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This paper reports a new flow-through fluoroimmunosensor, the function of which is based on antibodies immobilized on an inmunoreactor of controlled-pore glass (CPG), for determination of digoxin, used in the treatment of congestive heart failure and artery disease. The immunosensor has a detection limit of 1.20 microg L(-1) and provides high reproducibility (RSD=4.5% for a concentration of 0.0025 mg L(-1), and RSD=6.7% for 0.01 mg L(-1)). The optimum working concentration range was found to be 1.2 x 10(-3)-4.0 x 10(-2) mg L(-1). The lifetime of the immunosensor was about 50 immunoassays; if stored unused its lifetime can be extended to three months. A sample speed of about 10-12 samples per hour can be attained. Possible interference from substances with structures similar to digoxin (morphine, heroin, tebaine, codeine, pentazocine and narcotine) was investigated. No cross-reactivity was seen at the highest digoxin: interferent ratio studied (1:100). The proposed fluoroimmunosensor was successfully used to determine digoxin concentrations in human serum samples.

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An automated procedure for the design of an optimized (for both configuration and operating point) anaerobic digestion system is presented. The procedure is based on modern nonlinear programming algorithms and numerical models of the various system components (biological, thermal, and economic). The model simulates yearly digester system operation, and uses this to calculate the after-tax net present value for a particular system design. The optimal design is found using BIAS, a method of multipliers code. Substantial improvements in the net present value were found when the optimized design was compared to the designs in current use. A sensitivity analysis revealed that the price of energy and the energy conversion efficiency were the parameters which influenced system economics most strongly for the best system configuration at the optimal operating point.