Size exclusion chromatography – Inductively coupled plasma – Mass spectrometry for determining metal-low molecular weight compound complexes in natural wines

Removal of strontium by nanofiltration: Role of complexation and speciation of strontium with organic matter

Strontium (Sr) removal from water is required because excessive naturally occurring Sr exposure is hazardous to human health. Climate and seasonal changes cause water quality variations, in particular quality and quantity of organic matter (OM) and pH, and such variations affect Sr removal by nanofiltration (NF). The mechanisms for such variations are not clear and thus OM complexation and speciation require attention. Sr removal by NF was investigated with emphasis on the role of OM (type and concentration) and pH (2-12) on possible removal mechanisms, specifically size and/or charge exclusion as well as solute-solute interactions. The filtration results show that the addition of various OM (10 types) and an increase of OM concentration (2-100 mgC.L-1) increased Sr removal by 10-15%. The Sr-OM interaction was enhanced with increasing OM concentration, implying enhanced size exclusion via Sr-OM interaction as the main mechanism. Such interactions were quantified by asymmetric flow field-flow fractionation (FFFF) coupled with an inductively coupled plasma mass spectrometer (ICP-MS). Both extremely low and high pH increased Sr removal due to the enhanced charge exclusion and Sr-OM interactions. This work elucidated and verified the mechanism of OM and pH on Sr removal by NF membranes.

Assessment on Solubility and Solid Phase Chemical Fractionation of Manganese in Hot Infusions of Green and Roasted Mate

A solid phase chemical fractionation (SPCF) of the Mn in hot infusions prepared from commercial samples of roasted (RM) and green mate (GM) using a chelating resin Chelex 100 (NH4+ form) was performed to assess the relative lability of this essential trace element (ETE). In addition, total Mn contents in the RM and GM samples and their infusions were determined by flame atomic absorption spectrometry. Total polyphenol (TP) contents and the presence of soluble melanoidins (SM) were correlated with the Mn solubility in the RM and GM infusions. From the SPCF study, it was possible to observe that the soluble Mn forms in the mate infusions were essentially associated with relatively noninert chemical species (98.4-99.7%), suggesting that they may be potentially bioavailable. In addition, the soluble Mn contents in the GM infusions were 20.5% higher than those found in the RM. Mn solubility in the (RM) infusions was highly and directly correlated (r = 0.99) with the soluble TP, while in the GM infusions, it was high and inversely correlated with soluble TP (r =  -0.87). On the other hand, Mn solubility in the RM and GM infusions was weakly correlated with the SM. It should be stressed that GM infusions can contribute with 57 and 44% more than the RM infusions to the recommended adequate intake of Mn established for females and males, respectively. Moreover, this work is the first to evaluate and compare the relative lability of Mn and its solubility in the RM and GM infusions.

Characterizing metal-biomolecule interactions by mass spectrometry

Metal micronutrients are essential for life and exist in a delicate balance to maintain an organism's health. The labile nature of metal-biomolecule interactions clouds the understanding of metal binders and metal-mediated conformational changes that are influential to health and disease. Mass spectrometry (MS)-based methods and technologies have been developed to better understand metal micronutrient dynamics in the intra- and extracellular environment. In this review, we describe the challenges associated with studying labile metals in human biology and highlight MS-based methods for the discovery and study of metal-biomolecule interactions.

Democratization of Copper Analysis in Grape Must Following a Polymer-Based Lab-on-a-Chip Approach

Quality control in the food industry is of the upmost importance from the food safety, organoleptic and commercial viewpoints. Accordingly, the development of in situ, rapid, and costless analytical tools is a valuable task in which we are working. Regarding this point, the copper content of grape must has to be determined by wineries along the wine production process. For this purpose, grape must samples are sent to laboratories where the copper content is measured usually by flame atomic absorption spectrometry or by inductively coupled plasma mass spectrometry. We herein propose a straightforward, rapid, and inexpensive methodology based both on a film-shaped colorimetric polymer sensor and a smartphone method that at the same time can be used by unskilled personnel. The sensory polymer films change their color upon dipping them on the grape must, and the color evolution is analyzed using the digital color parameters of a picture taken to the film with a smartphone. Furthermore, the analytical procedure is automatically carried out by a smartphone app. The limit of detection of copper of the polymer sensor is 0.08 ppm. Following this approach, 18 production samples coming from the French Groupe ICV company were studied. The copper content of the samples was analyzed by the usual procedure carried out by the company (flame atomic absorption spectrometry) and by the method proposed in this work, ranging this content from 0.41 to 6.08 ppm. The statistical study showed that the results of both methods are fully consistent, showing the validity of the proposed method for the determination of copper in grape must within the frame of wine production wineries and industries.

Fast-SEC coupled to ICP-MS for selected metal determination and its stability over time in polish wine

Metal ions contribute to the wine browning (as reaction catalysts), turbidity (in complexes), and astringency (due to interaction with tannins). Being aware that bioavailability and metabolism of metal ions in the human body are strictly related with their concentration and the form they occur it is important to monitor not only the total content of metals but also their speciation. Thus, we can obtain more information about their potential toxicity to human health. Present research shows the application of fast size exclusion chromatography (Fast-SEC) coupled to ICP-MS for the evaluation of the distribution of elements in different sized complexes in Polish wine. The study was focused on the selected ten elements (Al, B, Ba, Cu, Fe, Mn, Ni, Pb, Sr, Zn). Additional information of this work was the evaluation of the metal complex stability over time. Based on the obtained results, it can be seen that metal complexes present in the studied wine samples are stable even 10 months after the wine bottle opening.

Graphical abstract

A fast, low-cost, sensitive, selective, and non-laborious method based on functionalized magnetic nanoparticles, magnetic solid-phase extraction, and fluorescent carbon dots for the fluorimetric determination of copper in wines without prior sample treatment

A new fluorimetric method for copper(II) determination in wines was developed combining functionalized magnetic nanoparticles (FMNP) and fluorescent carbon dots (FCD). To produce FMNP, Fe₃O₄ was coated with Al₂O₃ forming Fe₃O₄@Al₂O₃ core-shell magnetic nanoparticles and functionalized with PAN and SDS. FCD was synthesized from pineapple juice through hydrothermal carbonization. For copper determination, aliquots of wine, the FMNP dispersion, and Britton-Robinson buffer (pH = 4.0) were mixed under stirring to allow the adsorption of copper by FMNP. Cu-FMNP complex was attracted by a niobium magnet and, after discarding the non-magnetic material, the copper(II) ions were eluted with an FCD dispersion before fluorescence quenching measurements. The proposed method presented a linear range from 0.020 to 0.100 mg L^-1 (r² = 0.9953), RSD (intraday) < 3.0%, and recovery rates from 96 to 105 %. FMNP and FCD properties permitted extraction/preconcentration/determination of copper within 1 min with an enrichment factor of nine and without prior sample treatment.

Speciation of essential nutrient trace elements in coconut water

Coconut water (Cocos Nucifera) is shown to be a source of essential elements present in the form of low-molecular weight stable complexes known for their bio-availability. The total element concentrations were in the range of 0.2-2.7, 0.3-1, 3-14 and 0.5-2 ppm for Fe, Cu, Mn, and Zn, respectively, and varied as a function of the origin of the nut and its maturity. Speciation was investigated by size-exclusion chromatography - inductively coupled plasma mass spectrometry (ICPMS), and hydrophilic interaction liquid chromatography (HILIC) - electrospray-OrbitrapMS. The metal species identified included: iron complexes with citrate and malate: Fe^III(Cit)₃(Mal), Fe^III(Cit)₂(Mal)₂, Fe^III(Mal)₂, glutamine: Fe^III(Glu)₂ and nicotianamine: Fe^II(NA); copper complexes with phenylanine: Cu^II(Phe)₂ and Cu^II(Phe)₃ and nicotianamine: Cu^II(NA); zinc complexes with citrate: Zn^II(Cit)₂ and nicotianamine Zn^II(NA) and manganese complex with asparagine Mn^II(Asp)₂. The contributions of the individual species to the total elements concentrations could be estimated by HILIC - ICP MS.

Quantification of manganous ions in wine by NMR relaxometry

Proton relaxation in model and real wines is investigated for the first time by fast field cycling NMR relaxometry. The relaxation mechanism unambiguously originates form proton interaction with paramagnetic ions naturally present in wines. Profiles of a white Chardonnay wine from Burgundy, a red Medoc, and model wines are well reproduced by Solomon-Bloembergen-Morgan equations. Relaxation is primarily governed by interactions with Mn²⁺. A straightforward model-independent quantification of the manganese ion concentration (down to few tens of μg/L) is proposed.

Soluble non-toxic carbon nano-rods for the selective sensing of iron(iii) and chromium(vi)

A simpler methodology has reported for the fabrication of non-toxic functionalized soluble carbon nano-rods for the sensing of Fe(iii) and Cr(vi) in aqueous media.