FLOW-INJECTION ANALYSIS WITH BULK EXTRACTION BASED OPTICAL SENSOR MEMBRANES

The use of recently described optical sensing membranes as solid phase photometric detectors in flow-injection analysis is described. These membranes are based on ionophores and lipophilic pH indicators contained in poly(vinyl chloride). The flow-injection mode of operation not only automates measurements with these optode membranes but also allows on-line mixing of the samples with pH buffer. The method therefore represents a good solution to the pH cross-sensitivity of the membranes. Absorbance measurements were carried out with a light emitting diode/photodiode transducer which was connected directly to an integrated circuit logarithmic amplifier. This inexpensive detector system allows highly precise absorbance measurements. It is further demonstrated that simultaneous measurements can easily be carried out with a slightly modified assembly.