Developing a novel paper-based enzymatic biosensor assisted by digital image processing and first-order multivariate calibration for rapid determination of nitrate in food samples

Abstract

For the first time, a novel analytical method based on a paper based enzymatic biosensor assisted by digital image processing and first-order multivariate calibration has been reported for rapid determination of nitrate in food samples. The platform of the biosensor includes a piece of Whatman filter paper impregnated with Griess reagent (3-nitroaniline, 1-naphthylamine and hydrochloric acid) and nitrate reductase. After dropping a distinct volume of nitrate solution onto the biosensor surface, nitrate reductase selectively reduces nitrate to nitrite and then the Griess reagent selectively reacts with nitrite to produce a red colored azo dye. Therefore, the color intensity of the produced azo dye is correlated with nitrate concentration. After image capture, the images were processed and digitized in the MATLAB environment by the use of an image processing toolbox and the vectors produced by the digital image processing step were used as inputs of the first-order multivariate calibration algorithms. Several multivariate calibration algorithms and pre-processing techniques have been used to build multivariate calibration models for verifying which technique offers the best predictions towards nitrate concentrations in synthetic samples and the best algorithm has been chosen for nitrate determination in potato, onion, carrot, cabbage and lettuce samples as real cases.

Hyphenating paper-based biosensors with smartphones

“…However, it can be difficult to get accurate results; most dipstick assays rely on a range of colour changes to delineate ranges more clearly, whereby the user is comparing line colour intensity. As an alternative, some tests can include an optical reader, such as a handheld camera device [31] or even a smartphone camera [32], which can take away some of the subjectivity in analysing the results and also produce more accurate quantitation if needed.…”

“…Here, the smartphone cameras use a CMOS assay that assign a red, green, or blue value to each pixel photographed, and thus can measure broad colour shifts that occur at a test line. For example, Jalalvand et al [32] describe RGB measurements to detect nitrate in food samples. Their platform is similar to the dipstick assay; a piece of Whatman filter paper is impregnated with Griess reagent and nitrate reductase.…”

On line kinetic analysis of permeation profiles for UV filter loaded microemulsions using an automatic system with spectroscopic detection and a chemometric approach

“…32 SFS and PLS have been used together in many analytical applications. 33,34 However, few reports showing the application of these methods in the study of microemulsion based samples have been published. 35 This work aims to propose an on line automated system based on the use of the Franz diffusion cell to obtain the permeation kinetic constants of OMC in lab-synthesised microemulsions and emulsion commercial samples.…”

Evaluation of novel Griess-reagent candidates for nitrite sensing in aqueous media identified via molecular fingerprint searching

“…Nearly all of the commercially available on-eld/in situ environmental nitrogen-monitoring devices 6 measure nitrate and nitrite levels based on the nitrite-selective Griess reaction sequence (Scheme 1). 7 These techniques employ an aromatic amine (e.g. sulfanilamide 1), that in the presence of nitrite and an acid catalyst undergo diazotisation resulting in the formation of a reactive diazonium salt 2.…”