Application of dried spot cards as a rapid sample treatment method for determining hydroxytyrosol metabolites in human urine samples. Comparison with microelution solid-phase extraction

Two different rapid sample pretreatment strategies, dried spot cards, and microelution solid-phase extraction plates (μSPE), with ultra-high performance liquid chromatography coupled to tandem mass spectrometry (UPLC-MS/MS) have been developed and validated for the determination of hydroxytyrosol and its metabolites in spiked human urine samples. Hydroxytyrosol, hydroxytyrosol-3′-O-glucuronide, hydroxytyrosol-4′-O-glucuronide, hydroxytyrosol-3-O-sulphate, and homovanillic alcohol-4′-O-glucuronide were used as the target compounds. Using the FTA DMPK-A dried urine spot card under optimum conditions, with 5 μL of preconcentrated urine volume and 100 μL of methanol/water (50/50, v/v) as the elution solvent, the extraction recovery (%R) of the compounds studied was higher than 80 %, and the matrix effect (%ME) was less than 8 %. The stability of these cards and punching at the centre or side of the card were also studied, obtaining an excellent stability after 7 days of storage and complete homogeneity across the surface of the dried drop. The different μSPE parameters that affect the efficiency were also studied, and under optimum conditions, the %R and the %ME were higher than 70 % and lower than 17 %, respectively. The linearity range in dried urine spot cards was 2.5-20 μM for all the metabolites, with the exception of hydroxytyrosol-3-O-sulphate and hydroxytyrosol, which were 0.3-70 μM and 2.5-50 μM respectively. With regards to μSPE, the linearity range was 0.5-5 μM for all the studied compounds, except for hydroxytyrosol-3-O-sulphate, which was 0.08-5 μM. The quantification limits (LOQs) were 0.3-2.5 μM and 0.08-0.5 μM in dried spot cards and in μSPE, respectively. The two developed methods were then applied and compared for determining hydroxytyrosol and its metabolites in human 24 h-urine samples after a sustained consumption (21 days) of a phenol-enriched virgin olive oil. The metabolites identified were hydroxytyrosol in its glucuronide and sulphate forms, homovanillic alcohol in its glucuronide and sulphate forms, homovanillic acid sulphate and hydroxytyrosol acetate sulphate.     

Using expert’s rules as background knowledge in the ClusDM methodology

In complex domains it is usually quite difficult to introduce context information. However, sometimes that information should be taken into account to make decisions, because it provides some relevant knowledge that cannot be expressed using an attribute-value representation. This is the case of the determination of risk of contamination of soils. In this paper, we propose to use conjunctive rules to introduce additional background knowledge to a MCDM sorting method called ClusDM. ClusDM is based on the aggregation of the data with unsupervised clustering techniques. The paper presents a new algorithm to incorporate rules to guide the clustering process in a semi-supervised way. The paper also describes how it works in the case sorting a set of possible contaminated soils, and compares the results obtained by ClusDM when rules are used or not.     

Effect of the formation of silver nano‐binuclear complex on the refinement of cytotoxic and antibacterial potency of coumarin Schiff base: Spectroscopy,thermal, X‐ray diffraction analyses and density functional theory calculations

A new Schiff base (SCH) was prepared using 8‐acetyl‐7‐hydroxy‐4‐methylcoumarin and sulfaclozine. Its silver complex was also synthesized. These compounds were subjected to elemental and spectral analyses. The silver complex was also subjected to thermogravimetric analysis, molar conductance measurements, scanning electron microscopy, energy‐dispersive X‐ray analysis and X‐ray diffraction measurements. The formula of the complex was determined as [(Ag₂SCH(NO₃)₂]. The molar conductance indicates its non‐electrolyte character. The electronic structure and nonlinear optical parameters of SCH and its complex were investigated theoretically at the B3LYP/GENECP level. The geometry of the studied complex is non‐planar as indicated from the dihedral angles between central Ag metal ion and coordinated centres of SCH. Density functional theory calculations were also carried out to calculate the global properties of hardness, global softness and electronegativity. The calculated energy gap between HOMO and LUMO energies shows that charge transfer occurs within the studied complex. The total static dipole moment, the mean polarizability, the anisotropy of the polarizability and the mean first‐order hyperpolarizability were calculated and compared with those of urea as a reference material. The results of the mean first‐order hyperpolarizability showed that SCH and its silver complex are excellent candidates as nonlinear optical materials. The compounds were screened for their antimicrobial effect against various species of bacteria and fungi. Their anticancer activities were evaluated in vitro against the human cancer cell line MCF‐7 (human breast adenocarcinoma).     

Determination of organophosphorus pesticide residues in vegetables using solid phase micro-extraction coupled with gas chromatography–flame photometric detector

An adequate and simple analytical method based on solid-phase microextraction (SPME) followed by gas chromatography–flame photometric detection (GC–FPD) for the determination of eleven organophosphorus pesticide residues (i.e., ethoprophos, sulfotep, diazinon, tolclofos-methyl, fenitrothion, chlorpyrifos, isofenphos, methidathion, ethion, triazophos, leptophos) in vegetables samples (cabbage, kale and mustard) was developed. Important parameters that influence the extraction efficiency (i.e., fibre type, extraction modes, extraction time, salt addition, desorption time and temperature) were systematically investigated. Four types of commercially available fibres (i.e., 50/30 μm divinylbenzene/carboxen/polydimethylsiloxane (DVB/CAR/PDMS), 65 μm polydimethylsiloxane/divinylbenzene (PDMS/DVB), 100 μm polydimethylsiloxane (PDMS), and 85 μm polyacrylate (PA)) were evaluated. PA fibre exhibited the best performance and was used for the rest of the studies. The optimised extraction conditions were: extraction time, 30 min at room temperature; stirring speed, 1275 rpm; salt content, 10% NaCl; desorption time and temperature, 11 min at 260 °C; and no pH adjustment of the sample extract. The method was validated over the range 0.1–100 μg/L. Repeatabilities were satisfactory, ranging between 2.44% and 17.9% for all analytes. The limits of detection and quantitation ranged from 0.01 to 0.14 and 0.03 to 0.42 μg/L, respectively. The method was applied to twenty local vegetable (cabbage, kale and mustard) products. Chlorpyrifos (0.22–1.68 μg/kg) was the most detected pesticide in the tested samples. The obtained values are however lower than the Maximum Residue Limits (MRLs) as stipulated in the Food Act & Regulations of Malaysia.     

Homo- and heteroleptic lanthanide-iron alkoxides as precursors in materials synthesis

Bimetallic iron-lanthanide alkoxides were synthesized by reacting [Ln{N(SiMe₃)₂}₃] (Ln ?= ?Pr, Nd, Er) with [Fe₂(O^tBu)₆] in excess tert-butyl alcohol that triggered in-situ ligand exchange and Lewis acid-base interactions to form heterometallic compounds. Single crystal X-ray diffraction analyses of new compounds demonstrated that both Nd and Er containing compounds resulted in the formation of a hetero-bimetallic framework based on 1:1 Ln:Fe ratio, whereas higher Fe ratio (1:2) was observed when Pr was used as the rare earth metal, possibly due to its larger ionic radius (Pr(III): 0.99 ?Å). When the reaction was performed in the presence of chelating ligands (L: H-tfb-mea ?= ?N-(4,4,4-trifluorobut-1-en-3-on)-methoxyethyleneamine; H₂-tfb-en ?= ?N–N′-bis-(4,4,4-trifluorobut-1-en-3-on)-ethylenediamine), heteroleptic Ln-Fe derivatives were formed that were used in a representative case ([NdFe(L)(O^tBu)_m(HO^tBu)]) as efficient precursor to synthesize nanocrystalline NdFeO₃ ceramic.     

Isothermal crystallization kinetic of ZnO thin films

Zinc oxide (ZnO) thin films deposited by DC magnetron sputtering were annealed in nitrogen atmosphere at different temperatures ranging from 100 to 500 °C with a step of 100 °C; the annealing time was 6 h. In order to study the film’s crystallization kinetic, their structures were monitored by means of X-ray diffraction (XRD) analysis each hour. Variation in grain size, calculated from the XRD patterns, with annealing time and temperature, obeys the classical parabolic law of grain growth. Exponent n was found to be dependent on the annealing temperature; it ranged from 5.13 to 3.8 with increase in annealing temperature. From the obtained exponent n values we inferred that the grain growth mechanism is mainly governed by the atom jumping across the grain boundary. We have found that the grain growth is characterized by a low activation energy ranging from 22 to 24 kJ/mol.     

Molecular motility and affinity of expanded carbon dioxide + ketone systems analyzed by molecular dynamics simulations

We perform a molecular dynamics simulation for CO₂ + ketone mixtures to study the molecular motility and elucidate how CO₂ molecules are dissolved in a mixture. The self-diffusion coefficients increase with increasing CO₂ mole fraction (xCO₂)$(x_{\text{C}{\text{O}}_2})$ and decreased with increasing molecular weight. These results mean that the mobility of molecules depends on the molecular size. To study molecular aggregation around CO₂ molecules, radial distribution functions (RDFs) and the distance from neighboring molecules to CO₂ molecules were calculated. The RDFs indicate that the CO₂ molecule exists near the carbonyl oxygen atom. Because of the distance of the neighboring molecule from the CO₂ molecule, the CO₂ molecule is less likely to exist around a branched alkyl ketone than a normal alkyl ketone.