Determination by near infrared microscopy (NIRM) of nitrogen content in tomato(Solanum lycopersicum L.) leaf powder

The chemical analysis of plant samples is time consuming and expensive. Near infrared spectroscopy techniques were developed, inter alia, as a rapid technique to predict the chemical composition of foods. In this study near infrared microscopy (NIRM) was used for the first time to determine the nitrogen content in reduced quantity of tomato leaf powder. A total of 72 tomatoes sample corresponding to 6 groups of 12 plants under 6 levels of nitrogen concentration. This experiment was performed with 3 simultaneous repetitions (216 samples submitted to analysis in total). For the model constructed, 30 samples were used in the calibration stage and 30 samples were used in the independent validation stage. The calibration and validation sets analyzed were chosen to cover the full range of spectra variation obtained from the NIRM analysis. The nitrogen content was determined by combustion according to the Dumas method. Standard error of calibration (SEC), coefficient of determination at the calibration stage (R²c) and ratio of performance to deviation (RPDc) were excellent (R²c values higher than 0.90 and RPDc values higher than 3). The coefficient of determination at the validation stage (R²p) and standard error of prediction were excellent (R²p values higher than 0.90). A model using all the information from the samples of the calibration and validation sets was constructed to improve the accuracy of the future prediction. The study indicated that NIRM is a promising and suitable tool for a rapid, non-destructive and reliable determination of the chemical composition in tomato leaf powder