Fluorimetric determination of diacetyl and 2,3-pentanedione with isoniazide and a zirconium salt

Diacetyl and 2,3-pentanedione react with isoniazide in acidified solutions to give the corresponding hydrazones which, by reacting with a zirconium (IV) salt, form fluorescent complexes. Both reactions have been studied separately. Variables such as pH, heating time, and excess of reactives are discussed. The method may be used for the determination of these compounds in foods.     

Spectrophotometric determination of zirconium with pyridoxal salicyloylhydrazone

The synthesis, characteristics and analytical applications of pyridoxal salicyloylhydrazone are described. The reaction between zirconium(IV) and this reagent was studied spectrophotometrically. A yellow 1:2 Zr:L complex (? = 2.4 × 10⁴ l mol^-1 cm^-1 at 395 nm) is formed from pH 3.5 to 5 M hydrochloric acid in an aqueous solution containing 2% dimethylformamide and 28% ethanol. The method is highly selective and is applied to the determination of zirconium in a steel and a nickel—chromium alloy.     

Spectrophotometric determination of zirconium using robinetin

Summary The complex formation between zirconium and robinetin has been spectrophotometrically investigated and made use of in the determination of zirconium. The complex has been found to contain zirconium and the flavonol in the molar ratio of 12. It obeys Beer's law up to 3.0 ppm of Zr and its stability constant has been calculated to be l.5×10⁹. The reaction is quite sensitive and selective at high concentrations of hydrochloric acid (sensitivity 0.0045 g/cm²).

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Zusammenfassung Zur spektrophotometrischen Bestimmung von Zirkonium wird als Reagens Robinetin empfohlen, das mit Zr einen Komplex im Verhältnis 12 (ZrRobinetin) bildet. Die Stabilitätskonstante wurde zu 1,5 · 10⁹ bestimmt. Das Beersche Gesetz wird bis zu 3,0 ppm Zr befolgt. In stark Salzsauren Lösungen ist die Reaktion empfindlich und selektiv (Empfindlichkeit: 0,0045 g Zr/cm²).

     

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 aluminium with ferron and a quaternary ammonium salt

The reproducibility of the ferron method for aluminium has been greatly improved by the addition of cetyltrimethylammonium chloride (CTMAC). The improvement is attributed to reduction of the reagent blank and increased stability of Al(ferron)(3-)(3). The aluminium-ferron complex formed in the presence of CTMAC has an absorption peak at 385 nm. The interference from iron can be eliminated by application of a correction based on measurement at two wavelengths.     

Spectrophotometric study of a ternary zirconium/fluoride/alizarin complex with application to the determination of zirconium

A ternary zirconium/fluoride/alizarin complex is extracted into methyl isobutyl ketone. The apparent molar absorptivity at 556 nm is 1.52 × 10⁵ 1 mol^?1 cm^?1. The r.s.d. is 1.3% for 10 μg Zr (n = 12). There are several interferences, some of which can be masked with EDTA.     

Spectrophotometric determination of zirconium with 9-methyl-2,3,7-trihydroxy-6-fluorone

Summary 9-Methyl-2.3.7-trihydroxy-6-fluorone has been used as a new colorimetric reagent for zirconium. The rose-red complex shows maximum absorption, against the reagent blank, at 500 nm and obeys Beer's law from 0.1 to 2.5 ppm. The optimum concentration range is from 0.66 to 2.5 ppm, where the per cent relative analysis error is 2.96. The composition of the complex, obtained from Job's method, indicates that the complex in solution contains the metal and the reagent in a ratio of 11. The instability constant of the complex is 1.07 · 10^–6.     

Spectrophotometric determination of beryllium and zirconium using chromotrope-2C

Summary Disodium salt of o-carboxyphenylazo chromotropic acid (chromotrope 2C) has been used for the colorimetric determination of microamounts of beryllium and zirconium. The red-violet complexes show maximum absorption at 580 nm and the colour systems obey Beer's law from 0.025 to 0.375 ppm of beryllium and 2 to 12 ppm of zirconium. The optimum concentration ranges are from 0.125 to 0.375 ppm for beryllium and from 4 to 12 ppm for zirconium, where the percent relative errors per 1% absolute photometric error are, respectively, 3.014 and 3.22. The sensitivity of the reactions per cm² are 0.00067 g Be and 0.027 g Zr. The complexes, with the metal to reagent ratio of 11, have instability constants as 2.836 · 10^–6 for beryllium and 6.026 · 10^–6 for zirconium.     

Spectrophotometric determination of certain vicinal dihydroxybenzene derivatives in pharmaceutical preparations.

A simple, rapid and sensitive spectrophotometric method for the assay of certain adrenergic drugs, [pyrocatechol (PC), levodopa (LD), methyldopa (MD) and dopamine (DP)] is described. The method involves the oxidation of o-dihydroxybenzene derivatives by K2CrO4 followed by oxidative coupling with sulfanilic acid (SPA), leading to the formation of a red or violet colored product having maximum absorbance at 490-495 nm for LD, MD and DP or at 560 nm for PC. This method has been successfully applied to the determination of LD, MD and DP in tablets and injections of pharmaceutical preparation. The common excipients do not interfere with the proposed method. A statistical comparison of these results with those of a reported method shows good agreement and indicates no significant difference in precision.     

Spectrophotometric determination of iron in zirconium metal and in zirconyl chloride

Iron, present in zirconium metal or in zirconyl chloride, may be determined spectrophotometrically in 1 : 1 hydrochloric acid solution without prior separation from the zirconium. In a 1 : 1 hydrochloric acid solution, at the solubility limit of zirconyl chloride (0.28 g zirconium per 25 ml), 20 p.p.m. of iron may be detected.When smaller amounts of iron are to be determined (4 p.p.m.), a larger starting sample (5 g) of zirconium is crystallized from a 3 : 1 hydrochloric acid solution which reduces the lower limit of detection of iron to 4 p.p.m.     

Spectrophotometric investigation of the complexation equilibria of zirconium(IV) withlawsone and determination of zirconium

Summary The complexation equilibria of zirconium(IV) withlawsone (2-hydroxy-1,4-naphthoquinone) have been studied spectrophotometrically in 40% (v/v) ethanol at 20°C and at an ionic strength of 0.1M (NaClO₄). A complete picture of the solution equilibria in thepH range 1.5–4.0 is presented. The absorbance vs.pH graphs were analyzed to characterize the complexation equilibria in solution. A simple, rapid, selective, and sensitive method for the spectrophotometric determination of zirconium is proposed based on the formation of Zr(lawsone)₂ atpH 3.3(_max=450 nm, =1.13×10⁴l · mol^–1 · cm^–1). The interference caused by a number of ions can be masked by the addition of cyanide. The method has been applied to the determination of zirconium in some synthetic samples.

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Spektrophotometrische Untersuchung der Komplexierungsgleichgewichte von Zirkonium(IV) mitLawsone und Bestimmung von Zirkonium

Zusammenfassung Die Komplexierungsgleichgewichte von Zirkonium(IV) mitLawsone (2-Hydroxy-1,4-naphthochinon) wurden spektrophotometrisch in 40%igem Ethanol (v/v) bei 20°C und einer Ionenstärke von 0.1M (NaClO₄) untersucht. Ein vollständiges Bild der Gleichgewichte in Lösung impH-Bereich von 1.5 bis 4.0 wird präsentiert. Die Extinktions-pH-Kurven wurden analysiert, um die Komplexierungsgleichgewichte in Lösung zu charakterisieren. Eine einfache, schnelle, selektive und empfindliche Methode zur spektrophotometrischen Zirkoniumbestimmung auf der Basis der Bildung des Zr (lawsone)₂-Komplexes beipH=3.3(_max=450 nm, =1.13×10⁴l · mol · cm^–1) wird vorgestellt. Eine Anzahl störender Ionen kann durch Zugabe von Cyanid maskiert werden. Die Methode wurde zur Zirkoniumbestimmung in einigen synthetischen Proben eingesetzt.

     

Spectrophotometric determination of titanium,zirconium and hafnium with pyridoxal 3-hydroxy-2-naphthoylhydrazone

Summary The synthesis, characteristics and analytical applications of pyridoxal 3-hydroxy-2-naphthoylhydrazone are described. The reactions of titanium(IV), zirconium(IV) and hafnium(IV) with this reagent have been studied spectrophotometrically and the stoichiometries of the ternary complexes determined. Photometric methods for the determination of these ions are proposed, and the selectivity of these methods has been established.

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Spektrophotometrische Bestimmung von Titan, Zirkon und Hafnium mit Pyridoxal-3-hydroxy-2-naphthoylhydrazon

Zusammenfassung Synthese, Eigenschaften und analytische Anwendung von Pyridoxal-3-hydroxy-2-naphthoylhydrazon wurden beschrieben. Die Reaktionen von Titan(IV), Zirkon(IV) und Hafnium(IV) mit diesem Reagens wurden untersucht und die Stöchiometrie ihrer ternären Komplexe ermittelt. Photometrische Methoden für die Bestimmung dieser Ionen wurden vorgeschlagen und deren Selektivität untersucht.

     

Spectrophotometric determination of zirconium with 5,7-dibromo-8-hydroxyquinoline in presence of thiocyanate

The characteristics of the ternary complex formed between zirconium(IV) and 5,7-dibromo-8-hydroxyquinoline in presence of thiocyanate have been studied with an analytical point of view. The resulting colored species is extractable into chloroform with absorption maximum at 416 nm, which leads to the determination of the trace amounts of the metal ion. The method obeys Beer’s law in the range 0.2–9.0 μg Zr/mL having molar absorbitivity and Sandell’s sensitivity values of 1.05 × 10⁴ L/mol cm and 0.0087 μg Zr/cm², respectively. The ratio of zirconium(IV), 5,7-dibromo-8-hydroxyquinoline and thiocyanate in the extracted species is found to be 1: 2: 2. A large number of foreign ions do not interfere in the proposed method. The applicability of the procedure is tested by carrying out satisfactorily the analysis of a wide variety of samples.     

Spectrophotometric determination of zirconium with alizarin red S in the presence of polyvinylpyrrolidone

The absorbance of the microcolloidal zirconium/alizarin red S/polyvinylpyrrolidone complex is measured at 525 nm in acetate buffered medium at pH 4.75. The molar absorptivity is 3.8 × 10⁴ l mol^?1 cm^?1, which is much greater than that of the classical method. Sulphate and fluoride do not interfere.     

Proton affinities of ketones, vicinal diketones and α-keto esters: a computational study

The proton affinities of seven different ketones, vicinal diketones, and α-keto esters (acetophenone, 2,2,2-trifluoroacetophenone, 2,3-butanedione, 1-phenyl-1,2-propanedione, methyl pyruvate, ethyl benzoylformate, and ketopantolactone) have been evaluated theoretically using the conventional ab initio HF and several post-HF methods (MP2, MP4, CCSD), density functional methods with the B3LYP hybrid functional, as well as some ab initio model chemistries [CBS-4M, G2(MP2), and G3(MP2)//B3LYP]. The chemical compounds studied are frequently used substrates in the asymmetric hydrogenation over chirally modified platinum catalysts where the protonation properties of the chiral modifier and the substrates are of great interest. In most cases, the proton affinities (PAs) evaluated with the CCSD/6-311+G(d,p)//B3LYP/TZVP and G2(MP2) methods are in good agreement with the existing experimental ones. However, the previously reported PA of 2,3-butanedione seems to be too high by 10-15 kJ mol⁻¹. The B3LYP/TZVP//B3LYP/TZVP and MP2/6-311+G(d,p)//B3LYP/TZVP model chemistries predict proton affinities that are systematically higher and lower than the experimental PAs, respectively. If proton affinities are evaluated as the average of the PAs calculated with these two theoretical methods a very good agreement with the experimental results is obtained. The mean absolute deviation (MAD) from experiment of this combination method for the PAs of 13 test molecules is 4.0 kJ mol⁻¹. For 9 molecules composed only of first-row atoms the MAD is 2.5 kJ mol⁻¹. The B3LYP/TZVP//B3LYP/TZVP and MP2/6-311+G(d,p)//B3LYP/TZVP methods provide significant savings in computational time and disk space compared to the CCSD/6-311+G(d,p)//B3LYP/TZVP and G2(MP2) models. Therefore, it is suggested that if no experimental or highly accurate theoretical data is available (due to computational cost), the proton affinities of similar compounds as investigated in this paper, can be evaluated with the combination method. For the studied molecules, this method gives the following PAs (in kJ mol⁻¹): 788 (2,3-butanedione, exptl 802); 798 (2,2,2-trifluoroacetophenone, exptl 799); 811 (ketopantolactone); 813 (methyl pyruvate); 825 (1-phenyl-1,2-propanedione); 862 (acetophenone, exptl 861); 865 (ethyl benzoylformate).     

分光光度法测定黄花菜中总黄酮

建立了一种黄花菜中总黄酮的Al(NO3)3显色分光光度测定方法。研究表明:以芦丁为标样,在一定条件下,芦丁的浓度与吸光度呈线性关系,回归方程为A=0.0121c 0.0014,R2=0.9999,方法的回收率为98.1%~102.3%,相对标准偏差(RSD)为2.1%,测得黄花菜中总黄酮量为3.71 mg/g。     

Spectrophotometric determination of calcium in zirconium powder by use of murexide

An accurate spectrophotometric method is proposed for the determination of calcium in zirconium powder by use of murexide. A 0.4-g sample is dissolved in hydrofluoric and sulphuric acids, the solution evaporated to fumes of sulphuric acid, and a mercury cathode electrolysis made if more than 0.05% copper or nickel is present. Ammoniacal precipitation in the presence of ammonium chloride separates zirconium and other elements and an aliquot of filtrate is collected, equivalent to 0.2 g of sample. The ammonium salts are destroyed with nitric and hydrochloric acids and the calcium is determined with murexide. The high reagent blank is shown to be due to the reagent grade nitric acid, hydrochloric acid, and ammonium hydroxide.     

Spectrophotometric determination of niobium in zirconium with 4-(2-pyridylazo)resorcinol

The direct spectrophotometric determination of niobium in zirconium alloys with 4-(2-pyridylazo)resorcinol is described. Samples are dissolved in hydrofluoricsulphuric acid mixture and the colour developed without the removal of fluoride. In the presence of EDTA only Co²⁺, Ta⁵⁺ and V⁵⁺ cause serious interference. The molar absorptivity is 3.67 .10⁴ in the presence of 1 /smg of zirconium, and Beer's law is obeyed up to 1.0μg Nb/ml. The method can be applied to zirconium alloys containing as little as 0.005% niobium.