Photometric determination of aluminium with alizarin fluorine blue

In order to decide whether Alizarin Fluorine Blue (alizarin complexan, 3-amino-methylalizarin-N,N-diacetic acid) is a suitable reagent for the spectrophotometric determination of aluminium, values of the stability constants for some reactions of this reagent with aluminium(III) and iron(III) have been determined spectrophotometrically in a medium containing 20 % dioxan and 80 % water at ionic strength 0.1. The values of the constants that were determined are log K(Al)(AlHL) = 14.3, log K(2Al)(Al2L) = 25.3 and log K(Fe)(FeHL) = 19.6. These results were employed in the design of a method for the spectrophotometric determination of aluminium in the presence of iron and titanium. The Sandell sensitivity is 0.01 mug/cm(2) and the coefficient of variation for 34 determinations was 0.9 %.     

A photometric study of the complexation reaction between Alizarin complexan and zinc(II), nickel(II), lead(II), cobalt(II) and copper(II)

The complexation reaction between Alizarin complexan ([3-N,N-di(carboxymethyl)aminomethyl]-1,2-dihydroxyanthraquinone; H(4)L) and zinc(II), nickel(II), lead(II), cobalt(II) and copper(II) has been studied by a spectrophotometric method. All these metal ions form 1:1 complexes with HL; 2:1 metal:ligand complex were found only for Pb(II) and Cu(II). The stability constants are (ionic strength I = 0.1, 20 degrees C): Zn(2+) + HL(3-) right harpoon over left harpoon ZnHL(-) log K +/- 3sigma(log K) = 12.19 +/- 0.09 (I = 0.5) Ni(2+) + HL(3-) right harpoon over left harpoon NiHL(-) log K +/- 3sigma(log K) = 12.23 +/- 0.21 Pb(2+) + HL(3-) right harpoon over left harpoon PbHL(-) log K +/- 3sigma(log K) = 11.69 +/- 0.06 PbHL(-) + Pb(2+) right harpoon over left harpoon Pb(2)L + H(+) log K approximately -0.8 Co(2+) + HL(3-) right harpoon over left harpoon CoHL(-) log K 3sigma(log K) = 12.25 + 0.13 Cu(2+) + HL(3-) right harpoon over left harpoon CuHL(-) log K 3sigma(log K) = 14.75 +/- 0.07 Cu(2+) + CuHL(-) right harpoon over left harpoon Cu(2)L + H(+) log K approximately 3.5 The solubility and stability of both the reagent and the complexes and the closenes of the values of the stability constants make this reagent suitable for the photometric detection of several metal ions in the eluate from an ion-exchange column.     

Molecular mobility of counterion functional groups in ionic liquid 1-ethyl-3-methylimidazolium acetate according to 1H and 13C NMR relaxation data

1-Ethyl-3-methylimidazolium acetate was studied by NMR relaxation. The temperature dependences of the spin-lattice relaxation rates (1/T ₁) for ¹H and ¹³C were obtained. The curves with maxima were observed for the majority of the temperature dependences 1/T ₁, which provided a reliable temperature dependence of the correlation times (τ_c). In the low-temperature range, the proton relaxation rates tend to an asymptotic value, which is related, most likely, to spin diffusion manifested in the studied samples. The values of correlation times τ_c calculated for ¹H and ¹³C of the same functional group almost coincide at high temperatures, which confirms that the used approach is adequate for the determination of characteristic times of rotational reorientation of counterions in the studied ionic liquid.     

Studies of two-phase equilibria by liquid-liquid segmented flow extraction of dithiocarbamic acids into various solvents

A method for the study of two-phase equilibria by extraction in liquid-liquid segmented flow is presented. The main advantage of the method is the very rapid equilibration achieved. In many cases a contact time of 5 sec is sufficient. By performing the measurements needed on-line with the extraction the total residence time of a substance studied in the system can be kept below 10 sec. This makes it possible to study two-phase equilibria of moderately unstable compounds. Other advantages are the semi-enclosed design, which minimizes contact with solvent fumes and increases the speed of operation after the system has been set up. The system has been used for a study of the two-phase equilibria of dithiocarbamic acids. The dithiocarbamates are often used for the separation and preconcentration of metals, and co-extraction of the reagent can cause severe interference in the final determination. By means of the extraction constants presented, the extraction of diethyldithiocarbamic acid and pyrrolidine-dithiocarbamic acid into Freon 113, carbon tetrachloride, methyl isobutyl ketone and chloroform can be estimated.     

Comparison of segmentors for liquid-liquid extraction flow-injection analysis

The segmentation of two immiscible solvents in a continuous liquid—liquid extraction flow system has been studied with a computer-controlled photometric detection system (resolution time 3 msec). The T-shaped segmentors tested were made of fluoroplastic, glass (A4-T fitting) and a modified glass (A8-T fitting). The modified A8-T fitting gave the most repeatable segmentation (rsd 2%).     

Detection of phase biaxiality in liquid crystals by use of the quadrupole shift in 131Xe NMR spectra

An experimental method to unambiguously distinguish between uniaxial and biaxial liquid crystal phases is introduced. The method is based on the second order quadrupole shift (SOQS) observable in 131Xe NMR spectra of xenon dissolved in liquid crystals. It is shown that besides revealing the biaxiality, the 131Xe SOQS offers a novel method to determine the tilt angle in smectic C phases. As an example, the 131Xe SOQS in a ferroelectric liquid crystal is reported. It yields up a biaxial phase in between isotropic and smectic C phases.     

Design of a multi-channel dropping segmenter for liquid-liquid extraction continuous flow-injection analysis

A simple dual-channel dropping segmenter was used for the simultaneous introduction of aqueous solutions of a sample and an organic analytical reagent directly into a continuous flow of an immiscible organic solvent. Droplets of precisely defined volume of the homogeneous reaction mixture are formed at the junction of the inlet capillary system. Reaction and extraction take place simultaneously in the individual segments of the aqueous phase during the transport through the reaction/extraction coil. An analytical signal is measured by an “on-tube” fast-reading spectrophotometric detector and processed mathematically. The applicability of the method is demonstrated with the determination of Cu(II) ions with tetramethylene-dithiocarbamate in neutral medium in 0.1 M ammonium acetate buffer.     

Calculation of stability constants from photometric data

A method originally designed for the determination of stability constants by using a wedge calorimeter has been adapted to normal photometric measuring techniques. The calculations are simple and the method is especially suitable for use when the absorptivities of the absorbing species are unavailable because these species cannot be obtained alone in solution. Results of some determinations are given.     

A quantitative ionicity scale for liquid chloride salts

Knowledge of ionicity is requisite for successful identification of those salt qualities required to design and couple the most appropriate fluid for performance of an intended chemical function. We report on utilisation of (35)Cl(-) quadrupolar coupling constants (C(Q)) to quantitatively assess the ionicities of given chloride salts, by exploiting the electronic response of the quadrupolar chlorine atom as a function of its immediate chemical environment. We find that protic salts in particular, like their aprotic analogues, are highly ionised, while at the same time being highly associated, in stark contrast to literature reports claiming in general that they are of sub-ionic origin.