Page 37 - FoodFocusThailand No.161 August 2019

SPECIAL FOCUS

Pesticide Residue in Agricultural Products:
Importance and Analysis Techniques

Agricultural products, such as vegetables,
are often found of pests, especially worms,
aphids and fungi, encouraging farmers to
use pesticides and anti-fungal chemicals
to prevent damage on their agricultural
products.

Chemical substances commonly found using in
pesticides for agricultural products are divided into 4
groups: organophosphate, carbamate, pyrethroid, and
organochlorine. The first 3 groups are normally used in
agriculture and general products, while the fourth group,
which is the organochlorine, is prohibited in many
countries as the residue is difficult to decompose in the
environment and bioaccumulation in the human body
that triggers health problems.
The most common chemical residues are HPLC and GC techniques will be conducted in laboratory. Currently, there are 3
organophosphate and carbamate. They are group of methods of sample preparation as followed;
chemicals affecting the central nervous system and the • QuEChERS Method (Quick, Easy, Cheap, Effective, Rugged and Safe
peripheral nervous system. These chemicals, when Method) This method is interested by laboratories around the world and was officially
used in large quantities, cannot be completely recognized by the AOAC and CEN (Committee of European Normalization). For organic
eradicated by cleaning because the residue can be phase analysis, organic solution and small amounts of buffers are used. Dispersive
absorbed into the produce’s tissue. This results in Solid-Phase Extraction (d-SPE) is used for clean-up processes. This method can easily
pesticide residues in humans and affecting the health and quickly prepare samples of pesticides, with small cost, while has high effectiveness,
of people in the country. and also has good recoveries.
When it comes to export, chemical residues in the • Positive List Method This method has been used to prepare samples for analysis
agricultural products can lead severe impact on the of toxic residues in fruits and vegetables produced in Japan and imported products. It
country’s economy. We might be heard that the is also suitable for sample preparation for analysis of toxic residues in many researches.
European Union suspended imports of Thai fruits and The extraction, clean up or isolation, and separation are quite intensive. The suction
vegetables due to finding pesticide residues higher than method is deployed in the first clean up step, then partition technique, and clean up
the maximum residue limits (MRLs). In order to prevent again with SPE cartridge before analyzing the residue with GC technique.
an export problem of Thai agricultural products to the • Steinwandter Method In Germany, this method has been recognized in the
EU, Thai exporters must improve the quality and preparation of pesticide residues in fruits and vegetables. The Department of Agriculture
standard of vegetable crops to achieve required quality has also used this method to prepare samples for the analysis of toxic residues in
and standards from the upstream. Currently, toxic export fruits and vegetables. This method is similar to the Positive List method, but it
residues measurement can be divided as follows: does not use the suction for the first clean up process and without partition techniques.

Field Measurement Field measurement is a simple Electrochemical Technique This technique is receiving high attention and is
1and rapid method based on the principle of 3currently being developed to enable rapid detection of organophosphate in the field
substance’s color changing (Colorimetric). If there are measurement by using specific catalyst enzymes and electrochemical technique. It
detected substances, the color will be created. At has a high sensitivity at part per billion (ppb) and can detect other pesticide residues
present, there are a wide range of toxic residue detection in the organophosphate group that cannot be measured by the mobile test kit of the
kits available, such as GT-Pesticide Residual test kit, Department of Agriculture. However, this technique has only the ability to isolate
Pesticides Residue Test Kit (PR) and toxic residues substances in large groups. It cannot specify specific types of residues. Hence, when
detection in fruits and vegetables (TM KIT), etc. measuring real samples with a number of mixed organophosphate group, the results
may still be unclear about the type of residues. This method is suitable for preliminary
HPLC (High Performance Liquid Chromatography) measurements in the field before further measurement in the laboratory.
2and GC (Gas Chromatography) The principle of It can be seen that the analysis of toxic residues is very important to our daily lives
this method is separating the chemicals contained in whether directly or indirectly. From the above information, we have learnt that we can
the solution with mobile phase. The results will be shown primarily detect toxic residues by a field measurement. The field measurement is quite
as a specific graph of each substance. This method popular as it is convenient, fast, and we can know that the product is whether safe for
provides high accuracy; however, it needs to be consumption. But for export, it is often analysis in the laboratory. The certification from
measured in the laboratory due to the device is quite analysis laboratory is needed for export and to ensure that the product is safe and
large. Also, there are difficulties in sample preparation comply with the import regulations of each country.
and spend long time of measurement.

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