Development of a Portable Laser Spectrophotometer for Chlorophyll Measurement and Environmental Water Monitoring, Part 2

Overview

Objectives/Goals The purpose of this project is (1) to refine the construction of the previous laser spectrophotometer by making the instrument more sensitive and more susceptible to environmental light; (2) to optimize the instrument performance based on Beer#s Law; (3) to use the spectrophotometer for reliable field analysis of environmental waters; and (4) to obtain assurance of its performance. Methods/Materials A laser pointer emits 670 nm light was used for absorption spectroscopy of chlorophyll. The laser intensity was measured by using a pocket power meter. A neutral density filter was employed to reduce the laser intensity in an attempt to increase the instrument sensitivity. A 1-cm tube and a 2.5-cm container were compared as the sample cuvette. A light-block wrap was constructed with block-out cloth and used for minimizing the background environmental light. Environmental waters were collected and analyzed with this field-assembled portable laser spectrophotometer. Finally, the performance of this instrument was compared to that of a commercial, desk-top spectrophotometer. Results It was found the intensity of the source laser did not affect the absorbance sensitivity. The larger sample cuvette gave higher absorbance signals. The light-block wrap used to enclose the instrument was able to reduce environmental light readings to a negligible level. The measurements obtained were consistent with the cleanliness of the water sample. Finally, this portable laser spectrophotometer gave a similar sensitivity to that of the commercial spectrophotometer. Conclusions/Discussion A hand-held laser spectrophotometer has been designed and constructed with pocket components, and evaluated theoretically (Beer#s Law) and practically for chlorophyll measurement and water quality analysis. The sensitivity of the laser spectrometer is found to be comparable to that of a commercial unit. Finally, the laser spectrometer is proven useful and is ready for practical field-analysis.

Competition history

• CSEF 2002 Environmental Engineering · Entry S0806

Resources

• CSEF project summary ↗

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