Application of a new HPLC-ICP-MS method for simultaneous determination of Al(3+) and aluminium fluoride complexes

Rh(III) hydroxocomplexes speciation using HPLC-ESI-MS

A mixture of rhodium(iii) hydroxocomplexes formed during the polycondensation process in alkaline media has been fully characterized by the hyphenated high performance liquid chromatography with electrospray ionization mass spectrometry (HPLC-ESI-MS). The baseline separation was achieved using reverse phase ion-pair chromatography (RP-IP-HPLC) in gradient elution mode. When using SDS as the ion pair, the formation of all types of its associates with the molecules of acetonitrile, as well as oligomers of rhodium aquahydroxocomplexes, etc. was taken into consideration. As a result, it was shown that the test mixture is presented by [Rh(H2O)6]3+, [Rh2(μ-OH)2(H2O)8]4+, [Rh3(μ-OH)4(H2O)10]5+, [Rh4(μ-OH)6(H2O)12]6+.

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.

Preliminary investigation of aluminium fluoride complexes in aqueous solutions with capillary electrophoresis coupled with electrospray ionization mass spectrometry and with inductively coupled plasma mass spectrometry

RATIONALE

It is crucial to identify and confirm the original species of aluminium ions (Al³⁺ ) dissolved in water, since they behave differently. Depending on their species, the toxicity differs. Capillary electrophoresis (CE) coupled with electrospray ionization mass spectrometry (ESI-MS) and CE coupled with inductively coupled plasma mass spectrometry (CE/ICP-MS) were explored to identify and determine simple systems of Al species solutions at pH 3.0.

METHODS

The new combinations of techniques, namely, ESI-MS coupled with CE for identification of species and ICP-MS coupled with CE for confirmation, were applied to for the analyses of Al and fluoride (F) solutions.

RESULTS

Al monomers, some Al dimers and trimers were detected by CE/ESI-MS. CE/ICP-MS experiments were conducted with the assembled interface. As a result, the calibration line showed R²  = 0.9856, and the detection limits were 35 nL and 0.037 μM. The results were compared with data obtained using MINEQL+.

CONCLUSIONS

Most of the Al species detected were monomers; some dimers and trimers were detected by CE/ESI-MS, but they were not detected by CE-ICP-MS, probably owing to extremely low concentrations. The Al speciation technique was improved by CE/ESI-MS, and the Al species present at extremely low concentrations were ascertained by CE/ICP-MS. The use of coupled instruments will be one of the most powerful tools for identifying dissolved metal ions.

Speciation analysis of aluminium in plant parts of Betula pendula and in soil

The research presents the first results of aluminium speciation analysis in aqueous extracts of individual plant parts of Betula pendula and soil samples, using High Performance Ion Chromatography with Diode Array Detection (HPIC-DAD). The applied method allowed us to carry out a full speciation analysis of aluminium in the form of predominant aluminium-fluoride complexes: AlF_(x=2,3,4)^(3-x) (first analytical signal), AlF²⁺ (second analytical signal) and Al³⁺ (third analytical signal) in samples of lateral roots, tap roots, twigs, stem, leaf and soil collected under roots of B. pendula. Concentrations of aluminium and its complexes were determined for two types of environment characterised by different degree of human impact: contaminated site of the Chemical Plant in Luboń and protected area of the Wielkopolski National Park. For all the analysed samples of B. pendula and soil, AlF_(x=2,3,4)^(3-x) had the largest contribution, followed by Al³⁺ and AlF²⁺. Significant differences in concentration and contribution of Al-F complexes and Al³⁺ form, depending on the place of sampling (different anthropogenic pressure) and plant part of B. pendula were observed. Based on the obtained results, it was found that transport of aluminium is "blocked" by lateral roots, and is closely related to Al content of soil.

Reducing ZnO nanoparticles toxicity through silica coating

ZnO NPs have good antimicrobial activity that can be utilized as agents to prevent harmful microorganism growth in food. However, the use of ZnO NPs as food additive is limited by the perceived high toxicity of ZnO NPs in many earlier toxicity studies. In this study, surface modification by silica coating was used to reduce the toxicity of ZnO NPs by significantly reducing the dissolution of the core ZnO NPs. To more accurately recapitulate the scenario of ingested ZnO NPs, we tested our as synthesized ZnO NPs in ingestion fluids (synthetic saliva and synthetic gastric juice) to determine the possible forms of ZnO NPs in digestive system before exposing the products to colorectal cell lines. The results showed that silica coating is highly effective in reducing toxicity of ZnO NPs through prevention of the dissociation of ZnO NPs to zinc ions in both neutral and acidic condition. The silica coating however did not alter the desired antimicrobial activity of ZnO NPs to E. coli and S. aureus. Thus, silica coating offered a potential solution to improve the biocompatibility of ZnO NPs for applications such as antimicrobial agent in foods or food related products like food packaging. Nevertheless, caution remains that high concentration of silica coated ZnO NPs can still induce undesirable cytotoxicity to mammalian gut cells. This study indicated that upstream safer-by-design philosophy in nanotechnology can be very helpful in a product development.