Current Analytical Chemistry - Volume 5, Issue 4, 2009

The antioxidant activity of honey varies greatly depending on the honey's floral source. There is little knowledge about the profiles of antioxidant substances in honey from different floral sources. The variation in these profiles might be responsible for the widely varying ability of honey to protect against oxidative reactions. Honey is rich in polyphenol compounds, which act as natural antioxidants, and are becoming increasingly popular because of their potential role in contributing to human health. These compounds can also be used as indicators in studies about the floral and geographical origin of the honey. Therefore, we overviewed the current analytical methods for measuring polyphenols and antioxidant capacity in honey. The analytical procedure to determine individual phenolic compounds involves their extraction from the sample, analytical separation and quantification. The analytical separation techniques widely employed are gas chromatography, high-pressure liquid chromatography and capillary electrophoresis. The techniques to evaluate the antioxidant capacity are based on colorimetric assays such as DPPH, FRAP, TEAC (ABTS) and microplate fluorescence reader like ORAC assay.

Copper(II) hexacyanoferrate(III) (CuHCF) modified carbon paste electrode was used for the electroanalytical determination of dipyrone and acetaminophen in pharmaceutical preparations by cyclic voltammetry. Several parameters were investigated for the optimization of the sensor such as composition of the electrode, electrolytic solution, effect of pH, scan rate of potential and interference. The best conditions were found for an electrode composition in mass of 20% CuHCF, 55% graphite and 25% mineral oil in acetate buffer containing 0.05 mol L-1 of NaCl. The analytical curve was linear in the dipyrone and acetaminophen concentration ranged from 1.25 x 10-5 mol L-1 to 1.23 x 10-3 and 2.84 x 10-4 to 2.59 x 10-3 mol L-1 respectively, being successfully applied to the determination of dipyrone and acetaminophen in pharmaceutical preparations. The CuHCF modified carbon paste electrode presented comparable results to those obtained using iodimetry and ultraviolet spectrophotometry methods, respectively.

In this contribution, the rapid and simple determination of vitamins A and E, and vitamin E acetate as internal standard in human plasma by high-performance liquid chromatography with a column-switching technique was proposed. Restricted Access Material - RAM column 25 x 4 mm containing 25 μm C18 alkyl-diol silica support was integrated into lab-made column-switching HPLC system. A monolithic column Chromolith Performance RP-18e, 100 x 4.6 mm, (Merck) was used for simple separation of vitamins in gradient mode. The mobile phase I: methanol - 20 mM water solution of dodecyl sulfate sodium salt (30:70, v/v) was used for protein matrix elution, flow rate 1.3 ml min-1. Valve switching time was determined to 4 minutes after sample injection. The gradient elution of mobile phase II: methanol - water 90:10 (v/v) → 100% methanol, flow rate 1.0 ml min-1 was used as optimal condition of vitamins separation in relatively short time. Analysis time from raw sample to peaks evaluation was less than 15 min. UV detection was carried out at wavelength 285 nm. The recoveries of vitamins from spiked human plasma were 102.5% for vitamin A and 91.4% for vitamin E. Limits of detection were 0.24 μmol l-1 and 0.84 μmol l-1 for vitamin A and E, respectively.

A method for the determination and quantification of collagen types (I - V) using sample pretreatment has been developed. This work is a continuation of our previous work dealing with the determination of collagen types I and III in tissues [1]. The tissues (rat placenta and porcine cartilage) were firstly homogenized with a pestle in a grinding mortar with liquid nitrogen. Collagens were isolated from these tissues by cleavage with pepsin. The collagen types of interest were then precipitated successively by adding sodium chloride. For quantitation purposes, the sample preparation protocol has been simplified to the one-step precipitation of collagens from a solution containing 4.5 mol/L of sodium chloride. The fractions were fragmented by cyanogen bromide and digested with trypsin. After that, HPLC-MS/MS (high performance liquid chromatography coupled to an ion trap mass spectrometer) analyses of the resulting peptide mixtures (peptide maps) were performed. Based on these analyses, specific (marker) peptides for each of the collagen types were selected. The marker peptides were then synthesized and used to identify and quantify the above-mentioned collagen types in tissues using HPLC-MS/MS, and for determining the limits of detection and quantification. The applicability of this method for collagen analysis was demonstrated.

A novel dispersive liquid phase microextraction using a new temperature-controlled ionic liquid 1-isooctyl-3- methylimidazolium hexafluorophosphate was proposed as novel medium for the determination of dicofol and DDT in environmental water. For one new extraction, a 1.0 ml methanol solution containing 250 mg of the ionic liquid was sprayed into 25 ml of water sample. Meantime the ionic liquid will rapidly congregate, solidify and finally form large solid particles. The ionic liquid was collected and dissolved in 30 μl of acetone for analysis. Under optimal conditions, the enrichment factors were 532 for dicofol and 540 for DDT. Because developed extraction procedure includes all performance during liquid/liquid extraction and co-precipitation extraction, thus it has a wide application with very high extraction efficiency. Proposed extraction combined with gas chromatography mass spectrometry was a valuable alternative for analysis of dicofol and DDT in environmental water samples within the concentration range 0.005-3.0 μg l-1. The detection limits were 1.3 ng l-1 for DDT and 3.2 ng l-1 for dicofol.

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Gas chromatographic analysis of Aromatic Sulfur Compounds in distilled water and seawater samples has been performed after adsorption from 100 mL water sample onto a cartridge containing a mixture of 50 mg NH2- and 50 mg C18-bonded porous silica. The Aromatic Sulfur Compounds are desorbed with a mixture of acetone-trichloromethane (1:1), which is concentrated and analysed by gas-chromatography coupled to flame ionization or mass spectrometry detectors. The average recoveries of 80 ng mL-1 of each Aromatic Sulfur Compound from distilled water and 5.0-160 ng mL-1 from seawater samples are ≤ 93.5% with a standard deviation ≤ 2.7. The limits of detection are 0.1 and 0.08 μg mL-1 for thiophene-2-carboxaldehyde and benzothiophene, respectively, and 0.07 and 0.06 μg mL-1 for dibenzothiophene and thiantrene, respectively, in GC-FID with a relative standard deviation ≤ 8.2, whereas they are 0.08 and 0.06 μg mL-1 for thiophene-2-carboxaldehyde and benzothiophene, respectively, and 0.05 and 0.04 μg mL-1 for dibenzothiophene and thiantrene, respectively, in selected ions monitoring (SIM) with a relative standard deviation ≤ 7.8.

In this paper, a method for the determination of ILs, specifically 1-butyl-3-methyl imidazolium bromide( BMIB), was developped using mercaptoacetic acid (MAA) capped CdTe QDs as fluorescence probe. Under optimum conditions, the enhancement of fluorescence intensity of CdTe QDs was linearly in proportion to the concentration of BMIBin the range of 9.1x10-5-1.1x10-2 mol L-1 with a correlation coefficient of 0.996. The detection limit was 6.9x10-5 mol L-1. The proposed method was applied to the determination of trace BMIB in river water and tap water samples with satisfactory results.

Nano-silver coated silica gel was impregnated with ammonium pyrrolidine-dithiocarbamate (APDC) and used for the separation and preconcentration of lead prior to its determination by flame atomic absorption spectrometry. The silver coated silica gel was prepared by mixing slurried silica gel with solid silver nitrate and sodium boron hydride. The silver coated silica gel was then impregnated with ammonium pyrrolidine-dithiocarbamate. For enrichment/separation of the analyte, as an alternative to the conventional column technique, the housing of a syringe-mountable filter was filled with the sorbent and mounted to the tip of a 50 mL of syringe. In order to retain the analytes, the sample solution was drawn into the syringe and ejected back again by passing through the sorbent in the filter. The analyte on the sorbent was then eluted by drawing and ejected back an eluent. The effects of experimental conditions with regards to the amount of sorbent, pH of sample, concentration and kind of eluent, foreign ions, flow rates of sample and eluent on the recovery (retention and elution) of the analyte were investigated. All quantifications were performed with a flame atomic absorption spectrophotometer. The analyte was quantitatively retained at pH≤ 7 and eluted with 3.0 M of HNO3 applying a 20 mL min-1 of drawing and discharging rates (flow rates) for sorption and elution steps with less than 10% of RSD. In order to increase the sample volume and thereby concentration factor, several portions of sample were successively drawn and ejected back through the sorbent but eluted only once. The limit of detection of the method for lead was 0.36 ng mL-1 according to 3σ criteria (N=10). The validation of the proposed method was tested by using waste water certified reference materials and quantitative recoveries in the range of 95% confidence level were obtained. Finally, the presented method was used for the determination of lead in real water samples. The sorbent prepared is novel and its use in syringe mountable filter for enrichment/ separation is challenging.

This study focuses on the photoluminescence properties of loracarbef (LOR) ligand and its [Zn(LOR) (H2O)(Cl)]Cl, [Cd(LOR)(H2O)(Cl)]Cl, [Ni(LOR)(H2O)(Cl)]Cl, [Pd(LOR)(H2O)(AcO)]AcO and [Pt(LOR)(H2O)(Cl)]Cl complexes. LOR and the resulting metal complexes gave an intense emission (where λmax = 376 nm) upon irradiation by Ultra-Violet light. The photoluminescence quantum yields and long excited-state lifetimes of the ligand and its complexes were calculated. The LOR ligand has a photoluminescence quantum yield of 52% and long excited-state lifetime of 4.88 ns. The photoluminescence intensities and quantum yields of the metal complexes dramatically reduced with respect to that of the LOR ligand upon complexation with various metals. The structures of new complexes were characterized using spectroscopic techniques including FT-IR, electronic spectra, 1H-NMR and mass spectral data. In addition, all complexes were screened for antibacterial activity against several bacteria and yeasts, and results were compared with those of LOR.