| Research Abstract |
A highly sensitive detection system using a semiconductor laser (SCL) and a thin long flow-through cell (TLFCT) to match flow-based analysis, such as flow injection analysis (FIA), has been developed. The SCL was a GaAIAs semiconductor laser emitting at 780 nm (5mW), and the TLFTC,which has a 100 mm thin long light path, was made of a poly (tetrafluoroethylene) (PTFE) rod. The sensitivity was essentially improved about 10-fold in comparison to usual FIA-spectrophotometry using a 10 mm conventional flow cell. When this detection system was applied to the determination of total phosphorus (P) in water by molybdenum-blue spectrophotometry, the relative standard deviation, detection limit and linear range were 1.0% (n=10 at 20 mug P 1^<-1>), 0.6 (3sigma) and 1.0-50 mug P 1^<-1>, respectively, and the results for the samples were fairly consistent with those by the official method. It may also be possible to apply the present detection system to other flow-based analytical methods such as the liquid chromatography family.
The determination of dissolved silica in waters is one of the applications of the detection system to practical trace analysis. Other trace components in samples could also be measured by FLA with this detection system. The technology of the SCL is progressing rapidly. The output power doubles every year, and the cost is cut in half. The light pathlength of TLFTC may be further prolonged for further increasing the sensitivity. When an inexpensive SCL,which can be continuously adjustable in frequency, comes available, it will be ever more suitable and convenient for determinations of many trace components in samples to use this analytical technique. The new detection system may also be beneficial to other flow-based analytical techniques such as liquid chromatography.
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