Block diagram of the photometric system. 

Contexts in source publication

Context 1

... block diagram of the instrument is shown in figure 1. The instrument consists of a light source, a focusing lens, filters, photodetectors and a readout system. ...

Context 2

... development and use of chemicals in agriculture, animal husbandry, and human health and nutrition have increased the awareness of the importance of the chemical environment and the effects of synthetic compounds on the flora and fauna. While modern research and service-oriented laboratories of industrialized nations increasingly use sophisticated instruments, there is a growing need for compact, inexpensive and portable instruments that can perform determinations in regions far from the convenience of a modern laboratory [1]. Recent advances in low-cost, miniaturized detection technology [2–4] have made it possible to take traditional laboratory-based instrumental techniques, e.g. a UV/ visible spectrophotometer, to remote sites for in - situ monitoring. In flow spectrophotometry, multiple measurements on a processed sample are accomplished efficiently in order to permit implementation of simultaneous determinations, differential kinetic analysis, speciation, standard addition and blank compensation [5–8]. The present paper describes a brief performance evaluation of the photometric system that can be used for the continuous flow analysis of the determination of various parameters in clinical, environmental and food chemistry. Solid potassium permanganate was dried for 1 h at 100 C. A stock solution was prepared by dissolving potassium permanganate 0.2 g in 1 litre distilled water. A set of standards (0.5, 1.0 and 1.5 ml of stock solution diluted up to 4 ml with distilled water, known as I, II and III standards, respectively) was prepared by serial dilution of the stock solution. A 10% cobalt chloride solution was prepared by dissolving cobalt chloride in distilled water. These standards were analyzed immedi- ately after preparation. A block diagram of the instrument is shown in figure 1. The instrument consists of a light source, a focusing lens, filters, photodetectors and a readout system. The tungsten lamp was used as a light source and emitted radiation in the visible wavelength region. The photodiode used as a detector was placed on the opposite side of a flow cell of 10-mm path length. Source stability was achieved by a constant voltage transformer and an electronic regulator. The transmit- tance signals were fed through a preamplifier, a log amplifier and through an A/D converter to an 8051 microcontroller for processing and display of the absorbance. The lamp was allowed to warm up for 10 min before use. The system was designed to allow different modes of operation. The first operating mode was to check the zero position. It then calibrated to 100% trans- mission (T) with distilled water at max . The next operating mode was to flow the standard concentra- tion solution or for a particular solution of known absorbance. Absorbance was calculated according to following ...