Organic Pesticides Lab Report

1. Introduction

In the development of agriculture, pesticides are very important due the plant protection that they provide which in result boosts food production. We humans get exposed to these pesticides through the air, water, soil and even our food that we eat today.

The presence of all these pesticides resides is a major problem over the world. There have been several methods being done to analyze these pesticide residues in food commodities. Liquid chromatography can be used for the quantification of pesticide residues. Here we are estimating it in drinking water.

2. Experimental Section.

2.1. Materials

Alachlor, Malathion pesticide standards and Methanol acetonitrile were bought in the U.S. All reagents are freshly prepared in liquid

Sample Preparations

Unknown water and reagent blanks are prepared in the same manner. 20 ml test tubes are taken and 5ml of water is pipetted into each of the test tubes. The pesticide standards are now inserted into the test tubes at concentrations of 0.1,0.2,1,2,5,10 and 30 ng/ml-1. The mixtures are mixed and kept in equilibrium for 30 minutes. After the 30 minutes is done, the tests tubes are then immersed in a 100 degrees Celsius methanol water bath for 15 minutes. Once the samples become frozen, put in a lyophilizer at a temperature of -109 degrees Celsius. The samples are allowed to completely dry. After 6 hours remove from the lyophilizer. Acetonitrile at a PH of 7 (neutral) is added to each of the test tube samples. Mix the samples on a vertex shaker for 3 minutes and transfer to a 20 ml centrifuge tube and place in a TurboVap under 5-psi nitrogen at room temperature and allow it to completely dry. The dry resides are now put in 1ml of acetonitrile for testing (analysis).

4. Chromatographic Condition

10ml of the extract is now taken to be analyzed using a mass spectrometer and a liquid chromatograph. The analysis of all pesticides was performed using a liquid chromatograph with a software that is essential for data processing of the quantitative as well as qualitative

Discussions.

This method is used to accurately quantify pesticides in water samples. The lyophilization is advantageous to allow the complete of the samples to minimize error. The acetonitrile resulted in 82% - 104% extraction efficiency for Alachlor and Malathion in the water samples.

The different solvent gradient was fixed to contain both the physical and chemical properties of the pesticides. The advantage of using mass spectrometry is that there is an elimination of the component that interferes with the water sample thereby allowing a very accurate analysis.

The base peak of the pesticides was observed using the graph. The m/z at 270,110, 83 and 70 were obtained at DE 10, 30, 60 and 70 respectively for Alachlor and the m/z at 229, 88, 124, 79 and 63 were obtained at DE 10, 20, 40, 70 and 80, respectively for malathion.

From this we can see that the MS/MS recorded at different DE showed that the distribution pattern of base peak ions of various compounds depends upon used DE, in which some ions were used for confirmation and structure illustration and also some ion was used for quantification of compounds.

6.