Spectrophotometric determination of zirconium in steels with xylenol orange

Zirconium (0.005–0.25%) is determined after acid dissolution of the steel, and fusion of insoluble matter with sodium carbonate and sodium hydrogensulphate. Niobium and other interfering ions are removed by mercury cathode electrolysis. Residual small amounts of iron(III) are masked with ascorbic acid.     

Spectrophotometric determination of chromium with xylenol orange and methylthymol blue

A new simple and sensitive method for determining traces of chromium is described. Xylenol Orange and chromium(III) form a red complex at pH 3 on heating in boiling water for 20 min. The molar absorptivity is 19.0 x 10(3). No catalytic action of the bicarbonate ion, carbon dioxide, or chromium(II) generated by metallic zinc was observed. Methylthymol Blue is a less sensitive reagent for chromium, the molar absorptivity being 11.5 x 10(3).     

The application of metallochromic indicators in colorimetry—I The spectrophotometric determination of minute amounts of copper with analogues of glycine thymol blue

The possibility of application of five different metallochromic derivatives of Thymol Blue (I–V) to the spectrophotometric determination of micro amounts of copper has been studied. The derivative of proline (I), applied in a solution buffered with hexamethylenetetramine and hydrochloric acid, has proved best for this purpose. Absorbance of its copper complex shows only insignificant changes in the pH range from 4.9 to 5.4 and it conforms to Beer's law up to 25 μg of copper^II at 595 mμ. Larger quantities of iron^II, cobalt^II, nickel^II, zinc^II, lead^II, uranium^II and beryllium^II interfere.     

Spectrophotometric determination of lanthanum with neo-thorone

A method has been developed for the spectrophotometric determination of microgram amounts of lanthanum by means of neothorone, 2-ortho-arsonophenyl-azo-2-(1.8-dioxynaphthalen-3,6-disulphonic acid). The method is sensitive, and as little as 2 μg of lanthanum can lit; determined in 25 ml of final volume. The calibration curve conforms to Beer's law. The stoichiometric composition of the coloured complex has been determined.     

Spectrophotometric study of the reaction of gallium(III) with xylenol orange

The formation of complexes between gallium(III) and Xylenol Orange at pH 2 has been studied. Complexes with the mole ratio 1:1 and 1:2 have been found and the respective formation constants determined. The latter complex, for which the absorption spectrum has been calculated, is suitable for the spectrophotometric determination of gallium, and optimum conditions for its formation have been established.     

Spectrophotometric determination of rare earth elements by flow injection analysis based on their reaction with xylenol orange and cetylpyridinium bromide

Individual rare earth elements (REE) and their mixtures were determined by a FIA method based on the reaction with Xylenol Orange (XO) in the presence of cetylpyridinium bromide (CPB). Volumes of 30 microl of 2.5-25 microM REE solutions were injected into a carrier stream of 0.1M acetate buffer of pH 4.5 or 5.5 that was 0.06 mM in XO and 0.6 mM in CPB. At 1.8 ml/min flow rate, a sampling frequency of up to 100 samples per hour was achieved. The detection limits were in the range of 0.1-0.4 microg/ml REE and relative standard deviation of the measurement was 0.88% rel.     

Simultaneous spectrophotometric determination of o-cresol red, semi-xylenol orange and xylenol orange

A direct simultaneous spectrophotometric method for the determination of o-Cresol Red (CR), Semi-Xylenol Orange (SXO) and Xylenol Orange (XO) in mixtures in the presence of other components usually found in commercial SXO and XO reagents is presented. The method of selecting the most advantageous conditions for the spectrophotometric determination of the three dyes in different mixtures is given.     

Determination of trace amounts of thallium by adsorptive cathodic stripping voltammetry with xylenol orange.

Trace amounts of thallium(I) can be determined using adsorptive cathodic stripping voltammetry in the presence of Xylenol Orange (XO). The reduction current of the thallium(I)-XO complex ion was measured by square-wave cathodic stripping voltammetry. The peak potential was at -0.44 V vs. Ag/AgCl. The effect of various parameters (pH, ligand concentration, accumulation potential and collection time) on the response are discussed. The response was linearly related to the thallium concentration in the range 0.5-110 ng ml(-1) and 110-2000 ng ml(-1). The limit of detection was 0.2 ng ml(-1). The relative standard deviation for the determination of 80 ng ml(-1) thallium was 2.8%. Many common anions and cations did not interfere with the determination of thallium. The interference of lead was reduced by the addition of 0.003 M sodium carbonate. The voltammetric procedure was then successfully applied to the determination of thallium in various complex samples.     

Rapid photometric determination of neptunium with xylenol orange after extraction with Aliquat-336

A rapid method based on the extraction of neptunium(IV) by Aliquat-336 followed by its direct photometric determination in the organic phase employing xylenol orange is reported. Optinum conditions have been established for the extraction and determination of as little as 0.4 ppm of Np. The molar absorptivity of the red-coloured neptunium complex at 535 nm is 49535±361 1·mol⁻¹·cm⁻¹. Unlike the well-known absorptimetric method for estimating NP(IV) with Arsenazo III, this method tolerates many-fold excesses of fluoride, nitrite, nitrate, phosphote, oxalate as well as UO ₂ ²⁺ , Pu⁴⁺, Zr⁴⁺, etc., which are some of the major contaminants associated with neptunium during its reprocessing.     

Determination of trace amounts of zirconium in silicates by cation-exchange chromatography and spectrophotometry with xylenol orange

An ion-exchange scheme and colorimetric determination with Xylenol Orange are used for estimating traces of zirconium in silicate rocks.     

Chelate formation of zirconium with xylenol orange and semi-xylenol orange

The composition, formation constants, and molar absorptivities of the chelates of zirconium ion wtih xylenol orange and semi-xylenol orange are investigated spectrophotometrically in strong acid medium at ionic strength 3.0 (NaClO₄ and HClO₄). The data obtained were processed with a newly-constructed computer program and with LETAGROP/SPEFO. In the zirconium—xylenol orange system, Zr · H₃ L, Zr· H₄L, and Zr₂ · L are present with logarithmic overall formation constants of 37.80, 38.68, 43.47, and molar absorptivities of 3.10 × 10⁴ (485 nm), 5.98 × 10⁴ (528 nm), 9.50 × 10⁴ (551 nm) I mol^-1 cm^-1, respectively. The chelates Zr · L and Zr · HL were found in the zirconium—semi-xylenol orange system with logarithmic overall formation constants of 26.25 and 27.56, and molar absorptivities of 5.70 × 10⁴ (532 nm) and 8.30 × 10⁴ (535 nm) 1 mol^-1 cm^-1, respectively. Semi-xylenol orange is more sensitive and reliable than xylenol orange as a spectrophotometric reagent for zirconium.     

Spectrophotometric determination of microgram amounts of ampicillin with chloranil

Ampicillin trihydrate (12.5–750 μg) is determined spectrophotometrically using chloranil as π-acceptor at pH 9. The method is relatively accurate (with a recovery of 100 ± 1.0%) and precise (RSD ⩽ 1.7%) and can be used successfully for capsules and ampoules.     

Spectrophotometric determination of phosphate using lanthanum chloranilate

The spectrophotometric determination of phosphate using lanthanum chloranilate has been investigated. It is possible to determine 3–300 ppm of phosphate with an accuracy of ±2%, if suitable conditions are chosen. Chloride or nitrate ions do not interfere up to 400 ppm. Interference from sulphate ion can be compensated for by adding a large amount of sulphate both to the sample and to the standard solutions. This method is simpler, has less critical reaction conditions, and develops a much more stable coloration than the conventional heteropolyacid methods.     

Spectrophotometric determination of microgram amounts of chlorpromazine with chloranil

A simple spectrophotometric method for the determination of small amount of chlorpromazine has been developed. The reaction of chloranil as π-acceptor reagent with chlorpromazine was studied. The method is rapid, simple, and relatively sensitive and precise (RSD 1.8%). Beer's law was followed within the approximate concentration range of 50–900 μg in a final volume of 25 ml. Negative deviation was abserved beyond these limits. The general analytical and physical parameters were also established.     

Absorption characteristics of xylenol orange

Absorption characteristics of Xylenol Orange have been reinvestigated for the purpose of its spectrophotometric estimation. The molar absorption coefficient of Xylenol Orange at 580 nm and pH 10.0 is 3.12 x 10(4) l.mole(-1), cm(-1).     

Polarographic study of xylenol orange

In neutral medium the ring carbonyl group of xylenol orange is reduced in two one-electronsteps at a dropping mercury electrode. Step I is nearly reversible, but step II strongly irreversible. The half-wave potentials of both steps depend on pH, for the products of reduction, the dye radical formed in step I and the OH group produced in step II, behave as acids. From the E_1/2 vs. pH dependence, the pK of the dye radical is found to be 9.5, that of the hydroxy compound 5.6. On progressive acidification the height of step II continuously decreases, while that of step I increases. In solutions with pH<2, only a single (according to logarithmic analysis) one-electron, but overall (according to coulometry) two-electron step results. The ratio i^I/i^II for the two steps increases when larger amounts of alkali metal ions are added. The exaltation of the first wave at the expense of wave II is explained by an acid-dependent dismutation of the dye radical formed during the first one-electron step.     

Spectrophotometric determination of micro amounts of uranium

Uranium(VI) in the presence of numerous cations and anions is determined by the iron(II)-phosphoric acid-Ferrozine method at concentrations of 8-75,mug/25 ml with a relative precision of 3-1%.     

Surfactant-sensitized post-column reaction with xylenol orange for the determination of lanthanides by ion chromatography

The presence of the cationic surfactants cetylpyridinium chloride and hexadecyltrimethylammonium bromide in an alkaline 40% methanol medium was found to enhance sensitivity when xylenol orange is employed as the post-column reaction reagent for the determination of lanthanides by dynamic ion chromatography. Detection of individual lanthanides was carried out at 618 nm after separation by cation-exchange chromatography with gradient elution on a C₁₈ column. The eluent was -hydroxyisobutyric acid-sodium octanesulfonate, pH 3.8. Sensitivity enhancements by factors of three to six, compared with xylenol orange alone, were achieved at a cationic surfactant concentration of 2.4 mM. The calibration response was linear in the 0.05 to 5 μg ml⁻¹ analyte concentration range. Limits of detection below 3 ng were obtained for all the natural lanthanides and lanthanum. No sensitivity enhancement effects were observed with anionic (sodium dodecyl sulfate) and non-ionic (Triton X-100) surfactants under the conditions tested.