Chemiluminescent determination of Metsulfuron-methyl in surface water.

TONELLI, LAURA I.; ACEBAL, CAROLINA C.; LISTA, ADRIANA G.

Santa Fe, Argentina

Workshop; 2nd Latin American Pesticide Residue Workshop (LAPRW2009) - Pesticides in Food and Environmental Samples; 2009

Universidad Nacional del Litoral, Facultad de Ingeniería Química y Laboratorio Central, Co-organizado por Centros de Investigación de América Latina, Estados Unidos y Europa

Introduction: The use of pesticides in agriculture has greatly improved the food production all over the world. However, the excessive use of this kind of compounds that is required in intensive agriculture represents one of the principal sources of contamination in soils, ground waters and surface waters. The persistence and mobility of most of these agriculture products may cause important damage to the environment and human health.  Metsulfuron-methyl (MSM) is an herbicide that belongs to the sulfonylurea family. They have an aryl group bonded to an N- heterocycle by a sulfonylurea bridge (-SO2-NH-CO-NH-) [1]. MSM is widely applied in our fields owing to its significant action in plants protection [2], high selectivity and low toxicity. Objective: In order to verify the presence of residual MSM in regional surface waters, a new and simple continuous flow method with chemiluminescent (CL) detection is developed. Materials and method: A Flow Injection Analysis (FIA) method with CL detection has been developed. The method is based on the inhibition effect of the CL intensity of luminol-hexacyanoferrate (III) when MSM photoproduct is injected. To carry out the photodegradation on-line, a FIA manifold with a PTFE reactor coiled around a germicide lamp is used. Results: The optimized FIA system gives a calibration curve in the range 32.0 - 170.0 µg L-1 MSM. The relative standard deviation is 4.11% at 130 µg L-1 (n=9) and the detection limit is 11.7 µg L-1. The sample throughput is 50 h-1. The interference of cations (Na+, K+, Cu2+, Ca2+) and anions (F-, SO42-, CO32-, Cl-,  NO3-), usually present in water, is studied. Additionally, the effect of others herbicides like glyphosate and sulfometuron-methyl is also investigated. The method has been successfully applied for the determination of MSM residue in water samples, without previous treatment. To carry out the validation of the method, a recovery study on real samples is performed with satisfactory results (92-105%). Conclusion: The proposed method is a novel contribution for analytical community, because the MSM determination using CL detection has not been reported in the literature until now. In addition, the continuous flow system with a photodegradation step and CL detection is a simple, fast and inexpensive method to control residual MSM in water samples. [1] Caselli, M., Chemosphere, 2005, 59, 1137-1143 ; [2] Brown, H. M., Pesticide Science, 1990, 29, 263–281.