Determination of low concentrations of chlorite and chlorate ions by using a flow-injection system

A flow-injection method is reported for the determination of chlorite ion and chlorite and chlorate ions in mixtures at the submilligram per liter level in drinking water. The chlorite ion concentration is selectively determined by using its reaction with iodide ion at pH 2, which liberates iodine. Both species react with iodide ion in6 M HCl to produce iodine, the concentration of which is measured spectrophotmetricaly at 370 nm. The individual species are determined using multiplel regression. The method exhibits a linear range from 2 to 150 μM (0.1–10.1 mg l^-1) for chlorite ion and from 2 to μM (0.1–8.3 mg l^-1 for chlorate ion, with relative standard deviations of 0.4 and 1.2%, respectively.     

Direct potentiometric titration of thiosulfate,thiourea, and ascorbic acid with lodate using an iodide ion-selective electrode

A potentiometric method has been developed for the semi-automatic direct titration of thiourea, thiosulfate, and ascorbic acid with potassium iodate in strongly acidic solutions using an iodide ion-selective electrode to monitor the reaction and locate the endpoint. The method is simple, fast, precise, and accurate. Amounts ranging from 0.15–1.5 mg of thiourea (3.9 × 10^?4–3.9 × 10^?3, M), 0.3–3.0 mg of thiosulfate (5.4 × 10^?4–5.4 × 10^?3, M), and 0.5–5.0 mg of ascorbic acid (5.7 × 10^?4–5.7 × 10^?3, M) have been determined with an average error of about 1%. The method has been applied to the determination of ascorbic acid in tablets. Results checked closely with those obtained with a standard titrimetric method.     

Determination of chlorite at very low levels by using differential pulse polarography

A method is reported for the determination of μgl^?1 levels of chlorite by using differential pulse polarography. The electrochemical reduction of chlorite was studied between pH 3.7 and 14 and in an ionic strength range of 0.05–3.0 M. The optimum conditions are pH 4.1–4.4 and an ionic strength of 0.45 M. The current under these conditions is diffusion-controlled and is a linear function of chlorite concentration ranging from 2.77×10^?7 to 2.80×10^?4 M (19 μgl^?1 to 19 mg l^?1). The imprecision is better than ±1.0% and ±3.4% at concentrations of 2.87×10^?5 M and 1.74×10^?6M, respectively, with a detection limit of 1×10^?7 M (7μgl^?1). An interference study and the application of this method for determining chlorite in drinking water are reported.     

Fourier transform Infrared characterization of melanin free ink from selected cephalopods for identification of active functional groups responsible for antioxidant activity

The present investigation aims to explore the active functional groups that are responsible for the antioxidant property in MFI from three cephalopods such as Sepia pharaonis (CMFI), Sepioteuthis lessioniana (SMFI) and Amphioctopus aegina (OMFI) using Fourier Transform Infrared (FTIR) spectroscopy. Highest DPPH scavenging activity of 28.29 ± 0.41% and metal chelating activity of 47.62 ± 0.48% were shown by MFI from A. aegina (OMFI) at a concentration of 0.045 mg/ml and 0.04 mg/ml, respectively. Though the invitro antioxidant values of MFI were low, when added with sardine fish mince, it retarded the lipid oxidation during the entire storage period and it was very clear with the lower TBARS values compared to the control. FTIR analysis of CMFI, SMFI and OMFI revealed the presence of characteristic strong band at 3361.92 cm^?1, 3364.54 cm^?1 and 3373.96 cm^?1 and at 1642.20 cm^?1, 1636.21 cm^?1and 1635.53 cm^?1,respectively. The O–H and N–H stretching vibrations and alkenyl c = c stretch corresponding to the two vibrations in all the three spectra can be accountable for its antioxidant activities leading to its wide new applications as a natural antioxidant from marine resources.     

A rapid method for the spectrophotometric determination of palladium(II) and osmium(VIII)

Propionyl promazine phosphate is proposed as a new reagent for the rapid spectrophotometric determination of microgram amounts of Pd(II) and Os(VII). PPP instantaneously forms an orange-red 1:1 complex with Pd(II) in sodium acetate-hydrochloric acid buffer of pH 0.8 to 4.0 at room temperature. The reagent also forms an orange-red radical cation with Os(VIII) in 0.5 to 2.0 M hydrochloric acid. The Pd-PPP complex exhibits an absorption maximum at 490–500 nm with molar absorptivity of 7.1 × 10³ liter mol^?1 cm^?1. The Os-PPP radical cation has an absorption maximum at 505–515 nm with molar absorptivity of 2.21 × 10⁴ liters mol^?1 cm^?1. The Sandell sensitivity is 0.022 μg/cm² (Pd) and 0.008 μg/ cm² (Os). Beer's law is valid over the concentration range 0.2 to 21 ppm (Pd) and 0.2 to 4.2 ppm (Os). The proposed method offers the advantages of simplicity, rapidity, and without the need for heating or extraction. The reagent is used for the determination of Pd in the synthetic mixtures corresponding to Pd alloys used in jewelery and Os in osmiridium alloy.     

Dissociation rate measurements in SO2 + Ar mixtures behind incident shock waves

Dissociation rates of SO₂ in SO₂ + Ar mixtures at 6%, 11%, 15% and 20% of SO₂ were measured behind incident shock waves over a temperature range 4000–6000 K at initial pressures 1.0 to 2.5 Torr. The recorded laser schlieren signals exhibited two exponentials, the faster one due to vibrational relaxation and the slower one due to dissociation. The initial dissociation rate was calculated from the value of the density gradient at the point of intersection of the two exponentials. A least-squares analysis of the experimental data yielded the following empirical relations: k_SO2Ar = 3.34 × 10¹⁵ exp(?107.6 kcal mole^?1/RT) cm³/mole s, k_SO2SO2 = 5.02 × 10¹⁴ exp(?66.6 kcal mole^?1 kcal mole^?1/RT) cm³/mole s.     

Simultaneous Determination of Dipyrone and Papaverine in Pharmaceutical Formulation using PLS Regression and UV Spectrophotometry

Abstract

A combination of sodium dipyrone and papaverine hydrochloride is used as an analgesic and antispasmodic drug. A simple and rapid procedure is proposed for simultaneous determination of these drugs in commercial formulations (Melpaz^®) based on partial least squares (PLS) regression and UV spectrophotometric measurements in the range of 218–300 nm. The calibration set was built with 25 solutions in concentrations ranging from 15.0–35.0 mg ml^?1 for dipyrone and from 0.5–1.5 mg ml^?1 for papaverine in methanol. The relative standard deviation (RSD) was 1.05% for dipyrone and 1.55% for papaverine in pharmaceutical formulations. The percent of relative recovery was 95.9% for dipyrone and 95.2% for papaverine. Figures of merit, such as accuracy, precision, sensitivity and adjust were also determined. The methodology was validated by using an independent method, based on high performance liquid chromatography (HPLC).     

Extraction-spectrophotometric determination of tungsten as tungsten blue

Tri-n-butyl phosphate (TBP) is used to extract tungsten(IV) from 0.5 M hydrochloric acid containing molybdenum(VI) and other metals. Tungsten(VI) in the TBP solution is reduced by tin(II) chloride and n-butyl acetate is used for dilution. The tungsten blue formed in the TBP/n-butyl acetate medium (1:1) is measured at 615 nm. The apparent molar absorptivity is about 1000 1 mol^?1 cm^?1; calibration graphs are linear in the range 0.1–1.5 mg of tungsten.     

Spectrophotometric determination of Chromium(VI) using cyclam as a reagent

A simple, rapid, sensitive, and inexpensive method for spectrophotometric determination of chromium(VI), based on the absorbance of its complex with 1,4,8,11-tetraazacyclotetradecane (cyclam) is presented. The complex showed a molar absorbtivity of 1.5?×?10⁴?L?mol^?1?cm^?1 at 379?nm. Under optimum experimental conditions, a pH of 4.5 and 1.960?×?10³?mg?L^?1 cyclam were selected, and all measurements were performed 10?min after mixing. Major cations and anions did not show any interference; Beer's law was applicable in the concentration range 0.2–20?mg?L^?1 with a detection limit of 0.001?mg?L^?1. The standard deviation in the determination is ±0.5?mg?L^?1 for a 15.0?mg?L^?1 solution (n?=?7). The described method provides a simple and reliable means for determination of Cr(VI) in real samples.     

LC–MS–MS Method to Simultaneously Determine Six Probe Drugs for CYP450 Isozymes in Human Liver Microsomes

Here, we report a rapid and specific method based on high-performance liquid chromatography coupled with tandem mass spectrometry (LC–MS–MS) capable of quantifying six CYP450-specific probe substrates in human liver microsomal incubation mixtures simultaneously. These analytes were prepared by single-step extraction and detected in one run by switching polarity of electrospray ionization mode three times. Following optimization of the chromatographic conditions, the peaks were well separated, and retention times ranged between 2.0 and 8.4 min. The total run time for a single injection was within 9 min. This method was fully validated over linear range of 18.8–3,000.0 ng mL^?1 for diclofenac, 0.8–3,000.0 ng mL^?1 for dapson, 1.5–3,000.0 ng mL^?1 for dextromethorphan, 2.0–4,000.0 ng mL^?1 for omeprazole, 75.0–3,000.0 ng mL^?1 for chlorzoxazone and 0.8–3,000.0 ng mL^?1 for phenacetin using diazepam as internal standard. Samples were prepared by protein precipitation and analyzed on the LC–MS–MS equipped with ESI interface. For each analyte, inter- and intra-day precision (RSD%) were <15 % and accuracy was within 85–115 %. The specificity, precision, accuracy, stabilities and matrix effect were evaluated.     

Utilisation of kinetic-based flow injection methods for the determination of chlorine and oxychlorine species

Automated selective iodometric methods for the determination of chlorine and oxychlorine species have been developed for use in the drinking water industry. By utilising kinetic-based methods, linear ranges observed were: chlorine, 0.2–10 mg l^?1; chlorine dioxide, 0.3–10 mg l^?1; chlorite ion, 0.08–5 mg l^?1; and chlorate ion, 0.08–5 mg l^?1.     

An improved method for the spectrophotometric determination of fluoride by addition of sodium dodecyl sulphate to the fluoride/lanthanum (III)/Alizarin fluorine blue system

The conventional spectrophotometric method for the determination of fluoride, based on the fluoride/lanthanum(III)/alizarin fluorine blue ternary complex, is improved by addition of sodium dodecyl sulphate. In 15% (v/v) acetone medium, the absorbance of the binary reagent complex is decreased and the reaction time is only 3 min under sonication. Beer's Law is obeyed at 574 nm for fluoride concentrations in the ranges 0.075–0.30 and 0.20–1.2 mg 1^?1; the apparent molar absorptivities are (1.6 ± 0.1) × 10⁴ and (1.5 ± 0.1) × 10⁴ mol^?1 cm^?1 fluoride levels, respectively. This method is applied to the determination of fluoride in bottled mineral waters.     

Automated stopped-flow system in pharmaceutical and clinical analysis : Kinetic determination of acetaminophen in formulations and serum by using the iron(II)—2,4,6-tris(2-pyridyl)-s-triazine

The development of automated stopped-flow spectrophotometric systems, their potential in automated routine determinations using kinetic and fast equilibrium techniques and several examples of applications are briefly reviewed. The use of a compact, inexpensive laboratory-made stopped-flow system for the measurement of reaction rates and a fast equilibrium method for the determination of acetaminophen in formulations and serum are described. The reaction-rate method is based on monitoring the oxidation of acetaminophen by iron(III) in the presence of the chelating agent 2,4,6-tris(2-pyridyl)-s-triazine to form a highly absorbing complex of iron(II). The calibration graph is linear in the range 20–200 μg ml^?1, with a precision of 0.8–2.6%, a detection limit of 5.5 μg ml^?1 and a measurement throughput of 120 per hour. Common excipients do not interfere and the analysis of commercial formulations gave results similar to those of a reference method. The optimization of the experimental conditions was done by a kinetic study of the reaction and some kinetic parameters are given.The method for the determination of acetaminophen in serum is based on a rapid measurement of the absorbance of the reaction mixture after a delay time of 15 s in the presence of chlorpromazine, which catalyses the reaction. Acetaminophen is isolated by extraction with ethyl acetate and the calibration graph is linear in the range 0.5–6 μg ml^?1 with a detection limit of 0.04 μg ml^?1 and a precision of 1.5%. The proposed method showed a decreased interference from drugs that also react with iron(III).     

Iodometric determination of milligram and microgram amounts of levocetirizine in pharmaceuticals

Four simple, selective and sensitive methods are described for the determination of levocetirizine dihydrochloride (LCT) in bulk drug and in tablets. The methods exploit the well-known analytical reaction between iodide and iodate in the presence of acid solution. Iodide present is oxidized by iodate in an amount equivalent to the HCl present in LCT to iodine and the liberated iodine is determined by four different procedures which inturn quantify LCT at varying detection range and sensitiveness. Two direct titrimetric procedures involve titration of iodine by thiosulphate either towards starch end point (method A) or potentiometrically (method B). Both the methods have a reaction stiochiometry of 1: 1 (LCT: liberated iodine) and have quantification ranges of 2–20 mg LCT for method A and method B. The liberated iodine is also measured spectrophotometrically at 350 nm (method C) or the iodine-starch complex measured at 570 nm (method D). In both the methods, the absorbance is found to be linearly dependent on the concentration of iodine which in turn is related to LCT concentration. The calibration curves are linear over 5–40 and 1.25–12.5 mg mL^?1 LCT for method C and method D, respectively. The calculated molar absorptivity and Sandel sensitivity values are 1.0 × 10⁴ L mol^?1 cm^?1 and 0.0435 mg cm^?2, respectively for method C, and their respective values for method D are 2.9 × 10⁴ L mol^?1 cm^?1 and 0.0156 mg cm^?2. The intra-day and inter-day accuracy and precision studies were carried according to the ICH guidelines. The method was successfully applied to the analysis of two brands of tablets LCT. The accuracy was also checked by placebo blank and synthetic mixture analyses besides recovery study via standard addition procedure.     

Propericiazine as a reagent for the spectrophotometric determination of ruthenium(III)

Propericiazine forms an orange-red species with ruthenium(III) immediately in 6–8 M phosphoric or hydrochloric acid or 4.5–5.5 M sulphuric acid. The absorption maximum is at 511 nm and the molar absorptivity is 1.1 × 10⁴ 1 mol^?1 cm^?1. Beer's Law is obeyed over the range 0.2–9.4 mg 1^?1 (optimum range 0.5–9.0 mg 1^?1). Interferences are described. The method is used to determine ruthenium in synthetic zinc–magnesium alloy and uranium alloy (fuel) solutions.     

Spectrophotometric Determination of Antimony (III) By Solvent Extraction with Mandelic Acid and Malachite Green

Abstract

A sensitive and selective method has been developed for the spectrophotometric determination of antimony in the tervalent oxidation state. It was found that antimony (III) reacts with mandelic acid to form a complex anion extractable into chlorobenzene with malachite green in weak acidic media (pH 2.2 to 3.5) at room temperature and is determined indirectly by measuring the absorbance of malachite green in the extract at 628 nm. The calibration graph is linear for antimony (III) over the range 0.088–1.8 mg 1^?1 (7.2 × 10^?7–1.5 × 10^?5 mol 1^?1) with the apparent molar absorptivity ε × 6.9 × 10⁴ 1 mol^?1 cm^?1. Antimony (V) was slightly extracted in the presence of phosphate buffer with ε × 2.7 × 10³ 1 mol^?1 cm^?1.     

Upper limits for the rate constant for the reaction Br + H2O2 → HBr + HO2

Upper limits for the rate constant for the reaction Br + H₂O₂ → HBr + HO₂ have been measured over the temperature range 298 to 417 K in a discharge flow, system using a mass spectrometer as a detector. Results are K₁< 1.5 × 10^?15 cm³ s^?1 at 298 K and K₁< 3.0 × 10^?15 cm³ s^?1 at 417 K, respectively. The implication to Stratospheric chemistry is discus     

Optimization of Factors Influencing Microinjection Method for Agrobacterium tumefaciens-Mediated Transformation of Tomato

A simple and efficient protocol for Agrobacterium-mediated genetic transformation of tomato was developed using combination of non-tissue culture and micropropagation systems. Initially, ESAM region of 1-day-old germinated tomato seeds were microinjected for one to five times with Agrobacterium inoculums (OD₆₀₀?=?0.2–1.0). The germinated seeds were cocultivated in the MS medium fortified with (0–200 mM) acetosyringone and minimal concentrations of (0–20 mg?L^?1) kanamycin, and the antibiotic concentration was doubled during the second round of selection. Bacterial concentration of OD₆₀₀?=?0.6 served as an optimal concentration for infection and the transformation efficiency was significantly higher of about 46.28 %. In another set of experiment, an improved and stable regeneration system was adapted for the explants from the selection medium. Four-day-old double cotyledonary nodal explants were excised from the microinjected seedlings and cultured onto the MS medium supplemented with 1.5 mg?L^?1 thidiazuron, 1.5 mg?L^?1 indole-3-butyric acid, 30 mg?L^?1 kanamycin, and 0–1.5 mg?L^?1 adenine sulphate. Maximum of 9 out of 13 micropropagated shoots were shown positive to GUS assay. By this technique, the transformation efficiency was increased from 46.28 to 65.90 %. Thus, this paper reports the successful protocol for the mass production of transformants using microinjection and micropropagation techniques.     

Zn|ZnI2| iodine secondary galvanic cells using iodine adducts of nylon-6 and other polymers as positive electrodes

Zn|ZnI₂| iodine galvanic cells using carbon plate electrodes coated with polymer + carbon powder mixtures are rechargeable with minor self-discharge when a positive ion exchanging film is used as the separator. Among the polymers tested (nylon-6, Poly(tetrahydrofuran), poly(acrylonitrile), poly(methly methacrylate), poly(vinly Alcohol), poly(N-vinylpyrrolidone), and poly(4-vinylpridine)), nylon-6 and poly(tetrahydrofuran) have the highest ability to absorb iodine and afford secondary galvanic cells showing the best rechargeability: the secondary galvanic cells are rechargeable more than 500 times with about 100% current efficiency and 81–83% energy efficiency when charged and discharged at 2 mA/cm² at 25°C. The average charging and discharging voltages of the secondary cell using nylon-6 are 1.42 and 1.18 V, respectively. The cell prepared by using nylon-6 generates about 80 mA/cm² of an initial short-circuit current and 0.3–80 mA/cm² of a steady-state short-circuit current when the cell is dipped into a aqueous solution containing I^?₃. The steady-state short-circuit current increases with increasing I^?₃ concentration and a linear correlation holds between the logarithm of the steady-state short-circuit current and the logarithm of [I^?₃] in the range of [I^?₃] = 0.05–0.5 mol/1.     

Atomic absorption spectrometric determination of copper in calcium carbonate scale and carbonate rocks by direct atomization of solid samples

Powdered samples (1 mg) are mixed with 1 mg of powdered graphite and copper is determined by atomic absorption spectrometry in a miniature graphite cup placed in a graphite crucible. Optimum conditions were drying at 200 °C (30 s), ashing at 900 °C (30 s), atomizing at 2700 °C (15 s) and cleaning at 2800 °C (10 s). Samples were powdered to 1–10 μm particle size. Magnesium, manganese and iron did not interfere. The effect of calcium carbonate was eliminated by the graphite addition. Results for copper (0.5–5 μg g^?1) in the scale and rocks agreed well with values obtained for dissolved samples. Relative standard deviations (n=10) were 4.9% for 1.2 μg g^?1 copper and 14.8% for 0.577 μg g^?1.