Slurry-based procedures to determine chromium, nickel and vanadium in complex matrices by ETAAS

Two slurry-based ETAAS methodologies are compared to determine directly Cr, Ni and V in coal fly ash, soils and sediments: current slurry analysis (USS) and ‘slurry extraction’ (SE). Slurries for USS-ETAAS were prepared in 0.5% HNO₃. HF and HNO₃ were evaluated as chemical modifiers. HF was the extractant for the SE-ETAAS approach.A unique slurry-based procedure to measure Cr, Ni and V could not be established. Cr concentrations up to 100 μg g^{− 1} were accurately determined by USS (0.5% HNO₃; λ = 429.0 nm; LOD = 0.35 μg g^{− 1}) whereas higher contents required the SE procedure (sample grinding, 30% HF; LOD = 0.02 μg g^{− 1}). Both methods were appropriate to determine Ni (LOD = 0.11 and 0.08 μg g^{− 1}, for USS and SE, respectively). V was satisfactorily quantified only with the USS approach (LOD = 0.80 μg g^{− 1}).     

Speciation Stabilities of Iodine in underground Water by High Performance Liquid Chromatography-Inductively Coupled Plasma Mass Spectrometry

Specific determination for IO₃⁻ and I⁻ in ground water using high performance liquid chromatography-inductively coupled plasma mass spectrometry (HPLC-ICPMS) is described. Chromatographic separations were carried out using an ICS-A23 column. Iodine species were quantitatively eluted with 0.03 M ammonium carbonate. Under the Shield Torch high sensitive mode, the method detection limits for IO₃⁻ and I⁻ with injection of 1 ml were 0.035 μg l⁻¹ and 0.025 μg l⁻¹, respectively. The method was applied to the determination of iodide and iodate in ground water. However, the signal response difference between iodate and iodide was observed by both the HPLC-ICP-MS system and the ICP-MS system. Also, the same signal response difference was also observed in other laboratories. It was reported that the signal response and stability of iodine species vary with their solution medium. The instability of IO3 – and I – was controlled by using KOH as their solution storing media. The IO₃⁻ and I⁻ peak area ratios by HPLC-ICP-MS measurement were still close to 1:1 when the mixed standard solution was stored in the 0.01% KOH medium for 5 days.     

Selective separation of gold from iron ore samples using ion exchange resin

Gold in iron ore samples is separated from iron (major matrix cation), antimony and vanadium using anion exchange resin in (0.2 M) HBr, potassium peroxodisulfate and acetone:water:nitric acid media. The exchangeable anion Cl⁻ of the ion exchanger Dowex 1X 4 is replaced by Br⁻ using (6 M) HBr solution. Certified reference material DGP-M1, spiked ferric magnetic oxide, gold radioactive tracer ¹⁹⁸Au and gold standard solutions are used to study the adsorption efficiency and the yield recovery of tetrabromoaurate AuBr₄⁻ from the resin. Ten eluents have been tried to elute gold from the column, and it has been found that a 10 ml potassium peroxodisulfate and 240 ml acetone:water:nitric acid [125:5:5] solution fulfills the objective. The set up of the separation procedure allows quantitative adsorption of gold by the resin, while the major matrix cation (Fe) and others (Cd, Ag, Cu, V, Sb, Ti) have been passed through the column with the feeding solution (0.2 M) HBr. The resin selectivity coefficient (K) of separating Au from Fe has been found to be K_Fe^Au≈6.4×10¹¹. The eluted Au is treated with K₂S₂O₈ and H₂O₂ for spectrophotometric determination as rhodamine-B complex at 555.6 nm. The linearity, detection limit, precision, and accuracy of the determination method have been found to be up to 2.0 μg g⁻¹, 0.018 μg g⁻¹, 0.009 μg g⁻¹ and 3%, respectively.     

Determination of manganese and zinc in powdered chocolate samples by slurry sampling using sequential multi-element flame atomic absorption spectrometry

In the present work, a slurry sampling flame atomic absorption spectrometric method to determine directly manganese and zinc in powdered chocolate samples is proposed. The optimization step was performed using univariate methodology involving the following factors: nature and concentration of the acid solution, sonication time, and particle size. The established conditions led to the use of a sample mass of 150 mg, 2.0 mol L^− 1 nitric acid solution, sonication time of 15 min, and a slurry volume of 50 mL. This method allows the determination of manganese and zinc with detection limit of 52 and 61 ng g^− 1, respectively, and a precision expressed as relative standard deviation (RSD) of 2.6% and 3.2% (both, n = 10) for contents of manganese and zinc of 52.4 and 100.0 μg g^− 1, respectively. The proposed method was applied for determination of manganese and zinc in five powdered chocolate samples. In these, the manganese content varied from 42.8 to 52.7 and from 88.6 to 102.4 μg g^− 1 of zinc. The analytical results were compared with the results obtained by analysis of these samples after digestion using open vessel and acid bomb digestion procedures and determination using FS-FAAS. The statistical comparison by t-test (95% confidence level) showed no significant difference between these results.     

Mercury, zinc, manganese, and iron accumulation in leachate pond sediments from a refuse tip in Southeastern Brazil

This work evaluates Hg, Zn, Fe and Mn transfer from the leachate of a refuse tip based on their accumulation in a sediment core of 17 cm collected in a leachate pond of a small refuse tip ageing approximately 10 years. Sediment samples were digested with an acid mixture (50% acqua regia solution), heated at 70 °C during 1 h, in a thermal-kinetic reactor “cold finger”. The extract was analysed to obtain Hg content by cold vapour absorption atomic spectrometry (CVAAS). Fe, Mn and Zn contents were obtained by flame atomic absorption spectrometry (FAAS) after total decomposition of the samples. Concentration ranges along the core varied from 0.16 to 0.58 μg g^− 1; 7.3 to 145 μg g^− 1; 11.7 to 116 μg g^− 1 and 0.21% to 1.82% for Hg, Zn, Mn and Fe, respectively. All metals showed enrichment in the upper layers (above 6 cm) which probably correspond to the year 1996. Results indicated that Hg transfer is one order of magnitude higher than Zn and suggest that metals accumulation in sediments probably reduce their migration to groundwater.     

The rapid separation of trace metals from neutron-activated saline matrices by chelation on a poly-5-vinyl-8-hydroxyquinoline column

Instrumental neutron activation analysis of biological and environmental samples suffers from interferences caused by high salt concentrations. Poly-5-vinyl-8-hydroxy-quinoline coated on controlled pore diameter glass beads is suggested as a chelating column for the rapid removal of aluminum, vanadium, copper and manganese from neutron-activated sea-water samples. Separation from bulk elements is satisfactory at flow rates of 20 ml min⁻¹. With addition of carriers and with chemical yield determinations, relative standard deviations of 2–10% can be achieved for spike concentrations of 0.1 μg Mn ml⁻¹, 0.3 μg V ml⁻¹, 20 μg Al ml⁻¹ and 1.0 μg Cu ml⁻¹.     

Determination of zinc and copper in human hair by slurry sampling employing sequential multi-element flame atomic absorption spectrometry

The present work proposes a direct method based on slurry sampling for the determination of zinc and copper in human hair samples by multi-element sequential flame atomic absorption spectrometry. The slurries were prepared by cryogenic grinding and sonication of the samples. The optimization step was performed using univariate methodology and the factors studied were: nature and concentration of the acid solution, amount sample/slurry volume, sonication time, and particle size. The established experimental conditions are the use of a sample mass of 50 mg, 2 mol L^− 1 nitric acid solution, sonication time of 20 min and slurry volume of 10 mL. Adopting the optimized conditions, this method allows the determination of zinc and copper with detection limits of 88.3 and 53.3 ng g^− 1, respectively, and precision expressed as relative standard deviation (RSD) of 1.7% and 1.6% (both, n = 10) for contents of zinc and copper of 100.0 and 33.3 μg g^− 1, respectively. The accuracy was checked and confirmed by analysis of two certified reference materials of human hair. The procedure was applied for the determination of zinc and copper in two human hair samples. The zinc and copper contents varied from 100.0 to 175.6 and from 3.2 to 32.8 μg g^− 1, respectively. These samples were also analyzed after complete digestion in a closed system and determination by FAAS. The statistical comparison by t-test (95% confidence level) showed no significant difference between these results.     

Flow-injection hydride generation atomic absorption spectrometric study of the automated on-line pre-reduction of arsenate, methylarsonate and dimethylarsinate and high-performance liquid chromatographic separation of their -cysteine complexes

An automated on-line pre-reduction of arsenate, monomethylarsonate (MMA) and dimethylarsinate (DMA) using flow injection hydride generation atomic absorption spectrometry (FI-HGAAS) is feasible. The kinetics of pre-reduction and complexation depend strongly on the concentration of -cysteine and on the temperature in the following increasing order: inorganic As(V)<DMA<MMA. Arsenate is pre-reduced/complexed within less than 50 s at 70–100°C compared to 1 h at room temperature, while MMA and DMA require 1.5–2 min at 70–100°C and up to 1–2 h at room temperature. The characteristic masses and concentrations for 100 μl injections are 0.01 ng and 0.1 μg l⁻¹ in integrated absorbance and 0.2 ng and 2 μg l⁻¹ in peak height measurements, and the limits of detection are ca. 0.5 ng and 5 μg l⁻¹, respectively. In a high-performance liquid chromatography (HPLC)–HGAAS system, the -cysteine complexes of inorganic As(III), MMA and DMA are best separated within 7 min by HPLC on a strongly acidic cation exchange column such as Spherisorb S SCX 120×4 mm (5 μm) with a mobile phase containing 12 mmol l⁻¹ phosphate buffer (KH₂PO₄/H₃PO₄)–2.5 mmol l⁻¹ -cysteine, pH 3.3–3.5. Upon dilution to -cysteine levels below 10 mmol l⁻¹, which are compatible with HPLC separations, the DMA–cysteine complex is unstable on storage. No baseline separations are possible with anion exchange and reverse phase C₁₈ HPLC columns. The limits of detection with 50 μl injections in peak area mode are ca. 0.5 ng and 10 μg l⁻¹, respectively.     

Column Preconcentration of Aluminum and Copper(II) in Alloys, Biological Samples, and Environmental Samples with Alizarin Red S and Cetyltrimethylammonium-Perchlorate Adsorbent Supported on Naphthalene Using Spectrometry

A column method has been established for the preconcentration of aluminum and copper(II) with Alizarin Red S and a cetyltrimethylammonium-perchlorate ion pair supported on naphthalene, using a simple glass-tipped tube. Aluminum and copper(II) react with Alizarin Red S to form water-soluble colored chelate anions. These chelate anions form water-insoluble ternary complexes with the adsorbent on the inactive surface of naphthalene packed into a column. They are quantitatively retained in the pH ranges of 4.7-5.2 for aluminum and 5.0-10.0 for copper. The solid mass is dissolved out from the column with 5 ml of dimethylformamide (DMF) for aluminum and 5 ml of ethanol for copper and the absorbance was measured with a spectrometer at 525 nm for aluminum and at 529 nm for copper. The calibration curves were linear over the concentration ranges of 0.25-5.0 μg of aluminum in 5 ml of DMF solution and 0.50-12.0 μg of copper in 5 ml of ethanol solution. The molar absorptivities and Sandell′s sensitivities were respectively calculated to be 2.8 × 10⁴ liter · mol⁻¹ · cm⁻¹ and 9.62 × 10⁻⁴ μg · cm⁻² for aluminum and 2.5 × 10⁴ liter · mol⁻¹ · cm⁻¹ and 2.5 × 10⁻³ μg · cm⁻² for copper. Seven replicate determinations of sample solutions containing 2.5 μg of aluminum and 6.0 μg of copper gave mean absorbances of 0.520 and 0.480 with relative standard deviations of 1.67 and 0.33%, respectively. Interference due to various foreign ions has been studied and the method has been applied to the determination of aluminum in standard alloys, tea leaves, vehicle particulates, copper in coal fly ash, and commercial salt samples.     

Chitosan–magnetite nanocomposites (CMNs) as magnetic carrier particles for removal of Fe(III) from aqueous solutions

This research focuses on removal of Fe(III) from aqueous solution using chitosan–magnetite nanocomposites as potential sorbent. The presence of nanosized magnetic particles within the nanocomposites was confirmed by TEM and SAED analysis. The particles with diameter 508 μm and 84 μm, follow Frendlich sorption isotherm at 30 °C, and the Frendlich constants (K_F, 1/n) have been found to be 5.974 mg g⁻¹, 2.66 and 35.98 mg g⁻¹, 1.385, respectively. Out of various kinetic models, the experimental data for dynamic uptake of Fe(III) is best fitted on ‘pseudo-second order’ kinetic model. The linear nature of plots between log (% sorption) and log (time) is indicative of intra-particle diffusion. For the particles with diameters 508 μm and 84 μm, the value of k_id was found to be 1.78 mg l⁻¹ min^−0.5 and 2.13 mg l⁻¹ min^−0.5. The sorption mean free energy from the Dubinin–Radushkevic isotherm was found to be 7.04 kJ mol⁻¹ indicating chemical nature of sorption. The increase in chitosan content in sorbent particles is found to enhance the Fe(III) uptake. The various thermodynamic parameters have also been evaluated. Finally, the presence of Cu²⁺ ions in the sorbate is found to decrease the uptake of Fe(III).     

Determination of Proteins in a Mesofluidic Lab-on-Valve System

The application of a mesofluidic lab-on-valve system to the spectrophotometric determination of protein was investigated. Protein species in the sample solution reacts rapidly with Congo red at pH 4.1, which forms a complex with a maximum absorption at 496 nm. A univariant approach was used for the optimization of the experimental parameters. A sample volume of 20 μl was used along with 4.0 μl of Congo red solution of 0.9 g l⁻¹, and a flow rate for the detection process of 20 μl s⁻¹ was used. Under optimal conditions, a linear calibration curve was obtained in the range of 12.5–200 μg ml⁻¹ of bovine serum album, along with a detection limit (3σ) of 5.6 μg ml⁻¹ and a sampling frequency of 60 per hour. Protein concentrations in human serums, urine, milk, and yoghourt were determined using this procedure, and satisfactory agreements were obtained with that achieved using the Coomassie brilliant blue method.     

Spectrophotometric determination of zinc, cadmium, and lead after extraction of their morpholine-4-carbodithioates into molten naphthalene and replacement by copper

Zinc, cadmium, and lead react quantitatively in the pH ranges of 3.9–9.2, 3.5–11.2, and 5.5–10.5, respectively, to form water insoluble and thermally stable complexes which are easily extracted into molten naphthalene. The solid naphthalene containing the colorless complex is dissolved in chloroform and then replaced by copper to develop a yellow color in the chloroform layer. The absorbance in each case is measured at 435 nm against reagent blank. Beer's law holds over the concentration ranges of 3.5–95.0, 3.0–105.0, and 8.5–125. 0 μg for zinc, cadmium, and lead, respectively, into 10 ml of the chloroform solution. The molar absorptivities are calculated to be Zn, 1.048 × 10⁴ liters mol⁻¹ cm⁻¹; Cd, 1.054 × 10⁴ liters mol⁻¹ cm⁻¹, and Pb, 1.014 × 10⁴ liters mol⁻¹ cm⁻¹ with sensitivities in terms of Sandell's definition of 0.0062 μg Zn/cm², 0.010 μg Cd/cm², and 0.020 μg Pb/cm², respectively. Ten replicate determinations of sample solutions containing 30 μg of zinc, 18.7 μg of cadmium, and 42.5 μg of lead give mean absorbances 0.480, 0.175, and 0.208 with standard deviations of 0.0017, 0.0013, and 0.0015 or relative standard deviations of 0.35, 0.74, and 0.72%, respectively. The interference of various ions has been studied and the method has been applied to the determination of cadmium in various synthetic mixtures and zinc and lead in some standard reference materials.     

Inductively coupled plasma-mass (ICP-MS) and atomic emission spectrometry (ICP-AES): Versatile analytical techniques to identify the archived elemental information in human teeth

Human dental enamel is composed of sequentially calcifying growth layers that can provide an archival record of temporal changes such as past pollution events and changes in elemental nutrition. Human teeth and bones alike are mainly made out of calcium and a phosphorous rich crystalline building block called hydroxyapatite [Ca₁₀(PO₄)₆(OH)₂]. Divalent cations such as Zn²⁺, Pb²⁺, Sr²⁺, and Mg²⁺ can replace isovalent calcium sites, and phosphate and hydroxyl sites can substitute with anions, such as carbonate and fluoride, respectively. In this investigation inductively coupled plasma-atomic emission (ICP-AES) and mass spectrometry (ICP-MS) was used to determine lead, zinc, and strontium concentrations in deciduous teeth from contemporary populations from Solís, Mexico and Kalama, Egypt and permanent teeth from Bronze age Tell Abraq, United Arab Emirates and the 18th century New York African Burial Ground (NYABG) from Lower Manhattan. The concentration of lead in children's teeth from a semi-urban village in Egypt (ranged from 162 to 2.6 μg g^{− 1}; n = 10) and NYABG individuals (range 112–1.2 μg g^{− 1}; n = 6) showed the elevated lead levels while the ancient population from Tell Abraq had the lowest level (1.34 to 0.03 μg g^{− 1}; n = 10). Lead isotope ratios (i.e., ²⁰⁸Pb/²⁰⁶Pb and ²⁰⁷Pb/²⁰⁶Pb) of above individuals' teeth were measured using ICP-MS to discern their domicile. Zinc and Sr concentrations of teeth reflect the diet, nutritional and environmental history of individuals. The versatility of ICP-AES and ICP-MS as trace metal analytical techniques in unraveling elemental information embedded in hard tissue, like teeth, is demonstrated.     

Simultaneous determination of chloride, nitrate and sulphate in vegetable samples by single-column ion chromatography

A new ion chromatography method is described for the simultaneous determination of Cl⁻, NO₃⁻ and SO₄²⁻, using a selected eluent 1.3-mM sodium gluconate/1.3-mM borax (pH 8.5). The extraction methods of Cl⁻, NO₃⁻, SO₄²⁻ in vegetables are studied. The determination limits of Cl⁻, NO₃⁻, SO₄²⁻ are 0.17 μg/ml, 0.63 μg/ml and 0.81 μg/ml. The linear ranges are 060 μg/ml, 090 μg/ml and 090 μg/ml. The relative S.D. are <2.5%. The mean recoveries of Cl⁻, NO₃⁻, SO₄²⁻ in vegetables range from 97.0 to 104%.     

Combined use of Pd and HF as chemical modifiers for the determination of total chromium in produced waters from petroleum exploration by ET AAS

This work reports the evaluation of the combined use of Pd and HF as chemical modifiers for the direct determination of total chromium in waters derived from petroleum exploration employing electrothermal atomic absorption spectrometry (ET AAS). Such waters, usually called as produced waters, have complex composition presenting a number of organic and inorganic substances. When obtained from offshore operations they also present high salinity. In order establish conditions for chromium measurement pyrolysis and atomization curves were built up in different media and employing Pd and HF as chemical modifiers. Also, a detailed study about calibration strategy was performed. At best conditions, pyrolysis and atomization temperatures were 1200 °C and 2600 °C, respectively, and 10 μL of a 500 mg L^− 1 Pd solution was added together with 10 μL of a 50% (v/v) HF solution on 20 μL of sample. Obtained results indicate that, in this kind of sample, chromium can be determined by standard addition method or employing external calibration with standard solutions prepared in 0.8 mol L^− 1 NaCl medium. In order to evaluate the accuracy of the procedure, a recovery test was performed with seven spiked samples of produced waters. The detection limit, quantification limit and the relative standard deviation in 0.8 mol L^− 1 NaCl were also calculated and the values found were 0.45 μg L^− 1, 1.5 μg L^− 1 and 6.0% (at 2.5 μg L^− 1 level), respectively.     

Use of modified rice husks as a natural solid adsorbent of trace metals: characterisation and development of an on-line preconcentration system for cadmium and lead determination by FAAS

The use of rice husks as an alternative adsorbent in an on-line preconcentration system for Cd (II) and Pb (II) determination by flame atomic absorption spectrometry (FAAS) is described. The potential of rice husks as a natural adsorbent was evaluated as a material modified with 0.75 mol l⁻¹ NaOH solution and in the unmodified form. For this task, several techniques such as spectroscopy and thermogravimetry were used for elucidation of possible functional groups responsible for the uptake of Cd (II) and Pb (II). Furthermore, based on adsorption studies and adsorption isotherms applied to the Langmüir model, it was possible to verify that modified rice husks present a higher adsorption capacity for both metals. After establishing this material as a promising natural adsorbent, it was used for on-line preconcentration of Cd (II) and Pb (II) metals. The multivariate optimisation of chemical and flow variables was performed by using a full factorial design (2⁴) including the following factors: preconcentration time, preconcentration flow rate, concentration and volume of eluent. The optimum pH values used for on-line preconcentration were taken from prior univariate experiments. Under optimised conditions for Cd (II) determination (4 min of preconcentration at a 6 ml min⁻¹ preconcentration flow rate, in which comprises 24 ml of preconcentration volume, 200 μl elution volume and 1.0 mol l⁻¹ HNO₃ solution as eluent), the system achieved a detection limit of 1.14 μg l⁻¹ and an enrichment factor of 72.4. Similar conditions were used for Pb (II) determination (4 min of preconcentration, 6 ml min⁻¹ preconcentration flow rate, 300 μl elution volume and 1.0 mol l⁻¹ HNO₃ solution as eluent) from which a detection limit of 14.1 μg l⁻¹ and enrichment factor of 46.0 were achieved. Also, rice husks have been shown to be a homogeneous and stable adsorbent in which more than 100 preconcentration/elution cycles provide a relative standard deviation (RSD) of less than 6.0% on the analytical signal. The satisfactory accuracy of the method developed was obtained by using spiked water samples (mineral water and lake water) and spiked red wine samples. These values were confirmed by electrothermal atomic absorption spectrometry (ETAAS). The certified reference material [pig kidney (CRM 186)] and the reference material [beech leaves (CRM 100)] were also used.     

Sensitive spectrofluorimetric determination of ruthenium at nanotrace levels using 2-(α-pyridyl) thioquinaldinamide [PTQA]

A new spectrofluorimetric method for the determination of ruthenium with nonfluorescent 2-(α-pyridyl) thioquinaldinamide (PTQA) is described. The oxidative reaction of Ru(III) upon PTQA gives oxidised fluorescent product (λ_ex(max)=347 nm; λ_em(max)=486 nm). The sensitivity of the fluorescence reaction between ruthenium and PTQA is greatly increased in the presence of Fe (III). The reaction is carried out in the acidity range 0.01–0.075 M H₂SO₄. The influence of reaction variables is discussed. The range of linearity is 1–400 μg l⁻¹ Ru(III). The standard deviation and relative standard deviation of the developed method are ±1.210 μg l⁻¹ Ru (III) and 2.4%, respectively (for 11 replicate determinations of 50 μg l⁻¹ Ru (III)). The effect of interferences from other metal ions, anions and complexing agents was studied; the masking action is discussed. The developed method has been successfully tested over synthetic mixtures of various base metals and platinum group metals, synthetic mixtures corresponding to osmiridium, certified reference materials in spiked conditions and rock samples.     

A spot test for the detection of periodate

Perrhenate is quantitatively extracted into methyl isobutyl ketone from aqueous solutions containing copper(II), azide and an excess of 2,2'-bipyridine. Measurement of the extracted copper either by spectrophotometry or by atomic absorption spectrometry, allows the determination of perrhenate in the ranges 16–40 μg ml⁻¹ or 3–16 μg ml⁻¹ in the final dilution, respectively. The procedure is highly selective, being applicable in the presence of a large concentration of molybdate and a considerable number of foreign ions. The extracted species corresponds to the formula CuN₃(bipy)₂ ReO₄.     

Extraction and spectrophotometric determination of vanadium with 4-(2-thiazolylazo)resorcinol and tetraphenylarsonium and phosphonium chlorides

Extraction of vanadium-4-(2-thiazolylazo)resorcinol complexes by quaternary salts such as triphenylmethylarsonium iodide, tetraphenylarsonium chloride, and tetraphenylphosphonium chloride has been studied. Quantitative extraction is achieved with tetraphenylarsonium and tetraphenylphosphonium chlorides in the pH region between 3.5 and 5. The optimum conditions for the extraction and spectrophotometric determination of vanadium in the extract are: pH 3.8–4.0, the concentration of vanadium 0.1–0.4 μg/ml. Effective molar absorptivity at λ_max = 555 is (2.55 ± 0.05) × 10⁴ liters mol⁻¹ cm⁻¹. Beer's law is obeyed. Relative standard deviation is 2–10% depending on the concentration level. The composition of the extracted complexes was studied in the solution and in the solid state. For their characterization chemical and spectral evidence and comparison with the vanadium-PAR complexes have been combined.     

Solid Phase Extraction and Spectrophotometric Determination of Silver with 2-(2-Quinolylazo)-5-Dimethylaminophenol

A new chromogenic reagent, 2-(2-quinolylazo)-5-Dimethylaminophenol (QADMAP) was synthesized, and a sensitive, selective, and rapid method was developed for the determination of the μg/L level of silver ions. The method is based on the rapid reaction of silver(I) with QADMAP and the solid phase extraction of the colored chelate using a C₁₈ cartridge. The QADMAP reacts with Ag(I) in the presence of a citric acid-sodium hydroxide buffer solution (pH 5.0) and a sodium dodecyl sulfonate (SDS) medium to form a violet chelate of molar ratio 1 : 2 (silver to QADMAP). This chelate was enriched by solid phase extraction with C₁₈ cartridge, and the retained chelate was eluted from the cartridge using ethanol (with 1% acetic acid). In the ethanol medium (with 1% acetic acid), the molar absorptivity of the chelate was 1.25 × 10⁵ L mol⁻¹ cm⁻¹ at 584 nm. Beer’s law was obeyed in the range 0.01–0.6 μg/mL. The relative standard deviation for eleven replicate samples of 0.01 μg/mL was 1.86%. The detection limit is 0.02 μg/L in the original samples. The method was applied to the determination of μg/L levels of silver ions in water with good results.__________From Zhurnal Analiticheskoi Khimii, Vol. 60, No. 6, 2005, pp. 566–570.Original English Text Copyright © 2005 by Huang, Yang, Hu, Yin.This article was submitted by the authors in English.