Spectrophotometric Determination of Carbosulfan in Environmental Samples
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Journal of Scientific & Industrial Research 1088Vol. 67, December 2008, pp. 1088-1091 J SCI IND RES VOL 67 DECEMBER 2008 Spectrophotometric determination of carbosulfan in environmental samples Aruna Sao1, Ajai K Pillai1 and V K Gupta2* 1Chemistry Department, Govt V Y T P G, Autonomous College, Durg 491 001 2School of Studies in Chemistry, Pt Ravishankar Shukla University, Raipur 492 010 Received 22 June 2007; revised 14 August 2008; accepted 01 October 2008 This study presents carbosulfan determination by a novel rapid, simple, sensitive and an extractive method, which is based on alkaline hydrolysis of carbosulfan into phenol followed by coupling with diazotized p- amino acetophenone in alkaline medium. Red brown dye (λmax 465 nm) can be extractable in 2-methyl butanol, which makes reaction more sensitive with same λmax. Beer’s law is obeyed between 0.8-5.6 ppm and 0.1-0.6 ppm in aqueous and extractive system respectively. Molar absorptivity and Sandell’s sensitivity were found to be 4.46x 104 l mol-1 cm-1 and 0.0085 µg cm-2 respectively. Method has been satisfactorily applied for carbosulfan determination in various environmental samples. Keywords: p-Aminoacetophenone, Carbosulfan, Spectrophotometry Introduction measurement were used. Deminearalised distilled water Carbosulfan [2,3 dihydro-2, 2-dimethyl-7- was used in the experiment. A stock solution (1 mg ml-1) benzofuranyl {(dibutylamino) thio} methyl carbonates], of carbosulfan (Rallies, India) was prepared in ethanol. a widely used insecticide, nematicide and miticide, is Working standard was prepared by appropriate dilution safe for crops due to its good systemic properties, low of present stock. A solution of p-aminoacetophenone (1%, 1-3 residue and long-term effect . It acts (LD50, 250 mg w/v) was prepared in HCl (1:4). An aqueous solution kg-1) by inhibiting activity of cholinesterase, and also (0.2%, w/v) of sodium nitrite (Merck, Mumbai) was causes malaise, muscle weakness, dizziness and prepared. 1 N H2SO4 and 4 M NaOH were prepared in sweating, headache, salivation, nausea vomiting, distilled water; both were of AR grade. 0.2% Sodium abdominal pain and diarrhea, depression and pulmonary nitrite (1.5 ml) was added dropwise to 25 ml of diazotised edema4. Methods used to determine carbosulfan include p-aminoacetophenone (DpAAP) with stirring. Diazotized GC5, HPLC6, GC-MS7-8 and TLC9, and compound, kept in a brown bottle in cold, was stable spectrophotometric methods involving reagents like for 4 h. 2-aminobenzophenazone10, diazotized p-aminobenzoic acid11, 2, 4- dimethoxyaniline12, p-chloro aniline13, Proposed Method 2, 4, 6-trichloroaniline14 etc. Development in Aqueous system This study presents a simple, rapid and inexpensive 1 N H2SO4 (0.3 ml) was added to an aliquot of a spectrophotometric method based on alkaline working standard solution containing carbosulfan (8-56 hydrolysis of carbosulfan and its subsequent coupling µg) in graduated flask. It was hydrolyzed in corresponding is proposed. Proposed method has been satisfactorily phenol by adding NaOH (0.5 ml). Then DpAAP (1.5 ml) tested for carbosulfan determination in water, soil and was added and solution was kept for 5 min with occasional grain samples. shaking to ensure complete coupling. Then, 4 M NaOH (1.0 ml) was added and volume was made up to 10 ml. Materials and Methods Absorbance of red brown dye was measured at 465 nm Materials against a reagent blank. Toshaniwal spectrophotometer (model TVSP-25) for spectral and Systronics pH meter (model 331) for pH Development in Extractive System *Author for correspondence An aliquot containing carbosulfan (10-60 µg) was taken Tel: (0788) 2253868 in a 250 ml separatory funnel. Then, H2SO4 (0.3 ml), and SAO et al: SPECTROPHOTOMETRIC DETERMINATION OF CARBOSULFAN 1089 Table 1—Determination of carbosulfan in water and plant samples Samples Amount of Amount of carbosulfan Recovery carbosulfan found, µg* % Added, µg Proposed method Reported Proposed Reported method14 method method14 Watera 30 29.50±0.025 29.35±0.032 98.3 97.7 35 34.65±0.017 34.30±0.02 99.0 98.0 40 39.80±0.015 39.35±0.035 99.5 98.3 Riceb 20 19.10±0.042 19.0±0.055 95.5 95.0 30 29.45±0.036 29.20±0.033 98.2 97.3 40 39.30±0.015 39.15±0.020 98.25 97.8 Citrusc 30 29.65±0.028 29.30±0.05 98.8 97.6 35 34.15±0.035 34.10±0.045 97.57 97.4 Soild 20 19.10±0.05 19.05±0.04 95.5 95.25 30 29.05±0.03 29.15±0.03 96.8 97.2 *Average of seven replicate analyses aAmount of water sample =5 ml; b & cAmount of plant sample = 50 g; dAmount of soil sample = 25 g 4 M NaOH (0.5 ml) were added to hydrolyze. Solution method and by reported method14. Amount of carbosulfan was kept for 2 min with occasional shaking. Then, was computed from standard calibration curve DpAAP (1.5 ml) was added. After 5 min, 4 M NaOH (1 (Table 1). ml) was added, making volume to 100 ml and extracted with 5x5 ml portions of 2-methyl butanol-1. Red brown Determination of Carbosulfan in Soil Samples extracted dye was dried over anhydrous sodium sulphate. Various soil samples were collected from an Absorbance was measured at 465 nm. agricultural field where carbosulfan was sprayed as an insecticide. Weighed and ground samples were washed Determination of Carbosulfan in Water Samples with 2x10 ml portion of chloroform, and then evaporated Water samples, collected from agricultural fields to dryness under reduced pressure. Residue was where carbosulfan was sprayed as pesticide, were first dissolved in ethanol (5 ml) and volume was made up to extracted twice with chloroform (5 ml) in a separating 25 ml with distilled water. Aliquots were then spiked funnel. Then, extract was evaporated to dryness under with known amounts of carbosulfan and recovery was reduced pressure. Residue thus obtained was dissolved determined by proposed and the reported method14 in ethanol (5 ml) and diluted up to 50ml with double (Table 1). distilled water. Aliquots were then fortified with known amount of carbosulfan and recovery was verified as Results and Discussion given under preparation of calibration curve. Proposed method involves a derivative of carbosulfan Determination of Carbosulfan in Grain Samples by reaction of carbosulfan with H2SO4. After alkaline Sample of citrus fruit (50 g) and rice free from hydrolysis, it is subsequently coupled with DpAAP to pesticides were taken. Weighed samples were spiked give red brown dye in alkaline medium (Scheme 1). with known amounts of carbosulfan and kept for 3-4 h. Absorption spectrum of dye recorded against a similarly Samples were washed with double distilled water (100 prepared reagent blank was measured at 465 nm in ml) and extracted with 2x5 ml portions of chloroform. aqueous as well as in extractive system (Fig. 1, Curve A The chloroform extract was evaporated to dryness on a & B), where absorption due to the reagent blank was water bath kept at 50°C. Residue was dissolved in 5 ml negligible(Fig 1, Curve C). Hence, all absorption ethanol and volume was made up to 25 ml with distilled measurements were carried out at 465 nm against a water. Aliquots were then analyzed using proposed reagent blank. 1090 J SCI IND RES VOL 67 DECEMBER 2008 Step 1- Hydrolysis O C4H 9 O S N O H O C N C H O C N H C O 4 9 O 3 CH H SO H 3C I 3 2 4 CH 3 H C 3 Acidic Hydrolysis H 3C Carbosulfan Carbofuran O H O C N O OH H 3C H C O II CH 3 Alkaline Hydrolysis 3 H C 3 H 3C Carbofuran Phenol derivative of carbofuran Step 2 -Diazotisation NO- / H + III NH 2 2 + N + NCl– O O p-aminoacetophenone Diazotized p-aminoacetophenone Step 3 -Coupling OH H C O IV 3 – Alkaline Hydrolysis + N+ NCl H 3C O OH O H 3C H 3C N O N Red Brown Dye (Polymethine dye) my ax at 465nm Scheme 1 Beer’s law is obeyed over concentration range of 8- and sandell’s sensitivity were found to be 4.46 x 104 l 56 µg of carbosulfan per 10 ml (0.8-5.6 ppm) in aqueous mol-1cm-1 and 0.0085 µg cm-2 in aqueous system medium and 10-60 µg of carbosulfan per 100 ml respectively. Precision of method was checked by 6 (0.1-0.6 ppm) in extractive system. Molar absorptivity replicate analysis of carbosulfan (30 µg) per 10 ml in SAO et al: SPECTROPHOTOMETRIC DETERMINATION OF CARBOSULFAN 1091 that causes an error of not more than ±2% in absorbance values. Conclusions Proposed method is simple, sensitive and extractive and can be used satisfactorily for carbosulfan determination in soil, water and vegetable samples. e c n Validation of proposed method was based on fortification a b r studies and was considered satisfactory due to 95.0- o s b 99.5% recoveries. A Acknowledgements Authors thank Head, Department of Chemistry, Govt V Y T P G College, Durg for laboratory facilities. wavelength, nm References 1 Alvarez M, Physical properties of carbosulfan, FMC Report, Fig 1—Absorption maximum for dye and reagent blank 1995, 29-74 2 Bruce C L, James C M, Robert C H & Glenn H F, Determination aqueous system. Detection limit (DL= 3.3s/S) and of carbosulfan & carbosulfan residues in plants, soil & water quantitation limit (Q L = 10s/S) of carbosulfan determined by GC, J Agric Food Chem, 31 (1983) 220-223.