Determination of Cd(II) and Cd-metallothioneins in biological extracts using baker’s yeast and inductively coupled plasma optical emission spectrometry

The use of Saccharomyces cerevisiae as a sorbent material to separate Cd(II) and Cd-metallothionein complex (Cd-MT) has been explored. Solid–liquid phase extractions were carried out in batch mode and the main parameters of the process (pH, temperature, time of incubation, amount of biomass and analyte) were evaluated. Under optimized conditions, the yeast quantitatively retain (94 ± 5%) the Cd(II) while 97 ± 2% of the Cd-MT remain in the supernatant. On base of the findings of this study, a simple method is proposed to determine Cd(II) and Cd-MT in cytosols extracted from mouse kidney and crab hepatopancreas. Inductively coupled plasma optical emission spectrometry was used to quantify the analytes in solid and liquid phase. Determination of Cd in the solid phase was carried out by introducing a slurry of the yeast (0.0625 g/10 mL) directly to the inductively coupled plasma optical emission spectrometer. Mixed standards solutions, which also have been submitted to the extraction procedure, were used to quantify the analytes in the samples. Thus, matrix effects due to nebulization of the slurry were overcame. Limits of detection (3σ) for Cd(II) and Cd-MT were 1.5 and 1.2 μg L⁻¹, respectively. Relative standard deviations of signals were 4.2% for measurements in the slurry of solid phase and 2.1% for measurements in the liquid phase. Recoveries of the analytes in cytosol samples were between 76 and 114%. The concentrations of Cd(II) (2.4 ± 0.5 μg L⁻¹) and Cd-MT (3.0 ± 0.5 μg L⁻¹) found by using the proposed approach were close to those found by tangential-flow ultrafiltration technique (2.6 ± 0.7 μg L⁻¹ for Cd(II) and 3.7 ± 1.7 μg L⁻¹ for Cd-MT).     

Speciation Analysis of Inorganic Tin (Sn(II)/Sn(IV)) by Graphite Furnace Atomic Absorption Spectrometry Following Ion-Exchange Separation

A new method based on anion exchange resin separation and graphite furnace atomic absorption spectrometry (GFAAS) detection is proposed for the determination of inorganic tin species. The result showed that Sn(IV) was quantitatively retained on the resin when [HCl] = 9.0 mol · L⁻¹, but Sn(II) could not be adsorbed on the resin under the same condition. Thus, a separation of Sn(II) and Sn(IV) has been realized. When the concentration of NaOH solution was between 2.0–7.0 mol · L⁻¹, Sn(IV) that adsorbed on the resin could be eluated from the resin completely. Meanwhile, under the atmosphere and the nitrogen states, the translation between Sn(II) and Sn(IV) was investigated. Under the optimal conditions, the detection limit of Sn(IV) is 0.40 μg · L⁻¹ with RSD of 2.3% (n = 5, c = 2.0 μg · L⁻¹). The proposed method was applied to the speciation analysis of tin in different water samples and the recovery of total Sn was in the range of 98.7–101.7%. In order to verify the accuracy of the method, a certified reference water sample was analyzed and the results obtained were in good agreement with the certified value.     

Selective extraction and preconcentration of cerium(IV) in water samples by cloud point extraction and determination by inductively coupled plasma optical emission spectrometry

Cloud point extraction (CPE) was used for the selective extraction and separation of cerium(IV) from aqueous solutions. The method is based on the formation of cerium(IV)-n-p-tolylbenzohydroxamic acid (n-TBHA) complex that is extracted into the micellar phase (Triton X-114) at a temperature above the cloud point temperature (CPT). After phase separation, the surfactant rich phase was diluted up to 1.0 mL and determined by inductively coupled plasma-optical emission spectrometry (ICP-OES). Under the optimum extraction conditions and instrument parameters, by preconcentration of only 10.0 mL of sample in the presence of 0.09% Triton X-114, an enhancement factor of 13.8 was obtained. The analytical curve was linear in the range of 1.5–1200 μg L⁻¹ and the detection limit was 0.4 μg L⁻¹. The method was applied to the determination of Ce(IV) in water samples with satisfactory results.     

Preconcentration of Cd(II) and Cu(II) by solid phase extraction on cyanopropyl modified silica columns using 1,10-phenanthroline as the complexing agent

We describe the solid-phase extraction for the preconcentration and determination of Cd(II) and Cu(II) aqueous samples by inductively coupled plasma optical emission spectrometry. The preconcentration of analytes is accomplished by retention of their chelates with 1,10-phenanthroline in aqueous solution on a solid phase containing cyanopropylsilane bonded to silica gel in a column. The preconcentration factor is 80 for the cadmium ions and 120 for the copper ions with relative standard deviations of between 0.5 and 1.5%. The limits of detection (defined as “3 s” where “s” is the standard deviation of the blank determination) are 0.18 and 0.073 μg L⁻¹ for Cd(II) and Cu(II), respectively, and the corresponding limits of quantification (6 s) are 0.36 and 0.15 μg L⁻¹, respectively. As a result, a simple method was created for simultaneous preconcentration and determination of the metals in reference material and in plant sample material. Correspondence: Bożena Puzio, Institute of Chemistry, Silesian University, 40-006 Katowice, Poland     

Highly selective determination of palladium(II) after preconcentration using Pd(II)-imprinted functionalized silica gel sorbent prepared by a surface imprinting technique

A novel Pd(II)-imprinted amino-functionalized silica gel sorbent was prepared with the help of a surface-imprinting technique for the preconcentration and separation of Pd(II) prior to its determination by inductively coupled plasma atomic emission spectrometry. Compared to the traditional solid sorbents and non-imprinted polymer particles, the ion-imprinted polymers (IIPs) had a higher adsorption capacity and selectivity for Pd(II). The maximum static adsorption capacity of the imprinted and non-imprinted sorbent for Pd(II) was 26.71 mg g⁻¹ and 10.13 mg g⁻¹, respectively. The relative selectivity factor (α_r) of Pd(II)/Zn(II), Pd(II)/Au(III), Pd(II)/Ru(III), Pd(II)/Rh(III), Pd(II)/Pt(IV), Pd(II)/Ir(III), Pd(II)/Fe(III) and Pd(II)/Zn(II) is 39.0, 60.2, 92.0, 85.0, 50.0, 58.0 and 45.0, respectively. The detection limit (3σ) of the method is 0.36 μg L⁻¹. The relative standard deviation was 3.2% for eight replicate determinations of 10 μg of Pd²⁺ in 200 mL water sample. The method was validated by analyzing a standard reference material, and the results obtained were in good agreement with the standard values. The method was also applied to the determination of trace palladium in geological samples with satisfactory results.     

Study of Solid Phase Extraction Prior to Spectrophotometric Determination of Platinum with N-(3,5-Dimethylphenyl)-N′-(4-Aminobenzenesulfonate)-Thiourea

A highly sensitive, selective and rapid method for the determination of platinum based on the rapid reaction of platinum(IV) with N-(3,5-dimethylphenyl)-N′-(4-aminobenzenesulfonate)-thiourea (DMMPT) and the solid phase extraction of the Pt(IV)-DMMPT complex with C₁₈ membrane disks was developed. In the presence of pH = 3.8 buffer solution and cetyl trimethylammonium bromide (CTMAB) medium, DMMPT reacts with platinum to form a violet complex of a molar ratio of 1:3 (platinum to DMMPT). This complex was enriched by solid phase extraction with C₁₈ membrane disks, and an enrichment factor of 200 was obtained. The molar absorptivity of the complex is 9.51 × 10⁴ L · mol⁻¹ · cm⁻¹ at 755 nm, and Beer’s law is obeyed in the range of 0.01–3.0 μg mL⁻¹ in the measured solution. The relative standard deviation for eleven replicate samples of 0.01 μg mL⁻¹ level is 1.79%. The detection limit reaches 0.02 μg L⁻¹ in the original samples. This method was applied to the determination of platinum in water and soil samples. The relative standard deviations are 2.9–3.4%. The recoveries are 94–105%. The values of determination obtained agree with those of the ICP-MS method. The results are satisfactory.     

Determination of trace elements in liquid aspartame sweeteners by ICP OES and ICP-MS following acid digestion

In order to determine inorganic constituents and contaminants in liquid aspartame sweeteners, different brands of this product were analyzed by ICP OES and ICP-MS. The samples were submitted to acid digestion and parameters such as internal standardization and wavelengths, in the case of ICP OES, and a recovery test were evaluated. The analytes studied were As, Ca, Cd, Co, Cu, K, Fe, Mg, Mn, Na, Ni, Pb, Se and Zn. Since there is not a certified reference material for sweeteners, the accuracy of the proposed method was evaluated by recovery tests and the values were in the range of 90–110% for the majority of the analytes. The detection limits for the elements determined by ICP OES were in the range 0.01 (Mn)– 2.0 (K) μg g⁻¹ while those determined by ICP-MS were 0.001 μg g⁻¹ for all the elements except Mn and As (0.002 μg g⁻¹). The relative standard deviations were below 12% for ICP OES and below 14% for ICP-MS determinations. The mean concentration of the elements detected by ICP OES (Ca, Fe, K, Mg, Na, and Zn) varied according to the brand. The other analytes, were determined by ICP-MS. For these elements, a significant variation in their concentrations was also found for different samples, except for Co and Ni. The use of both multielemental techniques allowed the evaluation of the inorganic composition and the rapid determination of several elements in aspartame sweeteners, with adequate accuracy.     

Fluorimetric Determination of Gentamicin in Dosage Forms and Biological Fluids Through Derivatization with 4-Chloro-7-Nitrobenzo-2-Oxa-1,3-Diazole (NBD-Cl)

 A highly sensitive fluorimetric method has been developed for the determination of gentamicin. The method is based on its coupling with 4-chloro-7-nitrobenzo-2-oxa-1,3-diazole (NBD-Cl) in 50% (v/v) methanolic phosphate buffer (pH 7.2) to give an intensely fluorescent product having excitation and emission wavelengths at 465 nm and 530 nm, respectively. The experimental parameters were carefully studied and incorporated into the procedure. The fluorescence-concentration plot is rectilinear over the range 0.56–2.8 μg/mL (r = 0.999) with minimum detectability (S/N = 2) of 0.11 μg/mL (1.6 × 10⁻⁷ mol/L). The method was applied successfully to the determination of the drug in pharmaceutical dosage forms and the percentage recoveries were satisfactorily accurate and precise. The method was further applied to spiked human plasma samples, the percentage recovery was 97.9 ± 3.4. The interference encountered from endogenous amino acids could be eliminated through selective complexation with freshly prepared copper (II) hydroxide. A proposal of the reaction pathway is presented. The method can measure the intact drug, and can be used in presence of possible interference. Received April 18, 2001; accepted April 10, 2002     

Determination of rhodium in water samples using cloud point extraction (CPE) coupled with flame atomic absorption spectrometry (FAAS)

Cloud point extraction was applied as a method for preconcentration of rhodium after formation of a complex with 2-propylpiperidine-1-carbodithioate (2-PPC), and later determined by flame atomic absorption spectrometry using TritonX-114 as surfactant. Rhodium was complexed with 2-PPC in an aqueous phase and kept for 15 min in a thermostatted bath at 40 °C. Separation of the two phases was accomplished by centrifugation for 15 min at 4000 rpm. The chemical variables affecting the cloud point extraction were optimized and successfully applied to rhodium determination in various water samples. Under optimized conditions, the preconcentration system (100 mL sample) permitted an enhancement factor of 50. The detection limits obtained under optimal conditions was 0.052 ng mL⁻¹. The extraction efficiency was investigated at different rhodium concentrations (7.0–42.0 μg mL⁻¹), and good recoveries (96.42–99.14%) were obtained using this method. It has been applied to the determination of rhodium in water and was compared with reported methods in terms of Student’s ‘t’-test and variance ratio ‘f’-test.     

Cloud Point Preconcentration and Flame Atomic Absorption Spectrometric Determination of Cobalt and Nickel in Water Samples

 Cloud point methodology was successfully used to preconcentrate trace amounts of Co and Ni as a prior step to their determination by flame atomic absorption spectrometry. 1-Nitroso-2-naphthol and polyethylene glycol-p-nonylphenylether (PONPE 7.5) are used as hydrophobic ligand and nonionic surfactant, respectively. Optimization was performed of the variables effecting complexation and phase separation. Additionally, the influence of viscosity on the analytical signal was investigated. Under the experimental conditions used, preconcentration of only 10 mL of sample in the presence of 0.075% (v/v) PONPE 7.5 permitted the detection of 1.09 μg L⁻¹ of Ni and 1.22 μg L⁻¹ of Co with enhancement factors of 29 and 27 for Ni and Co, respectively. The relative standard deviations (n=5) at concentrations of 80 and 50 μg L⁻¹ for Co and Ni were 2.53 and 2.89%, respectively. Good recoveries in the range of 96–105% were obtained for spiked samples. The effect of different interferent species was studied. The proposed method was applied to the determination of Ni and Co in different water samples. Correspondence: Department of Analytical Chemistry, Faculty of Chemistry, Tabriz University, Tabriz, Iran. e-mail: manzoori@tabrizu.ac.ir Received September 1, 2002; accepted November 8, 2002     

Application of full factorial design for the preconcentration of chromium by solid phase extraction with Amberlyst 36 resin

The preconcentration of chromium(III) by solid phase extraction and its determination from aqueous solutions by flame atomic absorption spectrometry (FAAS) is investigated by applying an experimental design. The optimization of the preconcentration variables such as pH of the sample solution, flow rate of the sample solution and concentration of elution solution was carried out using 2³ full factorial design. The most important parameter affecting the preconcentration of chromium is the concentration of eluent. In the established experimental conditions, chromium can be determined with a relative standard deviation of 2.0% (N = 7) for a chromium concentration of 100 μg L⁻¹. The detection limit for chromium was 1 μg L⁻¹ (N = 20). The adsorption capacity of Amberlyst 36 is found to be 90.9 mg g⁻¹ for chromium. Effect of other ions on the procedure was also evaluated. The method was validated by the analysis of certified reference materials (tea leaves GBW 07605 and fish tissue IAEA-407). The method was applied to the determination of chromium in waste water, dam water, carrot, parsley and lettuce. Correspondence: Ali Rehber Türker, Department of Chemistry, Faculty of Science and Arts, Gazi University, TR-06500 Ankara, Turkey     

An Electrode-Separated Piezoelectric Sensor as a Surface Monitoring Technique for Anionic Surfactant Adsorption on Quartz Surface

 In the configuration of an electrode-separated piezoelectric sensor (ESPS), the quartz crystal surface is in a direct contact with the liquid phase. With the pre-adsorption of Ca²⁺ as the ionic bridge, anionic surfactant can adsorb on the negatively charged quartz surface (pH > 2.0). The adsorption process of sodium dodecyl benzenesulfonate (SDBS) was monitored in real time with the ESPS method. It was shown that the adsorption of SDBS on quartz surface by Ca²⁺ inducement was reversible with respective to the dilution of solution phase. The adsorption behavior can be analyzed using Langmuir model. The adsorption and desorption rate constants were estimated to be k _a  = (108.4 ± 6.4) mol⁻¹L s⁻¹ and k _d  = (2.57 ± 0.32) × 10⁻³ s⁻¹, respectively. The observed adsorption densities in the ESPS method were significantly greater than the true ones. The influence on surface roughness of the quartz disc on adsorption densities should be corrected by adding a calibration coefficient in the Sauerbrey equation. The saturation adsorption density is 0.223 μg/cm² for SDBS on quartz surface. Double layer occurs for the adsorption of SDBS on quartz surface. Received July 25, 2001. Revision September 17, 2001.     

Kinetic Determination of Trace Amounts of Cu(II) in Water Based on its Catalytic Effect on the Reaction of Mercaptosuccinic Acid and Cr(VI)

 A kinetic method is presented for the determination of Cu(II) in water. It is based on the catalytic effect of Cu(II) on the oxidation of mercaptosuccinic acid by chromate in acidic media. The extent of the reaction is followed spectrophotometrically at 345 nm and pseudo-first order rate coefficients are determined as a function of catalyst concentration. The optimum operating conditions regarding ionic strength, temperature and concentration of reagents were established. Interference by several ionic species was studied and the effects of Fe(III) and Pb(II) were suppressed by complexation with pyrophosphate. Calibration lines were obtained for both low (30–640 μg · l⁻¹) and high (640–1500 μg · l⁻¹) catalyst concentrations. The relative standard deviation for 625 μg · l⁻¹ Cu(II) is 6.1% (n = 5). The detection limit is 22 μg · l⁻¹. The method was applied to real samples of river water of the mining region of Baia-Mare, Northern Romania. The results were compared to those obtained by an officially standardized AAS method. Good agreement was attained. The method is inexpensive, fairly rapid and sensitive. Moreover, its working range covers the exact range of concentrations usually encountered in the mentioned geographic area. Received July 28, 2000; accepted December 10, 2001; published online June 24, 2002     

Establishment of heterodinuclear replacement complexation and its application to direct determination of iron in natural water with dibromo-o-nitrophenylfluorone

The chromophore dibromo-o-nitrophenylfluorone (DBNPF) was used to complex Fe(III) and Cu(II) at pH 5.88. Fe(III) can competitively replace Cu(II) from its dinuclear complex Cu(DBNPF)Cu, and forms the Cu(DBNPF)Fe heterodinuclear complex. The Fe-DBNPF and Cu-DBNPF complexes were also characterized by the spectral correction technique. The heterodinuclear replacement complexation (HRC) is proposed and first used for the quantitative detection of iron in trace level with high sensitivity and good selectivity by the light-absorption ratio variation approach. The limit of detection of Fe is 1.0 μg L⁻¹. The method has been successfully applied to the direct determination of Fe(II, III) dissolved and bound to suspended substances in natural water.     

Determination of atrazine, desethyl atrazine and desisopropyl atrazine in environmental water samples using hollow fiber-protected liquid-phase microextraction and high performance liquid chromatography

A new method based on hollow fiber-protected liquid-phase microextraction (LPME) was developed for the simultaneous determination of atrazine, desethyl atrazine and desisopropyl atrazine in environmental water samples. In LPME, analytes were extracted into 1-octanol immobilized in the micropores of a poly(vinylidene fluoride) porous hollow fiber membrane, and back extracted into the acceptor (4 M HCl) filled in the lumen of the hollow fiber. After LPME, the analytes trapped in the acceptor were analyzed with high-performance liquid chromatography after neutralization. The effect of extraction factors such as sample pH, acceptor pH, salinity, extraction time, stirring rate, and humic acid were studied. Under the optimized conditions, the limits of detection and relative standard deviations were respectively in the range of 0.5–1.0 μg L⁻¹ and 3.9–4.7% (n = 5). The proposed method was applied to determine atrazine, desethyl atrazine and desisopropyl atrazine in wastewater and groundwater samples. The three analytes were below the limits of detection, but good relative spiked recoveries over 90.1 ± 5.9% at 5 μg L⁻¹ spiked level were obtained.     

Cloud point extraction procedure for flame atomic absorption spectrometric determination of lead(II) in sediment and water samples

The conditions for cloud point extraction of lead(II) from aqueous solutions were investigated and optimized. The procedure is based on the separation of Pb(II) – brillant cresyl blue (BCB) complexes into the micellar media by adding the surfactant Triton X-114. After phase separation, the surfactant-rich phase was dissolved with 1 mol L⁻¹ HNO₃ in ethanol and diluted with 1 mol L⁻¹ HNO₃ solution before lead was determined by flame atomic absorption spectrometry. Optimization of the pH, ligand and surfactant quantities, incubation time, temperature, viscosity, sample volume, and interfering ions was performed. The effects of the matrix ions were also examined. The detection limits for three times the standard deviations of the blank for lead were 7.5 μg L⁻¹ for water samples and 0.33 μg g⁻¹ for sediment samples. The validity of cloud point extraction was checked by employing certified reference samples of Lake Sediment IAEA-SL-1 and Sewage Sludge BCR-CRM 144R. The procedure was applied to natural waters and sediment samples with satisfactory results (recoveries >95%, relative standard deviations <6.4%).     

Coprecipitation of lead and cadmium using copper(II) mercaptobenzothiazole prior to flame atomic absorption spectrometric determination

A coprecipitation method using a combination of 2-mercaptobenzothiazole (MBT) as a chelating reagent and copper as the coprecipitate carrier is described for the determination of trace lead and cadmium by flame atomic absorption spectrometry. The coprecipitation conditions, such as the effect of pH, the amount of carrier element and reagent, standing time, sample volume and matrix effects were examined in detail. It was found that lead and cadmium are coprecipitated quantitatively (≥95%) with Cu(II)-MBT at pH 9 and that the relative standard deviations (n = 7) were ≤1.6%. When using the enrichment factors of 150-fold for lead and cadmium, the detection limits (3s/b) obtained are 1.08 for lead and 0.04 μg L⁻¹ for cadmium. The method was validated with spiked sea water, stream water, well water, and vegetable samples.     

Chemiluminescence method for the determination of mitoxantrone by the enhancement of the tris-(4,7-diphenyl-1,10-phenanthrolinedisulfonic acid)ruthenium(II)–cerium(IV) system

2,5-Dimercapto-1,3,4-thiadiazole (DMTD) self-assembled monolayer on gold electrode was prepared and investigated by electrochemical measurement. The DMTD/Au electrode exhibited a significantly increased sensitivity and selectivity for Pb(II) in acetate buffer (pH 5.5) at a potential of −1.0 V (vs Ag/AgCl) for 4 min by anodic stripping voltammetry. The influence of various experimental parameters on the voltammetric response was studied. Under the optimized working conditions, the dependence of the stripping peak current response on concentration of Pb(II) was linear in the range of 1–45 μmol L⁻¹ with a correlation coefficient of 0.9988, and the detection limit was 0.10 μmol L⁻¹. The relative standard deviation of the results was 3.4% for six successive determinations of a 20 μmol L⁻¹ Pb(II) solution. A study of interfering substances was also performed. The method was applied to the determination of Pb(II) in water samples with satisfactory results. Correspondence: Hong Qun Luo, School of Chemistry and Chemical Engineering, Southwest University, 400715 Chongqing, China     

Determination of Cd(II), Cu(II) and Ni(II) in aqueous samples by ICP-OES after on-line preconcentration in column packed with silica modified with 2-aminothiazole

This work describes the synthesis and characterization of 2-aminothiazole modified silica gel (SiAT) and the studies of adsorption and pre-concentration (in batch and using a flow-injection system coupled with optical emission spectrometer) of Cd(II), Cu(II) and Ni(II) in aqueous medium. The adsorption capacity for each metal ions in mmol g⁻¹ was: Cu(II) = 1.18, Ni(II) = 1.15 and Cd(II) = 1.10. The results obtained in the flow experiments showed about 100% of recovering of the metal ions adsorbed in a mini-column packed with 100 mg of SiAT, using 100 μL of 2.0 mol L⁻¹ HCl solution as eluent. The quantitative sorption–desorption of the metal ions made possible the application of a flow-injection system in the pre-concentration and quantification by ICP-OES of metal ions at trace level in natural water samples. Correspondence: Pedro M. Padilha, Departamento de Química e Bioquímica, I.B., UNESP, 18618-000 Botucatu, SP, Brazil     

Selective Spectrophotometric Determination of Aluminium in the Presence of Beryllium and Lanthanide Cations

 A spectrophotometric method for the selective determination of Al(III) in the presence of Be and lanthanide cations is proposed. It is based on the selective reaction of Semi-Xylenol Orange with Al(III) at pH 2.6. The presence of 8% v/v of 1,2- ethanediol serves to stabilize the chelate formed by heating for 5 min at 100 °C. 0.5 mg each of Be(II), Ce(III), La(III), 4 mg of Mn(II), 1.2 mg of Pb(II), 1 mg of Tl(I), 40 mg each of Ca(II) and Mg(II) and 1.9 mg of sodium dihydrogen phosphate are tolerable. A ligand buffer of HEDTA-Pb is incorporated to further enhance the selectivity of the color reaction. Under the specified condition Semi-Xylenol Orange reacts with Al(III) to form a 1:1 chelate, its molar absorptivity at 526 nm was found to be 3.3 × 10⁴ L mol⁻¹ cm⁻¹. The linear regression equation for 2–20 μg of Al(III) is A = 0.04458C + 0.0112 (here C stands for the concentration of Al(III), μg per 25 mL), and correlation coefficient γ = 0.9988. The RSD at a level of 10 μg (n = 10) and LOQ were found to be 3.5% and 2 μg respectively. Author for correspondence. E-mail: weston@online.sh.cn Received November 15, 2002; accepted February 11, 2003 Published online June 13, 2003