Mirror-Coated Long-Path Cells for Colorimetry with the Use of a Bifurcated Optical Guide

Abstract

For sensitive measurement of the absorbance of aqueous solution, mirror-coated long-path cells have been constructed, in which introduction of light from a laser diode and collection of the reflected light passing through the analyte solution are done through the same end of the cells with the use of a bifurcated fiber. The absorbance of the solution has been enhanced about 20 to 30 times by using the present system. Also, the present mirror-coated long-path cells show a sharp response in turbidity with respect to the change toward smaller particle sizes in Latex gel. The present detection system has been coupled with the flow injection analysis of phosphate in molybdenum blue colorimetry. Detection of phosphate at 1 ng P/mL is possible with this measurement system—a result which is rather difficult to achieve with the use of a commercial auto-detection system.