Spectrophotometric study of pseudopurpurin-Pd(II) dimer complex. Spectrophotometric determination of traces of Pd(II)

We have studied spectrophotometrically the Pseudopurpurin-Pd(II) complex in an ethanolic-water medium ¦Ethanolamine ¦_optimum = 4 × 10⁻¹M; λ = 670 nm; 20% H₂O; stable for at least 4 hr; ¦Reagent¦_optimum = 5 × 10⁻⁵M; stoichiometry 2:2; log K = 17.7. A new method for the spectrophotometric determination of Pd traces is proposed for concentrations between 0.30 and 2.40 ppm. The relative error and the interferences of the method have been investigated.     

Spectrophotometric determination of copper(II) using oximidobenzotetronic acid

Summary Oximidobenzotetronic acid (OBTA) is proposed as a sensitive spectrophotometric reagent for the estimation of 0.5–3.0 ppm of copper(II) at 427 nm in 50% dioxan at p_H 5.3–7.5. For the estimation of 2 ppm Cu(II), 1.3 ppm Ni(II), 1.3 ppm Co(II), 3.2 ppm Fe(II), 10.3 ppm Fe(III), 9.7 ppm Ce(IV), 300 ppm acetate, 160 ppm oxalate, 95 ppm tartrate, 50 ppm citrate, as well as Zn(II), Cd(II), Hg(II)) Pb(II), Mn(II), As(III) as well as (V), Th(IV), Be(II), Ce(III), La(III), V(V) and Mo(VI), even when present in large quantities, do not interfere. The interference due to 25 ppm Bi(III), 20 ppm Sb(III), 20 ppm Sn(II), 25 ppm Sn(IV) and 30 ppm W(VI) can be removed by the addition of 95 ppm tartrate ions.

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Zusammenfassung Oximidobenzotetronsäure wurde als empfindliches Reagens zur spektrophotometrischen Bestimmung von 0,5 bis 3,0 ppm Kupfer(II) bei 427 nm in 50%iger Dioxanlösung bei p_H 5,3 bis 7,5 vorgeschlagen. Die Anwesenheit von 1,3 ppm Ni(II), 1,3 ppm Co(II), 3,2 ppm Fe(II), 10,3 ppm Fe(III), 9,7 ppm Ce(IV), 300 ppm Acetat, 160 ppm Oxalat, 95 ppm Tartrat, 50 ppm Citrat sowie die Anwesenheit auch großer Mengen Zn(II), Cd(II), Hg(II), Pb(II), Mn(II), As(III) bzw. (V), Th(IV), Be(II), Ce(III), La(III), V(V) und Mo(VI) stören die Bestimmung von 2 ppm Cu(II) nicht. Der störende Einfluß von 25 ppm Bi(III), 20 ppm Sb(III), 20 ppm Sn(II), 25 ppm Sn(IV) und 30 ppm W(VI) kann durch Zusatz von 95 ppm Tartrat beseitigt werden.

     

Spectrophotometric determination of manganese(II) with gluconic acid

Summary A new spectrophotometric method for manganese has been established, with gluconic acid as reagent. Manganese(II) solutions treated with gluconic acid at p_H>11.50 produce an intensely coloured complex, with absorption maximum at 440 nm. Beer's law is obeyed over the manganese concentration range 9.44–47.2g/ml. The method has been used with good results for determination of manganese in a garnet.

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Zusammenfassung Eine neue spektrophotometrische Methode für Mangan mit Glukonsäure als Reagens wurde ausgearbeitet. Mangan(II)-lösungen geben mit Glukonsäure bei p_H 11,50 einen intensiv gefärbten Komplex mit einem Absorptionsmaximum bei 440 nm. Das Beersche Gesetz ist zwischen 9,44 und 47,2g Mn/ml erfüllt. Bei der Bestimmung des Mangans in einem Granat wurden gute Ergebnisse erzielt.

     

Disposable biosensor based on cathodic electrochemiluminescence of tris(2,2-bipyridine)ruthenium(II) for uric acid determination

A new method for uric acid (UA) determination based on the quenching of the cathodic ECL of the tris(2,2-bipyridine)ruthenium(II)–uricase system is described. The biosensor is based on a double-layer design containing first tris(2,2-bipyridine)ruthenium(II) (Ru(bpy)₃²⁺) electrochemically immobilized on graphite screen-printed cells and uricase in chitosan as a second layer. The uric acid biosensing is based on the ECL quenching produced by uric acid over the cathodic ECL caused by immobilized Ru(bpy)₃²⁺ in the presence of uricase. The use of a −1.1 V pulse for 1 s with a dwelling time of 10 s makes it possible to estimate the initial enzymatic rate, which is used as the analytical signal. The Stern–Volmer type calibration function shows a dynamic range from 1.0 × 10⁻⁵ to 1.0 × 10⁻³ M with a limit of detection of 3.1 × 10⁻⁶ M and an accuracy of 13.6% (1.0 × 10⁻⁴ M, n = 5) as relative standard deviation. Satisfactory results were obtained for urine samples, creating an affordable alternative for uric acid determination.     

1,8-Dihydroxyanthraquinone-Mg(II) complex: III. Spectrophotometric determination of Mg(II) by extraction in isoamyl alcohol

In this paper a direct spectrophotometric method is proposed to determine Mg(II). This new method is based on the extraction in isoamyl alcohol of the complex formed between Mg(II) and 1,8-dihydroxyanthraquinone. The method permits the determination between 1.25 and 12.5 γ (in aqueous phase). The error and the molar absorptivity are values of 2.22% and 10,114 liters mol^?1 cm^?1, respectively. Also studied were the values of the constant of exchange and the interference levels caused by foreign ions.     

Spectrophotometric determination of cobalt(II) based on the ion-pair of tetrathiocyanatocobaltate(II) with neotetrazolium chloride

The ion-pair formed between tetrathiocyanatocobaltate(II) and [3,3′-(4,4′- biphenylene)bis(2,5-diphenyl)]-2H-tetrazolium chloride (neotetrazolium chloride) can be extracted into 4-methylpentan-2-one and used for the spectrophotometric determination of cobalt (2.5–9.8 μg ml^?1) at pH 3.5–5.0. The Sandell sensitivity of the method is 0.02 μg Co cm^?2. With suitabte masking, the method is quite selective and is applicable to nickel wire alloys.     

1,8-dihydroxyanthraquinone-Mg(II) complex: II. Spectrophotometric study. Determination of Mg(II)

The 1,8-dihydroxyanthraquinone (1,8-DHAn) shows a colored and fluorescent reaction with the ion Mg(II) in a hydroalcoholic and ammonical medium.In the present work we have studied spectrophotometrically the 1,8-DHAn-Mg(II) complex in a hydroethanolic and ammonical, 8 × 10^?4M medium. We found that the complex shows a maximum absorbance at 510 nm, and obeys a 1:1 stoichiometry with log K of 4.08.We propose a new method for the spectrophotometric determination of Mg(II) which is valid for concentrations between 0.25 and 2.00 ppm, and yields an error of 1.32%.     

Cetyltrimethylammonium bromide-enhanced chemiluminescence determination of uric acid using a luminol-hexacyanoferrate(III)-hexacyanoferrate(II) system.

A chemiluminescence (CL) method using flow injection (FI) was developed for the determination of uric acid based on the enhancement chemiluminescence intensity of luminol-hexacyanoferrate(III)-hexacyanoferrate(II) in the presence of cetyltrimethylammonium bromide and the uric acid species. The linear range was 7.0 x 10(-10) - 9.0 x 10(-7) M with a detection limit (3sigma) of 2.58 x 10(-10) M, which was about two orders of magnitude lower than those reported. The proposed method was used for the determination of uric acid in real samples.     

氧化苯胺蓝褪色光度法测微量锰

研究了在H2SO4介质中,锰(VII)能氧化苯胺蓝使其褪色,且褪色的程度随锰量变化呈线性关系,据此建立了测定锰的光度分析方法。实验测定波长为602nm,表观摩尔吸光系数为 2.72?104 L?mol-1?cm-1,锰的量在0 ~100?g/25mL范围内服从朗伯-比尔定律,茶叶中常见金属元素不干扰测定,方法在用于测定茶叶中微量锰时,其相对标准偏差在1.7%～2.9%之间,回收率为100.8%～103.2%     

Spectrophotometric determination of microamounts of quercetin based on its complexation with copper(II)

The complexation process of the transition metal Cu(II) with quercetin was studied. The investigation was conducted spectrophotometrically in ethanol at the maximum absorption wavelength of 458.5 nm. Cu(II)—quercetin complex composition (1: 1) was determined using the Job, Harvey—Manning, and mole ratio methods. Complex stability constant was calculated by the Job and mole ratio methods and the respective logarithm values were 7.53 ± 0.25 and 7.44 ± 0.03. A new method for quantitative determination of the quercetin content in solution was developed in this work. At the optimal conditions quercetin was determined in concentrations ranging from 0.202 to 1.006 μg cm⁻³ with relative standard error of 2.5 % to 5.5 %. The lower detection limit was 0.067 μg cm⁻³. The method was found very accurate, reproducible, and sensitive, capable to determine microamounts of quercetin in pharmaceutical preparations.     

Spectrophotometric determination of molybdenum based on charge transfer complexes sensitized by copper(II)

A new high sensitive spectrophotometric determination of trace molybdenum was investigated. The sensitivity of the determination of molybdenum, which based on the color charge transfer complex of molybdotungstophosphate-3,3′,5,5′-tetramethylbenzidine, was greatly enhanced by copper(II) ions in the presence of polyvinyl alcohol. The improved method maintained the features of simplicity, rapidity and selectivity, especially eliminating the interference from tungsten. Under the optimum conditions, Beer's law was obeyed over the range from 2 to 32 ng ml⁻¹ molybdenum with molar absorptivity being 4.92×10⁵ l mol⁻¹ cm⁻¹ at 660 nm. The relative standard deviation was 1.2% under nine determinations for 16 ng ml⁻¹ Mo(VI). The present method had been applied to the determination of trace molybdenum in tungsten ores with satisfactory results.     

Simultaneous electrochemical determination of uric acid and ascorbic acid on a glassy carbon electrode modified with cobalt(II) tetrakisphenylporphyrin.

A cobalt(II) tetrakisphenylporphyrin (Co(II)TPP) film modified glassy carbon electrode (Co(II)TPP-GCE) was prepared by just coating Co(II)TPP solution on the surface of the electrode. It can be used for the simultaneous determination of ascorbic acid and uric acid. The anodic peaks of AA and UA can be separated well. Owing to the strongly hydrophobic property of porphyrin, the modified electrode has good stability and long life. The linear range for UA and AA were 2.0 x 10(-6)-1.0 x 10(-4) M and 9.0 x 10(-6)-2.0 x 10(-3) M with detection limits of 5.0 x 10(-7) and 5.0 x 10(-6) M, respectively. Furthermore, metalloporphyrins of other kinds were also used to construct modified electrodes. Their performances were inferior compared with that of the Co(II)TPP modified electrode.     

阻抑褪色光度法测定水样中阴离子表面活性剂

在弱酸性的HCl-NaOAC缓冲介质中,溴化十六烷基吡啶(CPB)和曙红Y(EY)染料的混合溶液发生褪色,在该褪色的溶液中分别加入十二烷基硫酸钠(SDS)及十二烷基苯磺酸钠(SDBS)等阴离子表面活性剂(AS),溶液颜色发生改变,最大吸收波长都在514 nm处,并分别在548、546 nm处产生明显褪色。在吸收或褪色波长处,阴离子表面活性剂的浓度与增色或褪色程度呈良好线性关系,从而建立测定阴离子表面活性剂的光度法。在最大吸收波长处,SDBS体系、SDS体系中AS的浓度在0~2.06×10-5mol/L、0~2.63×10-5mol/L范围内遵守比尔定律,表观摩尔吸光系数分别为1.30×104、1.01×104L.mol-1.cm-1,检出限分别为8.14×10-7、9.96×10-7mol/L。若用双波长叠加,表观摩尔吸光系数达2.07×104、1.78×104L.mol-1.cm-1,检出限为4.82×10-7、8.34×10-7mol/L。方法具有较高的灵敏度和良好的选择性,用于水样中AS的测定。     

Spectrophotometric determination of traces of iron after extraction of Fe(II)-phenanthroline complex on polyurethane foam

A spectrophotometric method for the determination of traces of iron in glass and ceramic materials has been developed. The method involves formation of the Fe(II)-phenanthroline complex at pH 3-4 in aqueous medium, followed by its selective extraction and preconcentration on polyurethane foam from 2.5M perchloric acid and finally elution of the complex with acetone for spectrophotometric measurement at 510 nm. A wide linearity range from 0.05 to 3 mu g/ml Fe is obtained with the method. Co, Cu and Ni have no significant effect when they are present in the weight ratios Fe:Co < 1:2, Fe: Cu < 1:10 and Fe: Ni < 1:50. The method yielded satisfactory results when applied to various glass and ceramic samples.