Assessment of a mobile phone for use as a spectroscopic analytical tool for foods and beverages

Exploring smart phone based colorimetric technology for on-site quantitative determination of adulterant (neutralizer) in milk

There is a great concern regarding the safety of milk not only for human health but also for its economic consequences. The portable sensing devices, which can collect and analyze data within food supply chains at critical control points are lacking. Smart phones have now emerged as an integral part of each home, lab, farm and factory. It is having a provision of digital camera and computation; with widespread applicability including food analysis. The use of soda as a milk neutralizer is a usual practice but has a detrimental human health impact. This investigation explored an easy, economic, fast, repeatable, and field applicable Smartphone-based sensing technology, which was standardized and in-house validated for the quantitative determination of neutralizer in milk samples. The method had simple steps of spot-test response and digital image evaluation with the Red Green Blue process. The linearity of the method was shown by analytical curves ranging from 0.125% (1250 ppm) to 1% (10,000 ppm) that were characterized by R2 > 0.99. The limit of detection of 0.11% demonstrated the sensitivity of the method which was found better than the existing wet chemical spot test. Comparison with the existing spectroscopic method revealed no statistically significant difference between the observations using paired t-test at a confidence level of 95%.

Graphical abstract

Smartphone-based optical analysis systems

During the past few decades, there has been a growing trend towards the use of smartphone-based analysis systems. This is mainly due to its ubiquity, its increasing computing capacity, its relatively low cost and the ability to acquire and process data at the same time. Furthermore, there are many sensors integrated into a smartphone, for example a complementary metal-oxide semiconductor (CMOS) sensor. A CMOS sensor enables optical analysis for example by using it as a colorimeter, photometer or spectrometer. This review explores the current state-of-the-art smartphone-based optical analysis systems in various areas of application. It is organized into three sections, each of which investigates one class of smartphone-based devices: (i) smartphone-based colorimeters (ii) smartphone-based photo- and spectrometers and (iii) smartphone-based fluorimeters.

Miniature Spatial Heterodyne Raman Spectrometer with a Cell Phone Camera Detector

A spatial heterodyne Raman spectrometer (SHRS) with millimeter-sized optics has been coupled with a standard cell phone camera as a detector for Raman measurements. The SHRS is a dispersive-based interferometer with no moving parts and the design is amenable to miniaturization while maintaining high resolution and large spectral range. In this paper, a SHRS with 2.5 mm diffraction gratings has been developed with 17.5 cm^-1 theoretical spectral resolution. The footprint of the SHRS is orders of magnitude smaller than the footprint of charge-coupled device (CCD) detectors typically employed in Raman spectrometers, thus smaller detectors are being explored to shrink the entire spectrometer package. This paper describes the performance of a SHRS with 2.5 mm wide diffraction gratings and a cell phone camera detector, using only the cell phone's built-in optics to couple the output of the SHRS to the sensor. Raman spectra of a variety of samples measured with the cell phone are compared to measurements made using the same miniature SHRS with high-quality imaging optics and a high-quality, scientific-grade, thermoelectrically cooled CCD.