Layered double hydroxide nanoparticles for a smartphone digital image colorimetry-based determination of fluoride ions in water, milk and dental products.

A novel smartphone digital image colorimetry-based approach was developed for fluoride ion determination, using layered double hydroxide (LDH) nanoparticles (Mg2Al(OH)7) as sorbents for analyte preconcentration and as a source of a central metal ion for a colored complex formation. A cotton rotating disk provided effective retention of the LDH nanoparticles during solid-phase microextraction and elution, excluding time-consuming centrifugation process. In the proposed procedure, the nanoparticles acted as aluminum ion source for alizarin complexone-Al3+-F- complex formation. An image of Eppendorf tube, containing the colored complex solution was obtained by a smartphone and converted, using the RGB model for fluoride ion determination. The procedure had a linear range of 0.20-20 mg L-1 with a limit of detection of 0.06 mg L-1. The developed procedure provided effective fluoride separation from various matrices for its determination by a smartphone without additional sample pretreatment.

Alkyl polyglucoside-based supramolecular solvent formation in liquid-phase microextraction.

The phenomenon of alkyl polyglucoside-based supramolecular solvent formation in the presence of alkyl carboxylic acid acted as coacervation agent was described for the first time. Various alkyl polyglucosides and carboxylic acids were studied as the amphiphiles and coacervation agents, respectively. A possible mechanism of the new supramolecular solvent formation was presented. The physico-chemical properties of the developed alkyl polyglucoside-based supramolecular solvents were investigated. The green liquid-phase microextraction approach with the use of alkyl polyglucoside-based supramolecular solvent was developed and applied to epinephrine (hormone and biomarker for the diagnosis of adrenal glands neoplastic diseases) separation and preconcentration from human urine samples prior to its chromatographic determination. Caprylyl/capryl glucoside was found to be the most effective supramolecular solvent precursor for microextraction of the epinephrine (extraction recovery 95%). The microliter amount of the heptanoic acid was required to induce coacervation process and phase separation. The reduced fluidity of alkyl polyglucoside-based supramolecular solvent under cooling was used to simplify the collection of the extract phase by decantation. The green supramolecular solvent obtained was less viscous then known nonionic surfactant-based solvents and as result more compatible with the high-performance liquid chromatography with fluorometric detection.