SOLID-STATE MICROPROCESSOR-CONTROLLED DETECTOR FOR DOUBLET PEAK MEASUREMENTS IN FLOW-INJECTION ANALYSIS

A solid-state detector for time-based transmission measurements in flo w-injection analysis (FIA) based on a light-emitting diode (LED) sourc e and photodiode (PD) transducer with microprocessor controller is des cribed. The instrument components cost less than US$ 500. A simple pea k-finding algorithm was capable of accurate measurements of the time i nterval between doublet peaks (Delta t). Comparison of results, obtain ed using the detector, with theory for an acid-base reaction with brom othymol blue indicator is made. Linear relationships between the measu red Delta t and the logarithm of the injected concentration were obtai ned for two systems whose injection volumes were 987 and 1650 mu l. Th e correlation coefficients, based on 14 and 13 data points, were 0.99( 9) and 0.99(2), respectively. The detector could measure transmittance signals corresponding to 0.00098 absorbance above the baseline.