DEVELOPMENT OF A FIELD-PORTABLE PLASMA SPECTROPHOTOMETER BASED ON ELECTRIC ARC LIGHTER AND A WEBCAM AS DETECTOR

In the last decade, great efforts have been made to develop opto-chemical instruments with reduced size and weight. The instruments for optical emission spectroscopy have benefited with recent advances of miniaturization of optical and optoelectronic components and easy-operation control interfaces (e.g. Arduino). However, many portable/handheld instruments described in literature are still neither self-contained nor battery-operated, needing, in many cases, a computer connection for support and data processing1. In this sense, the construction of a handheld, low-cost, easy operation and battery-operated optical emission spectrophotometer based on arc plasma is presented. For this instrument, it is proposed the use of a commercial plasma arc cigarette lighter as source of optical excitation suitably adapted and coupled to a nebulization system based on a commercial USB portable humidifier. The emitted light is axially directed towards detection system which comprises a commercial UV diffraction grid (Edmund Optics) coupled to a Logitech C270 webcam without its glass protective filter. Webcam is interfaced with an Arduino NanoTM platform and controlled by a labmade software written in ActionScript 3.0 and exported as an AndroidTM application installed in a smartphone. Communication between smartphone and Arduino is made via bluetoothTM and the application converts RGB data from webcam to wavelength and generates the emission spectrum. Helium and argonium were investigated as carrier gases. All optic devices were isolated from environmental light into a black capsule. The entire instrument is electrically fed by a battery. Wavelength calibration was made using a commercial optical spectrometer. The proposed instrument is able to perform emission measurements in aqueous samples over the UV (280 – 400 nm) and/or visible region (400 – 700 nm) All these features give to the proposed instrument a compact character and computer independence, allowing its use in laboratorial and in situ analyses. Besides, the final costs of the instrument should be around U$ 200, a very inferior value in comparison to the available commercial instruments. Thereby, the developed instrument is really handheld, simple operation and self-contained components.