Regular Chemical Analyses
Global Fruit Point has fruit samples analysed on a regular basis to check if they contain residues of pesticides. We cooperate, amongst others, with the laboratory Dr. Specht Express (member of the Eurofins group). The team of the Dr. Specht laboratories analyses about 20,000 fruit and vegetable samples per year.
Reception and registration of the sample
The majority of the samples arrive by courier service by 10:00 AM. But samples can be delivered also during the weekend and outside the normal opening hours. Upon arrival of the sample, the laboratory staff checks if the merchandise delivered corresponds exactly with the description on the order form (origin, variety, brand, etc.).
The entire analysis process is documented in the computer system. The sample is registered with a reference number and a short description (weight, temperature, note if the sample is affected by decay).
To avoid samples being mixed up, every box is provided with a label with a bar code, the reference number and some basic information about the order. Photos are taken and integrated by WLAN in the sample documentation.
The order form accompanies the sample the whole way through the laboratory. Here again, a bar code guarantees the unmistakable identification of the sample. If the sample is from organic production, this is expressively stated on the order form. At the beginning and at the end of each stage of the process, the bar code is scanned, so the laboratory can keep track of the analysis at any time via the computer system.
IPS (Intelligent Sample Management System)
The whole analytical process is coordinated with the computer program IPS (Intelligent Sample Management System). The system calculates the time required for each step of the analysis and automatically distributes the samples between the various measuring instruments. This reduces the times of inactivity and waiting to a minimum.
Each office is equipped with a big flat screen showing the present stage of the different analyses. Each analytical step is marked with a specific colour.
Homogenization of the samples
The homogenization assures that possible residues in the sample material really correspond to the average distribution in the whole fruit. This step is very important to get an exact result.
The quantity of the sample material should be at least 1 kg. To avoid that possible residues are washed off the fruit, the material is used for analysis without previous cleaning.
The fruits are cut into pieces which are crushed with the big cutter. By means of a smaller homogenisator, the fruit is then converted into a fine pulp.
The enzymes of the fruit make the pulp turn brown.
The box with the sample material is kept for a week, the homogenized pulp (control sample) for three months.
Weighing and centrifuging
10 g of the fruit pulp are filled in a sample vessel.
The vessel is provided with a label with the sample number to ensure the clear identification of the sample.
An internal standard solution is added to the sample. The solution consists of various internal standard substances and acetonitrile used as extracting agent.
The sample vessel is agitated for about 5 minutes in the shaker, before adding a salt mixture that will later enable a separation between the acetonitrile and the water naturally contained in the sample material. The vessel is agitated for another 5 minutes. The laboratory staff uses the waiting time to complete and scan the corresponding documentation.
The sample is centrifuged for 2 minutes at 4,000 rpm.
Due to the centrifugal force the content of the vessel is divided into 4 layers:
- extracting agent (acetonitrile, uppermost layer) that contains the pesticides
- sample material (matrix) with white dots
- water contained in the sample material
- salt mixture (bottom layer)
After another cleaning process more sample material is extracted from the acetonitrile. By means of a pipette, the sample extract is filled into two small vials, one for analysis with the gas chromatograph (GC) and the other one for the liquid chromatograph (LC). To distinguish the two vials, the lids are of different colours.
Analysis with the gas chromatograph and the liquid chromatograph
The measuring instruments used for the express analysis (chromatographs) are named after racing cars.
There are, for example, liquid chromatographs with the names of Ferrari and Bugatti, and a gas chromatograph called Jaguar.
The so-called “multiple method” allows to verify with a single analysis the possible presence of more than 500 different substances in the sample material.
The monitor of the chromatograph shows the current status of the measurement.
Evaluation by computer
The measurement data are transmitted automatically to a computer program that displays the results of the analysis in graphic and numeric form. The blue curve shows the measurement data, and the red one the comparative standards used for evaluation purposes.
A congruency of the peaks of both curves indicates the presence of the corresponding substance in the sample material. Sometimes a peak may appear erroneously – those peaks are excluded from the evaluation.
The results are calculated in mg/kg. When a limit value is exceeded or the result is not exactly clear, the whole analysis is repeated.
Evaluation system “EVA”
The evaluation system “EVA” shows a list of samples to be evaluated, from which a sample can be selected with a mouse click. For some substances there are two measurement values, since in some cases the same substance is measured both with the GC and with the LC. The values relevant for the report are chosen with a mouse click and highlighted in green.
The “EVA” system shows which residues have been detected and in which degree of concentration. The maximum limits allowed for each substance are displayed automatically. The program automatically evaluates if the maximum limit (ML) or the acute reference dose (ARfD) is exceeded and to what extent the individual criteria of the food retail trade are observed. The critical values appear in red. When a substance remains below the detection limit, it is marked “n.n.” (not detectable).
The evaluation of the results follows the EU legislation or – for organic produce – the orientation values of the German Association of Natural Food and Products (BNN – Bundesverband Naturkost Naturwaren). To assess the plausibility, the values measured are compared with standard values from an internal list and/or an on-line database of the EU. If a result doesn’t seem plausible, the measurement is repeated with another instrument to exclude possible errors.
Evaluation and analysis report
The analysis report is generated automatically by computer, if desired by the customer, also in different languages. The report shows all residue values that exceed the detection limit. In the case of organic produce, all residue values detected are indicated in the report, without exception. Before the report is printed, the plausibility is checked once again and the content of the report is compared with the data of the order form. The report is then sent by email to the customer.
A green checkmark on the screen of the intelligent sample management system IPS indicates that the analysis has been successfully completed.
Residue Analyses by certified laboratories
Global Fruit Point has fruit samples analysed on a regular basis to check if they contain residues of pesticides.
To guarantee a secure quality, we closely cooperate with the following laboratories:
- Eurofins Dr. Specht Laboratorien
- Analytisches Institut Bostel
- GALAB Laboratories.
Thanks to the long-standing cooperation and the intensive communication with our partner laboratories, our residue analytics always comply with the latest technical standards.