Solid Phase Extraction and Spectrophotometric Determination of Silver with 2-(2-Quinolylazo)-5-Dimethylaminophenol

A new chromogenic reagent, 2-(2-quinolylazo)-5-Dimethylaminophenol (QADMAP) was synthesized, and a sensitive, selective, and rapid method was developed for the determination of the μg/L level of silver ions. The method is based on the rapid reaction of silver(I) with QADMAP and the solid phase extraction of the colored chelate using a C₁₈ cartridge. The QADMAP reacts with Ag(I) in the presence of a citric acid-sodium hydroxide buffer solution (pH 5.0) and a sodium dodecyl sulfonate (SDS) medium to form a violet chelate of molar ratio 1 : 2 (silver to QADMAP). This chelate was enriched by solid phase extraction with C₁₈ cartridge, and the retained chelate was eluted from the cartridge using ethanol (with 1% acetic acid). In the ethanol medium (with 1% acetic acid), the molar absorptivity of the chelate was 1.25 × 10⁵ L mol⁻¹ cm⁻¹ at 584 nm. Beer’s law was obeyed in the range 0.01–0.6 μg/mL. The relative standard deviation for eleven replicate samples of 0.01 μg/mL was 1.86%. The detection limit is 0.02 μg/L in the original samples. The method was applied to the determination of μg/L levels of silver ions in water with good results.__________From Zhurnal Analiticheskoi Khimii, Vol. 60, No. 6, 2005, pp. 566–570.Original English Text Copyright © 2005 by Huang, Yang, Hu, Yin.This article was submitted by the authors in English.     

The Color Reaction of Mercury(II) with the New Reagent 2-Methylthiophenyldiazoaminoazobenzene and Its Application

A new and very sensitive and selective chromogenic reagent, 2-methylthiophenyldiazoaminoa-zobenzene (MTDAA), was synthesized and studied in detail for the determination of trace mercury(II) in water samples. The method is based on the color reaction between MTDAA and mercury(II). It was found that mercury(II) reacts with MTDAA in Na₂B₄O₇-NaOH buffer solution (pH = 10.0) to form 1 : 2 red complexes; these show maximum absorption at 520 nm. Beer’s law is obeyed in 0–15 µg of mercury(II) in 25 mL of solution. The apparent molar absorptivity of the complex is 1.33 × 10⁵ L/(mol cm); its limit of quantification, limit of detection, and relative standard deviation are 0.75 ng/mL, 0.27 ng/mL, and 1.0%, respectively, giving better sensitivity. The influence of the reaction variables and the effect of interfering ions are reported; most of the metal ions in water samples can be tolerated in considerable amounts. Only a few ions can interfere with the determination of trace mercury(II), but these can be eliminated by prior extraction. The proposed method is sensitive, simple, and rapid. It has been applied to the determination of trace mercury(II) in water samples with satisfactory results.__________From Zhurnal Analiticheskoi Khimii, Vol. 60, No. 7, 2005, pp. 703–706.Original English Text Copyright © 2005 by Guo, Din, Tian, Liu, Chang, Meng.The text was submitted by the authors in English.     

Electrochemical Oxidation of Iodide in the Presence of Benzenesulfinic Acids and Its Application to the Quasi-Catalytic Determination of Benzenesulfinic Acids

The mechanism of the electrochemical oxidation of iodide in the presence of 4-toluenesulfinic acid was studied in an aqueous solution using cyclic voltammetry and controlled-potential coulometry. The results indicate that the anodically generated iodine reacts with 4-toluenesulfinic acid through a quasi-catalytic process. In addition, the results indicate the suitability of iodide as a mediator for the determination of 4-toluene-sulfinic acid in aqueous solutions. The quasi-catalytic peak currents are linearly dependent on the 4-toluene-sulfinic acid concentrations in the range 6.0 ×10⁻³ − 8.0 × 10⁻⁶ M.__________From Zhurnal Analiticheskoi Khimii, Vol. 60, No. 6, 2005, pp. 598–602.Original English Text Copyright © 2005 by Davood Nematollahi, Zinat Forooghi, Esmail Tammari.This article was submitted by the authors in English.     

Kinetic Determination of Mercury(II) at Trace Level from Its Catalytic Effect on a Ligand Substitution Process

A catalytic kinetic method (CKM) is presented for the determination of mercury(II) based on its catalytic effect on the rate of substitution of N-methylpyrazinium ion (Mpz⁺) onto hexacyanoferrate(II). The progress of the reaction was monitored spectrophotometrically at 655 nm by registering the increase in absorbance of the product [Fe(CN)₅(Mpz]²⁻ under the reaction conditions: 5 × 10⁻³ mol L⁻¹ [Fe(CN)₆]⁴⁻), 5 × 10⁻⁵ mol L⁻¹ [Mpz⁺], T = 25.0 ± 0.1°C, pH 5.00 ± 0.02 and ionic strength, I = 0.1 mol L⁻¹ (KNO₃). Quantitative rate data at specified experimental conditions showed a linear dependence of the absorbance after fixed time A _t on the concentration of mercury(II) catalyst in the range 20.06–702.1 ng mL⁻¹. The maximum relative standard deviations and percentage errors for the determination of mercury(II) in the range of 20.06–200.6 ng mL⁻¹ were calculated to be 1.7 and 2.7% respectively. The detection limit was found to be 7.2 ng mL⁻¹ of mercury(II). Accuracy (expressed in terms of recoveries) was in the range of 98–103%. Figures of merit and interference due to many cations and anions was investigated and discussed. The applicability of the method was demonstrated by determining the mercury(II) in different synthetic samples and confirming the results using atomic absorption spectrophotometry. The proposed method allowed determination of mercury(II) in the range 20.06–702.1 ng mL⁻¹ with very good selectivity and an output of 30 samples h⁻¹.__________From Zhurnal Analiticheskoi Khimii, Vol. 60, No. 6, 2005, pp. 654–661.Original English Text Copyright © 2005 by Surendra Prasad.This article was submitted by the author in English.     

Optimized and Validated Spectrophotometric Methods for the Determination of Roxatidine Acetate Hydrochloride in Drug Formulations Using 2,3-Dichloro-5,6-dicyano-1,4-benzoquinone and <Emphasis Type="Italic">p</Emphasis>-Chloranilic Acid

Two simple and sensitive spectrophotometric procedures are proposed for the determination of roxatidine in pure form and in tablets. Both methods are based on the charge transfer complexation reaction of the drug with 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) or p-chloranilic acid resulting in colored products. In both cases, the absorbance measurement was made at 530 nm. Beer’s law was obeyed in the concentration ranges 5–65 and 10–260 µg mL⁻¹ with DDQ and p-chloranilic acid, respectively. A series of variables were studied to optimize the reaction conditions. No interference was observed from the common excipients present in the formulations. The described methods were applied successfully for the analysis of roxatidine in pharmaceutical preparations. Statistical comparison of the results with those from our UV reference method shows excellent agreement. Both methods are validated statistically and do differ significantly in accuracy.__________From Zhurnal Analiticheskoi Khimii, Vol. 60, No. 7, 2005, pp. 715–722.Original English Text Copyright © 2005 by Nafisur Rahman, Mohammad Kashif.The text was submitted by the authors in English.     

A Catalytic Method for Determining Cadmium(II), Nickel(II), and Zinc(II) Inhibitor Metals

The inhibitory effect of Cd(II), Ni(II), and Zn(II) on the oxidation of 3,3′,5,5′ -tetramethylbenzidine with periodate was detected. The optimum reaction conditions were found, and the procedures were developed for determining 1 × 10⁻² to 10 μg/mL Cd(II), Ni(II), and Zn(II) in solution. The indicator reaction was performed on a number of supports. The maximum inhibitory effect was observed on silica gel-based plates for TLC. Procedures for determining 6 × 10⁻³ to 0.4 μg of these metals were developed. Silica gel plates with the immobilized reagent for cadmium (bromobenzothiazo) were used to preconcentrate cadmium. A selective test procedure was developed for determining 1 × 10⁻⁴ −3 × 10⁻³ μg/mL cadmium with the visual detection of the process rate. Upon the introduction of dimethylglyoxime into the indicator reaction, the inhibitory effect of nickel changed to its promoting effect and the detection limit for nickel was lowered. A procedure was developed for determining 3 × 10⁻⁴ −3 × 10⁻³ μg/mL nickel in solution and 7 × 10⁻³−4 × 10⁻¹ μg nickel on the surface of Sorbfil plates. An assumption was made about the reasons for the inhibitory effect of metal ions on the oxidation of aryl diamines with periodate.__________Translated from Zhurnal Analiticheskoi Khimii, Vol. 60, No. 6, 2005, pp. 662–669.Original Russian Text Copyright © 2005 by Beklemishev, Kiryushchenkov, Stoyan, Dolmanova.     

High-Performance Liquid Chromatographic Method for Determination and Pharmacokinetic Study of Chlorogenic Acid in the Plasma of Rats After Administration of the Chinese Medicinal Preparation Luying Decoction

A simple and sensitive high-performance liquid chromatographic method has been developed for determination of chlorogenic acid in rat plasma. Chlorogenic acid was extracted from plasma samples with methanol. HPLC analysis of the extracts was performed on a C₁₈ column (250 mm × 4.6 mm i.d., 5 µm particles). The mobile phase was acetonitrile −1% formic acid (9:91, v/v). The calibration plot was linear over the range 0.0420–2.10 µg mL⁻¹ and the lower limit of quantification was 0.0420 µg mL⁻¹. The method was reproducible and reliable with intra-day precision better than 8.2%, inter-day precision better than 9.1%, accuracy within ±8.3%, and mean extraction recovery above 84.4%. The validated method was successfully applied to pharmacokinetic studies of chlorogenic acid in rat plasma after administration of Luying decoction.     

Determination of Iron in Natural and Drinking Waters by Stripping Voltammetry

A thick-film graphite-containing electrode modified with calomel was proposed for determining iron(III) by stripping voltammetry. Of the organic reagents under study, pyrocatechol was found to be the most sensitive in determining iron(III). The detection limit for iron(III) was 3.6 × 10⁻¹⁰ M (0.02 µg/L) at a preconcentration time of 30 s. The analytical signal from iron(III) was a linear function of its concentration in the range from 0.05 to 5 µg/L. A procedure for determining total iron in drinking and natural water was developed and certified.__________Translated from Zhurnal Analiticheskoi Khimii, Vol. 60, No. 7, 2005, pp. 747–752.Original Russian Text Copyright © 2005 by Stozhko, Inzhevatova, Kolyadina.     

Spectrophotometric Determination of Metoclopramide in Pharmaceutical Preparations

A simple and rapid spectrophotometric method for the determination of metoclopramide is described. The method is based upon simple diazotization reactions with nitrite and aniline as the coupling reagent. The absorbance was measured at 410 nm. The method was optimized for acidity, the amount of reagents required, and the amount of sodium hydroxide. The range of linearity was 0.5–12.0 µg/mL. The method was successfully applied to the determination of metoclopramide in pharmaceutical preparations without any interference from common excipients.__________From Zhurnal Analiticheskoi Khimii, Vol. 60, No. 7, 2005, pp. 711–714.Original English Text Copyright © 2005 by Shah, Rasul Jan, Azam Khan, Amin.The text was submitted by the authors in English.     

Gas Chromatographic–Mass Spectrometric Method for Quantitation of Trimethylsilyl Derivatives of Nerve Agent Degradation Products in Human Plasma, Using Strong Anion–Exchange Solid-Phase Extraction

For unequivocal proof of the use of nerve agents such as sarin, soman, cyclohexylsarin, VX, and Russian VX, a simple and accurate method, gas chromatography–mass spectrometry (GC–MS) after trimethylsilyl derivatization, was explored for simultaneous determination of the corresponding alkyl methylphosphonic acids (AMPAs) and of methylphosphonic acid (MPA) in human plasma. GC–MS analysis was performed after solid-phase extraction, with a strong anion-exchange cartridge, from plasma samples previously deproteinized with mercuric acetate, and then derivatization with bis(trimethylsilyl)trifluoroacetamide containing 5% trimethylchlorosilane. All five AMPA derivatives and the MPA derivative were separated to baseline within 11 minutes without interference. Linear calibration plots were obtained over concentrations ranging from 50 ng mL⁻¹ to 5 µg mL⁻¹. The relative standard deviation of recoveries ranged from 1.9 to 9.7% and detection limits were 22 ng mL⁻¹ or below.Revised: 3 and 23 May 2005     

Microdetermination of sulfite with a piezoelectric crystal detector

A piezoelectric method is proposed for the determination of sulfite in concentration range 1 × 10^–7–1 × 10^–5 mol/1. The method is based on the redox reaction of sulfite with iodine followed by measuring frequency change of the piezoelectric crystal caused by the unreacted iodine. The method is applied to the determination of sulfite in liquor.     

Polymerization of 3-Methoxythiophene in a Direct-Current Discharge

Thin polymer films were obtained from 3-methoxythiophene at the cathode in a dc discharge. It was found using Fourier transform IR spectroscopy that thiophene rings were the main structural units of the polymer; aliphatic fragments and oxygen-containing groups were also present. The polymer based on 3-methoxythiophene was found to exhibit p-type intrinsic conduction with an activation energy of 0.045 eV. The conductivity of the polymer at 20°C was 10⁻⁸ Ω⁻¹ cm⁻¹, and doping with iodine resulted in a rise in conductivity to 10⁻³ Ω⁻¹ cm⁻¹.__________Translated from Khimiya Vysokikh Energii, Vol. 39, No. 5, 2005, pp. 382–385.Original Russian Text Copyright © 2005 by Drachev, Gil’man, Krasovskii, Costa-Belobrzeckaja.     

Comparison of Different Sorbents for Solid-Phase Extraction of Phenoxyalkanoic Acid Herbicides

An HPLC procedure for determination of phenoxyalkanoic acid herbicides in water samples is proposed. The analytical column Phenomenex C18(2) Luna 5 µm and UV detection at 225 nm were applied. Baseline resolution was achieved in isocratic mode with a mobile phase consisting of acetonitrile/acetic acid (40/60, v/v), adjusted to pH 2.5. SPE sorbents – C₁₈ BondElut, phenyl-silica, LiChrolut SAX and polymeric sorbents – were compared for isolation and preconcentration of 6 phenoxyalkanoic acid herbicides. Higher (above 95%) and more reproducible recoveries were obtained with polymeric and phenyl-silica sorbents using pure methanol for elution. The method was tested for river water samples with the limit of detection in the range of 2–3 µg L⁻¹ (for 50 mL sample) and a reproducibility of 5% RSD.     

Flow Injection Chemiluminescence Determination of Isoniazid Using On-Line Electrogenerated Manganese(III) as Oxidant

A novel flow injection chemiluminescence (CL) system for the determination of isoniazid has been proposed. It is based on the direct CL reaction of isoniazid and Mn(III) in sulfuric acid medium. The unstable Mn(III) was on-line electrogenerated by constant current electrolysis. The CL emission intensity was linear with isoniazid concentration in the range 0.1–10 μg/mL; the detection limit was 3.2 × 10⁻² μg/mL. The whole process could be completed in 1 min with a relative standard deviation of less than 5%. The proposed method is suitable for automatic and continuous analysis and has been applied successfully to the analysis of isoniazid in pharmaceutical preparation.     

Low-temperature sorption-luminescence determination of silver using silica gel chemically modified with mercaptopropyl groups

Silica gel chemically modified with mercaptopropyl groups extracts silver(I) from solutions in the acidity ranges from 4 M HNO₃ to pH 8 and from 0.01 M HCl to pH 7. The time it takes to attain a sorption equilibrium is no more than 2 min; distribution coefficient is 1 × 10⁵ cm³/g. Yellow-orange luminescence was produced in the adsorbent phase upon the UV irradiation of wet adsorbates cooled to the liquid-nitrogen temperature (77 K). This effect was used for the development of a procedure for the low-temperature sorption-luminescence determination of silver. The calibration graph was linear in the range 1–80 µg Ag per 0.1 g of adsorbent. The detection limit was 0.05 µg per 0.02 g of adsorbent. The relative standard deviation was no more than 6% for silver amounts higher than 5 µg.__________Translated from Zhurnal Analiticheskoi Khimii, Vol. 60, No. 4, 2005, pp. 390–393.Original Russian Text Copyright © 2005 by Losev, Elsuf ev, Trofimchuk.     

A test method for determining palladium in chloride solutions on the solid phase of a fibrous anion exchanger

The sorption of palladium(II) from chloride solutions on polyacrylonitrile fiber filled with the AV-17 anion exchanger (PANF-AV-17) and its subsequent determination with p-nitrosodiethylaniline on the solid phase were studied. The results of determining palladium with this reagent on the solid phase of polyacrylonitrile fiber filled with the KU-2 cation exchanger and the AV-17 anion exchanger were compared. A test method was developed for determining palladium on the PANF-AV-17 solid phase. Sorption was performed in the batch mode; the analytical signal was estimated by measuring the diffuse reflection coefficient or visually using a color scale. The detection limit was 0.005 µg/mL; the range of the calibration scale was 0–0.2 µg/mL at the volume of the test solution 10–20 mL. The accuracy of the procedure was verified by the added-found method in the analysis of tap water and a standard reference sample of natural sodium chloride water. The relative standard deviation was no more than 25%; the time of the analysis of 5 or 6 samples was 25–30 min.Translated from Zhurnal Analiticheskoi Khimii, Vol. 60, No. 1, 2005, pp. 85–90.Original Russian Text Copyright © 2005 by Dedkova, Shvoeva, Savvin.     

Speciation Stabilities of Iodine in underground Water by High Performance Liquid Chromatography-Inductively Coupled Plasma Mass Spectrometry

Specific determination for IO₃⁻ and I⁻ in ground water using high performance liquid chromatography-inductively coupled plasma mass spectrometry (HPLC-ICPMS) is described. Chromatographic separations were carried out using an ICS-A23 column. Iodine species were quantitatively eluted with 0.03 M ammonium carbonate. Under the Shield Torch high sensitive mode, the method detection limits for IO₃⁻ and I⁻ with injection of 1 ml were 0.035 μg l⁻¹ and 0.025 μg l⁻¹, respectively. The method was applied to the determination of iodide and iodate in ground water. However, the signal response difference between iodate and iodide was observed by both the HPLC-ICP-MS system and the ICP-MS system. Also, the same signal response difference was also observed in other laboratories. It was reported that the signal response and stability of iodine species vary with their solution medium. The instability of IO3 – and I – was controlled by using KOH as their solution storing media. The IO₃⁻ and I⁻ peak area ratios by HPLC-ICP-MS measurement were still close to 1:1 when the mixed standard solution was stored in the 0.01% KOH medium for 5 days.     

Caffeic Acid Decyl Ester: An Antioxidant Principle from <Emphasis Type="Italic">Phleum pratense</Emphasis>

The isolation, comprehensive structure elucidation, and assessment of the free radical scavenging activity of caffeic acid decyl ester (1) from the seeds of Phleum pratense have been described. The RC₅₀ value of this compound in the DPPH assay was found to be 3.60 × 10⁻³ mg/mL, whereas that of positive control, trolox, was 3.07 × 10⁻³ mg/mL.__________Published in Khimiya Prirodnykh Soedinenii, No. 3, pp. 237–239, May–June, 2005.     

Field determination of iodide in water

A simple, fast and sensitive spectrophotometric method for the quantification of iodine and iodide in waters is described. Firstly iodide has been oxidised by sodium nitrite to iodine in HCl medium and the resulting I₂Cl^– has been preconcentrated into toluene. This can be subsequently determined in the extract with brilliant green. A ten-fold preconcentration is obtained, the molar absorptivity is (4.2×10⁴) I mol^–1 cm^–1 at 635 nm. A detection limit of 4 ng/ml iodide in water can be reached. The effect of common anions and cations have been investigated. The method has been applied to the determination fo free iodine, total iodine and iodide in river, pond and well water.     

Kinetic Determination of Iodide by the Oxidation Reaction of Benzidine with Chloramine B

A kinetic method was developed for the determination of iodides by their catalytic effect on the oxidation of benzidine with Chloramine B. The determination limit of iodide is 2 × 10^–4 g/mL. It was demonstrated that the proposed method can be used for the determination of iodides in water, soil, and kelp.