Complexometric titration of Ti(IV) with 2-(5-chloro-2-pyridylazo)-5-dimethylaminophenol as indicator

A method for determination of titanium by a reverse titration with EDTA in the presence of hydrogen peroxide, with 2-(5-chloro-2-pyridylazo)-5-dimethylaminophenol as indicator, is presented; use of the method for analysis of titanium paints is also described.     

Spektrophotometrische bestimmung von scandium mit 4-2(-pyridylazo)resorcin

4-(2-Pyridylazo)resorcinol (PAR) forms 2 red chelates with scandium in aqueous solution at pH ? 2 or 5: SCRH²⁺ and ScR₂^-. The former can be used to determine 0.05–2.4 μg Sc/ml at pH 3.5–4.5 with μ = 0.4; measurement is done at 530 mμ. Many ions interfere and separation is necessary.     

Synthesis of stereoisomeric 4-(2-methylindolin-1-yl)- and 4-(2-methylindol-1-yl) derivatives of glutamic acid

The reaction of dimethyl (2S,4RS)-N-phthaloyl-4-bromoglutamate with 2-methylindoline afforded diastereomeric 4-(2-methylindolin-1-yl)-(S)-glutamic acid derivatives, whose oxidation gave rise to 4-(2-methylindol-1-yl)-(S)-glutamic acid derivatives.     

Spectrophotometric determination of fluoride in aqueous solution using 2-hydroxy-1-(2-hydroxy-4-sulfo-1-naphthyl azo)-3-naphthoic acid

Fluoride (5–70 μg) in a final volume of 100 ml was determined. The analysis was based on the colored reaction of Al-HHSNNA and the bleaching effect of fluoride on it. The method is simple and rapid, and the accuracy is satisfactory when applied to different types of water. The procedure compared favorably with the conventional colorimetric method (D. F. Boltz and J. A. Howell (Eds.), Colorimetric Determination of Nonmetals, 2nd ed., pp. 10, 128, 1978). It is worth noting that the introduction of alizarinfluorine blue in 1958 and the pF electrode in 1966—both of fundamental importance—cannot be ignored in the introduction of the present method for fluoride as these still hold.     

Titration of L-cysteine hydrochloride with standard nickel sulphate solution employing 1-(pyridyl-2′-azo)-naphthol-(2) as indicator

The estimation of cysteine hydrochloride can be carried out quantitatively against standard nickel sulphate solution using 1-(pyridyl-2′-azo)-naphthol-(2) in carbonate-bicarbonate buffer medium of pH 10.0. Other natural amino acids have no interference with the titration.     

Complexometric titration of copper(II) using nitrosochromotropic acid as a new metal indicator

Summary Nitrosochromotropic acid gives a violet coloured soluble complex with Cu^II in ammonium chloride-ammonium hydroxide buffer solution, which is less stable than Cu^II-EDTA complex. When microquantities of Cu^II solution containing 1 or 2 drops of nitrosochromotropic acid in the ph range 7.25 to 8.00, are titrated with EDTA, a sharp colour change from violet to orange occurs at the end point. The method of titration can be carried out from 20° to 40° C, but the copper complex dissociates at higher temperature and gives low results. The separation of Zn²⁺, Cd²⁺, Co²⁺, Ni²⁺, Pb²⁺ and alkaline earths, is necessary as they interfere in the titrations with EDTA.

---

Zusammenfassung Nitrosochromotropsäure bildet mit Kupfer(II) in Ammoniumchlorid-Ammoniak-Pufferlösung einen violett gefärbten löslichen Komplex, der weniger stabil ist als der Kupfer(II)-ÄDTA-Komplex. Mikromengen Kupfer(II) können imph-Bereich von 7,25–8,00 unter Zusatz von 1–2 Tropfen Nitrosochromotropsäurelösung als Indicator mit ÄDTA-Lösung titriert werden, wobei am Endpunkt ein scharfer Umschlag von Violett nach Orange erfolgt. Die Temperatur der Lösung soll 20–40° C betragen; bei höherer Temperatur erhält man zu niedrige Werte, da der Kupferkomplex dann dissoziiert. Zn²⁺, Cd²⁺, Co²⁺, Ni²⁺, Pb²⁺ und Erdalkalien müssen vor der Titration abgetrennt werden.

     

Complexometric titration of copper (II) using chromotropic acid dioxime as a metal indicator

Summary Chromotropic acid dioxime forms purple coloured complexes with copper in the p_H ranges 5.82 to 6.45 and 7.25 to 8.05 respectively which are less stable than the Cu^II-EDTA complex. On titrating these solutions with EDTA, the purple coloured complexes turn colourless or yellow at the end point. These titrations give satisfactory results in the temperature ranges 20 to 70° C and 20 to 50° C respectively. In acid medium, the titration of copper can be carried out in the presence of magnesium and alkaline earths, but zinc, cadmium, nickel, cobalt, aluminium and iron(III) interfere. The latter two elements can be masked by sodium fluoride. In ammoniacal medium, zinc, cadmium, cobalt, nickel, lead, magnesium and alkaline earths interfere.

---

Zusammenfassung Chromotropsäuredioxim bildet mit Kupfer im p_H-Bereich 5,82 bis 6,45 und 7,25–8,05 purpurrot gefärbte Komplexe, die weniger stabil sind als der Kupfer-ÄDTA-Komplex. Bei der Titration solcher Lösungen mit ÄDTA ergibt sich am Endpunkt ein Farbumschlag nach Farblos bzw. Gelb. Bei Temperaturen von 20–70°C bzw. 20–50°C werden gute Ergebnisse erzielt. Die Kupferbestimmung in saurem Medium kann in Gegenwart von Magnesium und Erdalkalien durchgeführt werden; Störungen werden verursacht durch Zink, Cadmium, Nickel, Kobalt, Aluminium und Eisen(III), wobei die beiden letzten jedoch mit Natriumfluorid maskiert werden können. Die Titration in ammoniakalischem Medium wird durch Zink, Cadmium, Kobalt, Nickel, Blei, Magnesium und die Erdalkalien gestört.

     

脱氧核糖核酸与对二甲氨基偶氮苯邻羧酸作用机理的荧光光谱研究

通过实验,采用荧光光谱法研究了对二甲氨基偶氮苯邻羧酸(JJR)与脱氧核糖核酸(DNA)结合反应的特征.由Stern-Volmer方程和双倒数曲线Lineweaver-Burk方程获得了反应的猝灭常数Ksv=1×106～2×106 L/mol、结合常数KA≈0.5×106 mol/L以及对猝灭的类型做出了推断.通过热力学参数、离子强度实验讨论并得到它们以氢键、嵌插入、范德华力等几种方式作用.该反应的最佳实验条件为pH值控制在6.1左右;加入顺序为JJR+DNA+(B-R)适宜反应体系;线性范围在0～100 mg/L之间.     

Spectrophotometric determination of cadmium with 1-[(5-chloro-2-pyridyl)azo]-2-naphthol

Summary Cadmium(II) reacts with l-[(5-chloro-2-pyridyl)azo]-2-naphthol (5-C1--PAN) in aqueous solution; the complex can be extracted with chloroform at pH 9–11 to give a red solution with an absorption peak at 566 nm. The colour in chloroform is stable and the system conforms to Beer's law; optimal range in the chloroform layer for measurement at 1.00-cm cells is 0.1–1 ppm cadmium. Common cations and anions do not interfere. Large amounts of some cations can be masked by potassium cyanide, the cadmium cyanide complex being demasked by formaldehyde. The proposed method is one of the most sensitive procedure for the determination of cadmium. The molar absorptivity in the chloroform extract is 6.6· 10⁴ 1 mole^–1 cm^–2 at 566 nm.

---

Zusammenfassung Cadmium reagiert mit 1-(5-Chlor-2-pyridyl) azo-2-naphthol, 5-C1--PAN, in wäßriger Lösung; der rote Komplex kann bei pH 9–11 mit Chloroform extrahiert werden und hat ein Absorptionsmaximum bei 566 nm. Die chloroformische Lösung ist stabil und entspricht dem Beerschen Gesetz; für die Messung in l-cm-Küvetten eignen sich am besten 0,1–1 ppm Cd. Übliche Ionen stören nicht. Große Mengen einiger Kationen können mit KCN maskiert werden, wahrend [Cd(CN)₄]^2– von Formaldehyd gespalten wird. Die vorgeschlagene Methode ist eine der empfindlichsten für die Bestimmung von Cd. Die molare Extinktion des chloroformischen Extraktes betragt bei 566 nm 6,6 · 10⁴ 1 · mol^–1 · cm^–2.

     

A novel polymeric (4-chloro-2-methylphenoxy) acetate complex of cadmium(II)

The infinite, two-dimensional polymer bis[(4-chloro-2-methylphenoxy)acetato] cadmium dihydrate was synthesized and characterized by elemental analysis and infrared spectroscopy. The crystal and molecular structure has been determined. The cadmium atom is six coordinated by four oxygen atoms from bridging carboxyl groups and two oxygen atoms from water molecules. The polymer net is stabilized by two O–H···O hydrogen bonds. Bond distances and angles within MCPA molecules are comparable to those found for the free acid and its complexes. The shortest cadmium–cadmium distance is 5.453(1) Å.     

Complexometric titration of submicromole amounts of thorium(IV) with photometric end-point detection

Summary Thorium(IV) can be determined in the microgram range by photometric titration with EDTA in the presence of an approximately equivalent amount of the indicator Semi-Xylenol Orange at pH 2 (HClO₄). Most other elements do not interfere. Interfering metal ions can be separated from thorium(IV) by electrolysis at a mercury pool cathode.

---

Zusammenfassung Mikrogrammengen Thorium(IV) lassen sich durch photometrische Titration mit EDTA in Anwesenheit einer äquivalenten Menge des Indikators Semixylenol-Orange bei pH 2 (HClO₄) bestimmen. Die meisten anderen Metalle stören die Bestimmung nicht. Störende Metallionen können durch elektrolytische Abscheidung an einer Quecksilberkathode von Thorium (IV) abgetrennt werden.

     

2-[2-(5-Bromopyridyl)azo]-5-dimethylaminophenol; a new sensitive reagent for cadmium

Cadmium(II) reacts with 2-[2-(5-bromopyridyl)azo]-5-dimethyl-aminophenol (5-Br-DMPAP) in aqueous solution; the complex can be extracted with organic solvents such as chloroform, 3-methyl-l-butanol and methyl isobutyl ketone at pH 8–10.5 to give a red solution which absorbs at 525–555 nm. The absorbance in organic solvents is stable and the system conforms to Beer's law; the optimal range in 3-methyl-1-butanol for measurement in 1.00-cm cells is 0.01–l p.p.m. cadmium. Moderate amounts of many cations and anions do not interfere, and interfering cations such as zinc, copper, manganese and nickel can be separated by extraction with dithizone. The 5-Br-DMPAP method is one of the most sensitive procedures available for the determination of cadmium; the molar absorptivity in a 3-methyl-1-butanol extract is 1.41·10⁵ 1 mol^?1 cm^?1 at 555 nm.     

Cylindrospermopsin determination using 2-[4-(2-hydroxyethyl)-1-piperazinyl]ethanesulfonic acid (HEPES) as the internal standard

Cylindrospermopsin (CYN) was determined by liquid chromatography/electrospray ionization-mass spectrometry (LC/ESI-MS) using 2-[4-(2-hydroxyethyl)-1-piperazinyl]ethanesulfonic acid (HEPES) as the internal standard. In the selected ion monitoring of LC/ESI-MS, m/z 414 for CYN and 237 for HEPES were monitored using the negative mode; the retention times of CYN and HEPES were 12.41 and 14.21 min, respectively. CYN was determined from peak area ratios of m/z 414/237. By the treatment of an anion exchange cartridge using a buffer at pH 10.5, CYN was isolated and condensed. No interfering peak was observed. Linearity of this method was observed at the range of 0.10-31.12 ng. Total coefficients of variation were 5.1 and 2.9% at 104 and 1038 μg CYN L⁻¹. The quantitative limit at a signal-to-noise (S/N) ratio of 10 was 0.16 ng.CYN concentration in natural waters is low. CYN in waters should be condensed for determination. This method including the treatment for isolation and condensation of CYN is useful for determination of CYN in environmental and/or drinking waters.     

阳离子型微乳液对镉（Ⅱ）—[4—（2—吡啶偶氮）—间苯二酚]的增敏作用

以十六烷基三甲基溴化铵／正戊醇／正庚烷／水微乳液为介质进行Ｃｄ（Ⅱ）－ＰＡＲ江度法测定，与以相同含量ＣＴＭＡＢ胶束体系比较，测定灵敏度增加，某些试验条件更为宽容，通过测定显色剂在水胶束相和水－微乳液中的分配系数ＫＤ，初步探讨了微乳液增敏作用机理。