Kinetic spectrophotometric determination of traces of sulfide in nonionic micellar medium

A sensitive kinetic spectrophotometric method for the determination of ng amounts of sulfide has been developed based on the reduction of Azure A by sulfide in the presence of Brij-35 at pH 7. The decrease in absorbance of Azure A at 600 nm is proportional to the concentration of sulfide over the range 25–1400 ng mL^–1. The variables affecting the rate of the reaction were investigated and the optimum conditions were established. The method is simple, rapid, precise, sensitive, and widely applicable. The limit of detection is 17 ng mL^–1, and the relative standard deviation of seven determinations of 500 ng mL^–1 sulfide was 2.1%. The method was applied to the determination of sulfide in spring water.     

Kinetic spectrophotometric determination of traces of sulfide

A method for the determination of sulfide based on the addition reaction of sulfide with magenta at pH 7 and 25 degrees C is described. The decrease in absorbance of magenta at 540 nm, its lambda(max), over a fixed time is proportional to the concentration of sulfide over the range of 25-2500 ng ml(-1). The limit of detection was found to be 15 ng ml(-1). Ten replicate analysis of a sample solution containing 1.5 mug ml(-1) sulfide gave a relative standard deviation of 0.8%. The effects of various cations and anions on sulfide determination have been reported and procedures for removal of interferences have been described.     

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.     

Kinetic spectrophotometric determination of traces of iron(II)

A simple method for the selective and sensitive kinetic spectrophotometric determination of iron (II) is described. The method is based on the oxidation reaction of reduced phenolphthalein by periodate in alkaline media. The change in absorbance was measured using the fixed time method. The effect of different variables on the reaction was investigated and optimum conditions were obtained. The calibration curve was linear in the range 50–3000 ng/mL, and a detection limit of 17 ng/mL was obtained. The relative standard deviation of ten replicate determinations of 200 ng/mL of Fe(II) was 1.2%. The determination of Fe(II) in the presence of a 50-fold amount of Fe(III) could be carried out. This article was submitted by the authors in English.     

Non-extractive derivative spectrophotometric determination of cobalt in neutral micellar medium

A sensitive derivative spectrophotometric method using 1-nitroso-2-naphthol has been developed for determination of trace amounts of cobalt in the presence of a neutral surfactant. Photometric parameters, viz., lambda(max), molar absorption coefficient and analytical sensitivity of the complex formed in micellar media are 420 nm, 3.18x10(4) l mol(-1) cm(-1) and 2.05 ng ml(-1), respectively. Beer's law holds from 0.20 to 3.0 mug ml(-1) of the analyte concentration. The method has a high sensitivity with a detection limit of 1.68 ng ml(-1). A selective determination of cobalt in presence of copper(II) or iron(III) using derivative spectral profiles and without any masking or pre-separation is also reported. Samples of drugs and standard alloys analysed by the proposed method yielded results comparable to those obtained using recommended procedures.     

Flow-injection spectrophotometric determination of novalgin in pharmaceuticals using micellar medium.

A sensitive flow-injection (FI) procedure with spectrophotometric detection in a micellar medium is proposed for the determination of novalgin. The method is based on the instantaneous formation of a red-orange product (lambda(max) = 510 nm) after the reaction between novalgin and p-dimethylaminocinnamaldehyde (p-DAC) in a dilute acid medium. The sensitivity of this reaction was increased by a factor of 5.6 in the presence of sodium dodecyl sulfate (SDS). Experimental design methodologies were used to optimize the chemical and FI variables. The calibration curve was linear in the range of 1.45 x 10(-6) to 2.90 x 10(-5) mol L(-1) with an excellent correlation coefficient (r = 0.9999). The detection limit was 1.31 x 10(-7) mol L(-1) (n = 20, RSD = 2.0%). No interferences were observed from the common excipients. The results obtained by the proposed method were favorably compared with those given by the iodometric reference method at 95% confidence level.     

Simultaneous derivative spectrophotometric determination of thorium and uranium in a micellar medium

Derivative photometric methods for trace analysis of Th(IV) and UO₂(II), and their simultaneous determination in mixtures using 5,8-dihydroxy-1,4-naphthoquinone in a micellar medium are reported. Molar absorptivity and Sandell's sensitivity of 1:2 Th(IV) and 1:1 UO₂(II) complexes at their λ_max, 614.5 nm and 637.0 nm are, 1.19 × 10⁴ 1/mol/cm and 1.12 × 10⁴ 1/mol/cm and 1.95 × 10⁻² μg/cm² and 2.13 × 10⁻² μg/cm² μg/cm², respectively. Calibration graph is linear over the range 9.28 × 10⁻²−18.56 μg/ml of Th(IV) and 9.52 × 10⁻²−19.04 μg/ml of UO₂(II). Though presence of Th(IV) and UO₂(II) causes interference in each others determination, 9.28 × 10⁻¹−9.28 μg/ml Th(IV) and 9.52 × 10⁻¹−9.52 μg/ml UO₂(II) when present together, can be simultaneously determined using derivative spectra.     

Derivative spectrophotometric determination of copper(II) in non-ionic micellar medium

A photometric method for trace analysis of Cu(II) with 1-(2-pyridylazo)-2-naphthol (PAN) in presence of a neutral surfactant, Triton X-100, has been reported in normal and derivative modes. The molar absorption coefficient () and Sandell's sensitivity (S) of PAN-Cu(II) complex at 555 nm is 5.21 x 10(4) l mol(-1) cm(-1) and 1.22 ng cm(-2) respectively. The detection limit of Cu(II) is 4.0 ng ml(-1) and Beer's law is obeyed in the range 0.08-4.00 mug ml(-1) of the analyte. Copper content of a number of commercially available alcoholic beverages, biological and standard alloy samples is reported. The results obtained are in excellent agreement with those obtained using AAS.     

Enhanced spectrophotometric determination of nicotinic acid in a sodium dodecyl sulphate micellar medium

The spectrophotometric determination of pyridine and pyridine derivatives by means of the K?nig reaction was studied in micellar media of sodium dodecyl sulphate (SDS), N-cetylpyridinium chloride and Triton X-100. The sensitivity was largely increased in SDS micellar medium. The attack of the pyridine ring with cyanogen bromide to produce a glutaconic aldehyde was not affected by the presence of SDS, but the yield of the coupling reaction with an arylamine to produce a polymethine dye was largely increased. In the SDS micellar medium, aniline was superior to other coupling reagents. The limits of detection (LODs) were 6 x 10(-7), 1 x 10(-6) and 5 x 10(-7)M for pyridine, pyrrol-ylmethylpyridine and nicotinic acid, respectively, and the reproducibility for 2 x 10(-5)M solutions was ca. 2%. In the absence of SDS, the LODs were 3 x 10(-6), 3 x 10(-6) and 9 x 10(-6)M, respectively, and the reproducibility was ca. 3.5%. Application was made to the determination of nicotinic acid in pharmaceuticals.     

Mixed micellar medium for the spectrophotometric determination of molybdenum in molybdenum/tungsten mixtures

Effects of cetyltrimethylammonium bromide (CTAB) and/or nonylphenoxypolyethoxyethanol (OP) on the absorption spectra of the complexes of molybdenum and tungsten with bromopyrogallol red (BPR) were studied. Based on these effects, a mixture of CTAB and OP was thus selected as a medium for the selective and sensitive determination of Mo in Mo/W binary mixtures. Under the optimum conditions, Beer's law was obeyed over the range 0.06-0.8 mug ml(-1) Mo with molar absorptivity being 1.3x10(5) l mol(-1) cm(-1) and detection limit 0.025 mug ml(-1). For 1.0 mug Mo, at least 20 mug W did not interfere in the determination of Mo with average recovery and relative standard deviation being 99.5% and <2%, respectively. The method developed maintained the features of simplicity and rapidity and, moreover, its selectivity and sensitivity enhanced greatly due to the use of CTAB/OP mixed micellar medium. When coupled with a compatible concentration method, the proposed method could be used for the determination of trace Mo in natural waters.     

A sensitive spectrophotometric determination of atrazine in micellar medium and its application in environmental samples

A sensitive analytical procedure based on solid phase extractive-spectrophotometry has been established for the determination of the widely used herbicide atrazine .The method is based on the Konig reaction in which atrazine reacts with pyridine reagent to form a quaternary pyridinium halide, which further forms glutaconic aldehyde in the presence of alkali. Glutaconic aldehyde is subsequently coupled with 4-aminoacetanilide in the micellar medium of anionic surfactant sodium dodecyl sulphate to give a yellow-orange dye. The produced dye was enriched on a C₁₈ cartridge and is measured spectrophotometrically at 460 nm. The sensitivity and selectivity of the method was largely enhanced in the micellar media and SPE on the C₁₈ cartridge and avoids the use of toxic solvents. Beer’s law was obeyed in the range 0.012–0.12 μg mL^?1. Molar absorptivity and Sandell’s sensitivity were found to be 1.52 × 10⁶ L mol^? 1 cm^?1 and 0.0002 μg cm^?2, respectively. The limit of detection and quantification were 0.001 and 0.003 μg mL^?1, respectively. The proposed method was applied successfully for the determination of atrazine in environmental and biological samples with a recovery range of 96–101 %. The method was found to be free from interference of a large number of foreign species. The accuracy and reliability of the method was further established by parallel determination by the reference method, and by recovery studies.     

Kinetic spectrophotometric determination of hydrazine

A sensitive kinetic method for determining low levels of hydrazine has been described. The method is based on the measurement of the rate of the reaction between hydrazine and Mo(VI) in the presence of hydrochloric acid. The redox reaction was monitored spectrophotometrically at 710 nm. The variable-time and fixed-time methods were used. The calibration graph was linear for hydrazine concentrations of 1.0 × 10⁻⁴-1.4 × 10⁻² M, using the fixed-time method of analysis. The method is simple, rapid, precise, sensitive and widely applicable.     

Kinetic spectrophotometric determination of hydrazine

A kinetic spectrophotometric method for hydrazine determination in the range of 9.36×10⁻⁷ to 4.37×10⁻⁵ mol dm⁻³, based on the inhibitory effect of hydrazine on the oxidation of Victoria Blue 4- R by KBrO₃, was developed and validated. Kinetic parameters are reported for both the indicating and the inhibiting reaction. The detection limit was established as 9.98×10⁻⁸ mol dm⁻³. The selectivity of the proposed method was tested considering the influence of different ions that may be present in real samples. The method was successfully applied for hydrazine determination in various samples (very pure water from the water-steam system of a power plant and Isoniazid tablets, a pharmaceutical product).      

Flow-injection spectrophotometric determination of arylamines and sulphonamides by diazotization and coupling in a micellar medium

In a sodium dodecyl sulphate (SDS) micellar solution, the rate of coupling of a diazonium ion with N-(1- naphthyl)ethylenediamine (NED) increases greatly, the protonation of the resulting azo dyes takes place at higher pH values and the dyes are more soluble. These favourable features were applied to the development of a simple flow-injection spectrophotometric procedure for the determination of diazotizable substances of pharmaceutical interest. Limits of detection in the range 0.2–0.5 μg ml^?1 (signal-to-noise ratio=3), with relative standard deviation of 0.7–3% (n=3) for 5 μg ml^?1 standards, were obtained.     

Kinetic spectrophotometric determination of sulfide using whole kinetic curve and a fixed time method

The univariate and multivariate calibration method was applied for the determination of sulfide based on the addition reaction of sulfide with new fuchsin at pH 8 and 25°C. The decrease in absorbance of new fuchsin at 540 nm over a fixed time is proportional to the concentration of sulfide over the range of 0.05-2.5 μg ml⁻¹. The experimental calibration matrix for partial least squares calibration (PLS) method was designed with 20 samples. The cross-validation method was used for selecting the number of factors. The root mean square difference (RMSD) was 0.0843. The effects of various cations and anions on sulfide determination have been investigated.     

Modified spectrophotometric method for the determination of traces of boron using quinalizarin in a sulfuric-acetic acid medium

Summary A modified spectrophotometric method for the determination of boron with quinalizarin in a sulfuric-acetic acid medium is proposed. The sensitivity of the method is 0.00037g/cm². The optimum concentration range is 0.06 to 0.25 ppm of boron.

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Zusammenfassung Eine modifizierte spektrophotometrische Bestimmungsmethode für Bor mit Chinalizarin in schwefelsaurer-essigsaurer Lösung wurde vorgeschlagen. Deren Empfindlichkeit beträgt 0,00037g/cm². Das optimale Konzentrationsbereich liegt zwischen 0,01 und 0,25 ppm Bor.

     

动力学光度法测定食品中的碘

催化动力学光度法测定痕量碘 ,大多使用Ｃｅ(ＩＶ) -Ａｓ(ＩＩＩ)体系[1 3] 。我们的实验发现在硫酸介质中 ,Ｉ- 能强烈催化高碘酸钾氧化苋菜红的褪色反应 ,在波长 5 2 5ｎｍ处 ,其反应速度与碘离子的浓度之间符合动力学一级反应关系式 ,并且此法灵敏度、选择性均较高。1　实验部分取两支 2 5ｍｌ比色管 ,各加入 2 0ｍｌ浓度为8 0× 1 0 - 3ｍｏｌ/Ｌ苋菜红溶液 ,3 5ｍｌ( 1 0ｍｏｌ/Ｌ)Ｈ2 ＳＯ4,2 0ｍｌＫＩＯ4( 0 2 0ｍｏｌ/Ｌ)溶液。向其中一支加入适量碘标准溶液 ( 1 μｇ/ｍｌ) (吸光度为Ａ) ,另一支不加碘 (吸光度为Ａ0 ) ,用水…     

Kinetic spectrophotometric determination of Fe(II) in the presence of Fe(III) by H-point standard addition method in mixed micellar medium

The H-point standard addition method was applied to kinetic data for simultaneous determination of Fe(II) and Fe(III) or selective determination of Fe(II) in the presence of Fe(III). The method is based on the difference in the rate of complex formation between iron in two different oxidation states and methylthymol blue (MTB) at pH 3.5 in mixed cetyltrimethylammonium bromide (CTAB) and Triton X-100 micellar medium. Fe(II) can be determined in the range 0.25-2.5 microg ml(-1) with satisfactory accuracy and precision in the presence of excess Fe(III) and other metal ions that rapidly form complexes with MTB under working condition. The proposed method was successfully applied to the simultaneous determination of Fe(II) and Fe(III) or selective determination of Fe(II) in the presence of Fe(III) in spiked real environmental and synthetic samples with complex composition.     

动力学光度法测定痕量甲醛

在稀硫酸溶液中,甲醛对KClO3氧化罗丹明6G褪色反应有催化作用,研究了其动力学条件,建立了测定痕量甲醛的动力学光度分析方法,线性范围为0.02～1.8μg/mL,检出限为1.5×10-8g/mL。该法用于湖水、饮料和漆料中痕量甲醛的测定,标准加入回收率为93.8%～108.5%,RSD为2.6%～3.4%。     

Kinetic-fluorimetric determination of magnesium in micellar medium

A simple method for the kinetic determination of magnesium(II) is described. The method is based on the reaction of 2-fluorenaldehyde 2-pyridylhydrazone with magnesium ion to originate a strong green fluorescence that decreases with time. The reaction is monitored at 520 nm, when excited at 375 nm, and the initial rate method is applied to perform the analytical procedure. Magnesium contents between 0.36 and 1.22 μm ml^?1 can be determined. The method is free from interferences of alkaline earth ions.