Speciation study of aluminium in beverages by Competitive Ligand Exchange–Adsorptive Stripping Voltammetry

Application of adsorptive stripping voltammetry based on PbFE for the determination of trace aluminum released into the environment during the corrosion process

This work presents a new fast and sensitive method for voltammetric determination of Al(III) as Al(III)-cupferron complexes, which was used for the analysis of solution after exposure of aluminum alloy AA2024. Experimental conditions of voltammetric measurement such as preconcentration time, potential, and operating parameters were optimized. The formed Al(III)-cupferron complexes were adsorbed on an in situ plated lead film electrode (PbFE) using the potentials of -1.2 V (15 s) and -0.7 V (60 s) versus Ag/AgCl electrode. The promising results were obtained in 0.1 mol L^-1 ammonia buffer at pH = 8.15 and 6 ∙ 10^-5 mol L^-1 Pb(II), 3 ∙ 10^-4 mol L^-1cupferron. The calibration graph was linear from 1 ∙ 10^-10 to 2 ∙ 10^-7 mol L^-1 with the calculated detection limit of 3.3 ∙ 10^-11 mol L^-1, repeatability with RSD of 4.9% (n = 5). The accuracy was established by analysis of the synthetic sample.

Chemical Speciation of Aluminum in Wine by LC-ICP-MS

Aluminum is very common in the natural environment and in everyday human life. We are living in the "aluminum age." Its average daily intake should not exceed a few mg/day. Unfortunately, despite the growing number of alarming data about the toxicity of this element, human exposure to aluminum is constantly increasing. The toxicity and bioavailability of aluminum depends mainly on the form in which it occurs. The main variables conditioning the form are the concentration, the type, the molar ratio of aluminum to ligand, the pH value, and the temperature. This research presents a new method for speciation analysis of both inorganic and organic aluminum complexes in model solutions by LC-ICP-MS. Different solutions with variable pH values and different Al/ligand molar ratios (fluorides and several organic ligands, e.g., citrates and oxalates ions) were used. The chromatographic separation process was carried out based on isocratic and gradient elution, using a cation exchange analytical column. All determinations have been confirmed based on chemical equilibrium modeling programs. The new developed method was successfully applied for the first time in speciation analysis of real samples: white and red wine.

Voltammetric determination of aluminum(III) as Al-Alizarin S complex in tea leaves and infusions

This work presents, for the first time, DPV methodology of indirect aluminum (III) determination in tea leaves and infusions using the renewable silver amalgam electrode. A self-referencing strategy was proposed which relies on alternate voltammetric curves registration with and without conditioning of the electrode surface. The developed procedure utilizing formation of aluminum-Alizarin S complex shows linearity in the range of 2-50 μg L^-1 of Al(III) concentration, with r > 0.997. In the case of the electrode conditioning LOD is 0.2 μgL^-1 and repeatability expressed by CV is 1-2%. Introducing an additional operation i.e. electrode activation results in decrease of sensitivity from 0.0162 to 0.0043 μA/μgL^-1. The method was verified using CRM (tea leaves). Due to the wide variety of tea origin, types and producers, four most popular sorts (black, green, red and white) were chosen, made by one manufacturer. It was demonstrated that the proposed methodology may be applied in Al(III) determination in tea leaves and infusions. Al(III) extraction effectiveness was also examined. It was verified, that lemon juice addition during brewing increases aluminum concentration in infusions. Using Principal Components Analysis it was demonstrated that automatic distinction of infusions brewed with and without lemon juice, based on unprocessed voltammetric signal, may be successfully realized.

Quantitative Determining of Ultra-Trace Aluminum Ion in Environmental Samples by Liquid Phase Microextraction Assisted Anodic Stripping Voltammetry

Direct detecting of trace amount Al(III) in aqueous solution by stripping voltammetry is often frustrated by its irreversible reduction, resided at −1.75 V (vs. Ag/AgCl reference), which is in a proximal potential of proton reduction. Here, we described an electroanalytical approach, combined with liquid phase microextraction (LPME) using ionic liquid (IL), to quantitatively assess trace amount aluminum in environmental samples. The Al(III) was caged by 8-hydroxyquinoline, forming a superb hydrophobic metal⁻chelate, which sequentially transfers and concentrates in the bottom layer of IL-phase during LPME. The preconcentrated Al(III) was further analyzed by a square-wave anodic stripping voltammetry (SW-ASV). The resulting Al-deposited electrodes were characterized by scanning electron microscopy and powder X-ray diffraction, showing the intriguing amorphous nanostructures. The method developed provides a linear calibration ranging from 0.1 to 1.2 ng L^−1 with a correlation coefficient of 0.9978. The LOD attains as low as 1 pmol L^−1, which reaches the lowest report for Al(III) detection using electroanalytical techniques. The applicable methodology was implemented for monitoring Al(III) in commercial distilled water.