Large quantities of chromium (Cr) are used in manufacturing processes worldwide. In the environment, Cr is mainly found as Cr(III) and Cr(VI). There are many differences between these species regarding their chemical and physical properties. For example, it is well known that Cr(VI) is carcinogenic because of its strong oxidation potential and ability to pass through cell membranes, whereas Cr(III) is an essential element and found in glucose tolerance factor. Methods for the determination of Cr have been widely studied. Among the available methods, flow injection analysis (FIA) is simple, rapid, and precise. In the present review, we summarize flow injection analysis methods for speciation analysis of chromium. The major approaches used for chromium speciation analysis use selective reaction with diphenylcarbazide combined with oxidation of Cr(III) to Cr(VI), solid phase extraction, and electrodialytic separation.
Unprecedented high throughput flow titration (maximally 43.1 titrations/min) has been realized by a triangular wave controlled flow ratiometry using an in-house LED-photodiode detector. The detector was fabricated mainly with quartz tubing, an LED, a photodiode and a DC power supply. While the total flow rate is held constant, a titrand (acid) is merged with a titrant (base) containing an indicator, the flow rate of which is linearly varied by the control voltage Vc supplied from a computer. Downstream, the intensity of the transmitted light is monitored with the detector and acquired in the computer as detector output voltage Vd. In the initial feedback-based mode, the lamp direction of Vc is changed from upward to downward, or vice versa, when the detector senses the equivalence point. In the subsequent fixed triangular wave controlled mode, the scan range and the scan rate of Vc are further limited and quickened, respectively, in order to increase the throughput rate. Equivalence point is determined by offsetting the effect of the lag time between the upstream merging and the downstream sensing. Although the present approach is an absolute method, calibration curves have been constructed for practical operation. The linearity of the curve is satisfactory (r2 › 0.993). The present method is well applicable to various titrations of acids and bases including acetic acid in commercial vinegars.
Open-source programming language, “Processing” is easy to study but it has a lot of useful features to build simple programs for data processing and/or hardware control by ourselves. Processing is free to download and to use, and the program built with Processing can be run on Windows, MacOS, and Linux. In this article, we explain the overview of Processing, how to install, and how to write programs in brief.