DEVELOPMENT OF LOW-COST SPECTROPHOTOMETER USING A DUAL-ARDUINO SYSTEM

Abstract

Rationale: A spectrophotometer is an analytical instrument used to measure the transmission or reflection of visible light, UV light, or infrared light for quantifying solution concentrations. Despite the importance of the spectrophotometer as a precious analytical instrument, it has not been possible for many STEM science laboratories to access spectrophotometers due to their lack of funding. Creating a spectrophotometer with an Arduino microcontroller might demonstrate the possibility that low-cost assembling procedures can give insight into spectrophotometry and affordable accessibility for young scientists. 
 Methods: An Arduino Uno was connected with an RGB LED and two light sensors that read the light intensity from two points, one from the front near to light input and the other from the back of the sample cuvette. A stepper motor could control the sample cartridge, which had 16 holders created with a 3D printer. The second Arduino Uno managed the stepper motor with an obstacle sensor to stop the cartridge at the exact sample reading point. The difference in the analog light intensity was recorded into variables for later calculating calibration curve with regression slope, intersection, and coefficient. 
 Results: Using three colors of food dyes and serial dilution solutions, it was found that this automated spectrophotometer could accurately measure the sample concentrations within approximately 5.7% error from the actual concentration. The performance of the Arduino spectrophotometer was supported with the comparable regression coefficients being near 0.98 or so in measuring standard serially diluted dye solutions of the food dyes within the spectrum of the dye concentration.
 Conclusion: With 8 dye samples of blind test trials, no difference in the measured concentration was found for those from the samples with concentration created blindly.