Aluminum is one of the most abundant elements in the Earth’s crust and is widely used in food packaging, water treatment, and consumer products. While it is considered an essential trace element, excessive exposure can be harmful. Elevated aluminum levels have been reported in bone and central nervous system tissues and are frequently observed in patients with kidney failure and Alzheimer’s disease.
Note that the presence of aluminum in biological samples reflects exposure and accumulation, not disease causation.
Because aluminum can enter the human body through food, beverages, pharmaceuticals such as antacids, and even cooking utensils, reliable and routine measurement remains an important analytical challenge.
Building a Selective Sensor
The research team designed a carbon paste sensor using graphite powder combined with a plasticizer and a chemical modifier known as p-chlorophenyl maleanilic acid (pCl-MA).
They evaluated several plasticizers, with tricresyl phosphate producing the most stable and reproducible sensor performance.
Potentiometric measurements were conducted using the new carbon sensor in conjunction with a standard Ag/AgCl reference electrode. The sensor’s analytical characteristics, including sensitivity, detection limit, linear working range, and response time, were analyzed systematically.
Even at Trace Levels, Performance was Strong
The sensor demonstrated a near-ideal Nernstian response for aluminum ions, with a slope of 20.32 ± 1.18 mV per decade across a wide concentration range from 1.0 × 10-6 to 1.0 × 10-1 mol L-1. The detection limit reached 3.3 × 10-7 mol L 1, enabling reliable measurement of aluminum at trace concentrations.
Stable operation was observed within a pH range of 4.0 to 6.0. At lower pH values, interference from hydrogen ions increased the sensor response, while higher pH conditions led to signal loss due to aluminum hydrolysis and hydroxide formation.
The sensor responded rapidly to fluctuations, reaching a stable potential within eight seconds. Temperature tests showed consistent performance between 10 and 60 °C, indicating good thermal stability under typical laboratory conditions.
Evaluating the Sensor Mechanisms
To understand how aluminum ions interact with the sensor surface, the team used Fourier-transform infrared spectroscopy, scanning electron microscopy, and energy-dispersive X-ray analysis. These techniques confirmed that aluminum binds to the pCl-MA modifier through its carboxylic and amide functional groups, forming a stable surface complex.
Microscopic imaging revealed visible changes in surface morphology after aluminum exposure, supporting the proposed complexation mechanism.
The sensor was applied to a range of real samples, including antacid Maalox, soft drinks packaged in aluminum cans and plastic bottles, and human serum samples from patients with chronic kidney failure, acute kidney failure, and Alzheimer’s disease.
The results revealed higher aluminum levels in canned soft drinks than in plastic-bottled equivalents, as expected with aluminum leaching from can packaging. Measurements obtained using the carbon sensor closely matched those from inductively coupled plasma (ICP) analysis, a gold-standard laboratory technique.
When benchmarked against previously reported aluminum-selective electrodes, the new sensor compared favorably in terms of detection limit, response time, linear range, and operational pH window.
While it does not replace advanced spectroscopic methods, the sensor could be a low-cost, fast, and straightforward option for aluminum monitoring in complex samples.
Reliable Al Measurement at a Low Cost
The study demonstrates that carbon paste sensors modified with carefully selected ionophores can deliver reliable aluminum measurements without the need for expensive instrumentation or extensive sample preparation.
The approach may be particularly useful for routine screening in environmental, pharmaceutical, and biomedical research settings.
Journal Reference
Basset M.H.A., et al. (2026). Quantitative determination of al (III) traces in soft drink, pharmaceutical products and biological fluids of kidney failure and alzheimer disease patients using carbon sensor. Scientific Reports 16, 626. DOI: 10.1038/s41598-025-32308-z,