fremy-s-salt and 1-nitroso-3-6-disulfonate

The solid ion-pair material produced from the reaction between benzyldimethyltetradecylammonium chloride (BDTA) and sodium perchlorate on naphthalene provides the basis for a simple, rapid and selective technique for pre-concentrating iron from up to 500 ml of aqueous solution. Iron reacts with disodium 1-nitroso-2-naphthol-3,6-disulphonate (Nitroso-R salt) to form a water-soluble coloured chelate anion. The iron chelate anion forms a water-insoluble, stable iron-Nitroso-R-BDTA complex on naphthalene packed in a column. Trace amounts of iron are quantitatively retained on naphthalene in the pH range 3.5-7.5 and at a flow-rate of 1-2 ml min-1. The solid mass is dissolved out from the column with 5 ml of N,N-dimethylformamide and iron is determined by means of an atomic absorption spectrometer at 248 nm. The calibration graph is linear for concentrations of iron over the range of 0.5-20 micrograms in 5 ml of final solution. The standard deviation and relative standard deviation were calculated. The detection limit of the method was 0.0196 micrograms ml-1 of iron. The sensitivity for 1% absorption was 0.072 microgram ml-1 (0.165 microgram ml-1 by direct atomic absorption spectrometry of aqueous solution). The proposed method was applied to the determination of iron in standard alloys and biological samples.

Topics: Adsorption; Alloys; Animals; Benzalkonium Compounds; Bivalvia; Chlorella; Chromatography; Ferric Compounds; Indicators and Reagents; Naphthalenes; Naphthalenesulfonates; Nitroso Compounds; Spectrophotometry, Atomic

The binding of two activating cations, Co2+ and Mg2+, and of one inhibitory cation, Ca2+, to D-xylose isomerase from Streptomyces violaceoruber was investigated. Equilibrium-dialysis and spectrometric studies revealed that the enzyme binds 2 mol of Co2+/mol of monomer. Difference absorption spectrometry in the u.v. and visible regions indicated that the environment of the first Co2+ ion is markedly different from that of the second Co2+ ion. The first Co2+ appears to have a six-co-ordinate. The conformational change induced by binding of Co2+ to the first site is maximum after the addition of 1 equivalent of Co2+ and yields a binding constant greater than or equal to 3.3 x 10(6) M-1. Binding of Co2+ to the second, weaker-binding, site caused a visible difference spectrum. The association constant estimated from Co2+ titrations at 585 nm agrees satisfactorily with the value of 4 x 10(4) M-1 obtained from equilibrium dialysis. Similarly, the enzyme undergoes a conformational change on binding of Mg2+ or Ca2+, the binding constants being estimated as 1 x 10(5) M-1 and 5 x 10(5) M-1 respectively. Competition between the activating Mg2+ and Co2+ and the inhibitory Ca2+ ion for both sites was further evidenced by equilibrium dialysis and by spectral displacement studies.

Topics: Aldose-Ketose Isomerases; Binding Sites; Binding, Competitive; Calcium; Carbohydrate Epimerases; Cations, Divalent; Cobalt; Macromolecular Substances; Magnesium; Naphthalenesulfonates; Nitroso Compounds; Protein Conformation; Spectrophotometry, Ultraviolet; Streptomyces

A substoichiometric extraction method with nitroso-R salt (NRS) has been studied for the determination of trace Co in crud. The Co-NRS complex is extracted substoichiometrically into Capriquat-CHCl3 at pH 6.5-9.0 in 20 min of shaking time. The analytical results obtained by the method are within 3% of relative error in the determination range of 5 to 50 micrograms. The proposed method is simple and has sensitivity of 0.5 micrograms, though Fe(II), Ni(II) and Cu(II) seriously interfere. The results applied for the determination of trace Co in crud are described.

Topics: Cobalt; Cobalt Radioisotopes; Hydrogen-Ion Concentration; Naphthalenesulfonates; Nitroso Compounds; Nuclear Reactors; Quaternary Ammonium Compounds