RESUMO
This study introduces the first micro-flow-batch analyzer (µFBA). A simple, low-cost, deep urethane-acrylate photo-resist ultraviolet-lithographic technique was used in its development. Details of the microfabrication process are presented including; the use of two superimposed photo-masks to improve the micro-channel and stop chamber border definition, as well as integration of an LED/phototransistor photometric pair, while using an open nylon-thread (fishing line) micro-mixing system for solutions homogenization. The system was used for photometric determination of Fe(II) in oral solution iron supplements employing the well-known 1,10-phenanthroline method, with instantaneously prepared micro-chamber calibration solutions. All analytical processes were accomplished by simply changing the timing parameters in the control software. It must be emphasized here that there was no outside preparation of the standard calibration solutions; the mixing was all done in-chamber/in-line, with all solutions maintained flowing while being proportioned for the measurement processes. The µFBA results were acceptable when compared to the reference method, and comparable to normal flow-batch systems. It was possible both to project and build a low-cost probe with high sample throughput (about 120 h(-1)), low relative standard deviations (about 1.1%), and reduced reagent consumption (30 times less than the reference method). The µFBA system based on urethane-acrylate presented satisfactory physical and chemical properties while keeping the flexibility, versatility, robustness, and multi-task characteristics of normal flow-batch analyzers. The µFBA system contributes to the advance of micro-analytical instrumentation, while realizing the basic principles of "Green Chemistry".
RESUMO
A flow-injection biamperometric method for determination of pantoprazole (PTZ) in pharmaceutical tablets is reported for the first time. The reversible redox couples Fe3+/Fe2+, Fe(CN)6(3-)/Fe(CN)6(4-), Ce4+/Ce3+, VO3(-)NO2+, and I2/I- were tested as indicating redox systems for biamperometric determination of PTZ in a flow-injection assembly with optimized flow parameters. The best results were obtained using V03(-)NO2+, which showed to be a selective and sensitive biamperometric indicating system for PTZ even in the presence of excipients and antioxidants that typically are found in drugs. The analytical graph was linear (r = 0.99945) in the range from 10 to 100 mg/L using 25 mmol/L VO3(-) as the reagent and water as the carrier stream and applying 100 mV between the 2 platinum wire electrodes. The limits of detection and quantitation were 200 and 667 microg/L, respectively, with a sensibility of calibration of 22.6 mV/mg/L. The proposed method was successfully applied to determine PTZ in commercial pharmaceutical tablets with a mean relative error of 1.60% (n = 5) and mean relative standard deviation of 3.10%. Recoveries close to 100% showed good agreement between the expected amount of PTZ in tablets (40 mg) and the results found by the application of the proposed method and demonstrated that the formulations used in the tablet compositions do not interfere in the PTZ analysis. The system had good stability, with a relative standard deviation of 3.80% for 9 sequential injections of a 60 mg/L PTZ solution. A sampling rate of about 100 samples/h was obtained.
