Before defining any sampling strategy, you must identify which pesticide is present and it's chemical properties such as solubility, soil adsorption coefficient, partition coefficient, vapor pressure, it's half life time and a rough idea of how much pesticide has been applied or spilled and when. Also, you must have an idea of how much pesticide is still in your environment because, you may wish to sample the soil, water, flora and fauna but depending on the previous mentioned properties it is not sure that you will be able to measure any pesticide residue.

On top of that, the first question you will have to answer is why you need to sample. What do you want to prove or to check, then review the chemical properties, the flow path and you will be able to define your sampling strategy.

But honestly, it will be better for you to get in touch with someone who is familiar with the sampling strategy, discuss with that person and after that, evaluate the cost of sampling as well as the cost of analysis the gather all this information and decide what you are going to do.

the sampling for pesticide residues may depend on whether you want to determine the pesticide residue deposited in soil, or the waters or the flora and fauna in the wetlands , so which sample will work on then from that position the sampling techniques are vast

as paul said, it will depends on what you want to sample, water is not easy to see hydrophobic compounds, but C-18 empore disk may be usefull for filtration to get suspended soils. bottom sediments allways better becouse its integrative properties

It depends on what of environmental matrix (air, soil, sediment, organisms) and what kind of pesticides you want to analyze. Please specify.

Before defining any sampling strategy, you must identify which pesticide is present and it's chemical properties such as solubility, soil adsorption coefficient, partition coefficient, vapor pressure, it's half life time and a rough idea of how much pesticide has been applied or spilled and when. Also, you must have an idea of how much pesticide is still in your environment because, you may wish to sample the soil, water, flora and fauna but depending on the previous mentioned properties it is not sure that you will be able to measure any pesticide residue.

On top of that, the first question you will have to answer is why you need to sample. What do you want to prove or to check, then review the chemical properties, the flow path and you will be able to define your sampling strategy.

But honestly, it will be better for you to get in touch with someone who is familiar with the sampling strategy, discuss with that person and after that, evaluate the cost of sampling as well as the cost of analysis the gather all this information and decide what you are going to do.

I perfectly agree with Alain

I don´t see any response from Shandrack that could lead the discussion. In my experience recent use pesticides are degraded very fast en the environment, so unless you can sample very quickly after application it is very likely that he will find very low concentrations or a lot of non-detects. Legacy pesticides, on the other hand, are very persistent and can be found even after many years of their use.

Sampling pesticide residues from the environment can best be performed by Mass spectrometry. Any combination can be used. But for high sensitivity I would prefer QTOF-MS/MS. following reference may help .

Alan, Hunter, Thompson., Anthony, John, Bjourson., Chris, Shaw., Stephen, McClean (2006). Bradykinin-related peptides from Phyllomedusa hypochondrialis azurea: mass spectrometric structural characterisation and cloning of precursor cDNAs. Mass Spectrom. 20: 3780–3788.

Youtube link http://www.youtube.com/watch?v=-iLtW6XQMmw.

http://www.youtube.com/watch?v=VUmcxNLHu4Y

Bioengineering aspect can also be studied by using Biosensors. Reference paper are

1. A,K. Singh.; A,W. Flounders.; J,V. Volponi.; C,S. Ashley.; K, Wally.; J,S. Schoeniger. Development of sensors for direct detection of organophosphates. Part I: immobilization, characterization and stabilization of acetylcholinesterase and organophosphate hydrolase on silica supports. Biosensors & Bioelectronics 14 (1999) 703–713.

2. A, L. Simonian.; A, W. Flounder.; J, R. Wild. FET-Based Biosensors for The Direct Detection of Organophosphate Neurotoxins. Electroanalysis 2004, 16, No. 22.

3. A,W. Flounders.; A,K. Singh.; J,V. Volponi.; S,C. Carichner.; K, Wally.; A,S. Simonian.; J,R. Wild.; J,S. Schoeniger. Development of sensors for direct detection of organophosphates. Part II: sol–gel modified field effect transistor with immobilized

organophosphate hydrolase. Biosensors & Bioelectronics 14 (1999) 715–722.

4. K,C.Gulla.; M,D.Gouda.; M.S Thakur.; N,G.Karanth. Reactivation of immobilized acetyl cholinesterase in an amperometric biosensor for organophosphate pesticides. Biochimica et Biophysica Acta (BBA) ,Journal- Protein structure and molecular enzymology , vol1597, Issue 1, p.133-139, 2002.

5. S,Okazaki.; H,Nakagawa.; K,Fukuda.; S,Asakura.; H,Kiuchi.; T,shigemori.; S,Takahashi. Reactivation of an amperometric organophosphate pesticide biosensor by 2-pyridinealdoxime methochloride. Sensors and actuators B: chemical vol66, issues1-3,p 131-134, 2000.

I hope this may help to find solution.

Dibya Dolridge Toppo

Department of Biotechnology,

School of Biomedical Sciences,

University of Ulster,

Northern Ireland,

UK

What type of environmental samples you are going to analyse water, soil , air or if any please specify. Different samples have different procedures Dr.K.N.Reddy

Thank you ALL for the response and the much information posted on the issue at hand. I am interested in sampling a certain wetland which is situated in an area which uses pesticides for agricultural purposes and I suppose that the wetland has been polluted by such pollutants. I however am interested in determining the levels of such pollutants in soil, water and selected plant materials....this seems to be so much work!!!. I need to know the sampling design appropriate for each sample matrix, is one design appropriate for all???

Sampling Designs

Scientific Sampling

1. Restricted random sampling – This type of sampling design involves certain restrictions to improve the validity of the sample.

2. Unrestricted random sampling – This is the best random sampling design due to no restrictions imposed, and every member in the population has an equal chance of inclusion in the sample.

• Lottery Technique

• Table of Random Numbers

3. Stratified random sampling – This type of design divides the population into two or more strata.

4. Systematic sampling – In this type of design the individuals of the population are arranged in a methodical manner.

5. Multistage sampling – This design is done in several stages.

6. Cluster sampling – In this type of design, the population is grouped into clusters or small units.

Also since most of the pesticide residues are volatiles the best time of sampling would be early morning and late evening for the air sample but water and soil sample can be collected at any time. The work is not much since you can have three objectives screening the pesticides in soil water and air,,,,, then after screening you quantify those that are significant and then identify those that are high in concentration using Gas chromatography, HPLC, and GC MS all available