Separation of gold, palladium and platinum from metallurgical samples using an amberlite XAD-7 resin column prior to their atomic absorption spectrometric determinations.

A simple and sensitive method for the separation and preconcentration of gold, palladium and platinum has been established prior to their atomic absorption spectrometric determinations. Analytes from 0.5 mol dm(-3) KI in a 2 mol dm(-3) HCl solution were recovered using an Amberlite XAD-7 column as halogeno complexes. The effects of some analytical parameters, including reagent amounts, sample volume and flow rates, on the quantitative recoveries of gold, palladium and platinum were investigated. The influences of some diverse ions were also studied. The proposed method has been applied for the preconcentration and separation of analytes from pure copper and anodic slime samples with satisfactory results (recoveries > 95%, relative standard deviations < 9.0%, relative error < or = 5%).     

Preconcentration of silver(I), gold(III) and palladium(II) in sea water with p-dimethylaminobenzylidenerhodanine supported on silica gel

A water-insoluble chelating material, p-dimethylaminobenzylidenerhodanine on silica gel (DMABR—SG) is described for preconcentration of trace amounts of silver(I), gold(III) and palladium(II) from water samples. Radioactive tracers (^110mAg and ¹⁹⁵Au) were used to study the behavior of silver and gold; palladium was monitored spectrophotometrically as its 1-(2-pyridylazo)naphthol complex in chloroform. In batch experiments, silver was quantitatively retained on the DMABR—SG at acidities ranging from 1.7 M to pH 5, and gold from 3 M to pH 5; equilibrium was achieved within 1 min for both elements. From sea water, silver ion was completely retained at pH 1.0–6.5 and gold ion at pH 1.0–3.5. In the case of palladium, shaking for about 20 min was required for quantitative retention at pH 1.0–5.0 for aqueous solution and at pH 1.0–7.0 for sea water. The chelating capacity of the DMABR—SG was 23 μmol Ag, 11 μmol Au and 11 μmol Pd per g. Quantitative recovery of silver and gold on DMABR—SG columns from sea water was achieved at higher flow rates (1–2 l h^-1 and 2–3 l h^-1, respectively) than with other chelating resins, e.g., Chelex 100, palladium required slower flow rate (150 ml h^-1). Silver retained on the DMABR—SG column was completely eluted with 20 ml of 2.5% sodium thiosulfate solution but palladium remained on the column. Silver, gold and palladium were quantitatively eluted with 20 ml of 0.1% thiourea in 0.1 M hydrochloric acid.     

Synthesis of amidinothioureido-silica gel and its application to flame atomic absorption spectrometric determination of silver, gold and palladium with on-line preconcentration and separation

A simple and highly selective flow injection (FI) on-line preconcentration and separation flame atomic absorption spectrometric (FAAS) method was developed for the determinations of trace amounts of silver, gold and palladium. The selective preconcentration of the noble metals was achieved in a wide range of sample acidity (0.1-6 M HNO₃ or HCl) on a microcolumn packed with amidinothioureido-silica gel (ATuSG). The analytes retained on the column were effectively eluted with 5.0% thiourea solution. The analytical procedure was optimized for sample acidity, elution, interferences, flow rate of sampling and eluting, and concentration of sample. Common co-existing cations and anions did not interfere with the preconcentration and determination of the three metals. At a sample loading flow rate of 4.5 ml min⁻¹ with 60 s preconcentration, detection limits (3σ) of 1.1 ng ml⁻¹ Ag, 13 ng ml⁻¹ Au and 17 ng ml⁻¹ Pd were obtained. The precisions (R.S.D., n=11) were 1.2% for Ag, 1.2% for Au and 1.7% for Pd, respectively. The detection limits can be further improved by increasing sample volume. The analytical results obtained by the proposed method for a number of standard reference materials were in good agreement with the certified values.     

Determination of gold,palladium and copper by flame atomic absorption spectrometry after preconcentration on silica gel modified with 3-(2-aminoethylamino)propyl group

A preconcentration method of gold, palladium and copper based on the sorption of Au (III), Pd (II) and Cu (II) ions on a column packed with 3-(2-aminoethylamino)propyl bonded silica gel is described. The modified silica gel was synthesized and characterized by FT-IR and C, H, N elemental analysis. At column preconcentration, the effects of parameters such as pH, volume, flow rate, matrix constituents of solutions and type of eluent on preconcentration of gold, palladium and copper were studied. The recoveries of Au (III), Pd (II) and Cu (II) were 98.93±0.51, 98.81±0.36 and 99.21±0.42 % at 95 % confidence level, respectively. The detection limits (δ) of the elements were 0.032, 0.016 and 0.012 μg ml⁻¹, respectively. The preconcentration method was applied for determination of gold and palladium in certified reference material SARM 7B and copper in river and synthetic seawater by FAAS. Gold, palladium and copper were determined with relative error lower than 10 %.     

Adsorption behavior of noble metal ions (Au, Ag, Pd) on nanometer-size titanium dioxide with ICP-AES.

The adsorption behavior of gold (Au), silver (Ag) and palladium (Pd) on nanometer-size titanium dioxide (NSTD) at low concentrations was studied using inductively coupled plasma atomic emission spectrometry (ICP-AES). A preconcentration procedure of the analytes was carried out using NSTD as a solid-phase extractant before their determination by ICP-AES. The optimum conditions for adsorption were studied in detail, and under the condition that Au, Ag and Pd ions could be adsorbed and recovered quantitatively. The static adsorption capacities of Au, Ag and Pd on NSTD were 22.63, 14.06 and 11.82 mg/g, respectively. For the elution of gold, silver and palladium, a mixture of 5% thiourea solution and 3 mol L(-1) HNO3 was used. The parameters tested included: pH conditions, contact time of the analytes with NSTD, flow rate, adsorption capacity and sorption kinetics. According to the definition of IUPAC, the detection limits (3sigma) of this method for Au, Ag and Pd with an enrichment factor of 50 were (0.016), (0.006) and (0.012) microg mL(-1), respectively, the relative standard deviations (RSD) were 8.7%, 4.5% and 7.4%, respectively (n = 6). Some geological samples were determined with satisfactory results.     

Determination of trace amounts of gold and silver in high-purity iron and steel by electrothermal atomic absorption spectrometry after reductive coprecipitation

Trace amounts of gold and silver in high-purity iron or steel were preconcentrated by reductive coprecipitation with palladium using ascorbic acid, and determined by electrothermal atomic absorption spectrometry (ET-AAS). Both gold and silver could be simultaneously separated and sensitively determined in 10 metals (aluminum, cobalt, chromium, copper, iron, manganese, molybdenum, nickel, vanadium and zinc). Comparable values were obtained for gold and silver in reference materials (low alloy steel) by the proposed method and a non-separation method; good agreement was found between the analytical values by both methods and the certified values. The proposed method is easy, simple and not dependent on sample composition and content. Moreover, gold and silver in metal samples could be simultaneously separated together with selenium and tellurium. The detection limits for gold and silver (3 σ) are 0.003 μg g^–1 and 0.002 μg g^–1, respectively. Received: 3 February 2000 / Revised: 11 April 2000 / Accepted: 16 April 2000     

Determination of trace amounts of gold and silver in high-purity iron and steel by electrothermal atomic absorption spectrometry after reductive coprecipitation

Trace amounts of gold and silver in high-purity iron or steel were preconcentrated by reductive coprecipitation with palladium using ascorbic acid, and determined by electrothermal atomic absorption spectrometry (ET-AAS). Both gold and silver could be simultaneously separated and sensitively determined in 10 metals (aluminum, cobalt, chromium, copper, iron, manganese, molybdenum, nickel, vanadium and zinc). Comparable values were obtained for gold and silver in reference materials (low alloy steel) by the proposed method and a non-separation method; good agreement was found between the analytical values by both methods and the certified values. The proposed method is easy, simple and not dependent on sample composition and content. Moreover, gold and silver in metal samples could be simultaneously separated together with selenium and tellurium. The detection limits for gold and silver (3 σ) are 0.003 μg g^–1 and 0.002 μg g^–1, respectively. Received: 3 February 2000 / Revised: 11 April 2000 / Accepted: 16 April 2000     

Quantitative evaluation main of the components in Paeoniae Radix Alba–Atractylodis Macrocephalae Rhizoma herbal pair by high‐performance liquid chromatography

The aim of this study was to investigate the influence of compatibility on the contents of main compounds in Paeoniae Radix Alba and Atractylodis Macrocephalae Rhizoma. Ten compounds were separated on an Inertsil ODS‐SP Extend C₁₈ column (250 mm × 4.6 mm, 5 μm) and detected by a diode array detector with the mobile phase consisting of aqueous phosphoric acid (0.1%, v/v; A) and acetonitrile (B) by linear gradient elution. All analytes showed good linearity over a wide concentration range (r² ≥ 0.9989). The limits of detection and quantification were <8.10 and 10.80 μg/mL, respectively. The intra‐ and interday variations were <4.36%. The average recoveries were observed from 94.90 to 103.38%, with relative standard deviation ranging from 1.23 to 3.15% for the analytes. The established method was reliable enough for global quality evaluation of Paeoniae Radix Alba, Atractylodis Macrocephalae Rhizoma, and their co‐decoctions.     

Transition metal nanoparticles protected by amphiphilic block copolymers as tailored catalyst systems

 Several stable palladium, platinum, silver, and gold colloids were prepared by reducing the corresponding metal precursors in the presence of protective amphiphilic block copolymers. Some palladium and platinum precursors with different hydrophobicities, namely palladium chloride PdCl₂, palladium acetate Pd (CH₃COO)₂, hexachloroplatinic acid H₂PtCl₆, and platinum acetylacetonate Pt (CH₃COCH=C(O–)CH₃)₂, have been used in order to investigate differences in their catalytic activity. The polymers investigated for their ability to stabilize such transition metal colloids were polystyrene-b-poly(ethylene oxide) and polystyrene-b-poly(methacrylic acid). The metal particle sizes and morphologies were determined by transmission electron microscopy and found to be in the M28.8nnanometer range. The catalytic activity of the palladium and platinum colloids was tested by the hydrogenation of cyclohexene as a model reaction. The protected palladium and platinum nanoparticles were found to be catalytically active, and final conversions up to 100% cyclohexane could be obtained. Depending on the choice of polymer block types and lengths, the precursor type, and the reduction method, different nanoparticle morphologies and catalytic activities could be obtained. These novel catalytically active metal–polymer systems are thus promising candidates for the development of tailored catalyst systems. Received: 10 June 1996 Accepted: 30 October 1996     

Trace Enrichment and Atomic Absorption Spectrometric Determination of Lead,Copper, Cadmium and Nickel in Drinking Water Samples by Use of an Activated Carbon Column

Abstract

A simple method for atomic absorption spectrometric determination of lead, copper, cadmium and nickel in drinking water samples after preconcentration by sorbing 1-(2-pyridylazo) 2-naphthol (PAN) complex of these metals on an activated carbon column has been established. The metal/PAN complexes were quantitatively retained on the activated carbon in the pH range 6-8. Metals retained on the activated carbon column were completely eluted with 2M HCl in acetone. This method was applied to the determination of lead, copper, cadmium and nickel in drinking water samples and good results were obtained (Recoveries >95%, relative standard deviations <7%, relative error <3%).     

火试金减杂-电感耦合等离子体原子发射光谱法（ICP-AES）法测定高冰镍的金、银、铂、钯含量

建立了火试金减杂-电感耦合等离子体原子发射光谱法（ICP-AES）测定高冰镍中金、银、铂、钯含量的分析方法。实验采用火试金富集、熔融、灰吹得到合粒,通过减杂法得到银含量,通过ICP-AES法测定得到金、铂、钯含量。金、银、铂、钯的加标回收率在99.53%-101.83%之间,相对标准偏差小于3%。此方法快速、简洁,准确度高、精密度好,能够满足高冰镍的测定需求。     

Modified analcime loaded with zincon as a useful material for the separation and preconcentration of trace palladium and its determination by third-derivative spectrophotometry

This work assesses the potential of natural analcime zeolite as a sorbent for the preconcentration of palladium. Palladium is quantitatively retained on modified analcime zeolite loaded with zincon using the column method in the pH range from 2.5 to 3.5 at a flow rate of 1 mL/min. The palladium complex was removed from the column with 5.0 mL of dimethylsulfoxide (DMSO) and determined by third-derivative spectrophotometry. The detection limit is 0.03 μg/mL (signal-to-noise ratio = 3) in the final solution. Since it is possible to retain 0.15 μg of palladium from 600 mL of solution passing through the column, elution with 5.0 mL of DMSO gives a detection limit of 0.25 ng/mL for palladium in the initial aqueous solution. The calibration curve is linear over the range 0.1 to 5.0 μg/mL of palladium(II) in the final solution with a correlation coefficient of 0.9996. Seven replicated determinations of 5.0 μg of palladium in 5.0 mL dimethylsulfoxide gave a mean d ³ A/dλ³ (peak-to-peak signal between λ₂ = 625 and λ₁ = 654 nm) of 0.64 with a relative standard deviation of 1.2%. The sensitivity of the method (d ³ A/dλ³) is 0.5843 mL/μg of palladium(II) from the slope of the calibration curve. The interference of a large number of anions and cations has been studied and the optimized conditions developed were utilized for the determination of trace palladium in various synthetic and water samples. The text was submitted by the authors in English.     

Use of fractional factorial design for optimization of digestion procedures followed by multi-element determination of essential and non-essential elements in nuts using ICP-OES technique

Two digestion procedures have been tested on nut samples for application in the determination of essential (Cr, Cu, Fe, Mg, Mn, Zn) and non-essential (Al, Ba, Cd, Pb) elements by inductively coupled plasma-optical emission spectrometry (ICP-OES). These included wet digestions with HNO₃/H₂SO₄ and HNO₃/H₂SO₄/H₂O₂. The later one is recommended for better analytes recoveries (relative error < 11%). Two calibrations (aqueous standard and standard addition) procedures were studied and proved that standard addition was preferable for all analytes. Experimental designs for seven factors (HNO₃, H₂SO₄ and H₂O₂ volumes, digestion time, pre-digestion time, temperature of the hot plate and sample weight) were used for optimization of sample digestion procedures. For this purpose Plackett-Burman fractional factorial design, which involve eight experiments was adopted. The factors HNO₃ and H₂O₂ volume, and the digestion time were found to be the most important parameters. The instrumental conditions were also optimized (using peanut matrix rather than aqueous standard solutions) considering radio-frequency (rf) incident power, nebulizer argon gas flow rate and sample uptake flow rate. The analytical performance, such as limits of detection (LOD < 0.74 μg g⁻¹), precision of the overall procedures (relative standard deviation between 2.0 and 8.2%) and accuracy (relative errors between 0.4 and 11%) were assessed statistically to evaluate the developed analytical procedures. The good agreement between measured and certified values for all analytes (relative error <11%) with respect to IAEA-331 (spinach leaves) and IAEA-359 (cabbage) indicates that the developed analytical method is well suited for further studies on the fate of major elements in nuts and possibly similar matrices.     

Solid-Phase Microextraction of Aliphatic Alcohols Based on Polyaniline Coated Fibers

The efficiency of polyaniline (PANI), coated gold wire was investigated for use as a fiber for solid-phase microextraction (SPME). Aniline monomers were electropolymerized on gold wires by applying a constant current to an acetate buffer containing NaClO₄ as supporting electrolyte for 30 min. These fibers were used for the extraction of some aliphatic alcohols from gaseous samples. The results obtained proved the ability of PANI fiber for sampling organic compounds from gaseous samples. From this work, optimum conditions for preparation and conditioning of fibers and for the extraction of analytes from gaseous samples were obtained. Under optimum conditions, one fiber was used for several equivalent analyses and the relative standard deviations (RSD) were <7% (n=6). However, fiber to fiber reproducibility was <9% (n=6). This fiber is firm and durable and is simply prepared. Calibration graphs were linear in the range: 0.1–10 g mL^–1 for aliphatic alcohols; the detection limit range was 15–75 ng mL^–1 (S/N=3) using a flame ionization detector.     

Sorption of silver,gold and palladium with a polythioether foam

Silver, gold and palladium can be sorbed by a thiopolymer of the type [HO(CH₂CH₂CH₂SS)_nCH₂CH₂OH]. The distribution coefficient for palladium increases with halide concentration, with iodide having the largest effect. Silver can be extracted from chloride, nitrate or picrate media. The different distribution coefficients for gold in hydrochloric acid and in sodium chloride suggest that different sorption mechanisms predominate.     

Simultaneous Determination of the Endogenous Free ��-Lipoic Acid and Dihydrolipoic Acid in Human Plasma and Erythrocytes by RP-HPLC with Electrochemical Detection

A highly sensitive, precise, and accurate reversed-phase high-performance liquid-chromatography/electrochemical detection method for simultaneous determination of the endogenous free ??-lipoic acid and dihydrolipoic acid in biological matrices was developed and validated. The two analytes were extracted from the samples with acetonitrile/10% metaphosphoric acid solution_(aqueous) (50/50 v/v). To determine the total lipoic acid, samples were treated with tris(2-carboxyethyl)phosphine solution in phosphate buffer, pH 2.5 with 85% orthophosphoric acid prior to deproteination. The two analytes were separated on a C₁₈ (150 × 4.6 mm, 5 ??m) analytical column using acetonitrile-50 mM phosphate buffer, pH 2.5 with 85% orthophosphoric acid (35/65 v/v) as the isocratic mobile phase pumped at a flow rate of 2.0 mL min^?1 at the column oven temperature of 35 °C. The column eluents were monitored at a potential of 0.9 V. These analytes were efficiently resolved in <7 min. The present method was sufficiently robust and specific for simultaneous determination of the two analytes and demonstrated acceptable values for linearity (r ² = 0.999 in the range of 0.1?C500 and 0.25?C1,000 ng mL^?1 for ??-lipoic acid and dihydrolipoic acid, respectively), recovery (>97%), precision (RSD% <2), and sensitivity (on column limit of detection, 150 and 375 fg for ??-lipoic acid and dihydrolipoic acid, respectively and limit of quantification: 0.5 and 1.25 pg for ??-lipoic acid and dihydrolipoic acid, respectively), indicating that the proposed method was more sensitive, precise, economical, and versatile, and has higher throughput than the previously reported methods for simultaneous determination of the two analytes.     

Stability-indicating HPLC method for acyclovir and lidocaine in topical formulations

A simple, rapid and accurate stability-indicating HPLC assay was developed for the determination of acyclovir and lidocaine in topical formulations. Chromatographic separation of acyclovir and lidocaine was achieved using a reversed-phase C₁₈ column and a gradient mobile phase (20 mm ammonium acetate pH 3.5 in water and acetonitrile). The degradation products of acyclovir and lidocaine in the samples were analyzed by ultra performance liquid chromatography-time of flight mass spectrometry. The HPLC method successfully resolved the analytes from the impurities and degradation products in the topical formulation. Furthermore, the method detected the analytes from the human skin leachables following the extraction of the analytes in the skin homogenate samples. The method showed linearity over wide ranges of 5–500 and 10–200 μg/ml for acyclovir and lidocaine in the topical product, respectively, with a correlation coefficient (r²) >0.9995. The relative standard deviations for precision, repeatability, and robustness of the method validation assays were <2%. The skin extraction efficiency for acyclovir and lidocaine was 92.8 ± 0.7% and 91.3 ± 3.2%, respectively, with no interference from the skin leachables. Thus, simultaneous quantification of acyclovir and lidocaine in the topical formulations was achieved.     

Fabrication of microporous organic network@silica composite for high-performance liquid chromatographic separation of drugs and proteins

Microporous organic networks (MONs) that exhibit good stability and hydrophobicity are promising candidates for performing HPLC separation of small organic compounds. However, their applications in separating large analytes as well as biomolecules are still limited by the microporous nature of MONs. Herein, we demonstrated the fabrication of a MON-functionalized silica (MON@SiO₂), exhibiting micro and mesopores for the HPLC separations of small drugs as well as large analytes, such as flavones, nonsteroidal anti-inflammatory drugs (NSAIDs), endocrine disrupting chemicals (EDCs), and proteins. MON was successfully modified on SiO₂ microspheres to yield the uniform and mono-dispersed MON@SiO₂. The separation mechanisms and performance of the MON@SiO₂ packed column were evaluated for a wide range of analytes, including neutral, acidic, basic compounds, drugs, and proteins. Compared with commercial C18 and SiO₂–NH₂ packed columns, the proposed MON@SiO₂ column afforded superior performance in the separations of flavones, NSAIDs, EDCs, and proteins. Moreover, the MON@SiO₂ column also offered good repeatability with intraday RSDs (n = 7) of <0.1%, <2.0%, <2.3%, and <0.7% for the retention time, peak height, peak area, and half peak width, respectively, for separating EDCs. This work proved the potential of using MONs in the HPLC separations of drugs and proteins.     

Determination of trace amounts of lead, arsenic, nickel and cobalt in high-purity iron oxide pigment by inductively coupled plasma atomic emission spectrometry after iron matrix removal with extractant-contained resin

Inductively coupled plasma atomic emission spectrometry (ICP-AES) was applied to the determination of lead, arsenic, nickel and cobalt in high-purity iron oxide pigment. Samples were dissolved with hydrochloric acid and hydrogen peroxide. The digest was passed through a column, which was packed with a polymer resin containing a neutral organophosphorus extractant, tri-n-butylphosphate. Iron was sorbed selectively on the resin and the analytes of interest passed through the column, allowing the effective separation of them from the iron matrix. Conditions of separation were optimized. The detection limits (3σ) in solution were 10, 40, 7 and 5 μg L⁻¹, and in pigment were 0.2, 0.8, 0.14 and 0.1 mg kg⁻¹ for lead, arsenic, cobalt and nickel, respectively. The recoveries ranged from 95% to 107% when sample digests were spiked with 5 μg of the analytes of interest, and relative standard deviations (n = 6) were 1.5-17.6% for the determination of the spiked samples. The method was successfully applied to the determination of trace amounts of these elements in high-purity iron oxide pigment samples.