Biphasic Extraction of Selected Heavy Metals From Corn With the Aid of Kosmotropic Salts

ABSTRACT

This study investigated the use of aqueous two‐phase extraction (ATPE) with kosmotropic salts for the extraction of toxic heavy metals from maize. Heavy metals, such as cadmium (Cd), chromium (Cr) and iron (Fe), are harmful to human health because they accumulate in the food chain and may cause kidney damage, cancer and nervous system problems. This study tested copper sulphate (CuSO ₄ ) and magnesium sulphate (MgSO ₄ ) as extracting agents under different conditions of salt concentration, solvent volume and maize mass. The extracted metals were analysed using atomic absorption spectroscopy (AAS). Results showed that CuSO ₄ was significantly more effective than MgSO ₄ , with the highest extraction achieved for cadmium, followed by chromium, and the least for iron. Response surface methodology (RSM) analysis confirmed that medium salt concentrations (30%–35%) and solvent volumes of 7–8 mL gave the best results. Fitting central composite design response model to the data generated a quadratic model with fits of R ²  = 0.90, R ²  = 0.90 and R ²  = 0.92 for Fe(I), Cr(III), and Cd, respectively. As we use environmental method (ATPE) to minimize those heavy metals (Cr(III), Cd(II) and Fe(I)) from corn, then corn can still be edible after exposure to ATPE because only water and ethanol are used. Comparison with international food safety standards revealed that Fe and Cr levels in maize were well within World Health Organization (WHO) limits. However, Cd(II) was found at 0.328 mg kg ⁻¹ , which is higher than both the WHO limit (0.2 mg kg ⁻¹ ) and the stricter South African standard (0.05 mg kg ⁻¹ ). This indicates a serious food safety risk. The study concludes that ATPE with CuSO ₄ is a promising, eco‐friendly and low‐cost method for extracting heavy metals from maize. However, further optimization and the use of complementary agents are recommended to improve cadmium extraction and ensure safe consumption.