SUMMARY The blueberry crop became an alternative for export-oriented production in Argentina. New market requirements related to product quality containing low levels of pesticides, require appropriate management of the crop production. Fungal diseases are the main causes of crop losses, thus the application of fungicides such as triazoles are needed for control. A series of processes that change over time the levels of residues on the plant tissue begins after the pesticides have been applied. The removal and gradual dissipation depend on many factors such as the nature of the plant, the chemical properties of the pesticides, time and conditions during application, weather, etc. The most relevant is the chemical degradation. The systemic nature of these fungicides and the rapid maturation of the berries seem to indicate that the total elimination of residues may not be reached. For these reasons, evaluating residual levels of these fungicides in fruits and blueberry juices, and estimation of degradation rates when applied on crops and under modified atmosphere storage conditions, are proposed as objectives of the present study. Chromatographic analysis of pesticides in food usually involve detection of trace levels of residues, requiring sample pretreatment steps, associated with potential losses of the analyte during different process stages, such as extraction, clean up, concentration and diluents for chromatography injections. In addition, they involve the use of large volumes of high purity organic solvents, mostly toxic and expensive. Solid phase microextraction emerged as a new methodology aiming to reduce time of analysis and costs, avoiding the use of solvents and increasing the sensitivity of methods by allowing the determination of trace levels of contaminants. The application of this new methodology has been in growing development during recent years. Hence, this extraction procedure was adopted for the determination of fungicides in the matrices previously mentioned. In comparison with traditional methods, this technique has some advantages such as the complete elimination of organic solvents, the simplification of the analytical steps, improvements in sensitivity and accuracy, better selectivity and lower limits of quantification, as well as the reduction of the analysis time and cost savings. Developments during the last years incorporated analytical procedures such as programmed temperature vaporization injector attached to chromatographic systems, in order to achieve greater sensitivity in gas chromatography and mass spectrometry. This injector is very important in different areas of application. It can be used to introduce large volumes of samples and when used in the solvent vent mode is able to concentrate a large amount of analyte in the system inlet. Then they are transferred to the column. The introduction of a large sample volume allows lower limits of detection and therefore it represents a great advantage for the determination of trace levels pesticides. However, it was necessary to establish and optimize some of the many variables that affect the efficiency of the vaporization process of pesticides, and the chromatographic detection and identification. If both methodologies are compared, is feasible to conclude that for analytes that are easily removed from aqueous solutions, solid phase microextraction is the best choice, with high injected mass and consequently leading to better chromatographic response than those observed in other methods. The use of the programmed temperature vaporization injector is more appropriate than traditional injection techniques when an organic solvent extraction is needed. The implementation and optimization of solid phase microextraction and large sample volume injection by multiple injections on solvent vent mode, in the programmed temperature vaporization injector, have allowed the determination and identification of triadimefon, penconazole, propiconazole and tebuconazole residues in fresh blueberries and blueberry juices spiked and in real samples by gas chromatography and mass spectrometry with adequate precision and high recovery and sensitivity. The limits of detection and quantification of these techniques are about two orders lower than the maximum residue guideline limits for these analytes and are comparable to those observed in published literature. On the other hand, when a sample contains very low residue levels, the sensitivity of the method could be significantly increased by extending the fiber immersion time. The implementation and optimization of the extraction process, using polidimetilsiloxan as polymers coating, and changes in the chromatographic conditions allowed determination of other pesticides commonly used for crops in the region. Residues of malathion, chlorpyrifos, tebuconazole, trifloxystrobin, chlorothalonil, fludioxonil and boscalid were detected and quantified in real samples. Spiked samples were used in all cases for calibration because of the matrix effect. Residues from packaging house samples varied from one to another season and the total positive samples were relatively low, approximately 12%. Generally this value was below the maximum residues limits, except for only 5% of the samples. The results obtained in blueberry juice, allowed concluding that the relative persistence of residues related to the initial charge in fruits is influenced by several factors, being the most important the temperature and enzymatic treatments. The dissipation curves of the evaluated pesticides showed a first-order reaction behavior. The kinetic constant was determined and the half life time calculated. These values vary depending on the analytes and application conditions. Continuous inspection of residues levels are needed since values relate to specific conditions, not necessarily repeatable, even for the same type of crop or geographical region. The optimized analytical techniques and obtained results are very relevant during decision making steps within productive sector. Registering the residues as a quality control step allows achieving greater competitiveness in markets, besides to protecting consumers health and reducing environmental pollution.