4-(N,N-diethylamino) benzaldehyde thiosemicarbazone in the spectrophotometric determination of palladium

4-(N,N-diethylamino)benzaldehyde thiosemicarbazone(DEABT) is proposed as a sensitive and selective analytical reagent for the spectrophotometric determination of palladium(II). The reagent reacts with palladium (II) in a potassium hydrogen phthalate-hydrochloric acid buffer of pH 3.0, to form a yellow complex. Beer's law is obeyed in the concentration range up to 3.60 microgmL(-1). The optimum concentration range for minimum photometric error as determined by Ringbom plot method is 0.36 - 3.24 microg mL(-1). The yellow Pd(II)-DEABT complex shows a maximum absorbance at 408 nm, with molar absorptivity of 3.33 x 10(4) dm3 mol(-1) cm(-1) and Sandell's sensitivity of the complex from Beer's data, for D = 0.001, is 0.0032 microg cm(-2). The composition of the Pd(II)-DEABT complex is found to be 1:2 (M:L). The interference of various cations and anions in the method were studied. The proposed method was successfully used for the determination of Pd(II) in alloys, catalysts, complexes and model mixtures with a fair degree of accuracy.     

Highly sensitive extractive spectrophotometric determination of palladium(II) in synthetic mixtures and hydrogenation catalysts using benzildithiosemicarbazone.

A simple and highly sensitive method was developed for the extractive-spectrophotometric determination of palladium with benzilidithiosemicarbazone. The metal ion formed a reddish brown complex with benzildithiosemicarbazone in a potassium chloride-hydrochloric acid buffer of pH 2.5, which was easily extractable into methyl isobutyl ketone. The 1:1 complex showed the maximum absorbance at 395 nm with a Beer's law range of 0.25-3.5 ppm. The molar absorptivity and Sandell's sensitivity were found to be 3.018 x 10(4) dm3 mol(-1) cm(-1) and 0.0035 microg cm(-2), respectively. The correlation coefficient of the Pd(II)-BDTSC complex was 0.998, which indicated an excellent linearity between the two variables. The repeatability of the method was checked by finding the relative standard deviation (RSD) (n = 10), which was 0.46%. The instability constant of the complex calculated from Edmond and Birnbaum's method was 2.41 x 10(-5), that of Asmus' method is 2.53 x 10(-5) at room temperature. The interfering effects of various cations and anions were studied. The proposed method was successfully applied to the determination of palladium(II) in synthetic mixtures and hydrogenation catalysts. The validity of the method was tested by comparing the results with those obtained using an atomic absorption spectrophotometer.     

Determination of palladium with thiocyanate and rhodamine b by a solvent-extraction method

Sensitive spectrophotometric and spectrofluorimetric procedures for the determination of palladium have been developed, based on solvent-extraction of the ion-pair formed between Rhodamine B and the anionic complex of Pd(II) with thiocyanate. With an organic to aqueous phase-volume ratio of 1:5, the molar absorptivity is 9.0 x 10(4) l.mole(-1).cm(-1) and the absorbance of the reagent blank is 0.026. Spectrophotometrically, palladium can be determined in the range 0.1-8.8 mug. Spectrofluorimetrically, it can be determined over the range 0.04-1.5 mug. The spectrophotometric procedure has been applied to the determination of palladium in dental alloys, organopalladium compounds and hydrogenation catalysts.     

A new selective chromogenic reagent for the spectrophotometric determination of thallium(I) and (III) and its separation using flotation and the solid-phase extraction on polyurethane foam.

A new sensitive chromogenic reagent, 9,10-phenanthaquinone monoethylthiosemicarbazone (PET), has been synthesized and used in the spectrophotometric determination of Tl(III). In HNO3, H2SO4 or H3PO4 acids, PET can react immediately at room temperature with Tl(III) to form a red 2:1 complex with a maximum absorption at 516 nm. The different analytical parameters affecting the extraction and determination processes have been examined. The calibration curve was found to be linear over the range 0.2-10 microg cm(-3) with a molar absorptivity of 2.2 x 10(4) dm3 mol(-1) cm(-1). Sandell's sensitivity was found to be 0.0093 microg cm(-2). No interference from macroamounts of foreign ions was detected, except for Pd(II). However, Pd(II) does not affect the determination process, because its complex with PET has its lambda(max) at 625 nm. The proposed method has been applied to the determination of Tl(I and III) in synthetic and natural samples after separation by flotation (in oleic acid/kerosene) and solid-phase extraction (on polyurethane foam) techniques. The two methods were found to be accurate and not subject to random error, but solid-phase extraction was preferred because it is cheap, simpler and there is no contamination risk coming from flotation reagents.     

Extractive spectrophotometric determination of Cobalt(II) in synthetic and pharmaceutical samples using Cyanex 923.

Cyanex 923 has been proposed as a sensitive analytical reagent for the direct extractive spectrophotometric determination of cobalt(II). Cobalt(II) forms a blue-colored complex with Cyanex 923 in the organic phase. The maximum absorbance of the complex is measured at 635 nm. Beer's law was obeyed in the range 58.9 - 589.0 microg of cobalt. The molar absorptivitiy and Sandell's sensitivity of the complex was calculated to be 6.79 x 10920 l mol(-1) cm(-1) and 0.088 microg cm(-2), respectively. The nature of the extracted species was found to be Co(SCN)2 x 2S. An excellent linearity with a correlation coefficient value of 0.999 was obtained for the Co(II)-Cyanex 923 complex. Stability and regeneration of the reagent (Cyanex 923) for reuse is the main advantage of the present method. The method was successfully applied to the determination of cobalt in synthetic mixtures and pharmaceutical samples was found to give values close to the actual ones. Standard alloy samples, such as high-speed tool BCS 484 and 485, have been tested for the determination of cobalt for the purpose of validating the present method. The results of the proposed method are comparable with atomic absorption spectrometry and were found to be in good agreement.     

Synthesis of N-o-methylphenyl-N'-(sodium p-aminobenzene-sulfonate) thiourea and its chromogenic reaction with palladium(II).

A new chromogenic reagent, N-o-methylphenyl-N'-(sodium p-aminobenzenesulfonate)thiourea (MSAT), has been synthesized and characterized by elemental analysis, (1)H-NMR, FT-IR and UV-Vis spectra. Based on the absorption spectrum of the colored complex of MSAT with palladium(II), a novel spectrophotometric method for the determination of palladium has been developed. In a pH 4.0 - 5.5 HAc-NaAc buffer solution, palladium(II) reacted with MSAT to form a stable yellow water-soluble complex with an apparent molar absorptivity of epsilon = 2.04 x 10(5) L mol(-1) cm(-1) at the maximum absorption of 318.0 nm. Beer's law was obeyed in the concentration range of 1.2 - 11.8 microg per 25 mL for palladium(II) with a correlation coefficient of 0.9997. The probable interfering ions and their tolerable limits have also been investigated in detail. The proposed method is simple, rapid, and sensitive, and has been applied to the determination of palladium in anode mud and ore samples with satisfactory results.     

Synthesis of 5-(5-nitro-2-pyridylazo)-2,4-diaminotoluene and its application to spectrophotometric determination of microamounts of palladium

A new pyridylazo reagent, 5-(5-nitro-2-pyridylazo)-2,4-diaminotoluene (5-NO(2)-PADAT) has been synthesized, and found to be a good chromogenic reagent for palladium. In sulfuric acid, hydrochloric acid and perchloric acid palladium reacts with 5-NO(2)-PADAT to form a 1:1 chelate, exhibiting an absorption maximum at 592 nm. The apparent molar absorptivity is 1.25 x 10(5) l(-1) mol(-1) cm(-1). Beer's law was obeyed in the range 0-0.9 microg ml(-1) Pd. Relatively large amounts of co-existing elements, including all other noble metals, can be tolerated. The method is simple and rapid, with high sensitivity and good selectivity and was applied to the determination of palladium in some industrial samples with satisfactory results.     

Complexometric determination of palladium(II) using thioacetamide as a selective masking agent

A simple, rapid and accurate complexometric method for the determination of palladium(II) is proposed, based on the selective masking property of thioacetamide towards palladium(II). In the presence of diverse metal ions, palladium(II) is complexed with excess of EDTA and the surplus EDTA is back titrated at pH 5-5.5 (acetic acid-sodium acetate buffer) with standard lead nitrate solution using xylenol orange as indicator. An excess of a 0.5% aqueous solution of thioacetamide is then added to displace EDTA from Pd(II)-EDTA complex. The released EDTA is titrated with the same standard lead nitrate solution as before. Reproducible and accurate results are obtained in the concentration range 0.5 mg - 17.80 mg of palladium with relative error of +/- 0.16% and coefficient of variation not exceeding 0.26%. The effect of diverse ions is studied. The method is used for the determination of palladium in its complexes, catalysts and synthetic alloy mixtures.     

A simple spectrophotometric method for the determination of copper in industrial, environmental, biological and soil samples using 2,5-dimercapto-1,3,4-thiadiazole.

A simple spectrophotometric method is presented for the rapid determination of copper at a trace level using 2,5-dimercapto-1,3,4-thiadiazole (DMTD) as a new spectrophotometric reagent. The method is based on the reaction of non-absorbent DMTD in a slightly acidic (0.002-0.014 mol dm(-3) sulfuric acid) aqueous solution with copper(II) to produce a highly absorbent greenish-yellow chelate product that has an absorption maximum at 390 nm. The reaction is instantaneous and the absorbance remains stable for 24 h. The average molar absorption coefficient and Sandell's sensitivity were found to be 5.65 x 10(4) dm3 mol(-1) cm(-1) and 10 ng cm(-2) of CuII, respectively. Linear calibration graphs were obtained for 0.1-20 microg cm(-3) of CuII; the stoichiometric composition of the chelate is 1:2 (Cu:DMTD). A large excess of over 50 cations, anions and complexing agents (e.g. tartrate, oxalate, citrate, phosphate, thiourea, SCN-) do not interfere in the determination. The method was successfully used for the determination of copper in several Standard Reference Materials as well as in some environmental water samples, biological samples, soil samples and solutions containing both copper(I) and copper(II) and complex synthetic mixtures. The method has high precision and accuracy (s = +/-0.01 for 0.5 microg cm(-1)).     

Isonitroso-4-Methyl-2-Pentanone for Solvent Extraction and Spectrophotometric Determination of Palladium (II) at Trace Level

Abstract

Isonitroso-4-methyl-2-pentanone (HIMP) is proposed as a new reagent for extraction and photometric determination of Pd(II). The reagent forms a yellow complex with palladium in the pH range 4.0-5.0. The complex extracted into chloroform was measured at 330 nm. The molar absorptivity was found to be 5.37 × 10³ 1 mol^?1 cm^?1 and Sandell's sensitivity 20 ng cm^?2 Beer's law was obeyed over the concentration range 0.1-10.0 μg/ml of palladium. The method is applicable for palladium estimation in Ores and catalysts.     

Extraction and spectrophotometric determination of Pd(II) with 3,4,4a,5-tetrahydro-3,3,4a-trimethyl-7-(substituted)-pyrimido(1,6-a)-benzimidazole-1-thiol (PBT)

A method for the extraction-spectrophotometric determination of palladium with 3,4,4a,5-tetrahydro-3,3,4a-trimethyl-7-(substituted)-pyrimido(1,6-a)benzimidazole-1-thiol (PBT) is described. PBT-Pd(II) complex is extracted from an acidic aqueous solution (0.01-0.5M HClO(4)) into a chloroform layer. The absorbance is measured at 438 nm and the molar absorptivity found to be 1.033 x 10(4)M(-1) cm(-1). The complex system conforms to Beer's law over the range 1.9-28.5 mug/ml palladium(II). The effects of pH (2-6), HClO(4) concentration, PBT concentration and shaking time were studied. The ratio of metal ion to ligand molecules in the coloured complex was found to be 1:4. The tolerance limit for many metals have been determined. Finally, the method has been applied successfully to the determination of palladium in synthetic mixtures and in the standard palladium carbon powder (palladium catalyst).     

A rapid and sensitive extractive spectrophotometric determination of copper(II) in pharmaceutical and environmental samples using benzildithiosemicarbazone.

Benzildithiosemicarbazone (BDTSC) is proposed as a sensitive and selective analytical reagent for the extractive spectrophotometric determination of copper(II). BDTSC reacts with copper(II) in the pH range 1.0-7.0 to form a yellowish complex. Beer's law is obeyed in the concentration range 0.5-0.4 microg cm(-3). The yellowish Cu(II)-BDTSC complex in chloroform shows a maximum absorbance at 380 nm, with molar absorptivity and Sandell's sensitivity values of 1.63 x 10(4) dm3 mol(-1) cm(-1) and 0.00389 microg cm(-2), respectively. A repetition of the method is checked by finding the relative standard deviation (RSD) (n = 10), which is 0.6%. The composition of the Cu(II)-BDTSC complex is established as 1:1 by slope analysis, molar ratio and Asmus' methods. An excellent linearity with a correlation coefficient value of 0.98 is obtained for the Cu(II)-BDTSC complex. The instability constant of the complex calculated from Edmond and Birnbaum's method is 7.70 x 10(-4) and that of Asmus' method is 7.66 x 10(-4), at room temperature. The method is successfully employed for the determination copper(II) in pharmaceutical and environmental samples. The reliability of the method is assured by analyzing the standard alloys (BCS 5g, 10g, 19e, 78, 32a, 207 and 179) and by inter-comparison of experimental values, using an atomic absorption spectrometer.     

Synthesis of palladium nanoparticles by sonochemical reduction of palladium(II) nitrate in aqueous solution

The sonochemical synthesis of stable palladium nanoparticles has been achieved by ultrasonic irradiation of palladium(II) nitrate solution. The starting solutions were prepared by the addition of different concentrations of palladium(II) nitrate in ethylene glycol and poly(vinylpyrrolidone) (PVP). The resulting mixtures were irradiated with ultrasonic 50 kHz waves in a glass vessel for 180 min. The UV-visible absorption spectroscopy and pH measurements revealed that the reduction of Pd(II) to metallic Pd has been successfully achieved and that the obtained suspensions have a long shelf life. The protective effect of PVP was studied using Fourier transform infrared (FT-IR) spectroscopy. It has been found that, in the presence of ethylene glycol, the stabilization of the nanoparticles results from the adsorption of the PVP chain on the palladium particle surface via the coordination of the PVP carbonyl group to the palladium atoms. The effect of the initial Pd(II) concentration on the Pd nanoparticle morphology has been investigated by transmission electron microscopy. It has been shown that the increase of the Pd(II)/PVP molar ratio from 0.13 x 10(-3) to 0.53 x 10(-3) decreases the number of palladium nanoparticles with a slight increase in particle size. For the highest Pd(II)/PVP value, 0.53 x 10(-3), the reduction reaction leads to the unexpected smallest nanoparticles in the form of aggregates.     

Spectrophotometric determination of palladium after solid-liquid extraction with 1-(2-Pyridylazo)-2-naphthol at 90 degrees C

An effective spectrophotometric determination of palladium with 1-(2-pyridylazo)-2-naphthol (PAN) using molten naphthalene as a diluent has been studied. A green complex of palladium with PAN is formed at 90 degrees C. In the range of pH 1.5-7.5, the complex is quantitatively extracted into molten naphthalene. The organic phase is anhydrously dissolved in CHCl(3) to be determined spectrophotometrically at 678 nm against the reagent blank. Beer's law is obeyed over the concentration range of 0.5-10 ppm. The molar absorptivity and Sandell's sensitivity are 1.2 x 10(4) l mol(-1) cm(-1) and 0.0070 mg cm(-2), respectively. The optimum conditions for determination are obtained. The interferences of various ions are observed in detail. The method has been applied to the determination of palladium in synthetic samples.     

Quinoline-2-aldehyde thiosemicarbazone (QAT) as spectrophotometric reagent for palladium and nickel

A procedure is described for the extractive spectrophotometric determination of nickel and palladium with quinoline-2-aldehyde thiosemicarbazone. At pH 7.5 nickel forms a 1:2 complex which is soluble in chloroform and has an absorption maximum at 460 nm. Palladium forms a 1:2 complex with maximum absorbance at 510 nm which can be extracted into MIBK from 1M HCl. Both complexes are stable and conform to Beer's law. The molar absorptivities for nickel and palladium are 1.58 x 10(4) and 2.6 x 10(3) 1.mole(-1). cm(-1) respectively. The proposed method is suitable for detection and determination of nickel and palladium in the presence of associated metal ions. The results of the analysis of synthetic mixtures and standard samples are reported.     

Spectrophotometric determination of palladium with 5,6-dimethyl-1,3-indanedione-2-oxime

A rapid, sensitive and selective method has been developed for the determination of palladium with 5,6-dimethyl-1,3-indanedione-2-oxime in acetate buffer (pH 5.5). Beer's law is obeyed over the range 0.15-4.17 mug/ml palladium(II). The molar absorptivity at 370 nm is 2.98 x 10(4) 1.mole(-1).cm(-1). The method has been applied for the determination of palladium in synthetic mixtures corresponding to PtIr and Oakay alloys. An interesting feature of the system is the abnormal shape of the Job and molar-ratio plots obtained.     

The surfactant sensitized analytical reaction of cerium(IV) with some triphenylformazan derivatives

Cationic surfactant, cetylpyridinium bromide (CPB), sensitizes the colour reaction of cerium(IV) with 1,3-o-hydroxyphenyl-5-phenylformazan(I), 1-m-hydroxyphenyl-3-o-hydroxyphenyl-5-phenylformazan(II) and 1-m-carboxyphenyl-3-o-hydroxyphenyl-5-phenylformazan(III). The formation of a soluble ternary complex of stoichiometric ratio 1:1:1 (Ce(IV)-R-CPB) is responsible for the observed enhancement in the molar absorptivity and Sandell sensitivity of the formed complex, when a surfactant is present. The ternary complex exhibits absorption maxima at 596, 571 and 607 nm (epsilon=6.05 x 10(4), 6.28 x 10(4) and 8.06 x 10(4)L mol(-1)cm(-1)) using triphenylformazan derivatives I, II and III, respectively. Beer's law is obeyed between 0.15 and 2.5 microg ml(-1), whereas, optimum concentration range applying Ringbom method is in the range 0.30-2.25 microg ml(-1). Conditional formation constants in the presence and absence of CPB for Ce(IV) complexes have been calculated. The proposed method has been successfully applied to the analysis of magnesium-base cerium alloys and synthetic mixtures corresponding to various cerium alloys.     

Synthesis and catalytic application of Pd complex catalysts: Atom‐efficient cross‐coupling of triarylbismuthines with haloarenes and acid chlorides under mild conditions

Palladium‐catalysed cross‐coupling reactions are some of the most frequently used synthetic tools for the construction of new carbon–carbon bonds in organic synthesis. In the work presented, Pd(II) complex catalysts were synthesized from palladium chloride and nitrogen donor ligands as the precursors. Infrared and ¹H NMR spectroscopic analyses showed that the palladium complexes were formed in the bidentate mode to the palladium centre. The resultant Pd(II) complexes were tested as catalysts for the coupling of organobismuth(III) compounds with aryl and acid halides leading to excellent yields with high turnover frequency values. The catalysts were stable under the reaction conditions and no degradation was noticed even at 150°C for one of the catalysts. The reaction proceeds via an aryl palladium complex formed by transmetallation reaction between catalyst and Ar₃Bi. The whole synthetic transformation has high atom economy as all three aryl groups attached to bismuth are efficiently transferred to the electrophilic partner.     

Simple and Simultaneous Method for Determination of Palladium(II) and Ruthenium(III) using Second-Order-Derivative Spectrophotometry

Abstract

A simple, sensitive, and selective second-order-derivative spectrophotometric method has been developed for the simultaneous determination of palladium(II) and ruthenium(III) using 2-hydroxy-3-methoxy benzaldehyde thiosemicarbazone (HMBATSC) as a chromophoric reagent. The reagent (HMBATSC) reacts with Pd(II) and Ru(III) at pH 3.0, forming soluble yellowish green and dark brown species, respectively. Palladium and ruthenium present in the mixture were simultaneously determined without solving the simultaneous equations by measuring the second derivative amplitudes at 445 nm and 385 nm, respectively. Further, the Beer's law was obeyed in the range 0.21–12.78 µg mL^?1 and 0.25–13.42 µg mL^?1 for Pd(II) and Ru(III), respectively. A large number of foreign ions did not interfere in the present method. The proposed method was successfully applied for the determination of palladium in hydrogenation catalysts and ruthenium in water samples.     

Preparation of palladium clusters protected by silica-supported,crosslinking, partially phosphorylated poly(vinyl alcohol) and their catalytic activity

The palladium cluster protected by silica-supported, crosslinking, partially phosphorylated poly(vinyl alcohol) (P-PVA) was prepared from a crosslinking P-PVA–Pd(II) complex by reduction in alcohol. The P-PVA–Pd complex and the palladium cluster protected by P-PVA were analyzed by electron spectroscopy, X-ray photoelectron spectrometry and transmission electron microscopy. The complex formation between the Pd(II) ion and phosphoric acid groups in P-PVA was important in the formation of a fine palladium cluster. Palladium clusters protected by silica-supported crosslinking P-PVA were used as catalysts for the hydrogenation of nitrobenzene or acrylic acid at 30°C under atmospheric pressure. The palladium cluster protected by crosslinking P-PVA supported on silica was the most active catalyst, was stable and had no by-products, compared with the palladium cluster protected by silica-supported noncrosslinking P-PVA or PVA.