Facile and Sensitive Spectrophotometric Determination of Propoxur in Formulations and Environmental Samples

A facile, rapid, and sensitive spectrophotometric method for the determination of propoxur in insecticidal formulations, fortified water, vegetables, agricultural wastewater, and agricultural soil samples has been elaborated. The proposed method is based on the hydrolysis of propoxur under basic conditions, followed by instantaneous azo coupling of the resulting 2‐isopropoxyphenol with the anilines 2a – c . This yielded the orange‐red chromophore 3a (λ_max=at 470 nm), the pale‐red coupling product 3b (490 nm), or the red derivative 3c (478 nm), which are stable for 46 h, 38 h, and 24 h, respectively, and could be readily analyzed spectrophotometrically.     

Determination of rhodium in water samples using cloud point extraction (CPE) coupled with flame atomic absorption spectrometry (FAAS)

Cloud point extraction was applied as a method for preconcentration of rhodium after formation of a complex with 2-propylpiperidine-1-carbodithioate (2-PPC), and later determined by flame atomic absorption spectrometry using TritonX-114 as surfactant. Rhodium was complexed with 2-PPC in an aqueous phase and kept for 15 min in a thermostatted bath at 40 °C. Separation of the two phases was accomplished by centrifugation for 15 min at 4000 rpm. The chemical variables affecting the cloud point extraction were optimized and successfully applied to rhodium determination in various water samples. Under optimized conditions, the preconcentration system (100 mL sample) permitted an enhancement factor of 50. The detection limits obtained under optimal conditions was 0.052 ng mL⁻¹. The extraction efficiency was investigated at different rhodium concentrations (7.0–42.0 μg mL⁻¹), and good recoveries (96.42–99.14%) were obtained using this method. It has been applied to the determination of rhodium in water and was compared with reported methods in terms of Student’s ‘t’-test and variance ratio ‘f’-test.     

Novel Reactions for the Simple and Sensitive Spectrophotometric Determination of Traces of Selenium in Environmental Samples

Two rapid, highly sensitive, and selective spectrophotometric methods for the determination of traces of selenium(IV) were studied. The methods are based on either the oxidation of 4‐aminoantipyrine (=4‐amino‐1,2‐dihydro‐1,5‐dimethyl‐2‐phenyl‐3H‐pyrazol‐3‐one; 4‐AAP; 1 ) by selenium in basic medium and coupling with N‐(naphthalen‐1‐yl)ethane‐1,2‐diamine dihydrochloride (NEDA; 2 ?2 HCl) to give a violet derivative 3 or on the oxidation of dopamine hydrochloride (=4‐(2‐aminoethyl)benzene‐1,2‐diol hydrochloride; DPH; 4 ?HCl) by selenium in H₂SO₄ medium and coupling with 1 to yield a red derivative 5 (see Scheme). The violet derivative 3 with λ_max 563 nm is stable for 8 days and the red derivative 5 with λ _max 495 nm for more than a week. Beer's law is obeyed for selenium in the concentration range 0.03–3.5 μg ml^?1 (violet derivative 3 ) and 0.07–2.5 μg ml^?1 (red derivative 5 ), respectively. The optimum reaction conditions and other important analytical parameters were established. Interference due to various non‐target ions were also investigated. The proposed methods, were applied to the analysis of selenium in polluted water, natural water, plant material, soil samples and synthetic mixtures. The results of the analyses were superior in precision to those obtained by reported methods.