Automatic spot preparation and image processing of paper microzone-based assays for analysis of bioactive compounds in plant extracts.

The colorimetric determination of the concentration of phytochemicals in plant extract samples using a spotting automatic system, mobile phone camera and a computer with developed software for quantification is described. Method automation was achieved by using a robotic system for spotting. The instrument was set to disperse the appropriate aliquots of the reagents and sample on a Whatman paper sheet. Spots were photographed and analysed by ImageJ software or by applying the developed MatLab based algorithm. The developed assay was found to be effective, with a linear response at the concentration range of 0.03-0.25g/L for polyphenols. The detection limit of the proposed method is sub 0.03g/L. The paper microzone-based assays for flavonoids and amino acids/peptides were also developed and evaluated as applicable. Comparing the results with conventional PµZP methods demonstrates that both methods yield similar results. At the same time, the proposed method has an attractive advantage in analysis time and repeatability/reproducibility.

The development of paper microzone-based green analytical chemistry methods for determining the quality of wines.

The colorimetric determination of the concentration of polyphenols, flavonoids, and anthocyanins in wine samples, using a mobile phone camera for sample spot capture on a paper microzone and a remote computer with dedicated software for quantification, is presented as an illustrative application of green analytical chemistry. A comparison of the results with conventional spectrophotometry demonstrates that both methods yield similar results. Developing the assay took approximately 2 months, and the use of chemicals, compared with spectrophotometry, was reduced by about two orders of magnitude: the paper assay consumed 0.4 mL of reagent for 100 samples, whereas the spectrophotometric assay required 100 mL. The relative testing times for 100 samples were 7 h by spectrophotometry and 2 h for paper-a savings on the order of 3.5. No analytical instrumentation was used for the colorimetry on paper microzones. Instead, the assay took advantage of the existing communication technology and free software. The assay was found to be effective, with a nonlinear response at the concentration range of 0.2-5 g/L. The detection limit of the proposed method is in sub-grams per liter.

Miniaturization of sampling for chemical reaction monitoring by capillary electrophoresis.

Purpose-made capillary electrophoresis set-ups for reaction kinetics monitoring featuring two automated injectors allowed the easy reduction of the needed reactant amount down to 500 microL. The first set-up is similar to the cross injector used frequently in lab-on-chip designs while the other uses falling droplets for sample/buffer delivery. The versatility of the system was demonstrated by the analysis of oxidation of C-vitamin by hydrogen peroxide. Pseudo first order reaction rates about 10(-3) s(-1) were measured with RSD = 1-3% in one experiment and RSD = 20% in interday/person experiment. Plate numbers were typically around 5000-20,000.

Application of 1-alkyl-3-methylimidazolium-based ionic liquids in non-aqueous capillary electrophoresis.

In many cases salts, which are liquid at room temperature show a better solubility in organic solvents, and can be used in nonaqueous capillary zone electrophoresis as ionic additives. In this study 1-alkyl-3-methylimidasolium-based ionic liquids were used as additives in separation media to assess the interactions between the analytes and the ionic additive present and to find an influence of the type and concentration of the ionic additive, also the nature of the nonaqueous medium employed. Different organic solvents (acetonitrile and methanol) contribute differently to the conversion of analytes into a charged form. Complexes with either an anionic or a cationic part of the ionic liquid additive were formed. This was the case for electrophoresis separation of Brønsted acids and polyphenolic compounds.

Application of capillary zone electrophoresis to the separation and characterization of poly(amidoamine) dendrimers with an ethylenediamine core.

Generations 0 through 5 of ethylenediamine-core poly(amidoamine) dendrimers were synthesized and capillary zone electrophoresis has been applied to the separation of different generations of synthesized dendrimers and for the characterization of individual generations.

Reactivity of Cd7-metallothionein with Cu(II) ions: evidence for a cooperative formation of Cd3,Cu(I)5-metallothionein.

Reaction of Cd7-metallothionein-2 (MT) with Cu(II) ions has been studied by a variety of spectroscopic techniques including UV-absorption, circular dichroism (CD) and luminescence spectroscopy. The addition of up to 5 Cu(II) equivalents to Cd7-MT resulted in a cooperative formation of the monomeric Cd3,Cu5-MT form, as revealed by the analytical data and the presence of isosbestic or isodichroic points in the respective UV and CD spectra. The presence of Cu(I) luminescence and the absence of Cu(II) EPR signal indicated that copper is bound in the Cu(I) oxidation state, i.e., Cd3,Cu(I)5-MT. Consequently, the reduction of Cu(II) ions is accompanied by the oxidation of thiolate ligands of the protein. The absorption features and the luminescence data at 77 K are consistent with the presence of an air-stable Cu(I)-cluster in Cd3,Cu(I)5-MT. The participation of other ligands, besides cysteine thiolates, in metal coordination cannot be ruled out. With more than 5 Cu(II) equivalents added a mixture of unstable MT metalloforms were formed. The concomitant reduction and binding of copper ions by metallated MT represent a new aspect of the MT structure.

Gelling galactans from the algal community of Furcellaria lumbricalis and Coccotylus truncatus (the Baltic Sea, Estonia): a structure-property study.

Extraction of Furcellaria lumbricalis by potassium hydroxide solution shows that the maximum gel strength of polysaccharides separated is attained by extraction at concentration 0.16 M KOH. Crude extract from this algal species has a complicated monosaccharide composition; a drastic increase of gel strength by alkaline extraction of the polysaccharide mixture cannot be explained through the composition of a major (kappa) fraction described earlier. Alkaline treatment is also suitable for accelerating the extraction of polysaccharides from Coccotylus truncatus overlaid with thick epithelium. Viscous galactans from C. truncatus are more stable to alkali, their composition is simpler and close to iota carrageenan. The formation of mixed kappa and iota carrageenan gels as a result of simultaneous extraction of both seaweeds causes levelling of theological properties of different extraction fractions.

Metal-induced dimerization of Cd7-metallothionein. Role of anions.

Inorganic phosphate participates in the nonoxidative Cd-dependent dimerization of Cd7-metallothionein (Cd7-MT) and is bound to the MT dimers. In order to obtain insight into the specificity of phosphate-MT interaction, an investigation has been made on the effect of a series of oxyanions and organic phosphates on Cd-induced dimerization of Cd7-MT. It has been demonstrated that from the oxyanions studied, only arsenate and tungstate can promote Cd-induced dimerization of Cd7-MT. Effect of arsenate is quantitatively similar to that of phosphate and appears at submillimolar concentrations, whereas tungstate promotes dimerization of MT at higher, millimolar concentrations. A number of other oxyanions, ie, molybdate, vanadate, and selenate as well as organic phosphates (phenyl phosphate, serine O-phosphate, D-ribose 5-phosphate, L-glycerol 3-phosphate, D-fructose 6-phosphate, D-glucose 6-phosphate, adenosine monophosphate (AMP), cyclic adenosine monophosphate (cAMP), nicotinamideadenine-dinucleotide (NADP), pyridoxal 5-phosphate) had no influence on Cd-induced dimerization of MT. Results obtained strongly indicate a highly specific role of inorganic phosphate in Cd-induced dimerization of Cd7-MT.