The determination of chromium(VI) in natural waters by differential pulse polarography.

A method utilizing differential pulse polarography for the determination of chromium(VI) in natural water is described. Additions of 0.62 μg Cu(II) ml^-1 and 0.55 μg Fe(III) ml^-1 did not interfere with the determination of 0.050 μg Cr(VI) ml^-1. The natural water samples containing chromium(VI) were buffered to approximately pH 7 with 0.1 M ammonium acetate and 0.005 M ethylene diamine and analyzed. Natural water samples of chromium content from 0.035 μg ml^-1 to 2.0 μg ml^-1 may be analyzed directly without further preparation. The detection limit is 0.010 μg ml^-1.     

Zero-Crossing Derivative Spectrophotometric Determination of Mercury(II) And Palladium(II) with 5-(3,4-Methoxyhydroxyphenylmethylene)-2-thioxo-1-3-thiazolidine and Cetyltrimethylammonium Bromide

Abstract

A method is proposed for the simultaneous determination of mercury(II) and palladium(II) by first-derivative spectrophotometry based on the absorption spectra of their complexes with 5-(3,4-Methoxyhydroxyphenylmethylene)-2-thioxo-1,3-thiazolidine [5-(3,4-methoxyhydroxybenzylidene) rhodanine]. Zero-crossing measurement technique is found suitable for the measurement of the first-derivative value at the specified wavelengths. Mercury(II) (0.4-1.4 μg ml^?1) and palladium(II) (0.08 - 1.8 μg ml^?1) in different ratios have been determined simultaneously. A critical evaluation of the proposed method is performed by statistical analysis of the experimental data.     

Rapid spectrophotometric determination of ruthenium(III) with prochlorperazine maleate

A rapid, simple spectrophotometric method for the determination of μg amounts of ruthenium, based on the formation of a pink complex between the metal and prochlorperazine maleate (PCPM) in sulphuric or hydrochloric acid solution, is described. The complex has an absorption maximum at 530 nm and its molar absorptivity is 6.733·10³ l mol^?1 cm^?1. The sensitivity is 0.0151 μg Ru cm^?2 for log I_o/I = 0.001. Beer's law is valid over the range 0.2–10 μg Ru ml^?1 ; the optimal range for spectrophotometric determination is 0.8–8.0 μg Ru ml^?1. Job's method of continuous variation, the mole ratio method and the slope ratio method indicate a 1:1 composition for the complex. The effects of acidity, time, temperature, order of addition of reagents, reagent concentration, and the interferences from various ions are reported.     

Utility of p-chloranilic Acid and 2,3 Dichloro-5,6-dicyano p-Benzoquinone (DDQ) for the Spectrophotometric Determination of Triamterene

Abstract

Two simple and sensitive spectrophotometric procedures are suggested for analysis of triamterene. The first procedure is based on the reaction of triamterene with p-chloranilic acid (p-CA) in methylene chloride to form a highly stable coloured product, exhibiting maximum absorbance at λ 530 nm. Beer's law is obeyed in the range of 40–220 μg.ml^?1 with a mean percentage accuracy of 99.98 ± 0.446. Limit of determination is 20 μg.ml^?1. In the second procedure, the drug is determined via charge transfer complex formation with 2,3 dichloro-5,6-dicyano p-benzoquinone (DDQ) using methylene chloride as a solvent. Here the reaction product has two well defined maxima at 460 nm and 530 nm where each has been utilized for quantitative determination. Beer's law is obeyed in concentration ranges of 25–125 μg.ml^?1 and 25–150 μg.ml^?1 with mean percentage accuracies of 99.92 ± 0.449 and 100.00 ± 0.511 for both maxima. 460 and 530 nm. respectively. Limit of determination is 12.5 μg.ml^?1 at both maxima. Optimum conditions for each procedure have been studied and the stoichiometry of both reactions was ascertained using Job's method of continuous variation. The validity of the suggested procedures was assessed by applying the standard addition technique using the drug capsules. Both procedures are statistically analyzed as compared with BP method for analysis of triamterene (non aqueous titration) revealing good accuracy and precision as indicated by t and F tests.     

Kinetic spectrophotometric determination of antimony(III) based on induced oxidation of tris(1,10-phenanthroline)iron(II) by chromium(VI)

The method involves the measurement of the extent of the induced reaction, which ceases a few seconds after initiation. Antimony(III) can be determined in the range 0.4–10 μg ml^-1. The standard deviation is ±0.25 μg. The method is applied to marine sediments.     

Simultaneous determination of Sb(III) and Sb(V) by partial least squares regression

A method for simultaneous spectrophotometric determination of Sb(III) and Sb(V) using multivariate calibration method is proposed. This method is based on the development of the reaction between the analytes and pyrogallol red at pH 2.00. The selection of variables was studied. A series of synthetic solutions containing different concentrations of Sb(III) and Sb(V) were used to check the prediction ability of the partial least squares model. The calibration curves were linear over the range of 0.3-3.4 and 0.3-3.0 μg ml⁻¹ for Sb(III) and Sb(V), respectively. The detection limits were 0.177 and 0.200 μg ml⁻¹ for Sb(III) and Sb(V), respectively.     

Colorimetric Determination of Propofol in Bulk form,Dosage Form and Biological Fluids

ABSTRACT

Propofol is coupled with 2, 6-dichloroquinone-4-chlorimide (DCQ) in a reaction buffered at pH 9.6 to give a colored product having an analytically useful maximum at 635 nm. The factors affecting the color generation were optimized and incorporated in the procedure. The reacted propofol has a molar absorptivity of 3.9 × 10^?4 L mol^?1 cm^?1, and Beer's law is obeyed for concentrations 1-5 μg ml^?1 with detection limit 0.25 μg ml^?1. The method was found applicable to biological fluids (plasma and urine) spiked with propofol at concentration levels 1-5 μg ml^?1 for plasma and 1-5 μg 0.5 ml^?1 urine (less sensitivity is obtained with urine volumes above 0.5 ml) with detection limits 0.28 μg ml^?1 for plasma and 0.4 μg 0.5 ml^?1 urine. The average recovery for the commercial preparation (1% w/v propofol emulsion intravenous injection for infusion) was 99.54% with an RSD of 1.05%. The method was validated by an adopted HPLC method. The results obtained by the HPLC method for the commercial preparation were statistically compared with the proposed method and evaluated at the 95% confidence limits.     

Chemiluminescence determination of barbituric acid using Ru(phen)(3)(2+)-Ce(IV) system

A chemiluminescence (CL) method for the determination of barbituric acid (BA) was proposed, which is based on the enhancement of BA to the CL intensity of Tris-(1,10-phenanthroline)ruthenium(II) (Ru(phen)₃²⁺)-cerium(IV) (Ce(IV)) system. The concentration of BA is proportional to the CL intensity in the range of 5.0×10⁻³-2.0 μg ml⁻¹. The detection limit is 6.9×10⁻⁴ μg ml⁻¹. The relative standard deviation (R.S.D.) of determining 11 samples containing 0.20 μg ml⁻¹ BA is 3.2%. This CL method has been successfully applied to the determination of BA in the synthetic samples. The mechanism of CL reaction was studied.     

Kinetic-Spectrophotometric Determination of Molybdenum(VI) Based on Its Catalytic Effect on the Thionine-Hydrazine Reaction

Abstract

A kinetic method for the determination of trace amounts of Mo(VI) (0.05-4 μg ml^?1) based on its catalytic effect on the reduction of thionine by hydrazine monochloride in strongly acidic media is reported. The reaction is monitored spectrophotometrically by measuring the decrease in absorbance of thionine at 605 nm after a fixed time (5 min.). The detection limit of the method is 23 ng ml^?1 and the relative standard deviation (RSD) for 0.05 μg ml^?1 of Mo(VI) is 1.2% (n=7). The method is almost free from interferences, especially from large amounts of tungsten. The procedure was successfully applied to the determination of trace amounts of molybdenum in steel.     

2-(α-pyridyl)thioquinaldinamide: a novel fluorimetric reagent in inorganic trace analysis. : Part 2. A simple selective determination of selenium(IV) at Ultratrace Levels

The very sensitive fluorimetric determination of selenium(IV) is based on its oxidation of the non-fluorescent 2-(α-pyridyl)thioquinaldinamide in slightly acidic solution (0.05–0.15 M sulphuric acid). The excitation and emission wavelengths are 350 nm and 500 nm, respectively. Linear calibration graphs are obtained for different ranges of selenium concentration between 0.01 ng ml^?1 and 0.5 μg ml^?1. Over sixty ions either do not interfere or can be masked in the determination of 1 ng ml^?1 Se(IV). The method is applied successfully to various synthetic mixtures and to a native sulphur sample. The reaction is fast and the fluorescent system is stable for 24 hours.     

Amperometric determination of formaldehyde via the hexacyanoferrate(III) -coupled dehydrogenase reaction

An enzymatic method with amperometric detection was developed for the determination of formaldehyde. Formaldehyde is first oxidized by reaction with NAD⁺ in the presence of formaldehyde dehydrogenase. The resulting NADH is then oxidized by hexacyanoferrate(III) in the presence of diaphorase to produce hexacyanoferrate(II). The anodic current generated by oxidation of the hexacyanoferrate(II) at the surface of a glassy carbon working electrode, held at a potential of 0.40 V vs. an Ag/AgCl reference electrode, is measured. The effects of solution conditions are examined and a linear relationship between rate of current change and formaldehyde concentration is obtained from 0.01 to 0.5 μg ml^?1 with a correlation coefficient of 0.9998. The relative standard deviation for the proposed method is 6.4% at 0.01 μg ml^?1 formaldehyde and 0.88% at 0.5 μg ml^?1.     

Spectrophotometric determination of cobalt(II) based on the ion-pair of tetrathiocyanatocobaltate(II) with neotetrazolium chloride

The ion-pair formed between tetrathiocyanatocobaltate(II) and [3,3′-(4,4′- biphenylene)bis(2,5-diphenyl)]-2H-tetrazolium chloride (neotetrazolium chloride) can be extracted into 4-methylpentan-2-one and used for the spectrophotometric determination of cobalt (2.5–9.8 μg ml^?1) at pH 3.5–5.0. The Sandell sensitivity of the method is 0.02 μg Co cm^?2. With suitabte masking, the method is quite selective and is applicable to nickel wire alloys.     

The application of the ph-stat method to metal ion-catalyzed reactions

The pH-stat method, which is well known in organic chemistry and biochemistry, is used for the kinetic determination of metal ion catalysts. Indicator reactions that involve protons can be followed by controlled addition of standard base or acid. This is illustrated by the following examples: determination of copper(II) (0.03–0.3 μg ml^-1) with the indicator reaction ascorbic acid—peroxydisulphate; determination of molybdenum(VI) (0.2–2.5 μg ml^-1) with the indicator reaction thiosulphate—hydrogen peroxide; determination of zirconium(IV) (0.2–2 μg ml^-1) with the indicator reaction iodide—hydrogen peroxide; and determination of vanadium(V) (0.2–2 μg ml^-1) with the indicator reaction iodide—bromate. For one example, the copper—ascorbic acid—peroxydisulphate reaction, it is shown that the pH-stat method has distinct advantages over closed systems, giving considerably better sensitivity for the determination of copper (0.5–5 ng ml^-1 ).     

Kinetic spectrophotometric determination of trace manganese (II) with dahlia violet in nonionic microemulsion medium

A new catalytic kinetic spectrophotometric method has been developed for the determination of trace amount of manganese (II) in nonionic microemulsion medium. The method is based on the catalytic effect of manganese (II) on the oxidation of dahlia violet by potassium periodate with nitrilotriacetic acid as an activitor in the presence of nonionic microemulsion. Under the optimum conditions, the calibration graph is linear in the range of 0.0004-0.0056 μg ml⁻¹ of manganese (II) at 580 nm. The detection limit achieved is 3.75×10⁻⁵ μg ml⁻¹. Manganese (II) in foodstuff samples was determined with satisfactory results.     

“Stat” methods in continuous flow analysis : Determination of Copper,Iron, Iodide and Hydrochloric Acid

A continuous flow “stat” method is described in which a certain arbitrarily imposed state in the flowing stream is automatically maintained by regulating the rate of flow of one of the components. The electronic system is regulated by measuring a physical phenomenon in the flowing solution. The method is illustrated by the examples of a continuous flow absorptiostat [Fe(III)/S₂O₃^2-/Cu(II)]for determinations of copper(II) (1–10 μg ml^-1), iron(III) (25–250 or 12.5–125 μg ml^-1), as well as for determination of iodide (12.8–128 μg ml^-1). A continuous flow conductostat [HCl/NaOH] for determination of 1–2.5 × 10^-4 M HCl is also described. This analytical technique is intended for automatic continuous monitoring of sample streams.     

Determination of 1-(2-chloroethyl)-3-(trans-4-methylcyclohexyl)-1-nitrosourea by reaction with 2,4-dinitro-β-henylethylamine

A method for the determination of 1-(2-chloroethyl)-3-(trans-4-methylcyclohexyl)-1-nitrosourea (methyl-CCNU) in body fluids is described. After extraction from urine or plasma with diethyl ether, methyl is treated with 2,4-dinitro-β-phenylethylamine to. The urea is separated of the amine and treated with trifluacetic anhydride; the trifluoroacetyl derivative is quantified by gas chromatography. Calibration graphs were linear urine, plasma and aqueous standards of metal-CCNU over the range 0.4–2.0 μg ml. The limits of detection for methyl-CCNU are in urine and 0.08 μg ml^?1 in plasma.     

Spectrophotometric Determination of Metoclopramide and Oxybuprocaine Through Ion Pair Formation with Thiocyanate and Molybdenum(V) or Cobalt(II)

Abstract

Two spectrophotometric methods involve the formation of two different ion pairs between the drug and inorganic complexes, Mo(V) and Co(II) thiocyanates followed by their extraction with dichlor?methane and o-nitrotoluene, respectively. The optimum conditions for the ion pair formation are established. The methods permit the determination of metoclopramide and oxybuprocaine hydrochlorides over a concentration range of 1-20 μg ml^?1 and 20–240 μg ml^?1 using Mo(V) and Co(II) thiocyanates, respectively. Molar ratio of drug to Mo(V) or Co(II) indicates a 2:1 ratio for the two drugs studied in the presence of excess thiocyanate concentration. Results of the analysis of drug substances and their dosage forms by the proposed methods are in good agreement with those obtained by the official methods.     

The determination of hydrazine and 1,1-dimethylhydrazine,separately or in mixtures,by high-pressure liquid chromatography

A rapid, sensitive liquid chromatographic method for the determination of hydrazine and 1,1-dimethylhydrazine, separately or in mixtures of varying proportions, is described. The procedure involves salicylaldehyde derivative formation followed by chromatography on a reversed phase (octadecylsilane) column with acetonitrile (52%)—0.14 M potassium dihydrogenphosphate (48%) as a mobile phase and u.v. (254 nm) detection. This system is sensitive to 2 μg ml^-1 of hydrazine and 5 μg ml^-1 of 1,1-dimethylhydrazine and has a relative standard deviation of less than 1%. Monomethylhydrazine forms an unstable salicylaldehyde hydrazone; although it cannot be determined, it can be detected (sensitivity 5 μg ml^-1 ) and does not interfere with quantitative measurement of either hydrazine or 1,1-dimethylhydrazine.     

Polarographic determination of isoniazide, N-acetylisoniazide and isonicotinic acid by superimposed sinusoidal tension]

The a.c. polarographic determination of isoniazid (INH), N-acetylisoniazid (AcINH) and isonicotinic acid (INA) is described. Under the optimal conditions of pH, ionic strength and electrical parameters, the limits of detection are 0.5 μg ml^-1 for AcINH, 0.2 μg ml^-1 for INH, and 0.03 μg ml^-1 for INA.     

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).