Cost-effective Spectrophotometer Sophia Lerebours, Miles Meloni, Taran Singh, Lyra Lu, Alessandra Barlas Supervised by Cristianna Colella, Queens College CUNY and Dr. Oskar Pineño, Hofstra University
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Introduction Spectrophotometers are optical instruments that measure light intensity of wavelengths Used in enzymatic reactions, DNA and RNA concentrations, impurity detection, concentration detection, structure elucidation, protein characterization, and more. They can be applied to various fields such as physics, molecular biology, chemistry, and biochemistry. Commercially-available spectrophotometers come with a hefty price tag of upwards of ten thousand dollars. Because of this, it is hard to gain access to a spectrophotometer without access to a lab, and the variety of uses a spectrophotometer possesses can only reach a limited number of people. Using the Arduino microcontroller and 3D printer, we were able to design and program an affordable and accurate mini spectrophotometer for use at home at a fraction of the cost of commercially available models.
MATERIALS • • • • • • • • • • • •
Custom 3D printed dark chamber Photoresistor Light source: One white LED and one RGB LED Potentiometer Two buttons Arduino Uno Compatible breadboard Cuvette Simple wires A computer Computer to Arduino USB cable Two 330 resistors
METHODS Following set-up like the diagram above, the Arduino code can be run through the computerconnected Arduino Uno board. A cuvette, acting as a reference blank, will be placed in the slot within the darkroom, in order to calibrate the spectrophotometer. Once the lid is placed over it, the chamber will block most outside light. An appropriate light wavelength (white, red, green, or blue) is selected via turning the potentiometer; the code determines the color of the LED that is used within the darkroom by receiving the value being inputted and mapping it to a 1-4 scale which is used to select the setting of the light. The 0% absorbance value can be manually set by pressing the black button after the cuvette is in place; recalibration is necessary each time a different light color is used. After calibration, varying target solutions can be placed within the cuvette, and the yellow button will trigger an absorbance reading of the provided sample. With the successive button press, the Arduino calculates and records the percent absorbance and prints it onto the serial display.
References 1. Rodda, N., Salukazana, L., Jackson, S., & Smith, M. (2011, August 10). Use of domestic greywater for small-scale irrigation of food crops: Effects on plants and soil. Retrieved August 11, 2020, from https://www.sciencedirect.com/ science/article/pii/S1474706511001914 2. Sustainable Earth Technologies. (n.d.). Retrieved August 11, 2020, from https://www.sustainable.com.au/greywatertreatment
Conclusion • Spectrophotometers are used to measure the light absorbance of a liquid. This is used to determine the concentration of a certain substance in a homogenous mixture, mostly for enzymatic reactions and nucleic acid concentration. • Although background light can enter the dark chamber of the Arduino-based spectrophotometer, the code adjusts for excess light with the calibration feature. • Its cost makes experimentation more affordable. By removing a financial barrier, more scientists could use the tool in their research. • Currently, the device draws its power from a computer which physically limits where it can be used. This issue could be resolved by using a battery as the source of electricity and an LCD display so the user can view the inputs and outputs in real time. • Because the spectrophotometer calculates the percent light absorbance, it may not be as accurate for experiments that require very sensitive measurements. Future Applications • As the human population continues to rise, water conservation and management has become more important. • Greywater, which is any wastewater from domestic use, excluding sewage, has both domestic and commercial applications including s erving as toilet water and hydrating crops or personal gardens. • Our home-made spectrophotometer provides an inexpensive method to determine the quality of greywater, which would be very advantageous. • One application of the Arduino-based spectrophotometer is testing different sources of greywater to determine the ideal reading for plant growth. This would allow greywater to be used to a larger potential.