Flow injection spectrophotometric determination of bromoxynil herbicide by diazotization method.

A flow injection spectrophotometric method is proposed for the determination of bromoxynil herbicide. Bromoxynil was hydrolyzed with HCl and the resulting product, 3,5-dibromo-4-hydroxyaniline, was diazotized with nitrite and coupled with aniline. The absorbance of the azo dye was measured at 500 nm. The conditions were optimized for diazotization using FIA. The range of linearity was found to be 0.01 to 5 ppm with a molar absorptivity of 1.27 x 10(5) L mol(-1) cm(-1). The % recovery for the determination of bromoxynil was found to be 91%. The sampling frequency was 80 samples per hour for FIA. The method is simple, fast, and has been successfully applied to the determination of bromoxynil in commercial formulations and food samples.     

Flow Injection Spectrophotometric Determination of 2,4‐D Herbicide

2,4‐Dichlorophenoxy acetic acid herbicide is spectrophotometrically determined by diazotization method in a flow injection assembly. The method is based on base hydrolysis of herbicides. The hydrolyzed product 2,4‐dichlorophenol is reacted with diazotized sulfanilic acid. The absorbance of the resulting coloured product was measured at 480 nm. The calibration graph is linear over the range of 0.2–20 μgmL^?1, with a relative standard deviation of (RSD) of 7.2% and sample throughput of 90 samples h^?1. The % recovery for determination of 2,4‐dichlorophenoxy acetic acid was found to be 92.0–95.3%. The method is easy, simple and faster than the established chromatographic method. The method was applied for determination of 2,4‐dichlorophenoxy acetic acid herbicide in commercial formulations and for residue determination in fruits and food samples.     

Spectrophotometric determination of isoproturon using p-aminoacetophenone and its application in environmental and biological samples

A simple and sensitive method for the determination of isoproturon, a widely used herbicide is described here which is based on alkaline hydrolysis of isoproturon to its corresponding primary amine followed by diazotization and coupling with p-aminoacetophenone in alkaline medium. The absorption maxima of the coloured compound formed is measured at 525 nm. Beer's law is obeyed over the concentration range of 0.5-5.0 mug in a final solution volume of 25 ml (0.02-0.2 ppm). The molar absorptivity and Sandell's sensitivity were found to be 8.6x10(5) l mol(-1) cm(-1) and 0.0002 mug cm(-2), respectively. The method has been satisfactorily applied to the determination of isoproturon in environmental and biological samples.     

A rapid technique for determination of nitrate and nitric acid by acid reduction and diazotization at elevated temperature

A rapid technique for determination of nitrate by acid reduction and diazotization at elevated temperature has been standardized. The technique is based on quantitative diazotization of sulfanilamide by nitrate on incubation in boiling water bath for 3, 5 or 10 min in presence of high concentration of HCl, ca. 64.5%. The diazotized sulfanilamide is coupled at room temperature to N-1-(naphthyl)-ethylenediamine dihydrochloride, and the chromophore evaluated spectrophotometrically at 540 nm. The technique provides linear estimate of nitrate over the test range of 0.5 through 10 μg N mL⁻¹ sample with all test incubation time periods using alkali nitrate and nitric acid as sources of nitrate anion. Urea treatment enables selective determination of nitrate in presence of nitrite with overall 99 ± 1% recovery, and without affecting nitrate determination (P > 0.1) or its regression coefficient. The technique has obvious advantages over metal-reduction technique. It is simple, rapid, selective in presence of nitrite, and an inexpensive method for routine determination of nitrate with detection range 0.5–10 μg N mL⁻¹ sample. Besides, the technique provides opportunity to detect nitric acid as low as 35 μM even in presence of other acids.     

Use of a diazocoupling reaction for sensitive and selective spectrophotometeric determination of furosemide in spiked human urine and pharmaceuticals

Two simple, sensitive, and selective spectrophotometric methods for the determination of 5-(aminosulfonyl)-4-chloro-2-((2-furanylmethyl)amino)benzoic acid (furosemide, FUR) are described. The methods are based on acid hydrolysis of FUR to free primary aromatic amine and diazotization followed by coupling with N-1-napthylethylene diamine (NEDA) (method A) or 4,5-dihydroxynaphthalene-2,7-disulfonic acid (chromotropic acid, CTA) (method B). The colored reaction product can be measured spectrophotometrically at 520 nm (method A) or 500 nm (method B). Beer’s law is obeyed over the ranges of 1.75–21.0 μg mL⁻¹ and 2.5–30.0 μg mL⁻¹, for method A and method B, respectively. Apparent molar absorptivities and Sandell’s sensitivities (in L mol⁻¹ cm⁻¹ and μg cm⁻² per 0.001 absorbance unit, respectively) were 1.34 × 10⁴ and 0.0253 using NEDA as the coupling agent, and 8.5 × 10³ and 0.0389 using CTA for the same purpose. Analysis of solutions containing seven different concentrations of FUR gave a correlation coefficient of 0.9979 using NEDA and 0.9984 using CTA, while the slope and the correlation coefficient of the regression equation were calculated. The reaction stoichiometry in both methods was evaluated by the limiting logarithmic method and was found to be 1: 1 (diazotized FUR: NEDA or diazotized FUR: CTA). The methods were successfully applied to the determination of FUR in spiked human urine and in pharmaceutical formulations. The recovery of FUR from spiked urine was satisfactory resulting in the values of (109.4 ± 4.37) % using NEDA and (113.0 ± 4.74) % using CTA. Results of the analysis of pharmaceuticals demonstrated that the proposed procedures are at least as accurate and precise as the official method while a statistical analysis indicated that there was no significant difference between the results obtained by the proposed methods and those of the official method.     

Liquid chromatographic method for the micro-quantitative determination of clodinafop in soil, wheat and Phalaris minor

A liquid chromatographic method was developed for the determination of clodinafop-propargyl herbicide. Clodinafop-propargyl was converted to clodinafop acid by alkaline hydrolysis as clodinafop-propargyl rapidly forms bioactive clodinafop acid in soil and plant environment. Recovery methods for both the acid and ester from different matrices were standardized. The sensitivity of the method for ester and acid was 5 and 2 ng, respectively, with limits of detection of 0.5 and 0.1 microg ml(-1). The method was standardized for the determination of clodinafop residues in soil and plant samples using HPLC. The recovery of clodinafop from soil and plant samples with ethyl acetate was significantly higher (78-83%) than those with dichloromethane, toluene and methanol (60-70%). The limit of determination of clodinafop in soil and plant samples ranged between 1 and 1.2 ng g(-1). In field soil, residues of clodinafop dissipated with a half-life of 3.44 days.     

Photometric assay of 1-naphthylamine by azo dye formation with diazotized sulfisomidine - application to waters

A simple and sensitive photometric method for the trace determination of 1-naphthylamine has been worked out. The method is based on the coupling reaction of the determinand in acidic medium with diazotized sulfisomidine, to form a purplish violet water-soluble mono azo dye that shows maximum absorption at 540 nm with a molar absorptivity of 4.47 x 10(4) l mol(-1) cm(-1). Beer's law is obeyed over the concentration range 5-70 mug of 1-naphthylamine in a final volume of 25 ml, i.e. 0.2-2.8 p.p.m. with a relative error of -0.7 to +1.7% and a relative standard deviation of 0.35-4.2%, depending on the concentration level. Moreover, the method does not require either temperature control or solvent extraction. Interferences due to foreign species have been examined. The developed method has been applied to the determination of 1-naphthylamine in river water and sea water.     

Spectrophotometric determination of chlordiazepoxide and nitrazepam

The use of ethyl acetoacetate in the spectrophotometric determination of chlordiazepoxide and nitrazepam has been investigated. The procedure is based on coupling the diazotized drugs with ethyl acetoacetate, which possesses an active methylene group. The products have absorption maxima at 408 and 482 nm and apparent molar absorptivities of 2.74 x 10(4) and 4.11 x 10(4) 1.mole(-1).cm(-1), respectively. The method is simple, highly sensitive and suitable for 1-16 mug/ml concentrations of the two compounds, with mean recoveries of 100.3 +/- 1.2 and 99.8 +/- 1.0% respectively.     

Study of the electro-adsorptive behaviour of the herbicide nitralin by means of voltammetric techniques

The electroanalytical behaviour of the herbicide Nitralin has been studied by means of different voltammetric techniques. Nitralin is adsorbed on the mercury electrode and gives 2 reduction waves at -0.6 and -0.7 V versus Ag AgCl reference electrode, for pH values > 10. The electrochemical process is irreversible and strongly influenced by pH solution. A systematic study of the several instrumental and accumulation variables affecting the stripping response was carried out using square wave (SWV; Osteryoung's method) and differential pulse voltammetry (DPV) as redissolution techniques. The limits of detection were 4.4 x 10(-1) mol 1(-1) (AdS-SWV) and 3.5 x 10(-11) mol 1(-1) (AdS-DPV), with variation coefficients of 4.17 and 3.90% respectively, at a concentration level of 8 x 10(-9) mol 1(-1) (n = 10). A method, based on AdS-DPV, for the determination of Nitralin in ground-water is proposed. A detection limit of 8.7 x 10(-11) mol 1(-1) (AdS-DPV) was reached in real samples.     

A sensitive determination of paraquat by spectrophotometry

A sensitive spectrophotometric method for the determination of a widely used herbicide, paraquat using a versatile reducing agent sodium borohydride is described. Paraquat is reduced with sodium borohydride in an alkaline medium to give a blue radical ion with an absorbance maxima at 600 nm. Beer's law is obeyed in the range of 0.05-0.5 mug ml(-1) of paraquat. The molar absorptivity and Sandell's sensitivity are found to be 2.9 x 10(5) l mol(-1) cm(-1) and 0.0006 mug cm(-2) respectively. The important analytical parameters and the optimum reaction conditions were evaluated. The method is free from the interference of other commonly used pesticides and metal ions. The method was applied successfully to the determination of paraquat in human samples, such as blood, urine and mother's milk compared to food and environmental samples.     

Electrochemical behavior and voltammetric determination of the herbicide metribuzin at mercury electrodes

The electrochemical behavior of the herbicide metribuzin (4-amino-6-tert-butyl-4,5-dihydro-3-methylthio-1,2,4-triazin-5-one) at mercury electrodes was studied in aqueous solutions by direct current (DC) and tast polarography, differential pulse (DPV) and cyclic voltammetry (CV), and controlled-potential coulometry. The electrolysis products were separated and identified by chromatographic techniques combined with mass spectrometric detection. The reduction process in acid media includes two irreversible steps. In the first four-electron step the N-NH2 and the 1,6-azomethine bonds are reduced. The second step leads to the formation of 5-tert-butyl-2,3,4,5-tetrahydroimidazol-4-one at the mercury-pool electrode. The first reduction step combined with adsorptive accumulation of the herbicide molecule at the mercury electrode surface was used for its determination by differential pulse adsorptive stripping voltammetry (DPAdSV). Calibration curves were linear in the range 1-30 microg L(-1) with a detection limit of 0.27 microg L(-1) (1 nmol L(-1)) under the conditions used (buffer pH 4.5, Eacc = -0.45 V relative to Ag/AgCl and tacc = 10 s). Preconcentration on solid-phase extraction columns (SPE-phenyl) was used for the determination of very small amounts of metribuzin in river water samples. Recovery was approximately 97%. The reproducibility of the analytical procedure including SPE treatment and DPV determination was expressed as relative standard deviations of 2.53 and 3.66% for 2 and 6 microg L(-1) metribuzin, respectively.     

固相萃取-高效液相色谱法同时测定大豆和大米中的磺酰脲类和二苯醚类除草剂残留

建立了大豆和大米中磺酰脲类和二苯醚类除草剂多残留同时检测的高效液相色谱分析方法。样品经乙腈提取,正己烷液-液分配,C18固相萃取小柱净化后,采用高效液相色谱方法分离,以乙腈-三乙胺盐酸溶液作流动相,梯度洗脱,紫外检测器检测。对样品前处理和色谱分析条件进行了优化,8种除草剂(甲磺隆、氯磺隆、苄嘧磺隆、吡嘧磺隆、三氟羧草醚、精恶唑禾草灵、乙氧氟草醚、乙羧氟草醚)在0.05~2.0 mg/L范围内线性关系良好。方法的定量限(S/N=10)为0.01~0.02 mg/kg,能达到国家有关上述除草剂残留限量的要求。大豆和大米样品的平均加标回收率分别为91.6%~116.1%和76.6%~110.8%,相对标准偏差(RSD)为1.0%~12.2%。所建立的方法在30 min内可完成一次检测,具有简便快速、灵敏可靠的特点,适用于大豆和大米中除草剂多残留的测定。     

Determination of the herbicide desmetryne in organised media by adsorptive stripping voltammetry

An electroanalytical method for the determination of the herbicide desmetryne at nanomolar levels in dispersed media, based on adsorptive stripping voltammetry, is reported. The adsorption of desmetryne at the hanging mercury drop electrode was checked both in micellar solutions, where the anionic surfactant sodium pentanesulphonate was chosen as the most suitable surfactant agent, and in oil-in-water emulsions prepared with ethyl acetate as the organic solvent. In a micellar medium formed with 0.02% sodium pentanesulphonate and with 0.1 mol l(-1) Britton-Robinson buffer (pH 1.5), the herbicide could be determined over the 1.0 x 10(-8)-4.0 x 10(-7) mol l(-1) concentration range, when an accumulation potential of -0.70 V was applied for 50 s. On the other hand, in an oil-in-water emulsion formed with 2% ethyl acetate and 0.04% sodium pentanesulphonate as emulsifying agent in 0.1 mol l(-1) HClO(4), desmetryne could be determined over the 2.0 x 10(-9)-1.0 x 10(-7) mol l(-1) concentration range. The limits of detection were 2.4 x 10(-9) and 4.2 x 10(-10) mol l(-1) in micellar and emulsified media, respectively, with R.S.D.s (n=10) 3.6 and 3.7%. The degree of interference from some other s-triazines on the desmetryne differential pulse response was also evaluated. Finally, the method developed in emulsified medium was applied to the determination of desmetryne in spiked apple juice.     

Spectrophotometric Determination of Aminoglutethimide by Diazotization and Subsequent Coupling

Abstract

Three simple and sensitive spectrophotometric methods for the determination of aminoglutethimide are described. The first method is based on the diazotization of the drug and the reaction product is quantified spectrophotometrically at 273 nm. The second and third methods involve coupling of the diazotized salt of the drug with either ethyl acetoacetate (EAA) in alkaline medium or N-(1-naphthyl)ethylenediamine hydrochloride (NED) in acid medium, to give colored reaction products measurable at 368 nm and 558 nm, respectively. The optimization of different experimental conditions is described. The proposed methods were applied successfully to the determination of amino-glutethimide in tablets with good accuracy and precision. The reliability of the developed methods were established by comparing the obtained results with those given by the official United States Pharmacopeial XXII methods.     

Diazotized reagent for spectrophotometric determination of glyphosate pesticide in environmental and agricultural samples

A new sensitive spectrophotometric method for the determination of glyphosate herbicide in environmental and agricultural samples is developed. The reaction is based on diazotization followed by coupling of glyphosate with p-dimethyl amino benzaldehyde. The resulted complex absorption spectra was observed at λ_max = 420 nm. The effects of other metal ions and pesticides were also tested for selective determination of glyphosate. The analytical parameters were optimized and have been successfully applied for determination of glyphosate in various environmental samples such as soil, water and vegetables. This method has a lower limit detection of 6 μg of glyphosate. Beer's law is obeyed over the concentration range of 6.0 μg–24.0 μg glyphosate in 25 mL of the final solution at 420 nm. The standard deviation and relative standard deviation calculated are 0.0055 and 1.023, respectively. The molar absorptivity of the colored system is 1.91 × 10¹⁰ L mol^?1cm^?1 and Sandell's sensitivity is found 0.408 × 10^?5 μg cm^?2. The proposed method is simple, sensitive, highly reproducible and time saving as compare to those complicated time consuming methods.     

Sensitive determination of propoxur by spectrophotometry using 3-aminopyridine.

A simple spectrophotometric method for the determination of propoxur, a widely used insecticide, in various environmental samples and pesticide formulations is described. The method is based on the coupling of the hydrolysis product of propoxur with diazotized 3-aminopyridine in an alkaline medium, to form an azo-dye which has a maximum absorbance at 463 nm. Beer's law is obeyed over the concentration range of 0.05 to 1.2 microg ml(-1) of propoxur. The molar absorptivity and Sandell's sensitivity are found to be 3.10 x 10(4) l mol(-1) cm(-1) and 0.007 microg cm(-2), respectively. The important analytical parameters and optimum reaction conditions were evaluated. The method is free from the interference of other commonly used pesticides and inorganic metal ions.     

2-Amino-5,7-dimethyl-1,8-naphthyridine as a fluorescent reagent for the determination of nitrite

A new fluorescent reagent 2-amino-5,7-dimethyl-1,8-naphthyridine (ADMND) was proposed for the determination of trace nitrite. The reaction is based on the diazotization of naphthyridine amine with nitrite to form a diazonium salt that hydrolyzed when boiling to give hydroxyl group substituted naphthyridine. Fluorescence quenching degree of ADMND by nitrite ion is linear in the nitrite concentration range of 1 x 10(-7) to 2.5 x 10(-6)mol l(-1) with a detection limit of 4.06 x 10(-8)mol l(-1). Reaction and determination acidity for nitrite is the same which made the method much simpler compared with the widely accepted fluorescence method with DAN as a fluorescence reagent.     

Flow-injection spectrophotometric determination of sulfadiazine and sulfamethoxazole in pharmaceuticals and urine.

A rapid and sensitive flow-injection spectrophotometric method is proposed for the determination of sulfadiazine and sulfamethoxazole. This method is based on the diazotization of sulfonamide with sodium nitrite, and a coupling reaction of the diazo-compound with alpha-naphthylamine. The optimum experimental conditions are obtained by using the controlled and weighted centroid simplex method. The linear ranges for the determination of sulfadiazine and sulfamethoxazole are 0.2-20 microg ml(-1) and 0.1-20 microg ml(-1), and their detection limits are 0.06 microg ml(-1) and 0.05 microg ml(-1), respectively, and the sampling frequency is 130 samples per hour. The method has been used to determine sulfadiazine and sulfamethoxazole in pharmaceuticals and urine without separation. The results are in agreement with those obtained by a high-performance liquid chromatograph technique at the 95% confidence level.     

Volumetric determination of primary arylamines and nitrites, using an internal indicator system

A new nitrite titration method is presented. The titration is performed in the presence of a standard solution of 4,4'-sulphonyl-dianiline and diphenylamine, which is used as an internal indicator. An intense red colour develops during the titration as a result of a simultaneous diazotization and coupling process. A very sharp end-point is given by a colour change to yellow. The titration is performed at a temperature of about 45 degrees in the presence of large amounts of nitrate. The method is specific and precise. It is suitable for the direct volumetric determination of various easily diazotized primary arylamines, sulphonamides and other amino-compounds which can be determined by nitrite titration. It is suitable also for the indirect determination of nitrites. The method is applicable on the semimicro and macro scales.     

Spectrophotometric determination of Fe(III) in alkaline solutions without neutralization

Spectrometric study on the complexation of Fe(III) with an organic reagent obtained by coupling 3-methyl-1-phenyl-5-pyrazolone with diazotized 3-hydroxy-4-amino-benzene sulphonic acid was carried out in alkaline solutions. A 1:2 Fe(III): reagent water soluble complex is formed. The optimum pH is 9.0-11.8. The maximum absorbance of the complex lies at lambda = 560 nm, where the absorbance of the reagent is low. The molar absorptivity is 9000 l.mole(-1).cm(-1) at pH = 11.6. The value of the stability constant determined at 20 +/- 1 degrees C, pH = 11.6 and lambda = 560 nm is 4 x 10(5)M. The Beer-Lambert law is followed for iron concentration in the 0.2-5.0 mug/ml range. The spectrophotometric method was tested on synthetic solutions and thus applied for determination of traces of Fe(III) in several samples of alkaline hydroxides and carbonates without the neutralization of the solutions.