(1040-A) Colorimetric analysis of aluminum present in deodorants using a paper-based microfluidic device

Aluminum is the third most abundant element in the Earth's crust. It can be toxic to the nervous, skeletal, and hematopoietic systems. Aluminum is used in cosmetic products such as deodorants, and although the blood-brain barrier prevents it from entering the brain, there is evidence that it can affect the nervous system. Aluminum exposure is being studied in relation to Alzheimer's disease, breast cancer, and other illnesses. In this regard, the development of affordable methods for aluminum detection is essential, as standard analytical methods include atomic absorption spectroscopy and atomic emission spectroscopy, which are expensive and require trained personnel.
μPADs (microfluidic paper-based devices) are a promising option due to their ease of use and low cost. In this work, a PAD and a μPAD were developed, manufactured by combining chromatographic paper and pouch film; The PAD geometry has 8 columns and 5 zones each, and the μPAD has a central zone and 4 analysis zones. The zones were impregnated with silver nanoparticles for better color uniformity and improved analysis, which was performed in the red color channel.
Deodorant samples were prepared by liquid-liquid extraction, acid digestion, and simple dilution. The chelation capacity of Eriochrome Cyanine R (ECR), the chromophoric reagent used, is related to pH, being ideal in the range of 4.5 to 6. In the optimization process, the use of auxiliary solutions was eliminated, simplifying the method. The optimal ratio of ECR and aluminum was 3 μL of 1500 mg L⁻¹ ECR to 7 μL of 2-6 mg L⁻¹ aluminum on the PAD and 4 μL of ECR to 32 μL of aluminum on the μPAD. Nanoparticles such as graphene oxide, carbon nanotubes, and silver nanoparticles improved the system's response, with silver nanoparticles yielding the best results.
A calibration curve was established after optimization, showing a linear range of 2-6 mg L⁻¹ for aluminum concentration, and R² = 0.999, LOD = 0.3 mg L⁻¹, and LOQ = 0.93 mg L⁻¹ for the PAD. Three samples were analyzed, and the results were compared. The values obtained by the reference method were considered as the true values, calculating the relative errors. The sample preparation method with the best results was acid digestion with nitric acid and hydrogen peroxide, resulting in errors ranging from 5.4% to 18.2% on the PAD and from 3.6% to 10.1% on the μPAD, along with a better precision. The μPAD device was successfully developed, being low-cost and simple as proposed. Three samples were analyzed and compared with a reference method, and the samples showed comparable results between the devices and the reference method.