Molecular absorbance and fluorescence measurements are usually performed by benchtop or portable USB spectrophotometers or fluorometers. However, even the simplest configuration of these instruments requires considerable financial input, which is not affordable to many universities and research groups especially when public politics withdraw funds from science. Light-emitting diodes (LEDs) based devices can be an interesting alternative for low-cost, portable yet reliable measurements of absorbance of fluorescence. Especially if associated with the fabrication of 3D structures by additive manufacturing techniques. Although there are many reviews in the literature dedicated to discussing the theoretical aspects and analytical performance of LED-based devices, we consider that these reviews are not easily applicable for beginners in electronics. It results in the intimidation to employ such powerful tools which could have a huge impact mainly to small and/or initial groups. In this tutorial, we present a guide that will help students and researchers to construct “lab-built” devices based on simple optoelectronic components and 3D printing to perform molecular absorbance and fluorescence measurements for analytical methods. Finally, with this tutorial guide, we anticipate a large spread of the usage of LED devices for reliable analytical measurements that can be extensively used in many scenarios.

Food safety is a constant and necessary concern due to the worldwide increase of the food demand. The monitoring of quality parameters demands the development of accurate, easy and fast procedures. The aim of this work was to develop a cheap, miniaturized and trustworthy salting-out assisted liquid-liquid extraction (SALLE) procedure for the determination of pesticides in wines. Sample and acetonitrile were mixed and the addition of NaCl and CH3COONa were used for separation of aqueous and organic phases. After centrifugation, the organic phase was directly injected into a liquid chromatograph. The developed SALLE procedure consumed at least 25-fold less reagent compared to conventional QuEChERS procedure. Additionally, the d-SPE step of the QuEChERS method was suppressed, without efficiency losses. The developed procedure was compared to the conventional methodology and no significant difference was observed. It was successfully applied to the determination of three pesticides in wines by liquid chromatography. Low consumption of sample and solvent, low residues generation, simple instrumentation are notable advantages. The suppression of the d-SPE step simplified the process and the risk of analyte losses.