Spectrophotometric determination of the lanthanides with chlorophosphonazo III

The molar absorptivities of the lanthanide complexes with chlorophosphonazo III over the pH range 1-4 were found to increase with atomic number to maximum values near 7000 1.mole(-1).mm(-1) for holmium, erbium and thulium and then to decrease slightly for ytterbium and lutetium. The complexes were found to be stable for up to 65 hr. The addition of alkali metal salts depressed the apparent absorptivity of the complexes but no interference was observed for the phosphate ion.     

Spectrophotometric determination of plutonium with chlorophosphonazo III

Summary Plutonium(IV) forms a Chlorophosphonazo III complex in 0.5–2M hydrochloric acid. Maximum absorbance occurs at 620 and 685 nm. Beer's law is obeyed over the range of 0–50g per 10 ml and the molar absorptivity is 3.7×10⁴ mol^–1 cm^–1 at 690 nm. Plutonium can be determined in the presence of fluoride, sulfate and phosphate. However, lanthanides, thorium, uranium and zirconium interfere seriously.

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Zusammenfassung Plutonium(IV) bildet in 0,5-bis 2-m Salzsäure mit Chlorphosphonazo III eine Komplexverbindung, deren Absorptionsmaxima bei 630 und 685 nm liegen. Bis 50 g/10 ml entspricht die Farbe dem Beer'schen Gesetz; die molare Extinktion bei 690 nm beträgt 3,7·10⁴l·Mol^–1·cm^–1. Plutonium kann damit in Gegenwart von F^–, SO₄ ^2– und PO₄ ^3– bestimmt werden. Lanthanide, Th, U und Zr stören jedoch ernstlich.

     

Spectrophotometric determination of aluminium with chlorophosphonazo I

Aluminium reacts with Chlorophosphonazo I at pH 4-6 to form a water-soluble 1:1 red-violet complex. The absorption maximum is at 610 nm and the apparent molar absorptivity is 1.96 x 10(4) l.mole(-1).cm(-1). The apparent instability constant has been calculated to be 1.8 x 10(-4). The colour of the complex is stable for 24 hr. Beer's law is obeyed over the concentration range up to 0.8 mug ml . Titanium and zirconium interfere seriously.     

Spectrophotometric determination of silicon in thorium oxide

A method is described for the spcctrophotometric determination of microgram quantities of silicon in the presence of thorium. Thorium oxide is dissolved by heating it at 70 to 8o°C in 4M HNO₃ that contains 2 drops of HF. Under these conditions, no silicon is lost through volatilization. The silicon is estimated as the blue ailicomolybdate complex. Under the conditions selected for development of color, a precipitate of thorium molybdate is obtained ; the thorium molybdate is, however, dissolved without affecting the color of the complex by the addition of tartrate and adjusting the pH of the solution to 3.0. The lower limit of detection is about 5 p.p.m. of silicon.     

Spectrophotometric determination of trace level thorium with n-phenylbenzohydroxamic acid

A method for the determination of thorium(IV) based on thorium-PBHA complex, which is extracted into amyl alcohol, is described. The thorium is back-extracted from amyl alcohol with 0.2M hydrochloric acid and estimated spectrophotometrically with thorin. The system has a maximum absorbance at 545 nm and obeys Beer's law between 0.5 to 12.5 ppm and the molar absorption coefficients is 1.7·10 1·mol^?1·cm^?1., Various parameters for the extraction and back-extraction and the effect of diverse ions have been studied.     

Spectrophotometric determination of microamounts of thorium with thorin in the presence of cetylpyridinium chloride as surfactant in perchloric acid

A simple and more sensitive spectrophotometric method is developed for determination of thorium using thorin as a chromogenic reagent in the presence of cetylpyridinium chloride (CPC) in perchloric acid. The reaction was instantaneous and complex was found stable for 168 h. A significant bathochromic shift was noted in the presence of CPC. The determination range was enhanced from 25 to 30 μg mL^?1 with molar absorptivity of 2.95 × 104 L mol^?1 cm^?1 at 25 ± 5 °C. Sandell’s sensitivity was calculated to be 6.8 ng cm^?2 at 581 nm. Relative standard deviation was reduced from 4.25 to 2.5. The interference of Ni²⁺, Mn²⁺, Sn⁴⁺, phosphate, EDTA, sulphate and tartrate has been reduced significantly in the presence of surfactant. The validity of the proposed method was tested by determining thorium in Certified Reference Materials.     

Spectrophotometric determination of bismuth(III) with o-hydroxyhydroquinonephthalein in the presence of Brij 58

A simple and sensitive spectrophotometric determination of bismuth(III) is based on the reaction between bismuth(III) and o-hydroxyhydroquinonephthalein in the presence of Brij 58 in acidic media. The calibration graph is linear over the range 0-3.5 mug/ml bismuth(III) in the final solution, and the apparent molar absorptivity at 520 nm is 9.03 x 10(4) l. mole(-1). cm(-1). The proposed method is 2-10 times more sensitive than other methods, and simpler. It has been applied to the assay of bismuth(III) in pharmaceutical preparations, such as dermatol and bismuth subnitrate, with good results.     

Spectrophotometric determination of chromium(III) with bromopyrogallol red in the presence of Septonex

A new spectrophotometric method has been developed for the determination of chromium(III) with bromopyrogallol red in the presence of the cationic tenside, carbethoxypentadecyltrimethylammonium bromide (Septonex) at pH 4.0 and within a concentration range from 0.1 to 1.4 μg Cr(III) ml⁻¹.     

Direct spectrophotometric determination of rare earths in organic extracts with chlorophosphonazo III

The highly sensitive spectrophotometric determination of rare earths after extraction into di(2-ethylhexyl)phosphoric acid and trioctylamine is described. A sample of extract is diluted with n-butanol, the solution of chlorophosphonazo III in n-butanol is added, and the solution is made up to defined volume. Absorbance is measured at 660–665 nm against a reagent blank. The method is suitable for the study of the extraction of individual rare earths by different organic extrahents.     

Flow injection spectrophotometric determination of calcium in rain and snow with chlorophosphonazo III

Summary A spectrophotometric flow injection technique for the determination of calcium based on its color reaction with chlorophosphonazo III(CPA-III) is described. The complex formation of CPA-III with calcium ions was carried out in the presence of 0.01 mol/l oxalate at pH 2.8. Most of the common foreign ions did not interfere. Only strontium, barium and rare earth metals interfered. Under the optimum conditions, the calibration curve was linear up to 1.2 ppm calcium and the detection limit was 0.01 ppm for a sample volume of 120 l. The relative standard variations for 0.4 and 1.0 ppm calcium were 0.354 and 0.352%, respectively. The method was successfully applied to the determination of calcium in rain and snow.     

Spectrophotometric determination of thorium with Xylenol Orange and cetyltrimethylammonium bromide

The thorium-Xylenol Orange reaction sensitized by cetyltrimethylammonium bromide ( = 5.51 x 10(4) l.mole(-1).cm(-1)) is accompanied by a bathochromic shift from 570 to 600 nm. The system is more selective than the binary system, because the reaction pH is lowered from 4.0 to 2.5; Beer's law is obeyed for 0.04-4.00 ppm of thorium.     

Spectrophotometric determination of rare earth elements and thorium with arsenazo

The simultaneous spectrophotometric determination of rare earth elements (lanthanum and gadolinium) and thorium with arsenuzo is described. In 0.05 N nitric acid, thorium alone forms a colored complex with the reagent; at PH 7.2 both thorium and the rare carths form colored complexes. Satisfactory results were obtained with weight ratios of Th/rare earths ranging from 0.2 to 10.     

Spectrophotometric determination of thorium as molybdothoric acid with basic dyes

Color developments based on the ion-association complexes of molybdothoric acid with three basic dyes (BD), rhodamine B(RB), butylrhodamine B(BRB) and nile blue (NB), were investigated in aqueous acidic solution in the presence of poly(vinyl alcohol) (PVA). Their spectrophotometric behavior, such as the conditions suitable for the reactions and the effects of foreign ions, were thoroughly studied. The ThMoBD ratio in the complexes was found to be 1123. Their absorption maxima were at 570, 570 and 590 nm with apparent molar absorptivities of 3.50 × 10^–6, 3.63 × 10⁶ and 4.45 × 10⁶ dm³ mol^–1 cm^–1, respectively. Beer's law was obeyed up to 0.8, 0.8 and 0.7 g thorium per 25 ml, respectively. The detection limits (3) were 1.1, 1.8 and 3.4 ng ml^–1, respectively, and for 0.02 ug ml^–1 solution of thorium the relative standard deviations were 3.0, 2.9 and 1.5%, respectively (n = 11). The proposed methods were applied to the determination of trace amounts of thorium in some geological samples.     

Spectrophotometric determination of thorium with arsenazo III in the organic phase after extraction with di-(2-ethylhexyl)orthophosphoric acid

A simple, direct colorimetric determination of thorium extracted from chloride solution with di-(2-ethylhexyl)orthophosphoric acid is described; the colour is developed in the organic phase by adding arsenazo III and then isopropanol. Two different procedures are outlined for different thorium levels; maximum absorbance occurs at 660 nm and Beer's law is obeyed within limited ranges. Molar extinction coefficients for the two methods are 4.93 · 10⁴ and 8.77 · 10⁴ respectively. With the more sensitive method, 0.696 μg Th/ml was determined with 0.0028 as standard deviation. The effects of the various parameters were studied. Among 69 foreign cations tested, serious interferences are U(VI), Se (IV), Ti(IV), Y and the rare earths. Of the common anions, only large amounts of sulpliate slightly interfered. Several ways of overcoming interferences are suggested, with particular-reference to uranium.Several extensions of the method are outlined; 2 p.p.b. Th in aqueous media can be determined by modifying the extraction step. The procedure also appears to be extremely sensitive for the light rare-earth elements.     

Contributions to the basic problems of complexometry--XXIII: determination of thorium, scandium and some lanthanides in the presence of each other

A new method is described for the determination of thorium, scandium, and the sum of light lanthanides, in the presence of each other. The method is based on the titration of thorium plus scandium with DCTA (1,2-diaminocyclohexanetetra-acetic acid) at pH 2.5-3.5, with Xylenol Orange as indicator. After addition of TTHA (triethylenetetraminehexa-acetic acid) the thorium-DCTA complex is converted into the thorium-TTHA complex according to the equation Th-DCTA + TTHA = TH-TTHA + DCTA. Simultaneously, free lanthanum, cerium, praseodymium and neodymium react with TTHA. The excess of TTHA and the liberated DCTA are then determined by titrations with zinc and with lanthanum solutions according to the equations DCTA + TTHA + 3Zn = Zn-DCTA + Zn(2)-TTHA and DCTA + TTHA + 2La = La-DCTA + La-TTHA. From the results, the amounts of thorium and scandium, and the sum of the lanthanide concentrations, can easily be calculated. Further possibilities, e.g., determination of heavier lanthanides, are briefly discussed.     

Spectrophotometric determination of samarium(III) with chrome azurol S in the presence of cetylpyridinium chloride

A sensitive, simple method for the determination of trace amounts of samarium by spectrophotometry is described based on the formation of the samarium-chrome azurol S (CAS) complex in micellar medium. The molar absorptivities of the complexes at pH 7.5 at 505 nm were 3.6x10(4) and 1.4x10(5) l mol(-1) cm(-1) for water media and cetylpyridinium chloride (CPC), respectively. Beer's law is obeyed from 0.05-2 mg l(-1) of samarium at 505 nm as Sm-CAS-CPC complex. Optimal conditions such as reagent amounts, and pH for the samarium determination were reported. The effects of foreign ions were also investigated. The proposed method was successfully applied to the determination of samarium contents in synthetic samples.     

Spectrophotometric determination of gallium(III) with phenylfluorone in the presence of hexadecylpyridinium bromide and pyridine

Phenylfluorone reacts with gallium in the presence of hexadecylpyridinium bromide and pyridine to form a water-soluble chelate with an absorption maximum at 570 nm and constant absorbance in the pH range 4.0-5.5. At this wavelength, Beer's law is obeyed up to 4.3 x 10(-6)M gallium. The sensitivity is very high and the molar absorptivity is 1.48 x 10(5) 1.mole(-1).cm(-1). The chelate has been utilized in the determination of gallium at the mug level. The ratio of gallium to phenylfluorone in the complex is 1:2.     

Spectrophotometric determination of lanthanum, thorium and iron(III) with chromotropic acid azo dyes of the pyridine series

Highly sensitive methods for the determination of lan thanum, thorium and iron(III) have been developed with the sodium salts of 2-(pyridyl-2-azo)chromotropic acid, 2-(pyridyl-3-azo)chromotropic acid and 2-(2-carboxypyridyl-3-azo)chromotropic acid. Optimum concentration ranges are of the order 1-20 ppm. The effect of diverse ions (cations and anions) including those of rare-earths are reported. The nature of the complexes has been investigated and values for the instability constants are given.     

Comparative study of the masking effect of various complexans in the spectrophotometric determination of uranium with arsenazo III and chlorophosphonazo III

Results are presented for the masking of 35 elements with the complexans DTPA, EGTA and TTHA in the spectrophotometric determination of uranium(VI) with Arsenazo III at pH 1.8 +/- 0.2 and with Chlorophosphonazo III at pH 1.1 +/- 0.2. The complexans EDTA and DCTA were found to be less suitable because at low pH they tended to precipitate. DTPA is shown to be especially attractive for masking other elements in the determination of uranium(VI) at low pH.