limit is 0.01 ppm with a sensitivity of 20 ng/0.005 absorbance of uranium. The extraction constants of uranium crown hydroxamic acid complexes are determined. The selectivity factors (Kuranyl/Kn+M) for uranium crown hyrdoxamate evaluated by comparing the Kuranyl with the stability constants for competing metal cations (Kn+M) and anions (KnA−) and were found to be remarkably large. Uranium is preconcentrated and also determined spectrophotometrically. The molar absorptivity is 1.0×104 l−1 mol−1 per cm at 390 nm and system obeys Beer’s law in the range 2.0–30 ppm of uranium. Uranium has been determined in standard and environmental samples.

The present article discusses the role of versatile method of adsorption for removal of dye from waste water. An attempt is been made to provide information about the various parameters important in selecting an adsorbent for this purpose. The focus of authors is to provide in depth information about the low cost adsorbents from agricultural waste. The paper also throws light on factors affecting dye removal by adsorption process. Extensive literature has been surveyed and conclusion has been drawn from the studies done, to determine factors affecting the adsorption by agricultural adsorbents.

Prosopis juliflora bark, an agricultural by product, acts as an effective adsorbent for the removal of dyes. In the present study, the effectiveness of Prosopis juliflora bark in absorbing Direct yellow 12 from aqueous solution has been studied as a function of agitation time, dye concentration, adsorbent dose, pH and temperature. The maximum adsorption of dye by Prosopis juliflora bark occurred at pH of 3. Characterization of adsorbent like proximate analysis, point zero charge and bulk density are evaluated with the standard methods. Experimental results indicated that more than 85% of removal of dye is possible with the use of this low cost adsorbent Prosopis juliflora bark. It is proposed that Prosopis juliflora bark is an agriculture waste, locally available, environmentally benign (green) at low cost is suitable for the removal of synthetic anionic dye from aqueous solution.

The adsorption of dyes from aqueous solutions using various adsorbents has proved to be a promising approach in wastewater treatment units. Recently a number of adsorbents have been tested for their utility for waste water treatment. This paper investigates the utility of Prosopis Juliflora Bark Powder (PJB), an agricultural waste available in large quantity in India, as low-cost adsorbent to remove basic dye (Basic violet 14, BV14). Batch mode experiments were conducted at 35žC to study the effects of adsorbent dosage, initial concentration of BV14, contact time and pH on dye adsorption. Physico-chemical characters of PJB were studied. The Point zero charge of Prosopis Juliflora Bark was estimated by pH drift method and surface functional groups by Fourier transform infrared (FTIR) spec-troscopy before and after adsorption. The experimental results indicate potential of PJB as an adsorbent for removal of Basic Violet or Basic Fuchsine as an adsor-bent for the removal of dyes from aqueous solutions This method is beneficial for the waste water treatment. It was estimated that eco friendly and cost effective materials can be prepared as adsorbents for the removal of dyes.