How Is Pesticide Analysis Performed?
How Is Pesticide Analysis Performed?
How Is Pesticide Analysis Performed?
Pesticide analysis is a laboratory process carried out to determine whether a sample contains pesticide residues and, if so, in what amount. The analysis consists of correct sampling, sample preparation, extraction, instrument analysis, and result evaluation steps.
How Does the Pesticide Analysis Process Work?
Pesticide analysis is generally carried out in the following order:
A sample is collected.
The sample is delivered to the laboratory under suitable conditions.
The sample is homogenized.
Pesticide residues are separated from the sample using a solvent.
The extract is cleaned.
It is analyzed using LC-MS/MS or GC-MS/MS instruments.
The results are calculated and reported.
The purpose of this process is to reliably detect pesticide residues in the sample.
Sampling in Pesticide Analysis
For pesticide analysis to produce accurate results, the sample must represent the product. The sample should not be taken from a single point, but from different points of the product batch.
Things to consider during sampling:
Clean and suitable packaging should be used.
The sample should not be contaminated by the external environment.
The product should be transported without being crushed or spoiled.
The cold chain should be maintained when necessary.
Sample information should be recorded completely.
An incorrectly collected sample may lead to inaccurate results even if the laboratory analysis is performed correctly.
How Is the Sample Prepared in the Laboratory?
The sample arriving at the laboratory is first registered. It is then prepared for analysis.
At this stage, the sample is usually broken down, ground, or mixed to make it homogeneous. Homogenization allows an analysis portion with similar characteristics to be taken from every part of the sample.
Then, a specific amount of sample is weighed and the extraction process begins to separate the pesticides.
How Is Pesticide Extraction Performed?
Extraction is the process of transferring pesticide residues from the sample into the solvent phase. In food samples, the QuEChERS method is commonly used for this process.
In the QuEChERS method, generally:
A homogenized sample is weighed.
A suitable solvent such as acetonitrile is added.
A salt mixture is added.
The sample is shaken.
Centrifugation is performed.
The liquid phase containing the pesticides is separated.
This step enables pesticides to be separated from the sample matrix and made suitable for analysis.
Extract Clean-Up Process
The liquid phase obtained after extraction does not contain only pesticides. Components from the sample such as fat, pigments, sugar, organic acids, and similar substances may also pass into the extract.
For this reason, the extract is cleaned. The clean-up process helps obtain more accurate and reliable results during instrument analysis.
After clean-up, the sample becomes suitable for instrument analysis.
Which Instruments Are Used in Pesticide Analysis?
The most commonly used instruments in pesticide analysis are:
LC-MS/MS
GC-MS/MS
LC-MS/MS is mostly used for the analysis of non-volatile pesticides that can be separated by liquid chromatography.
GC-MS/MS is preferred for the analysis of volatile and heat-stable pesticides.
In comprehensive pesticide analyses, these two instruments are often used together. This allows pesticides with different chemical properties to be screened more comprehensively.
How Is Pesticide Analysis Performed with LC-MS/MS?
In LC-MS/MS analysis, the prepared extract is injected into the instrument. The instrument first separates the pesticides chromatographically, then identifies and quantifies them using a mass spectrometer.
This method enables many modern pesticides to be detected at low levels.
How Is Pesticide Analysis Performed with GC-MS/MS?
In GC-MS/MS analysis, the extract is introduced into the gas chromatography system. Suitable pesticides are separated in this system and measured using a mass spectrometer.
GC-MS/MS is especially used for the analysis of volatile and heat-stable pesticides.
How Is the Amount of Pesticide Calculated?
Calibration standards are used to calculate the amount of pesticide. The laboratory prepares pesticide standards at known concentrations and measures them in the instrument.
The signal from the sample is then compared with these standards. In this way, the amount of pesticide in the sample is calculated.
Results are generally reported in the following units:
mg/kg
µg/kg
mg/L
µg/L
How Is the Pesticide Analysis Result Evaluated?
At the end of the analysis, the detected pesticide amount is compared with the limits determined for the relevant product. These limits are generally expressed as MRL, or maximum residue limit.
The following information is considered during evaluation:
Which pesticide was detected?
How much pesticide was found?
What is the product type?
What is the applicable limit value?
Is the result below or above the limit?
If the detected amount is below the relevant limit, the product may be considered compliant. Results above the limit may indicate non-compliance according to regulations.
How Is a Pesticide Analysis Report Prepared?
After the analysis is completed, the laboratory prepares the results as a report. The report generally includes the following information:
Sample information
Analysis method
Analysis date
Detected pesticides
Measured amounts
Unit information
LOQ value
Evaluation result
The report shows the status of the analyzed sample in terms of pesticide residues.
How Is Pesticide Analysis Performed in Brief?
In brief, pesticide analysis is performed as follows:
A sample is collected, homogenized in the laboratory, pesticides are extracted with a solvent, the extract is cleaned, analyzed using LC-MS/MS or GC-MS/MS, and the results are compared with limit values and reported.