LAUSR

Near‐infrared spectroscopy (NIR) associated with chemometric methods has been widely used in the determination of various compounds, as it is a fast, nondestructive, and analytical method with minimal sample preparation and universal application. In addition, the trend of miniaturization has allowed the development of new portable equipment, increasing the possibilities of point‐of‐use analysis at low cost. In this context, the objective of this study was to develop a portable analytical methodology using a low‐cost DLP NIRscan Nano spectrophotometer (Texas Instruments®) connected to a smartphone for data storage. For this, an app called NanoMetrix was developed, created natively for Android from Android Studio IDE, according to a software design standard known as Model‐View‐ViewModel (MVVM). To demonstrate the applicability of the method, 36 samples of plant tissue were analyzed to determine total nitrogen content. The calibration models were compared to those obtained with the SOLO+MIA software (Eigenvector Research, Inc.), 8.6.1. The results presented root mean square error of calibration (RMSEC) 1.90 and 1.82 g kg−1, root mean square error of prediction (RMSEP) 2.00 and 1.97 g kg−1, and R2pred 0.973 and 0.975, for the NanoMetrix application and the SOLO+MIA software, respectively. Therefore, the results indicate that the NanoMetrix integrated with the portable spectrophotometer, besides the acquisition of spectra, allows the processing of data in the field and reducing the time for the analysis and obtaining the results. Also, the chemometric associated with the NIR spectroscopy is a viable alternative to replace, or complement, the methods used for nitrogen determination.