American and Indian scientists collected and described in the three standard solutions to the spectrophotometer in which the radiation source mounted LEDs, which the device’s cost was only $ 63. Although the spectrophotometer was ten times cheaper than commercially available, he did not give them the sensitivity and accuracy of analysis. Study with a detailed description of the device, schematics of electrical circuits and checks is published in the journal PLoS One.
Spectrophotometers are almost in every modern laboratory that carries out chemical analysis of substances. They are quite cheap in comparison to more complicated devices and have sufficient characteristics for solving a wide range of important problems: the determination of many organic, inorganic and medicinal substances. However, in a world of many laboratories, where the price is two thousand dollars for these devices makes them either the most expensive equipment in the institution or makes it impossible to acquire them.
Modern spectrophotometers use a tungsten filament lamp as a light source in the range from 350 to 2500 nanometers, of which using a relatively complex system of lenses, slits, and diffraction gratings stands out almost monochromatic (single wavelength) radiation. This radiation passes through the cuvette with the analyzed solution is partially absorbed in it and then hits the detector. The fraction of the absorbed radiation by a solution is used to determine the concentration of analytes.
The use of monochromatic radiation is necessary to reduce the interfering effects that may arise due to the impurity absorption of light by substances in solution. Relatively expensive modern spectrophotometers provide the bandwidth (range of wavelengths) from four to 20 nanometers, while the cheap LEDs can emit light with a bandwidth from 10 to 60 nm depending on the selected color.
Michael Prairie (Michael Prairie) with colleagues from Norwich University replaced the bulb and optical system for LEDs and created the spectrophotometer unit cost of $ 63, which can be done in the laboratory, with a basic knowledge of electronics. Scientists compared the capabilities of the device with four modern commercially available spectrophotometers price from two to eight thousand dollars. For example, three standard solutions of iron, manganese and fluoride in various concentration ranges commonly encountered in drinking water, researchers have identified key details of the characteristics of the device.