HPLC-CUPRAC post-column derivatization method for the determination of antioxidants: a performance comparison between porous silica and core-shell column packing.

BACKGROUND: An HPLC method employing a post-column derivatization strategy using the cupric reducing antioxidant capacity reagent (CUPRAC reagent) for the determining antioxidants in plant-based materials leverages the separation capability of regular HPLC approaches while allowing for detection specificity for antioxidants. METHODS: Three different column types, namely core-shell and porous silica including two chemically different core-shell materials (namely phenyl-hexyl and C18), were evaluated to assess potential improvements that could be attained by changing from a porous silica matrix to a core-shell matrix. Tea extracts were used as sample matrices for the evaluation specifically looking at catechin and epigallocatechin gallate (EGCG). RESULTS: Both the C18 and phenyl-hexyl core-shell columns showed better performance compared to the C18 porous silica one in terms of separation, peak shape, and retention time. Among the two core-shell materials, the phenyl-hexyl column showed better resolving power compared to the C18 column. CONCLUSIONS: The CUPRAC post-column derivatization method can be improved using core-shell columns and suitable for quantifying antioxidants, exemplified by catechin and EGCG, in tea samples.

Design and Synthesis of a New Class of Twin-Chain Amphiphiles for Self-Assembled Monolayer-based Electrochemical Biosensor Applications.

A new class of twin-chain hydroxyalkylthiols (mercaptoalkanols) featuring a nearly constant cross-section and the potential for modification of one or both termini are available with complete regioselectivity through Pd-mediated couplings of benzene diiododitriflate, including an example of a previously unreported coupling to generate an ortho-substituted arene bis acetic acid. Self-assembled monolayers (SAMs) prepared from the new amphiphiles demonstrate improved stability in an electrochemical sensor system compared with monolayers prepared from analogous single chain thiols.

Application of synchrotron FTIR microspectroscopy for determination of spatial distribution of methylene blue conjugated onto a SAM via"click" chemistry.

We report, for the first time, the application of synchrotron FTIR microspectroscopy to determine the spatial distribution of methylene blue conjugated onto a self-assembled monolayer surface via Sharpless "click" chemistry.

Fabrication of an electrochemical DNA sensor array via potential-assisted "click" chemistry.

Here we report the fabrication of a 3-pixel electrochemical DNA sensor array via potential-assisted "click" chemistry. We found that the sensors in the array exhibit close to identical sensor performance when compared to sensors constructed via conventional "click" chemistry.

Folding-based electrochemical DNA sensor fabricated by "click" chemistry.

Here we report a folding-based electrochemical DNA (E-DNA) sensor fabricated by Sharpless "click" chemistry; the "click" chemistry-based E-DNA sensor compares favorably to a sensor fabricated via the conventional "two-step approach".

Leachable 226Ra in Philippine phosphogypsum and its implication in groundwater contamination in Isabel, Leyte, Philippines.

Phosphogypsum (PG), the major waste material in phosphate fertilizer processing, has been known to contain enhanced levels of naturally-occurring radionuclides especially (226)Ra. The lack of radioactivity data regarding Philippine phosphogypsum and its environmental behavior in the Philippine setting has brought concern on possible contamination of groundwater beneath the phosphogypsum ponds in Isabel, Leyte, Philippines. The radioactivity of Philippine phosphogypsum was determined and the leaching of (226)Ra from phosphogypsum and through local soil was quantified. Level of (226)Ra in groundwater samples in Isabel, Leyte, Philippines was also quantified to address the primary concern. It was found that the (226)Ra activity in Philippine phosphogypsum is distributed in a wide range from 91.5 to 935 Bq/kg. As much as 5% of (226)Ra can be leached from Philippine PG with deionized water. In vitro soil leach experiments suggest that the soil in the phosphate fertilizer plant area would be able to deter the intrusion of (226)Ra into the water table. Compared to reported values of natural groundwater levels of (226)Ra, the concentration of this radionuclide in Isabel, Leyte groundwater suggest that there is no (226)Ra intrusion brought about by the presence of phosphogypsum ponds in the area.

kappa-Carrageenan gel as agent to sequester paralytic shellfish poison.

The action of k-carrageenan gel to sequester paralytic shellfish poison (PSP) was tested and characterized. When an extract from a Philippine strain of Pyrodinium bahamense var. compressum was used as PSP solution, the PSP-sequestering property of kappa-carrageenan gel was found to be dependent on gel surface area, interaction time, and polysaccharide concentration. The interaction was also found to be affected by high concentrations of monovalent cations. The characteristics of kappa-carrageenan as a PSP-sequestering agent all point to cation exchange as its mechanism of action. It is also proposed that the polysaccharide gel can be utilized as an agent to alleviate PSP intoxication.