In this work, a new version of an automatic injector is proposed, keeping the rectangular geometry. In this version, a small DC motor was employed to perform the displacement of the central part. The effectiveness of the injector was confirmed through the development of a procedure for the photometric determination of ethanol in distilled spirits based on the reaction with dichromate in a sulfuric acid medium and photometric detection using an LED based photometer. The system demonstrated the best analytical performance, versatility and simplicity of operation, also including the following features: linear response (r = 0.9972) for the concentration range of 10 to 50% (v/v) ethanol, 2.0% for the limit of detection (v/v) of ethanol, a relative standard deviation of 2.0% (n = 10) for a sample with an ethanol concentration of 40% (v/v), K2Cr2O7 and H2SO4 consumptions of 5.8 mg and 198 µL, respectively, and effluent generation of 0.73 mL per determination.
flow injection analysis; automatic injector commutator; ethanol in distilled spirits; multicommutation; LED photometer
