A field test-kit for analyzing arsenic concentration in water samples is
provided. The kit includes a portable infrared beam photometer for
measuring light absorbance in aqueous specimens. An infrared light
emitting diode is configured to direct a beam of light through a
specimen. A photodetector diode measures the intensity of light passing
through the specimen. The photodetector output voltages relate to the
light absorbed in the specimen and are displayed on a liquid crystal
display screen. The kit is assembled using off-the-shelf electronic and
opto-electronic components that have low power requirements. Dry cell
batteries or solar cells power the kit. To test for arsenic, molybdenum
based chemistries are used to selectively bind and convert arsenates and
phosphates in the specimen into molybdenum-blue color complexes. The
light absorbance of a specimen with both arsenates and phosphates bound
in molybdenum-blue color complexes is compared to that of a reference
specimen in which phosphates but not arsenates are bound and converted.
The differential light absorbance of the two specimens is used to arrive
at a quantitative value for the arsenic concentration in the water
sample.