Exploring Smartphone-based Spectrophotometry for Nutrient Identification and Quantification

TL;DR

The in-depth analyses, discussions, and results demonstrate the potential use of smartphone-based spectrophotometry as an accessible method to identify and quantify nutrients and pave the way for future developments that can apply this approach to the human body.

Abstract

Imbalanced nutrition is a global health issue with significant downstream effects. Current methods of assessing nutrient levels face several limitations, with accessibility being a major concern. In this paper, we take a step towards accessibly measuring nutrient status within the body. We explore the potential of smartphone-based spectrophotometry for identifying and quantifying nutrients in a solution by building and testing two prototype devices. We compared the prototypes and found that the limitations posed by the initial, simpler prototype were well addressed in the more portable and reliable second-generation device. With the second-generation prototype, we created and implemented a semi-automatic signal processing and analysis pipeline for analyzing absorption spectra. We thoroughly evaluated the prototypes by analyzing the effect of four different light sources and three reference spectra strategies. Results demonstrate that an LED bulb light source performed best, and all reference spectra strategies performed similarly. We then compared the second-generation prototype to a benchtop laboratory spectrophotometer to further validate the device. We applied the Beer-Lambert Law to demonstrate that our prototype is able to quantify the amount of vitamin B12 in a solution with an accuracy of up to 91.3%. Our in-depth analyses, discussions, and results demonstrate the potential use of smartphone-based spectrophotometry as an accessible method to identify and quantify nutrients and pave the way for future developments that can apply this approach to the human body.

Figures (11)

• Figure 1: Basic spectrophotometer components, adapted from vo-215-2013.
• Figure 2: First generation device prototype seen from above. The constructed spectrophotometer is on the left, and a CFL source is on the right. It is lined with black construction paper and covered with a lid during operation to limit outside light. The sample is placed in the middle.
• Figure 3: Blank sample (distilled water) as imaged with the first generation prototype and analyzed by the Theremino Spectrometer software. CFL bulb peaks labeled for calibration.
• Figure 4: The three test nutrients had distinct absorbance spectra in the first-generation prototype. Results for vitamin B12 appeared to be the most similar to the physical properties of the solution (a pink-red color). Prevalent noise in the spectra necessitated further testing and an improved design.
• Figure 5: Replicated spectrophotometer assembly where (a) the custom-designed cuvette holder attaches to (b) the 3D printed design, making up (c) the final assembly. The (d) design schematic is reprinted from the source bruininks-inexpensive-2022.