A highly sensitive flow-through phototransducer for unsegmented continuous-flow analysis demonstrating high-speed spectrophotometry at the parts per 109 level and a new method of refractometric determinations

Abstract

A simple photometric detector is described which, because of the high stability of the light source, permits determinations of metal ions at the parts per 109 level with 4-(2-pyridylazo)resorcinol as the spectrophotometric reagent. By virtue of the design of the transducer it also functions as a refractometer capable of determinations of solutions of organic and inorganic compounds down to a lower limit of approximately 0.01%m/m. The theory of this function is discussed.A gallium phosphide light-emitting diode and a silicon phototransistor act as light source and sensor, respectively. The output current from the phototransistor is converted into voltage by the current to voltage converter described.The transducer is designed as a flow-through cell which, when used in conjunction with standard unsegmented continuous-flow apparatus, is capable of sampling rates of up to 300 per hour with a relative standard deviation of the result of 1.5%. At slower flow-rates, with a sampling rate of 160 per hour, the relative standard deviation is less than 1%.