| Abstract |
Food not only covers the basic need for survival but is also an important factor for maintaining public health. Major part of food is covered by agricultural products. Over the last decades, in the intention to meet the ever increasing needs of the population, agriculture has evolved into an overly intensive production process. The increase in production requires the use of pesticides. Today, everyone agrees that pesticides are one of most dangerous groups of substances for public health and a sneaky enemy for the environment. Purpose of this master thesis is to determine the plant protection substances in conventional and organic apple samples.
The paper is structured in two parts, the theoretical and the experimental.
The theoretical part involves first of all a literature review, followed by an extensive reference to the nutritional value of apples and to the health benefits arising from their consumption, as well as to their diseases and to the ways of plant protection.
Then, conventional farming is discussed, the practices it follows and their consequences on the environment and the living organisms. Moreover, organic farming is also analysed, the principles on which it relies and its objectives.
Following, reference is made to plant protection substances. Their use over time is reviewed, the methods of integrated plant protection and biological control are described, pesticides are classified and their consequences of their use on human beings, other living organisms and the environment are mentioned, as well as the maximum permitted levels in food, as established by the European Union.
Finally, the sample processing method (QuEChERS) and the analysis and quantification techniques used (GC-MS, LC-MS) are described.
In the experimental part, first of all, as the purpose of this paper, the residues of 40 pesticides in conventional and organic farming products are determined. Then, the sampling is mentioned (87 apple samples from 83 conventional and 4 organic farming) and the sample preparation process is described. The sample processing method used is the QuEChERS which is deemed appropriate for multi-residue analyses. The detection and quantification of plant protection products was successfully performed with the use of gas chromatography–mass spectrometry (GC-MS) and liquid chromatography–mass spectrometry (LC-MS).
During the methodology control procedure, the response linearity was determined and found at satisfactory levels (approaching one). The values of the limits of detection (LOD) and quantification (LOQ) were found below the lowest selected concentration levels in almost all cases.
Residues of pesticides were identified in a large rate of samples (83%) and in some of them, more than one pesticide was detected. Up to 8 different pesticides were found in one sample.
The most detectable compounds were identified. The most frequently detected is the fungicide Carbendazim (42.5% of the samples), followed by the pesticide Thiacloprid (25.3% of the samples) and, finally, Chloropyrifos (23% of the samples).
The residue concentrations were found below the maximum residue limits (MRL) except for four cases. The substances Carbendazim, Imidachloprid, Carbaryl and Methomyl were found to exceed the maximum limit at 0.2% of the samples in total. Finally, the organic samples were found free of residues.
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