APPLICATIONS OF BIPOLAR PULSE CONDUCTANCE TO FLOWING STREAMS (ENZYMES, HPLC, IMMOBILIZED, FIA).

摘要

The use of flowing streams, particularly flow injection analysis (FIA), to facilitate analytical measurements has increased significantly in the past several years. Conductance has generally not been used as a detector for flowing streams. Two reasons for this are conductance's lack of selectivity and instrumental limitations. This work presents the results of experiments in applying Bipolar Pulse Conductance (BICON) as a detector in flowing streams.;Initial experiments are performed to gain insight into the design of conductometric flowcells. Solution resistance is monitored as a function of electrode placement and cell spacer thickness. Three electrode placements are used; side by side, diagonal opposing and directly opposing. It is determined that for maximum current and minimum cell volume, the directly opposing electrodes are the configuration of choice.;A combination of BICON and an exponential dilution apparatus is then used to create a rapid method for determination of the Critical Micelle Concentration (CMC) of surfactants. Results are presented for several surfactants. The effects of n-butanol on the CMC of tetradecyltrimethylammonium bromide is also investigated. The results are comparable to ones previously reported. The exponential dilution method offers an increase in speed and sample preparation over traditional methods.;A new method for conductometric monitoring of enzymatic reactions is also presented. A flow injection (FIA) set-up, with multiple conductance cells, is used. The enzymatic hydrolysis of urea, catalyzed by urease, is used as an example in developing the technique. Serum and urine control standards are used to assess the precision and accuracy. The conductometric method is shown to be equal to, or better than existing methods in the areas of detection limits, working range, precision, accuracy, and sample preparation. The method has a sample throughput of 20/h. The conductometric method is also extended by using it as a detector for amino acids separated by HPLC. This detection method, although not as sensitive as others, benefits by requiring no derivatization step. A discussion of the types of enzymatic reactions which might lend themselves to conductometric detection is given and several reactions are identified as meeting these criteria.