锗(IV)-茜素红-VOSO4-EDTA体系极谱吸附催化波研究

报导了在酸性缓冲液中锗(IV)-茜素红-VOSO4-EDTA体系的配合吸附平行催化波的研究.锗的最低检出量为1.0x10^-^9mol.dm^-^3.研究了催化波的机理.     

Construction and performance characteristics of new fentanyl-selective plastic membrane electrode.

The construction and performance characteristics of an ion-selective electrode for fentanyl-drug cation, based on an ion-pair complex with tetrakis[3,5-bis-(trifluoromethyl)phenyl]borate anion in a PVC matrix were studied. A linear response for 1 x 10(-5) mol dm-3 to 1 x 10(-2) mol dm-3 drug with a slope of 57.9 +/- 0.5 mV/decade was established. The optimum pH range was 2 to 6. The lower detection limit was 6.29 x 10(-6) mol dm-3 fentanyl citrate (2.1165 micrograms cm-3 fentanyl). There were negligible interferences from a number of inorganic cations, structural analogues, and some common drug additives in injections. The electrode proposed has been successfully applied to determine fentanyl citrate in injections. The results correlated well with those obtained by the United States Pharmacopoeia standard procedure.     

Triton X-100存在下钴与α-(α-噻唑偶氮)-5-二甲氨基苯甲酸的胶束显色反应

本文简化并改进了2-(2-噻唑偶氮)-5-二甲氨基苯甲酸(TAMB)的合成方法. 详细研究了在非离子表面活性剂Triton X-100存在下TAMB与钴的胶束增敏显色反应.     

6-Chloro-3-hydroxy-2-(5'-methylfuryl)-4H-chromene-4-one as an analytical reagent for micro determination of molybdenum(VI).

6-Chloro-3-hydroxy-2-(5'-methylfuryl)-4H-chromene-4-one (CHMFC) has been used as an analytical reagent for the spectrophotometric determination of molybdenum. Molybdenum(VI) in the presence of several cations, anions and complexing agents forms a yellow 1:2 complex with CHMFC. The complex is quantitatively extractable into 1,2-dichloroethane from 1 mol dm(-3) acetic acid medium and is stable for more than 6 h. The complex shows an absorption maximum at 438 nm with a molar absorptivity of 5.36 x 10(4) dm3 mol(-1) cm(-1) and Sandell's sensitivity equal to 0.0017 microg Mo cm(-2). The method obeys Beer's law up to 1.9 microg Mo ml(-1). The relative standard deviations are 0.2% for solutions and 0.5-1.5% for solid samples. The method is simple, selective, precise and rapid, and has been satisfactorily applied to the micro determination of molybdenum in various synthetic and standard samples.     

Interaction of 2- and 4-mercaptopyridine with pentacyanoferrates and gold nanoparticles

2-Mercapto- and 4-mercaptopyridine (2- and 4MPy) react with the [Fe(CN)(5)(H(2)O)](3-) complex, forming the S-coordinated [Fe(CN)(5)(2MPy)](3-) and the N-coordinated [Fe(CN)(5)(4MPy)](3-) complexes. The rates of formation and dissociation of the [Fe(II)(CN)(5)(2MPy)](3-) complex were determined as k(f) = 294 dm(3) mol(-1) s(-1) and k(d) = 0.019 s(-1) by means of stopped-flow technique. The equilibrium constants for the iron(II) and -(III) species were calculated as K(f)(II) = 1.5 x 10(4) mol(-1) dm(3) and K(f)(III) = 1.3 x 10(6) mol(-1) dm(3), in comparison with 2.6 x 10(5) and 3.4 x 10(4) mol(-1) dm(3), respectively, for the 4MPy isomer. In the presence of gold nanoparticles, both 2- and 4MPy can displace the stabilizing citrate species, leading to substantial aggregation in aqueous solution, as deduced from the surface-enhanced Raman spectroscopy effect and from the decay of the 520-nm plasmon band accompanied by the rise of the characteristic exciton band at 650 nm. The [Fe(CN)(5)(4MPy)](3-) complex promotes strong stabilization of the gold nanoparticles by interacting through the S atom. On the other hand, the labile [Fe(CN)(5)(2MPy)](3-) complex induces aggregation, delivering the 2MPy ligand to the gold nanoparticles.     

A highly selective spectrophotometric determination of niobium (V) using 3-hydroxy-2-[1'-phenyl-3'-(p-chlorophenyl)-4'-pyrazolyl]-4-oxo-4H-1-benzopyran as a complexing agent

3-Hydroxy-2-[1'-phenyl-3'-(p-chlorophenyl)-4'-pyrazolyl]-4-oxo-4H-1benzopyran (HPCPB) is used as an analytical reagent for the spectrophotometric determination of niobium in trace amounts with which it forms a yellow coloured complex (4:1) in perchloric acid medium. The complex is extractable into chloroform and shows absorption maximum at 407-418 nm with a molar absorptivity of 2.79 x 10(4) L mol(-1) cm(-1) and Sandell's sensitivity equal to 0.0033 microg Nb(V) cm(-2), respectively. Beer's law holds good in the range 0-1.2 microg Nb ml(-1), with a standard deviation of +/- 0.0015 absorbance units. The method is free from the interference of a large number of elements and handles satisfactorily the analysis of various samples of varying complexity.     

Determination of 25-hydroxyvitamin D3 in human serum by fluorescence labelling and high-performance liquid chromatography.

A method is described for the determination of 25-hydroxyvitamin D3 in human blood serum. The problems of sensitivity and selectivity encountered with previous techniques were avoided by the formation of a highly fluorescent Diels-Alder adduct following solid-phase extraction of the vitamin. After excess of reagent had been eliminated, quantification was achieved by high-performance liquid chromatography. The recovery of the vitamin from serum was 76.4 +/- 1.76%. The precision of the method was determined, and the relative standard deviations were 8.38% at a concentration of 47.0 x 10(-9) mol dm-3, 6.74% at a concentration of 99.8 x 10(-9) mol dm-3 and 3.79% at a concentration of 146.8 x 10(-9) mol dm-3. The detection limit for the adduct was 2.93 x 10(-14) mol injected, for a signal-to-noise ratio of 3:1, and serum concentrations of 0.25 x 10(-9) mol dm-3 could easily be quantified. No interference from endogenous or exogenous substances was observed.     

Interaction forces in thin liquid films stabilized by hydrophobically modified inulin polymeric surfactant. 2. Emulsion films

The interaction forces in emulsion films stabilized using hydrophobically modified inulin (INUTEC SP1) were investigated by measuring the disjoining pressure of a microscopic horizontal film between two macroscopic emulsion drops of isoparaffinic oil (Isopar M). A special measuring cell was used for this purpose whereby the disjoining pressure Pi was measured as a function of the equivalent film thickness hw. The latter was determined using an interferometric method. In this way Pi-hw curves were established at a constant INUTEC SP1 concentration of 2x10(-5) mol.dm-3 and at various NaCl concentrations. At a constant disjoining pressure of 36 Pa, a constant temperature of 22 degrees C, and a film radius of 100 microm, hw decreased with an increase in the NaCl concentration, Cel, and reached a constant value of 11 nm at Cel=5x10(-2) mol.dm-3. This reduction in film thickness is due to the compression of the electrical double layer, and at the above critical NaCl concentration any electrostatic repulsion is removed and only steric interaction remains. This critical electrolyte concentration represents the transition from electrostatic to steric interaction. At a NaCl concentration of 2x10(-4) mol.dm-3 the Pi-hw isotherms showed a gradual decrease in hw with an increase in capillary pressure, after which there was a jump in hw from approximately 30 to approximately 7.2 nm when Pi reached a high value of 2-5.5 kPa. This jump is due to the formation of a Newton black film (NBF), giving a layer thickness of the polyfructose loops of approximately 3.6 nm. The film thickness did not change further when the pressure reached 45 kPa, indicating the high stability of the film. Pi-hw isotherms were obtained at various NaCl concentrations, namely, 5x10(-2), 5x10(-1), 1.0, and 2.0 mol.dm-3. The initial thicknesses are within the range 9-11 nm, after which a transition zone starts, corresponding to a pressure of about 0.5 kPa. In this zone all films transform to an NBF with a jump, after which the thickness remains constant with a further increase in the disjoining pressure up to 45 kPa, with no film rupture. This indicates the very high stability of the NBF in the presence of high electrolyte concentrations. The high emulsion film stability (due to strong steric repulsions between the strongly hydrated loops of polyfructose) is correlated with the bulk emulsion stability.     

Study of the absorption spectra of the 4f electron transitions of the praseodymium complex with ciprofloxacin and its analytical application

Ciprofloxacin (CPFX) is proposed as a reagent for the derivative spectrophotometric determination of praseodymium in mixed rare earths. The absorption spectra of 4f electron transitions of the praseodymium complex with CPFX was studied by normal and derivative spectrophotometry. The stoichiometry of the praseodymium-CPFX complex was calculated by the molar ratio and continuous variations methods. A ratio of Pr to CPFX of 1:3 was found. The absorption bands of the 4f electron transitions of the complex were enhanced markedly. Using the third derivative spectrum. Beer's law was obeyed up to 35 microg cm(-3) of praseodymium. The relative standard deviation is 0.62% for 14 microg cm(-3) of praseodymium. The detection and quantification limits were 0.17 and 0.56 microg cm(-3) of praseodymium, respectively. A method for the direct determination of praseodymium in mixtures of rare earths with good accuracy and selectivity is described.     

Determination of ascorbic acid in pharmaceuticals and urine by reverse flow injection.

Two reverse flow injection (FI) methods, using spectrophotometric detection, are proposed for the determination of ascorbic acid. Both methods are based on its reaction with the ethylenediaminetetraacetic acid-CoIII complex in a medium of 5% diethylamine. In the first method, using the peak-height FI technique, ascorbic acid is determined over the range from 2 x 10(-4) to 5 x 10(-3) mol dm-3 and in the second, using the peak-width FI method, the working range is extended (2 x 10(-3)-5 x 10(-2) mol dm-3). Both FI methods were applied to the determination of ascorbic acid in pharmaceuticals while the peak-height FI technique was also used to determine ascorbic acid in urine.     

铑(Ⅲ)与5-(5-氯-2-吡啶偶氮)-2,4-二氨基甲苯的配合物催化氢波研究

本文建立了一种催化极谱法测定痕量铑的新方法.先使铑(Ⅲ与5-Cl-PADAT在pH5的HOAc-NaOAc3缓冲溶液中生成稳定的配保物,再于适量HClO~4底液中进行极谱测定.并研究了影响极谱催化波的各种因素及波的性质,确定该波为铑(Ⅲ)与5-Cl-PADAT配合物的催化氢波,提出了可能的电极过程,并进行了实验验证.该法测定铑的线性范围为3.9×10^-12-3.9×10^9mol·dm^-3,检出限为1.9×10^-12mol·dm^-3.已应用于镍基金合金及催化剂中铑的测定.     

Spectrofluorimetric flow injection method for the individual and successive determination of L-cysteine and L-cystine in pharmaceutical and urine samples.

A flow injection configuration is proposed for the determination of L-cysteine and L-cystine individually and for mixtures of both analytes. The procedure is based on the rapid oxidation of L-cysteine by thallium(III) with concomitant formation of fluorescent thallium(I). The inclusion of a selecting valve and of a copper-coated cadmium column in the configuration allows the successive determination of two analytes. Linear calibration graphs were obtained between 5 x 10(-6) and 5 x 10(-5) mol dm-3 of L-cysteine and between 2 x 10(-6) and 2 x 10(-5) mol dm-3 of L-cystine. The applicability of the method to the determination of L-cysteine and L-cystine in pharmaceutical preparations was demonstrated by investigating the effect of potential interferents and by the analysis of commercial preparations. The method was successfully applied to the determination of L-cysteine and L-cystine in urine samples.     

Use of 1-(2-thiazolylazo) 2-naphthol in rapid determination of iron in geological matrices

The present work describes the use of 1-(2-thiazolylazo)-2-naphthol (TAN) as a spectrophotomeric reagent for iron determination. TAN reacts with iron(II) forming a brown complex with absorption maximum at 575 and 787 nm. The following parameters were studied: complex stability, pH effect, amount of the TAN, buffer selection, amount of acetate buffer, reductor effect, order of addition of reagents and adherence to Beer's Law. The results demonstrated that iron can be determined with TAN in a pH range of 4.0-6.2 with an apparent molar absorptivity of 1.83 x 10(4) 1 . mol(-1) . cm(-1) (at 787 nm) and 1.41 x 10(4) 1 . mol(-1) . cm(-1) (at 575 nm). Beer's Law is obeyed for at least 3.00 microg/ml. The TAN reacts with other cations, but at 787 nm only the iron(II)-TAN complex absorbs. So, iron can be determined selectively in the presence of several cations. A procedure based on the direct mixture of the sample and a chromogenic solution is proposed, where iron can be determined rapidly and easily. Such procedures were used for the determination of iron in several geological matrices. No significant differences were obtained for TAN method and certificate results.     

Diazacoronand linked beta-cyclodextrin dimer complexes of Brilliant Yellow tetraanion and their sodium(I) analogues

Complexation of the Brilliant Yellow tetraanion, 3(4-), by two new diazacoronand linked beta-cyclodextrin (beta CD) dimers 4,13-bis(2-(6A-deoxy-beta-cyclodextrin-6A-yl)aminooctylamidomethyl- and 4,13-bis(8-(6A-deoxy-beta-cyclodextrin-6A-yl)aminooctylamidomethyl)-4,13- diaza-1,7,10-trioxacyclopentadecane, 1 and 2, respectively, has been studied in aqueous solution. UV-visible spectrophotometric studies at 298.2 K, pH 10.0 and I = 0.10 mol dm-3 (NEt4ClO4) yielded complexation constants for the complexes 1 x 3(4-) and 2 x 3(4-), K1 = (1.08 +/- 0.01) x 10(5) and (6.21 +/- 0.08) x 10(3) dm3 mol-1, respectively. Similar studies at 298.2 K, pH 10.0 and I = 0.10 mol dm-3 (NaClO4) yielded K3 = (4.63 +/- 0.09) x 10(5) and (3.38 +/- 0.05) x 10(4) dm3 mol-1 for the complexation of 3(4-) by Na+ x 1 and Na+ x 2 to give Na+ x 1 x 3(4-) and Na+ x 2 x 3(4-), respectively. Potentiometric studies of the complexation of Na+ by 1 and 2 by the diazacoronand component of the linkers to give Na+ x 1 and Na+ x 2 yielded K2 = (2.00 +/- 0.05) x 10(3) and (1.8 +/- 0.05) x 10(3) dm3 mol-1, respectively, at 298.2 K and I = 0.10 mol dm-3(NEt4ClO4). For complexation of Na+ by 1 x 3(4-) and 2 x 3(4-) to give Na+ x 1 x 3(4-) and Na+ x 2 x 3(4-) K2K3/K1 = K4 = 8.6 x 10(2) and 9.8 x 10(3) dm3 mol-1, respectively. The pKaS of 1H4(4+) are 7.63 +/- 0.01, 6.84 +/- 0.02, 5.51 +/- 0.04 and 4.98 +/- 0.03, and those of 2H4(4+) are 8.67 +/- 0.02, 8.11 +/- 0.02, 6.06 +/- 0.02 and 5.14 +/- 0.05. The larger magnitude of K1 for 1 by comparison with K1 for 2 is attributed to the octamethylene linkers of 2 competing with 3(4-) for occupancy of the annuli of the beta CD entities while the competitive ability of the dimethylene linkers of 1 is less. A similar argument applies to the relative magnitudes of K3 for Na+ x 1 and Na+ x 2. Increased electrostatic attraction probably accounts for K3 > K1 for Na+ x 1 x 3(4-) and 1 x 3(4-) and for Na+ x 2 x 3(4-) and 2 x 3(4-). The lesser magnitudes of K2 and K4 for Na+ x 1 and Na+ x 1 x 3(4-) compared with those for Na+ x 2 and Na+ x 2 x 3(4-) are attributed to the octamethylene linkers of 2 producing a more hydrophobic environment for the diazacoronand than that produced by the dimethylene linkers of 1. 1H NMR spectroscopic studies and the syntheses of 1 and 2 are described.     

Adsorption of Trivalent Cations on Silica

The temperature effect on the magnitude of adsorption was used to explain the mechanism of adsorption of gadolinium on silica at very low concentrations. Standard enthalpy of adsorption of gadolinium equals 36 kJ mol-1 for a total Gd concentration of 2 x 10(-8) mol dm-3 and 67 kJ mol-1 for 2 x 10(-5) mol dm-3. This result confirms the hypothesis that the Gd adsorption at low initial concentration is governed by formation of strong ternary surface complexes involving anionic impurities. Copyright 1999 Academic Press.     

极谱法测定铑的铑(III)-5-Br-TAMB-CPC配合物新体系及其作用机理的探讨

本文建立了利用Rh(III)-5-Br-TAMB-CP配合物吸附波体系测定铑的电化学分析方法。研究了该体系吸附波的性质及阳离子表面活性剂CPC在体系中的作用机理。该方法灵敏度高, 选择性好, 可用于催化剂中铑的测定。     

Spectrophotometric studies and applications for the determination of yttrium in pure and in nickel base alloys

Yttrium reacts with 5-(4'-chlorophenylazo)-6-hydroxypyrimidine-2,4-dione (I), 5-(2'-bromophenylazo)-6-hydroxypyrimidine-2,4-dione (II), 5-(2',4'-dimethylphenylazo)-6-hydroxypyrimidine-2,4-dione (III), 5-(4'-nitro-2',6'-dichlorophenylazo)-6-hydroxypyrimidine-2,4-dione (IV), 5-(2'-methyl-4'-hydroxyphenylazo)-6-hydroxypyrimidine-2,4-dione (V) to form a dark pink complexes, having an absorption maximum at 610, 577, 596, 567 and 585 nm, respectively. The complex formation was completed spontaneously in theil buffer solution and the resulting complex was stable for at least 3 h after dilution. Under the optimum conditions employed, the molar absorptivities were found to be 1.60 x 10(4), 1.29 x 10(4), 1.96 x 10(4), 1.45 x 10(4) and 1.21 x 10(4) l mol(-1) cm(-1) and the molar ratios were (1:1) and (1:2) (M:L). The linear ranges were found within 95 microg of yttrium in 25 ml solution. One of the characteristics of the complex was its high tolerance for calcium and hence a method of separation and enrichment of microamounts of yttrium by using calcium oxalate precipitate was developed and applied to measure yttrium in nickel-base alloys. Interfering species and their elimination have been studied. The precision and recovery are both satisfactory.     

Amitriptyline-selective plastic membrane sensors and their pharmaceutical applications.

The construction and general performance characteristics of potentiometric amitriptyline-plastic membrane sensors, based on ion-pair complexes with triphenylstilbenylborate and tetra(2-chlorophenyl)borate, respectively, are described. Both electrodes show near-Nernstian responses over the range 1 x 10(-2)-7 x 10(-6) mol dm-3 with a detection limit of about 5 x 10(-6) mol dm-3. The electrodes proved useful in the determination of amitriptyline hydrochloride in pure drug substances and pharmaceutical preparations. They were also applied to the determination of content uniformity and dissolution rate of sugar-coated amitriptyline tablets. The physical processes were numerically simulated by typical equations.     

Amperometric enzyme electrode for theophylline.

An amperometric biosensor for theophylline, based on the recently isolated enzyme theophylline oxidase, is described. The enzyme is entrapped, together with a ferricytochrome C cofactor, within a polymeric (Nafion) coating. The anodic detection (at +0.4 V versus Ag-AgCl) is facilitated by the addition of a redox-mediating hexacyanoferrate(III) ion. The influence of various experimental variables is described. The limit of detection is 2 x 10(-6) mol dm-3 theophylline, with linearity prevailing up to 3 x 10(-4) mol dm-3. The fast response and wash times permit rapid flow-injection measurements, with a frequency of 180 samples h-1 and a relative standard deviation of 3.0-4.0%. Prospects of using this electrode for clinical diagnostics are discussed.