On-line preconcentration system using a minicolumn of polyurethane foam loaded with Me-BTABr for zinc determination by Flame Atomic Absorption Spectrometry

On-line Determination of Zinc in Water and Biological Samples after Its Preconcentration onto Zincon Anchored Polyurethane Foam

A fast and sensitive on-line procedure for the determination of zinc in water and biological samples was developed. Zinc was preconcentrated in a mini-column packed with polyurethane foam (PUF) chemically modified with zincon via -N=N- bonding. The optimal conditions for preconcentration were pH 8.5 and sample flow rate of 4.0 mL min(-1). Quantitative desorption of Zn(II) was obtained by 0.1 mol L(-1) hydrochloric acid and subsequent spectrophotmetric determination using 4-(2-pyridylazo)-resorcinol at 498 nm. The obtained detection limit was found to be 3.0 ng mL(-1), precision (RSD) was 4.8 and 6.7% at 20 and 110 ng mL(-1), respectively, for 60 s preconcentration time and enrichment factor was 31. The linearity range was from 10 to 120 ng mL(-1) and maximum sample throughput was 20 h(-1). Finally, the method was successfully applied to the determination of zinc in tap water, Nile River water and human urine samples with RSD in the range of 1.1 - 8.3%.

Flow injection online solid phase extraction system using Amberlite XAD-16 functionalized with 8-hydroxyquinoline for copper and zinc determination by flame atomic absorption spectrometry

A newly functionalized resin has been applied in an on-line preconcentration system for copper and zinc determination.

Utility of solid-phase spectrophotometry to determine trace amounts of zinc in environmental and biological samples

A solid-phase spectrophotometric analysis has been proposed for preconcentration and determination of Zn(II) in real samples. The procedure is based on sorption of zinc(II) as 5-(2-benzothiazolylazo)-8-hydroxyquinoline (BTAHQ) complex on dextran-type anion-exchange gel (Sephadex DEAE A-25). The influences of the analytical parameters, including pH of the aqueous solution, amounts of BTAHQ, and sample volume, were investigated. The absorbance of the gel at 675 and 750 nm, packed in a 1.0-mm cell, was measured directly. The molar absorptivities were found to be 2.50×10(7) and 9.55×10(7)L mol(-1) cm(-1) for 500 and 1000 ml, respectively. Calibration was linear over the range of 0.05-1.10 μg L(-1) with a relative standard deviation of less than 1.60% (n=10). The detection and quantification limits of the 500-ml sample method were 12 and 40 ng L(-1) on using 50 mg. For the 1000-ml sample, the detection and quantification limits were 7.5 and 25 ng L(-1) using a 50-mg exchanger. Increasing the sample volume can enhance sensitivity. No considerable interferences were observed from other investigated anions and cations on the Zn(II) determination. The proposed method was applied to determine zinc in environmental samples, including natural water, food, certified reference materials, meat, and biological samples, comparing the results simultaneously with those obtained using a flame atomic absorption spectrophotometer, whereby the validity of the method was tested.

Synthesis and application of alizarin complexone functionalized polyurethane foam: preconcentration/separation of metal ions from tap water and human urine

A new chelating sorbent has been synthesized by the covalent condensation of alizarin complexone (ALC) to polyurethane foam (PUF) through -N=C- group. The material was characterized by IR, (1)H NMR and chemical proof. Iminodiacetic acid groups are found in the prepared sorbent and the reaction proceeded via condensation between the toluidine moieties in the PUF and non-hydrogen bonded carbonyl group in ALC. Also, the possibility of elimination reaction between the groups (NH(2), NH and OH) in the polymer and carboxylic groups in the reagent was excluded. The material has been used to separate/preconcentrate Cu(2+), Zn(2+) and Cd(2+) prior to their determination by flame atomic absorption spectrometry (FAAS). Chemical and flow variables such as sample pH, sorbent capacity, sample flow rate and interference from co-existing ions were investigated. All metal ions are quantitatively desorbed by 0.1 mol L(-1) nitric acid solution. The procedure provides concentration factor 100 and limits of detection 0.013 microg mL(-1). The method was validated by the analysis of certified reference materials and real samples such as tap water and human urine.

Simultaneous preconcentration of copper, zinc, cadmium, and nickel in water samples by cloud point extraction using 4-(2-pyridylazo)-resorcinol and their determination by inductively coupled plasma optic emission spectrometry

A procedure for simultaneous separation/preconcentration of copper, zinc, cadmium, and nickel in water samples, based on cloud point extraction (CPE) as a prior step to their determination by inductively coupled plasma optic emission spectrometry (ICP-OES), has been developed. The analytes reacted with 4-(2-pyridylazo)-resorcinol (PAR) at pH 5 to form hydrophobic chelates, which were separated and preconcentrated in a surfactant-rich phase of octylphenoxypolyethoxyethanol (Triton X-114). The parameters affecting the extraction efficiency of the proposed method, such as sample pH, complexing agent concentration, buffer amount, surfactant concentration, temperature, kinetics of complexation reaction, and incubation time were optimized and their respective values were 5, 0.6 mmol L(-1), 0.3 mL, 0.15% (w/v), 50 degrees C, 40 min, and 10 min for 15 mL of preconcentrated solution. The method presented precision (R.S.D.) between 1.3% and 2.6% (n=9). The concentration factors with and without dilution of the surfactant-rich phase for the analytes ranged from 9.4 to 10.1 and from 94.0 to 100.1, respectively. The limits of detection (L.O.D.) obtained for copper, zinc, cadmium, and nickel were 1.2, 1.1, 1.0, and 6.3 microg L(-1), respectively. The accuracy of the procedure was evaluated through recovery experiments on aqueous samples.

Otimização multivariada e aplicação do sorvente SiO2-Nb2O5 para determinação em linha de Ni(II) em matriz aquosa

Neste estudo foi desenvolvido uma metodologia para determinação de Ni(II) em amostras de água usando a extração em fase sólida (SPE) em um sistema por injeção em fluxo (FI) e detecção por espectrometria de absorção atômica em chama (F AAS). O adsorvente utilizado para a extração e pré-concentração do Ni(II) foi a sílica gel modificada com óxido de nióbio(V). Variáveis químicas e de fluxo do sistema em linha foram otimizadas usando planejamento fatorial completo (N = 2k + 3). As condições iniciais do sistema FI-F AAS foram volume de amostra de 10 mL e concentração de Ni(II) de 100 µg L-1. O tampão Sörensen foi selecionado neste estudo. A resposta analítica utilizada foi absorvância integrada. Após a otimização foram obtidos os parâmetros analíticos de mérito: faixa linear de trabalho estudada de 5-100 µg L-1; R = 0.9999; RSD = 1,5% (35 µg L-1, n = 7); limite de detecção de 0,8 µg L-1; limite de quantificação de 2,7 µg L-1 e fator de enriquecimento de 92,25. Foram analisadas amostras de água do rio Araranguá e a da rede de abastecimento da cidade de Florianópolis, ambas do estado de Santa Catarina. As duas amostras não apresentaram concentração de níquel acima do limite de detecção e após fortificação das mesmas os valores de recuperação foram na faixa de 100,2 a 103,8%.

Use of 8-hydroxyquinoline-chitosan chelating resin in an automated on-line preconcentration system for determination of zinc(II) by F AAS

This study presents the development of an on-line preconcentration system for zinc(II) determination in aqueous samples. The analyte was trapped in a mini-column filled with a chelating resin based on a chitosan biopolymer modified with 8-hydroxyquinoline obtained by the diazotization reaction. Flow and chemical variables of the system, as well as the potential interference ions, were optimized through a multivariate procedure. The factors selected were sample pH, eluent concentration (HNO(3)), and sample and eluent flow rates. It was verified through a full factorial design that the sample pH and eluent flow rate factors were statistically significant at the 95% confidence level. A final optimization of the significant factors was carried out using a Doehlert matrix. The preconcentration system was linear between 2.5 and 75 microgL(-1), with a regression coefficient of 0.9995. The enrichment factor was 17.6. The limits of detection and quantification were 0.8 and 2.5 microgL(-1), respectively. The repeatability and the analytical frequency were, respectively, 2.7 (25.0 microgL(-1), n=8) and 18 samples per hour. Results for recovery tests using mineral water samples were between 85 and 93%. Certified reference materials were analyzed in order to check the accuracy of the proposed method.

Online preconcentration and determination of trace amounts of zinc in nature waters

A simple, sensitive, reliable and flexible flow injection spectrophotometric method is proposed for on-line preconcentration and determination of trace amounts of zinc in water. At the presence of Tween-80 in pH 9.3 buffer solutions, the shade of color of Zn (II)-PAN complex is in a linear relation to the zinc amount at the point of the maximum absorption peak of 560 nm. The optimal experimental conditions, including reaction conditions and preconcentration conditions, had been obtained. The linear range of the proposed method was between 2.0 and 360 mug L(-1) and the detection limit was 0.42 mug L(-1). The relative standard deviation was 3.55% and 2.14% for 5.0 mug L(-1) and 50 mug L(-1) of zinc standard solution (n = 8). The method had been successfully applied to zinc determination in water samples and the analytical results were satisfactory.

Minicolumn Field Sampling-Preconcentration of Trace Zinc from Seawater and Its Laboratory Detection by Flow Injection Flame Atomic Absorption Spectrometry

A simple field sampling-preconcentration method for zinc determination in seawater is described. Seawater was collected in situ by pumping it through a minicolumn packed with a chelating resin (Chelite P) connected to a field flow preconcentration system (FFPS). These packed minicolumns retain the dissolved zinc, and once are loaded with the analyte, they are returned to the laboratory where they are sequentially inserted into a flow injection system for on-line zinc elution with diluted hydrochloric acid and flame atomic absorption spectrometric detection. A factorial design has been used to optimize the FFPS and the flow injection elution process. The proposed method has a linear calibration range from 0.07 to at least 9.4 microg L(-1) of zinc, with a detection limit of 0.02 microg L(-1) and a throughput of 26 samples h(-1). Validation was carried out against certified reference water samples. This procedure has been successfully applied to the determination of Zn in seawater samples from Galicia (Spain).