Application of the solid-phase micro-extraction technique coupled to GC-MS in the control of the impact of the pest treatment products in the industrial unit on the industrialized food products Quality

In this investigation, solid phase extraction (SPME) is applied in order to determine the concentrations of insecticides and rat poisons detected in the samples taken on the industrial finished product. Gas chromatography, coupled with mass spectroscopy (GC-MS) is used as an analytical instrument for this purpose. In order to obtain an optimal extraction, different process parameters are examined and optimized. Relevant results are obtained using 30 minutes non-specific binding property time, with 30 minutes stirring mode with magnetic stirring and a temperature of 30 °C. The efficiency of insecticides, poisons for rats, has been demonstrated, and pesticides are likely to be at a high concentration in finished industrial products.


Introduction
Pesticides (rat poisons and insecticides) are compounds characterized by their diversity and their different physicochemical properties [1][2] .Their adverse side effects have been quickly identified.It turns out that the toxicity related to their molecule structure is, in principle, not limited due to the associated species which should be evinced.It has been demonstrated that they are particularly toxic, not only to humans but also to the environment [3][4] .These molecules tend to accumulate in different biotic and abiotic matrices, including water, air, soil, aquatic organism, blood and food [5][6][7][8][9][10][11][12][13][14][15][16][17][18] .It is noted that pesticides are among the oldest organic synthetic chemicals used in agriculture activities all over the world, since 1940, due to their energetic efficiency against pests and diseases [6][7] .However, pesticides are very toxic and persistent in the environment, which tends to accumulate in living organisms.Due to their low degradation and high solubility in organic materials [19][20] , they quickly enter the food chain as contaminants reaching humans through the consumption of drinking water and agricultural food products [8][9][10][11] .Although most of them have been banned from use, they are still detected in ecosystems [9][10] .
Recently, the analysis of pesticide residues has received increasing attention in different parts of the world, including in North African countries.In particular, it has been remarked that the pesticides [16][17][18][19][20][21][22] , monitoring in industrial products is very important and requires high precision, unique selectivity and high sensitivity techniques [12][13] .
In agribusiness industries, the use of pesticides (rat poisons and insecticides) in the treatment of production and storage areas eliminates the apparition of pests that may impair the quality of the finished products or the production process.The law frames the latter and controlled by the ONSSA (National Office of Sanitary Safety of Food Products) within the framework of effective normative use of such chemical products, without an impact on industrial food products ready for consumption.
In this present work, we first verify the impact of the use of these products (rat poisons, insecticides) used to treat pests in closed industrial areas (storage areas, production areas).Then, we check the presence or the absence of traces and concentrations of these products in the finished products.For this purpose, we adopt the method of the microextraction on the solid phase SPME, with the use of the chromatography gas coupled to mass spectroscopy (GC-MS).This coupling SPME/GC-MS provides excellent sensitivity and precision even at deficient concentrations.

Materials and methods
In this section, we give the essential on the used methods, including materials.

SPME solid phase micro-extraction method
For the detection and the quantification of molecules of the industrial products by the solid phase microextraction method (SPME), we immersed the SPME fiber in the studied samples.This step was carried out at room temperature for 15 minutes.The procedure is illustrated in (Figure 1).

Figure 1. Adsorption and desorption process by SPME
The used fiber consists of a Carboxen/PDMS/DVB 50/30 μm phase.The chemical compounds are first concentrated on the fiber (adsorption phase), then they are thermally desorbed in the GC-ECD injector.The analysis conditions are the same as the ones mentioned above [21][22] .

Optimizing SPME
To increase the sensitivity and the effectiveness of the SPME method, optimization of various parameters such as the temperature, the exposure time, the duration and the mode of agitation, the effect of the pH and adding salt was performed.

Calculation method
The concentration is determined according to the method of qualification of peaks, taking into account the volume of the final extract and the volume of the sample analyzed for each identified molecule.For the SPME the method, the concentration is calculated using the following equation:

Ce = Ae x Ci Ast
Where Ce is the concentration of a compound in the sample.Ae indicates the air of a compound in the sample.Ast is the peak air of the studied compound.Ci represents the initial concentration of the studied compound and V denotes the volume of the sample to be dosed in mL.Ve is the volume of extract in mL.The percent recovery (PR%) or yield of each compound was calculated using the peak air.Concretely, this has been done using the following equation: Where Ce represents the concentration of the sample and Ci denotes the standard initial concentration.

Results and Discussions
In this section, we present the obtained results and the corresponding discussions.
The stability and validity of the used method were checked before generating any results in this investigation.
The validation of an analytical method consists of the determination relevant parameters as the fidelity, which itself represents a set of dispersion characteristics including repeatability, intermediate fidelity and reproducibility.
As criteria for estimating the stability, an examination repeatability test was performed.It consists of testing to evaluate stability; a repeatability test was performed.It consists of testing the same size in conditions as stable as possible and at close intervals.This measure of the variation of the results is carried out under the same conditions.The precision can be obtained when the same investigator repeats the method under the same conditions (reagents, equipment, adjustment and laboratory) in a short time interval.This makes it possible to evaluate the accuracy of the method under normal operating conditions.
To study the SPME stability, a series of five repetitions analysis was performed on the chemical compost concentration (5μg/L) under optimized conditions.The obtained results are shown (Figure 2).From Figure 2, it can be seen that for each product, there is no variation with an identical yield value obtained for all tests.
With the method, stability checked, the samples were analyzed.The studied industrial areas are given in Figure 3. Several varieties of insecticides were used in this study.First, a profiling of the active ingredient of each industrial formulation was performed (rat poison/insecticide).To be able to identify them, an analysis study should be performed.Indeed, samples are taken randomly in all the products before and after the surface treatment to evaluate the impact of the treatment in the quality of the finished products.
After treatment, the SPME fiber was implanted at the oven outlet of the cooking belt, to take advantage of the optimal adsorption conditions already established in our preliminary technique implementation study.
The following results represent the analytical profiles of the different peaks found by SPME/GC analysis: MS (Figure 5).In what follows, we discuss the product analysis after 6 hours spent from the moment of surface treatment with insecticide raticide.Figure 6 represents the results obtained after the analysis of the food products produced in zone 1 after 6 hours of the surface treatment.(Figure 6).

Figure 6. Analysis results of the finished product by SPME coupled to GC-MS after 6 hours of treatment
After 6 hours of the surface treatment by spraying using pesticides and rat poisons, the presence of certain chemical products at low concentration was observed.This implies that the 6 hours' treatment is not sufficient to eliminate these chemicals by spray.
Figure 7 shows the results obtained by SPME coupled to GC-MS after analysis of industrial production in a firm surface treated by spraying for 12 hours.It is noted that after 18 hours of surface treatment, the presence of surface treatment products in the finished industrial products can be neglected.These observations suggest that an 18h treatment time is a minimum period needed to eradicate most of the undesirable chemicals left in the product.
The results obtained by SPME coupled to GC-MS after analysis of industrial production in a firm surface after 24 hours of surface treatment by spraying are illustrated in Figure 9. Several pest control products used for closed production surfaces were studied, along with their impact on the quality of production.Several industrial formulation profiles of insecticides and rat poisons were developed using the SPME technique coupled to GC-MS with repeatability and reproducibility, in order to establish and verify the validity of the analytical method adopted.The present study respects the ISO quality norms.It has been observed that the use of these products may hurt the quality of the agri-food production treated by chemical spraying in the first 6 hours after treatment.
It has also been observed that the use of SPME coupled to GC-MS in the routine quality analysis is an economical, efficient and stable method concerning repeatability and reproducibility.It allows for accurate identification of all elements present at different concentrations, even at traces levels.

Conclusion
The present work was focused on the study of the impact of rat poison and insecticides in closed industrial facilities (storage areas, production areas).The main focus was to use micro-extraction on the solid phase SPME in the presence of the chromatography gas coupled to a mass spectrum (GC-MS) to reveal the presence of chemicals traces.
Several assays were carried out by SPME coupled to the GC-MS on a sample product in a closed environment, treated with rat poison, taken at different times with an interval of 6 hours, according to the iso quality standard adopted by the agri-food production.It has been shown that the interval of 18h of production break after chemical treatment is necessary to avoid the presence of remaining traces of the said chemical.Thus, avoiding the alteration of the finished product.It was also revealed that the coupling SPME/GC-MS provides great sensitivity and precision even at low concentrations.

Figure 2 .
Figure 2. Variation stability of SPME a series of five repetitions analysis was performed on the chemical compost concentration (5μg/L)

Figure 3 .
Figure 3.The overall scheme of the building of products and storage treated by chemicals Having discussed the stability of five products, we present now the results and give the corresponding discussions.Production areas (ZONE 1 and ZONE 2) were treated by spraying a liquid insecticide at the end of the production at 9 pm.The treated products are illustrated in Figure 4.

Figure 4 .Figure 5 .
Figure 4. Distribution of treatment areas by type of product used

Figure 7 .
Figure 7. Analysis results of the finished product by SPME coupled to GC-MS after 12 hours of treatment After 12 hours of surface treatment, two molecules were present at low concentrations.It has been shown that the resumption of production after 12 hours of surface treatment can present risks on the

Figure 8 .
Figure 8. Analysis results of the finished product by SPME coupled to GC-MS after 18 hours of treatment

Figure 9 .
Figure 9. Analysis results of the finished product by SPME coupled to GC-MS after 24 hours of treatment After 24 hours of surface treatment, a complete absence of undesirable chemicals is observed.