# Development of a Fast, Low-Cost, and Green Method to Quantify Allura Red AC Dye in Candies through Digital Images Using a Smartphone

## TL;DR

A new smartphone-based method was developed to quickly and affordably measure Allura Red AC dye in candies, ensuring food safety with minimal environmental impact.

## Contribution

A green, low-cost, smartphone-based colorimetric method for quantifying Allura Red AC dye in candies was developed.

## Key findings

- The DIA-RD method achieved accuracy comparable to traditional UV–vis methods while reducing sample preparation time from 6 hours to 5 minutes.
- E129 concentrations in candy samples were all below legal limits using both the UV–vis and DIA-RD methods.
- The DIA-RD method complies with green analytical chemistry principles and is suitable for routine quality control.

## Abstract

The artificial azo dye Allura Red AC (E129), widely used
in candy,
may pose health risks, such as hypersensitivity and hyperactivity,
underscoring the need for its monitoring and quantification to ensure
food safety. This study adapted a traditional sample preparation approach
aligned with the principles of green analytical chemistry (GAC) and
introduced a low-cost, smartphone-based colorimetric method employing
digital image acquisition. The technique enables the simultaneous
capture of both the analytical curves and the samples in a single
image by using a 3D-printed digital imaging chamber. The data were
processed using the RGB color model and analyzed by partial least-squares
with REDGIM software. For the adapted UV–vis method, accuracy
at two concentration levels ranged from 77.33% ± 1.53 to 98.35%
± 0.07, with a limit of quantification (LQ) of 2.26 × 10–6 mg mL–1 and a limit of detection
(LD) of 7.47 × 10–7 mg mL–1. For the DIA-RD method, accuracy ranged from 78.04% ± 1.42
to 98.42% ± 0.06, with a LQ of 1.67 × 10–4 mg mL–1 and a LD of 5.51 × 10–5 mg mL–1. E129 concentrations in ten candy samples
ranged from 7.00 × 10–4 to 5.16 × 10–3 mg mL–1 using the UV–vis
method and from 7.33 × 10–4 to 4.83 ×
10–3 mg mL–1 using the DIA-RD
method, all below the legal limit of 3.0 × 10–1 mg mL–1 established by Brazilian and international
regulations. The DIA-RD method significantly reduced sample preparation
time, enabling data acquisition and processing in 5 min compared to
6 h with the UV–vis method. It complies with GAC principles
and shows a strong potential for routine quality control of candy
products.