Spectrophotometric and second-derivative spectrophotometric determination of mercury in organomercurials by means of benzyl 2-pyridyl ketone 2-quinolylhydrazone

Mercury(II) reacts with benzyl 2-pyridylketone 2-quinolylhydrazone (BPKQH) in the pH range 9.0-10.4, to form a stable 1:2 (metal:ligand) complex which has a sharp absorption maximum at 475 nm and molar absorptivity 5.01 x 10(4) 1.mole(-1).cm(-1). It is proposed for use in spectrophotometric determination of mercury at microg/ml levels and analysis for organomercurials. The sensitivity of the method can be increased significantly by employing derivative spectrophotometry, making mercury determination at ng ml levels feasible.     

Fluorimetric determination of dissociation constants of aryl-substituted alkylammonium ions

Although the absorption spectra of aryl-substituted alkylammonium ions are insensitive to prototropic dissociation, the fluorescence quantum yields of these ions are often very different from those of their uncharged conjugate bases. This is shown to be the result of different rates of non-radiative deactivation in excited acid and conjugate base and is analytically useful for the determination of pK_a values. The pK_a values of six drugs (procaine, butacaine, benoxinate, cinchonine, propranolol and dibucaine) which are aryl-substituted alkylammonium ions were evaluated fluorimetrically and are presented here.     

Fluorimetric determination of dissociation constants and ph-controlled fluorescence analysis of purines and pyrimidines

Fluorimetrically determined pH-titration curves have been obtained for twelve purines and pyrimidines at room temperature, in aqueous solution. The pK(a) values for these compounds have been determined fluorimetrically and potentiometrically. Except for 6-mercaptopurine and uric acid, there is close agreement between the two sets of pK(a) values, but a large difference for the corresponding excited singlet-state values, pK(S1)(a), which were calculated previously. This indicates that the excited singlet-state proton-transfer rate is much slower than the fluorescence-decay rate of purines and pyrimidines in our experimental conditions. A direct, simple, pH-controlled fluorimetric method is proposed for the determination of purines and pyrimidines. The limits of detection vary between 60 ng ml and 5.4 mug ml .     

Uranyl complexes with di-2-pyridyl ketone and di-2-pyridyl sulphide

Uranyl complexes of the type UO₂L_nX₂, where L is di-2-pyridyl ketone or di-2-pyridyl sulphide and n = 2 (X = Cl, NCS, ClO₄) or n = 1 (X = NO₃), have been prepared and characterized by elemental analyses, molar conductivity and thermoanalytical measurements.IR spectral data suggest that both ligands in all complexes act as bidentate chelating agents through the two nitrogen atoms. Alcoholation of the carbonyl group occurs in the complexes of di-2-pyridyl ketone obtained from alcoholic media.Conductivity measurements indicate that the thiocyanate and nitrate complexes are non electrolytes in MeNO₂ solution whereas the perchlorate complexes are 1:2 electrolytes.     

Fluorimetric determination of acidity constants of naphthoic and anthroic acids

A fluorimetric method of determining the acidity constants (pK_a values) of some naphthoic and anthroic acids is presented, based on the changes in fluorescence of solutions of these acids in water on changing the pH. The method is useful in the absence as well as in the presence of excited-state proton transfer. In the latter case, when the excited-state protonation occurs in the same pH region as the ground-state dissociation, resolution of the two processes can be accomplished by addition of a suitable quencher such as iodide. The method permits the accurate determination of the pK_a value of fluorescent compounds, even when they are poorly soluble in water, because of the high sensitivity of the spectrofluorimetry.     

Rate constants for the reactions of benzyl and methyl-substituted benzyl radicals with O2 and NO

Rate constants for reactions of benzyl, o-niethylbenzyl and p-meihylbenzyl radicals with O₂ and NO have been measured at room temperature. The radicals were generated by UV flash photolysis and the time decay measured by absorption at ≈ 300 nm. The rate constants are: benzyl (0.99 ± 0.07 and 9.5 ± 1.2), o-methylbenzyl (1.2 ± 0.07 and 8.6 ± 0.8) and p-mithyl-benzyl (1.1= 0.10 and 8.9 = 0.9) for O₂ and NO respectively in units of 10^?12 cm³ molecule^?1 s^?1.     

Spectrophotometric determination of palladium with pyridine-2-aldehyde-2-quinolylhydrazone

A new, sensitive colorimetric procedure for the determination of microgram quantities of palladium(II) with pyridine-2-aldehyde-2-quinolylhydrazone is described. The reaction is practically instantaneous and not sensitive to variations in salt concentration. The platinum group metals do not interfere, and the analysis is possible with milligram amounts of these metals present.     

Polarographic investigation of syn-phenyl 2-pyridyl ketone oxime

The polarographic reduction of syn-phenyl 2-pyridyl ketone oxime to -(2-pyridyl)benzylamine over the pH range 0.78–12.88 is reported. Two waves are observed, both of which are pH-dependent. The complex electrode reaction is discussed and a mechanism advanced to describe the reduction of the oxime group over the pH range considered.     

Analytical study of the phenyl-2-pyridyl ketone azine-palladium system. Photometric determination of palladium

Phenyl-2-pyridyl ketone azine reacts with palladium(II) to produce a yellow 1:1 complex (λ_max = 425 nm, ? = 10.4 × 10³M^?1 cm^?1 in aqueous ethanolic solution) and a red-violet 3:1 complex (λ_max = 530?540 and 380?390 nm). The yellow complex in aqueous ethanolic solution has been used for the spectrophotometric determination of trace amounts of palladium. The method has been applied to the determination of palladium in some catalysts and one mineral.     

Thermodynamic study of the β-cyclodextrin benzyl-2-pyridyl ketone 2-pyridyl hydrazone inclusion process

Benzyl-2-pyridylketone-2-pyridylhydrazone and -cyclodextrin form a 1 : 1 adduct in water with a standard free energy change, G ^o, in the region of 14.2 kJ mol^–1 at 25°C, and an association constant of 275 M^–1 in the pH range 5–7. These values have been obtained by using the fluorimetric spectral changes associated with the inclusion process.     

Picoline-2-aldehyde thiosemicarbazone: The acid dissociation constants and reactions with various metals

The acid association constants for picoline-2-aldehyde thiosemicarbazone have been determined by potentiometry and spectrophotometry. Results are calculated by the modified computer programs SCOGS and PITMAP. Protonation sites are suggested for these reactions. A spectrophotometric survey has been performed of the reaction between PATS and several metal ions.     

Potentiometric and spectrophotometric determination of the dissociation constants of cefetamet

Summary The dissociation constants of cefetamet-Na have been determined using potentiometric titrations and spectrophotometry. The investigations were carried on in water solutions at constant temperature and ionic strength, and at differentH ₀ andpH values. Potentiometric investigations were performed at three different temperatures and ionic strengths. The concentration dissociation constants and the corresponding thermodynamic dissociation constants were calculated by a computer program. The mixed dissociation constants (pK) of cefetamet-Na have been determined spectrophotometrically in theH ₀ range from -5.80 to 0.00 and atpH values from 0.00 to 12.70 and are in good agreement with values achieved by graphical methods as well as with those obtained by potentiometric methods. Based on the determined values, the thermodynamic parameters (G, H, S) were calculated atI=0.1M.

---

Potentiometrische und spektrophotometrische Bestimmung der Dissoziationskonstanten von Cefetamet

Zusammenfassung Die Dissoziationskonstanten von Cefetamet-Na wurden mittels potentiometrischer Titrationen und auf spektrophotometrischem Weg bestimmt. Die Untersuchungen wurden in wäßriger Lösung bei konstanter Temperatur und Ionenstärke und verschiedenenH ₀- undpH-Werten durchgeführt. Potentiometrische Messungen wurden bei drei verschiedenen Temperaturen und Ionenstärken vorgenommen. Die stöchiometrische Dissozation und die entsprechenden thermodynamischen Dissoziationskonstanten wurden mit Hilfe eines Computerprogramms berechnet. Die gemischten Dissoziationskonstanten (pK) wurden spektrophotometrisch imH ₀-Bereich von -5.80 bis 0.00 und impH-Bereich von 0.00 bis 12.70 bestimmt und stimmen sowohl mit Werten, die mit Hilfe der graphischen Methode erhalten wurden, als auch mit potentiometrisch bestimmten gut überein. Aus den ermittelten Werten der Dissoziationskonstanten wurden die thermodynamischen Parameter (G, H, S) fürI=0.1M berechnet.

     

Synthesis and analytical properties of di-2-pyridyl ketone guanylhydrazone

The synthesis and analytical properties of di-2-pyridyl ketone guanylhydrazone (DPGH) are described. The reagent was tested with 37 cations but only Co(II), Ni(II), Cu(II), Fe(II) and Pd(II) gave colored complexes. The spectral characteristics of the reagent and the above complexes as well as the procedures for a selective determination of total iron, cobalt(II), copper(II), nickel(II) and palladium(II) are reported.     

Di-2-pyridyl ketone 2-furoylhydrazone as a reagent for the fluorimetric determination of low concentrations of aluminium

The synthesis and properties of di-2-pyridyl ketone 2-furoylhydrazone as an analytical reagent are described. A rapid procedure for the fluorimetric determination of aluminium at the 10-100 ng ml level, at pH 6.1-6.5 (lambda(exc) 395 nm, lambda(em) 465 nm) has been established. Interferences have been evaluated, and the procedure has been applied satisfactorily to determination of aluminium in sea-water.     

Differential pulse polarography and voltammetry of di-2-pyridyl ketone benzoylhydrazone

Summary The differential pulse polarographic (DPP) and voltammetric (DPV) behaviour of di-2-pyridyl ketone benzoylhydrazone (DPKBH), has been investigated over a wide pH range (2.1–11.5). The effect of various operational parameters on the reduction current are discussed and the mechanism of the electrode reaction is also included. Both methods DPP and DPV are applied for the analytical determination of this reagent and the detection limits are found to be 1.24 mol/l and 0.86 mol/l, respectively. The DPP behaviour of DPKBH in the presence of Pb(II), Cd(II) and Cu(II) is studied and the behaviour of the Cu(II)-DPKBH complex is fully investigated. The voltammetric determination of Cu(II), based on the accumulation of its complex at the hanging mercury drop electrode, is described. Statistical analysis of the calibration curve data is included.On leave from Assuit University, Egypt     

Spectrophotometric determination of the second dissociation constants of the aminoquinolines

The second dissociation constants representing the transition from monocation to dication for all of the isomeric aminoquinolines have been determined as pKa' values. The analogous values for 2- and 4-aminopyridine have been recalculated using a revised H_O scale. The accurate determination of the second pKa values follows from measurement, for the first time, of the ultraviolet spectra of all the mono- and dications of the aminoquinolines.