Quantitative determination of chloride by means of flow injection analysis with spectrophotometric detection in the UV/VIS range

Chloride is determined indirectly by Spectrophotometric flow injection analysis. Two systems are compared, both based on the principle of ion exchange of easily detectable anions versus chloride from suitable mercury salts. The first method is based on the exchange of chloride with chloranilate which is detected at 332 nm or at 306 nm in neutral or in acidic medium respectively. In the second case, chloride reacts with Hg(SCN)₂. The liberated thiocyanate forms a strongly coloured complex with Fe(III) in acidic solution with an absorption maximum at 460 nm. Both methods have a detection limit of about 5 mol Cl^–/l (175 ng/ml). In the case of the thiocyanate method, the relative standard deviation is about 2% (7 measurements) in the range of 5 to 150 mol/l and decreases significantly to a value of approximately 0.2% at higher concentrations; for the chloranilate method it is 10% for lower and about 1% for higher concentrations respectively.     

Iron-Chloranilate Intercalation Compounds: Synthesis,Crystal Structures,and Thermal Properties

Abstract

Hydrogen bond supported new iron-chloranilate assemblies, {(Hpy)[Fe(CA)₂(H₂O)₂](H₂O)}_n (py = pyridine, H₂CA = chloranilic acid, C₆H₂O₄Cl₂) (1), and [(phz)₂[Fe(CA)₂(H₂O)₂](H₂O)₂]_n (phz = phenazine, C₁₂H₈N₂) (2) have been synthesized and characterized. Compound 2 crystallizes in the monoclinic, space group C2/m (#12), with a= 29.135(6) Å, b= 16.886(6) Å, c = 15.017(5) Å, ß = 165.907(1)°, V= 1798(2) ų, Z = 2. In both the compounds two chloranilate dianions and two water molecules are coordinated to the iron ion making anionic monomers [Fe(CA)₂(H₂O)₂]^?, which are the building blocks of the compounds. The coordination environment around the iron ion in the building block is a distorted octahedron, where two water molecules sit on the trans position to each other. [Fe(CA)₂(H₂O)₂]^? anions form common layer structures, supported by hydrogen bonds. Hpy⁺ are intercalated in between the layers of 1 by electrostatic and hydrogen bonding interactions and phz are intercalated in that of 2 by electrostatic interactions. DSC traces of 1 show anomaly at 174 K, indicating phase transition in the compound.     

Synthesis and characterization of lanthanum chloranilate complex: application to spectrophotometric determination of anions

Lanthanum chloranilate complex has been synthesized and characterized using different techniques like Infrared spectroscopy and CHN analysis. It has been used for the development of spectrophotometric method of determination of anions like fluoride, EDTA and iodate. The determination is based on the reaction of these anions with the lanthanum ion in the chloranilate complex resulting in the liberation of an equivalent amount of chloranilate anion, the colour of which was measured. The experimental conditions, which affect the optical density, are studied to get maximum sensitivity. Interference studies were carried out with various ions. The method has been applied to the determination of these ions in actual samples viz. EDTA in detergents and iodate in salt.     

Synthesis, crystal structure and magnetic properties of a chloranilate-bridged manganese(II) chain compound: [Mn(bipy)(CA)]n (bipy = 2,2′-bipyridine, CA = chloranilate anion)

The compound [Mn(bipy)(CA)]_n (where bipy is 2,2′-bipyridine and CA²⁻ is the dianion of 3,6-dichloro-2,5-dihydroxy-1,4-benzoquinone) has been synthesized and its crystal structure determined by single-crystal X-ray diffraction at room temperature. The crystal is built from infinite chains of chloranilate-bridged manganese(II) affording a zigzag structure, with the bipyridine ligands being stacked between the chains. The variable-temperature (2.0–300 K) magnetic susceptibility and EPR data are reported and a weak antiferromagnetic exchange interaction is observed with the exchange parameter estimated as J = −0.20 cm⁻¹.     

An improved flow system for chloride determination in natural waters exploiting solid-phase reactor and long pathlength spectrophotometry

A single and sensitive spectrophotometric method for chloride ions determination based on a commuted flow system with a 100 cm optical path flow cell and a solid-phase reactor containing immobilized silver chloranilate was proposed. This procedure exploited the AgCl formation in the solid-phase reactor leading the chloranilate ions, monitored spectrophotometrically at 530 nm. The analytical signals were 75-fold higher and the sensitivity was 12-fold than that achieved with a 1 cm flow cell, allowed a chloride determination in the 0.5-100 mg l⁻¹ range. The R.S.D. was 1.1% (n = 20) with a sample throughput of 80 h⁻¹ and a waste generated of ca. 100 ng of chloranilate ions per determination. Four samples of natural waters from São Carlos and Araraquara cities were evaluated using the proposed method. Results agreed with the obtained by a reference method at the 95% confidence level.