An ESIPT based fluorescent probe for highly selective and ratiometric detection of periodate.

Periodate is widely used in organic and bioorganic chemistry, and also related to food and environmental safety. To best of our knowledge, there is no efficient tools reported for simultaneously quantifying periodate with high accuracy and discriminating periodate from other forms of iodine. We have synthesized, characterized and applied a first ratiometric fluorescent probe (PDS-2) for simultaneous monitoring of changes of periodate based on the excited-state intramolecular proton transfer mechanism. This PDS-2 based fluorescent technique may enable for a better understanding of periodate related biological and chemical processes. Also, it is an efficient tool for public health, food safety and environmental protection.

Sequential flow injection determination of iodate and periodate with spectrophotometric detection.

A flow injection (FI) system is described for the sequential determination of periodate and iodate based on their reaction with iodide at pH 3.5. Two sample plugs were injected into the same carrier stream sequentially. One injection is for the iodate determination and the other for the sum of iodate and periodate determination. For iodate determination, molybdate solution buffered at pH of 3.5 was used for selective masking of periodate. The influences of reagent concentrations were studied by a univariable method and the influence of FI manifolds was studied using univariable and simplex method. Periodate and iodate can be determined in the range of 0.050-5.0 and 0.050-10 microg/ml, respectively. The 3 sigma limit of detection was 0.030 and 0.050 microg/ml for periodate and iodate, respectively. The proposed method has been applied for the sequential determinations of periodate and iodate in water samples.

Flow-injection spectrophotometric determination of periodate and iodate by their reaction with pyrogallol red in acidic media.

A simple and efficient flow-injection method was used with good results to determine periodate and iodate in water. The method is based on the reaction of periodate or iodate with pyrogallol red in sulfuric acid media. The reaction was monitored spectrophotometrically by measuring the decrease in absorbance of pyrogallol red at 470 nm. The chemical and FIA variables were established using the univariate and simplex optimization methods. The calibration curve was linear over the concentration ranges of 0.8-73.0 and 2.0-100.0 microM for IO4- and IO3-, respectively. The detection limits were 0.7 and 1.0 microM for IO4- and IO3-, respectively. The sample throughput was 20 +/- 5 h(-1). The influence of potential interfering ions in the determination of the anions was tested. The relative standard deviations for 4.20 and 5.73 microM periodate and iodate were 1.8 and 2.2%, respectively.

Spectrofluorimetric flow injection determination of trace amounts of periodate.

A sensitive, rapid and selective procedure is proposed for the flow injection determinations of periodate by spectrofluorometric detection. The method is based on the reaction of periodate with Alizarin Navy Blue in basic solution. The reagents and manifold variables influence on the sensitivity have been investigated and the optimum conditions are established. Periodate can be determined for the range of 0.250-5.00 microg ml(-1) with a limit of detection of 0.08 microg ml(-1), and with a sample rate of 15 +/- 2 samples h(-1). The relative standard deviations for eight replicate determination of 0.500 and 5.00 microg ml(-1) was 1.3 and 1.1%, respectively. Periodate can be determined in the presence of iodate and bromate. The proposed method was used to determination of periodate in water samples.

Nano-scale islands of ruthenium oxide as an electrochemical sensor for iodate and periodate determination.

In this study, a promising electrochemical sensor was fabricated by the electrodeposition of nano-scale islands of ruthenium oxide (ruthenium oxide nanoparticles, RuON) on a glassy carbon electrode (RuON-GCE). Then, the electrocatalytic oxidation of iodate and periodate was investigated on it, using cyclic voltammetry, chronoamperometry and amperometry as diagnostic techniques. The charge transfer coefficient, α, and the charge transfer rate constant, ks, for electron transfer between RuON and GCE were calculated as 0.5 ± 0.03 and 9.0 ± 0.7 s(-1) respectively. A comparison of the data obtained from the electrocatalytic reduction of iodate and periodate at a bare GCE (BGCE) and RuON-GCE clearly shows that the unique electronic properties of nanoparticles definitely improve the characteristics of iodate and periodate electrocatalytic reduction. The kinetic parameters such as the electron transfer coefficient, α, and the heterogeneous electron transfer rate constant, k', for the reduction of iodate and periodate at RuON-GCE surface were determined using cyclic voltammetry. Amperometry revealed a good linear relationship between the peak current and the concentration of iodate and periodate. The detection limits of 0.9 and 0.2 µM were calculated for iodate and periodate respectively.

Electrosorption of Os(III)-complex at single-wall carbon nanotubes immobilized on a glassy carbon electrode: application to nanomolar detection of bromate, periodate and iodate.

A simple procedure was developed to prepare a glassy carbon electrode modified with single-wall carbon nanotubes (SWCNTs) and Os(III)-complex. The glassy carbon (GC) electrode modified with CNTs was immersed into Os(III)-complex solution (direct deposition) for a short period of time (60s). 1,4,8,12-Tetraazacyclotetradecane osmium(III) chloride, (Os(III)LCl(2)).ClO(4), irreversibly and strongly adsorbed on SWCNTs immobilized on the surface of GC electrode. Cyclic voltammograms of the Os(III)-complex-incorporated-SWCNTs indicate a pair of well defined and nearly reversible redox couple with surface confined characteristic at wide pH range (1-8). The surface coverage (Gamma) and charge transfer rate constant (k(s)) of the immobilized Os-complex on SWCNTs were 3.07 x 10(-9)molcm(-2), 5.5 (+/-0.2)s(-1), 2.94 x 10(-9)molcm(-2), 7.3 (+/-0.3)s(-1) at buffer solution with pH 2 and 7, respectively, indicate high loading ability of SWCNTs for Os(III) complex and great facilitation of the electron transfer between electroactive redox center and carbon nanotubes immobilized on the electrode surface. Modified electrodes showed higher electrocatalytic activity toward reduction of BrO(3)(-), IO(3)(-) and IO(4)(-) in acidic solutions. The catalytic rate constants for catalytic reduction bromate, periodate and iodate were 3.79 (+/-0.2) x 10(3), 7.32 (+/-0.2) x 10(3) and 1.75 (+/-0.2) x 10(3)M(-1)s(-1), respectively. The hydrodynamic amperometry of rotating modified electrode at constant potential (0.3V) was used for nanomolar detection of selected analytes. Excellent electrochemical reversibility of the redox couple, good reproducibility, high stability, low detection limit, long life time, fast amperometric response time, wide linear concentration range, technical simplicity and possibility of rapid preparation are great advantage of this sensor.

Bacillus pumilus polysaccharide cross-reactive with meningococcal group A polysaccharide.

A polysaccharide, antigenically and structurally related to meningococcal group A polysaccharide, was isolated from Bacillus pumilus Sh-17. This enteric bacterium has been implicated as a source of natural meningococcal group A immunity (Myerowitz et al., 1973). The B. pumilus polysaccharide was composed of a homopolymer of (1-6)-N-acetyl-manosamine-1-phosphate, glycerol phosphate teichoic acid-containing N-acetylglucosamine and alkali-labile alanine esters, and a mucopeptide. The cross-reaction was due to the poly-(1-6)-N-acetyl-mannosamine-1-phosphate in the B. pumilus and the meningococcal group A polysaccharides, based on the following evidence. Both polysaccharides contained N-acetyl-mannosamine phosphate. Periodate oxidized the mannosamine phosphate residues of the polysaccharide and destroyed their precipitating activity with meningococcal group A antiserum. Mild acid treatment released phosphomonoesters and destroyed the meningococcal group A precipitating activity of both polysaccharides. N-acetyl-mannosamine-6-phosphate inhibited the precipitation reaction between strain Sh-17 and meningococcal group A antisera. Only mannosamine phosphate was detected in trichloroacetic acid extracts of Sh-17 polysaccharide and meningococcal group A antigen-antibody precipitates.

A spectrophotometric method for the microdetermination of periodate.

1. A method is described for measuring the concentration of periodate over the range 0.2-20mum by adding 1,2-di-(p-dimethylaminophenyl)ethane-1,2-diol to a sample solution. Periodate cleaves this compound to from two molecules of p-dimethylaminobenzaldehyde, the extinction of which is then read at 352mmu. 2. The method has been used to follow the course of periodate oxidations of serine methyl ester, ribonuclease A and ribonuclease S-protein. Addition of the reagent stops further periodate reaction by reducing the remaining periodate to iodate. 3. The presence of protein does not interfere with the assay.

Morphology and histochemistry of the endometrial cup.

The luminal and cut surface of endometrial cups were examined by scanning electron microscopy. The distribution of PAS-positive and lipid materials in cup tissue was studied and most of the lipid material was localized in the large polyhedral cup cells. The lipid droplets gave positive reactions for DNPH in the cholesterol test of Schultz. They also exhibited autofluorescence and were therefore considered to be steroidal in nature. The significance of this possibility, particularly with regard to maintenance of early pregnancy in the mare, is discussed.

Immunochemical detection of glycosphingolipids on thin-layer chromatograms.

A sensitive immunochemical method was developed for the detection of glycosphingolipids on thin-layer chromatograms. The procedure involves oxidation of diol groups of glycosphingolipids with sodium periodate, derivatization of the formed aldehyde groups with digoxigenin-hydrazide, and reaction of the bound digoxigenin with an alkaline phosphatase-labeled polyclonal anti-digoxigenin antibody. The latter is detected by an insoluble indigo-like dye as a result of dephosphorylation of 5-bromo-4-chloro-3-indolyl phosphate. The detectability of all glycosphingolipid species was improved over that of the orcinol and resorcinol staining methods. Two nanograms of the standard gangliosides GM1, GD1A, and GT1 was detected, whereas the detection limit for short-chain neutral glycosphingolipids was in the range of 20-50 ng. Long-chain glycosphingolipids were detectable with a particularly high sensitivity. Selective staining of the gangliosides could be achieved by the use of low periodate concentrations.

Simultaneous determination of iodate and periodate by capillary zone electrophoresis: application to carbohydrate analysis.

Iodate and periodate were rapidly (in 11 min) separated from each other with high column efficiency by capillary zone electrophoresis, using a fused silica tube (50 microns i.d., 80 cm) and 100 mM acetate buffer, pH 4.5, as carrier. On-column uv detection at 222 nm allowed sensitive detection down to the picomole level, and measurement of relative peak area to that of pyromellitic acid (internal standard) enabled reproducible determination of these ions. This method was proved useful for periodate oxidation analysis of various carbohydrates.

Study of alpha-methyldopa oxidation by tyrosinase.

The pathway for alpha-methyldopa oxidation to alpha-methyldopachrome, by mushroom tyrosinase, is proposed. Characterization of intermediates in this oxidative reaction and stoichiometry determination have both been undertaken. The steps for alpha-methyldopa transformation into its aminochrome would be: alpha-methyldopa----o-alpha-methyldopaquinone-H+----o-alpha- methyldopaquinone----leuko-alpha-methyldopachrome----alpha- methyldopachrome. The stoichiometry for this conversion corresponded to the equation: 2 o-alpha-methyldopaquinone-H+----alpha-methyldopa + alpha-methyldopachrome. At very acid pH values, another route implying the addition of water to the quinonic ring, competes with the first one. Two chemical pathways can be proposed from alpha-methyldopaquinone-H+, the relative importance of which is determined by the pH. A theoretical and experimental kinetic approach was applied to this oxidative reaction. Rate constants and thermodynamic activation parameters of the chemical steps, have been evaluated. The results obtained confirmed that alpha-methyldopa oxidation by tyrosinase followed a scheme similar to that established for L-dopa and alpha-methylnoradrenaline.

Coupling of different isoenzymes of horseradish peroxidase influences the sensitivity of enzyme immunoassay.

Labelling of IgG with various HRP isoenzymes purified by preparative isoelectric focussing influences the yield and the specific activity of the conjugates. Alkaline isoenzymes were preferably coupled by glutaraldehyde whereas application of the periodate method additionally formed relatively large quantities of conjugates with acidic isoenzymes of a high purity number, but a low specific activity. In an enzyme immunoassay for alpha fetoprotein the detection limit can be varied by a factor of 6 and even by a factor of 20 by use of the conjugates with different isoenzymes coupled by the glutaraldehyde method and the periodate method, respectively. In order to achieve enzyme immunoassays of the highest sensitivity, antibodies should be coupled to horseradish peroxidase after removing acidic isoenzymes from the enzyme preparations.

Monitoring of carbohydrates with periodate in effluents from high-pressure liquid chromatography columns.

Application of periodate to monitoring of carbohydrates in effluents from borate anion-exchange columns is described. The effect of temperature to speed the reaction in a postcolumn reactor was investigated at pH 5.0 and 8.6. The alkaline conditions increase sensitivity for some carbohydrates due to overoxidation. Temperatures up to 100 degrees C may be employed to detect less reactive sugars such as cyclitols. Peaks are detected by an absorbance decrease at 260 nm with a high-pressure liquid chromatography detector. The reagent permits detection of a wide variety of carbohydrates, aldoses, ketoses, alditols, cyclitols, and oligosaccharides with sensitivities of less than 1 nmol.