Solid-phase extraction of Fe(III), Pb(II) and Cr(III) in environmental samples on amberlite XAD-7 and their determinations by flame atomic absorption spectrometry

Vortex-assisted magnetic solid phase extraction of Pb and Cu in some herb samples on magnetic multiwalled carbon nanotubes

This study is the development of a new solid phase extraction method based on using magnetic multiwalled carbon nanotubes impregnated with 1-(2-pyridylazo)2-naphthol (PAN) for separation, preconcentration, and flame atomic absorption spectrometric determination of Pb(II) and Cu(II). Optimization of the method was done by investigating pH effect, amount of magnetic multiwalled carbon nanotubes impregnated with PAN, eluent type and volume, matrix effects, and volume of the sample. The optimum adsorbent amount was found to be 75 mg and the optimum pH value was found as 5.5. The detection limits were 16.6 μg L^-1 for Pb(II) and 18.9 μg L^-1 for Cu(II). The relative standard deviations (RSD%) were less than 4%. Two certified reference materials: SPS-WW2 wastewater and NCS-DC73349 (bush branches and leaves) were used to test the validation of the method. The method was successfully applied to the analysis of Pb(II) and Cu(II) ions in daisy, mint, paprika, sage, rosemary, daphne leaves, heather, green tea, andViburnum opulussamples.

Dispersive liquid-liquid microextraction of lead(II) as 5-(4-dimethylaminobenzylidene) rhodanine chelates from food and water samples

A dispersive liquid-liquid microextraction procedure for lead(II) as its 5-(4-dimethylaminobenzylidene) rhodanine complex has been established prior to its microsampling flame atomic absorption spectrometric determination. The influences of various analytical parameters including pH, solvent type and volume, dispersive solvent type and volume, 5-(4-dimethylaminobenzylidene) rhodanine amount, salt effect, and centrifugation time and speed were investigated. The effects of certain alkali, alkaline earth, and transition metal ions on the quantitative extraction of lead(II) were also studied. Quantitative recoveries were obtained at pH 6. The enrichment factor was calculated as 125. The detection limit for lead is 1.1 μg/L. The accuracy of the method was tested with the additions recovery test and analysis of the standard reference materials (SPS-WW2 waste water, NIST SRM 1515 apple leaves, and TMDA-51.3 fortified water). Applications of the present procedure were tested by analyzing water and food samples.

Separation and speciation analysis of zinc from Flammulina velutipes

Orthogonal experiment was applied to optimize the water extraction parameters of zinc from Flammulina velutipes, and then the extracts were separated by membrane filter (0.45 μm) and D101 macroporous resin. Six different species of Zn were obtained and the Zn content of various species were determined by flame atomic absorption spectrometry. The optimized conditions for the extraction of Zn were: ratio of dried material to water, 1:30; extraction temperature, 75°C; extraction time, 120 minutes. About 34.43 μg Zn was extracted from 1 g dried F. velutipes powder under the optimal conditions. The recovery value for Zn was 96.5% with a low relative standard deviation. In addition, the content of the organic state of Zn was more than that of the inorganic state, and most of the organic state Zn was found in the polysaccharide and protein fractions.

Preconcentration procedures for the determination of chromium using atomic spectrometric techniques: A review

Chromium is one of the regulated toxic metals in the environment. Naturally, this element exists mainly in two oxidation: Cr(III) and Cr(VI). In general, Cr(VI) is more toxic than Cr(III). Cr(VI) affects human physiology, accumulates in the food chain and causes severe health problems ranging from simple skin irritation to lung carcinoma. Hence, the determination of chromium traces as well as its speciation in environmental samples is a very important task. In recent years, several preconcentration methods such as coprecipitation, liquid-liquid extraction, dispersive liquid-liquid microextraction, cloud point extraction, and solid phase extraction have been developed and widely used. The aim of this study is to review the recent literature (mainly last 5 years) on the preconcentration technologies those have been used in chromium removal before the determination step by atomic spectrometric techniques. Their advantages and limitations in application are also evaluated.

Amberlite IR-120 modified with 8-hydroxyquinoline as efficient adsorbent for solid-phase extraction and flame atomic absorption determination of trace amounts of some metal ions

In this study, a solid-phase extraction method combined with atomic absorption spectrometry for extraction, preconcentration, and determination of iron (Fe(3+)), copper (Cu(2+)), and lead (Pb(2+)) ions at trace levels in water samples has been reported. The influences of effective parameters such as flow rate, pH, eluent conditions (type, volume, and concentration), sample volumes, and interference of matrix ions on metal ions recoveries were studied. Under optimized conditions, the limits of detection were found in the range of 0.7-2.2 μg L(-1), while preconcentration factors for Fe(3+), Cu(2+), and Pb(2+) ions were found to be 166, 200, and 250, respectively, and loading half time (t (1/2)) values were less than 2 min for all analyte ions. The proposed procedure was applied for the determination of metal ions in different water samples with recovery of >94.4% and relative standard deviation less than 4.4% for N = 5.

Solid phase extraction and preconcentration of Cu(II), Pb(II), and Ni(II) in environmental samples on chemically modified Amberlite XAD-4 with a proper Schiff base

A new chelating resin, Amberlite XAD-4 loaded with N,N-bis(salicylidene)cyclohexanediamine (SCHD), was synthesized and characterized. The resin Amberlite XAD-4-SCHD was used for selective separation, preconcentration, and determination of Cu(II), Pb(II), and Ni(II) ions in water samples by flame atomic absorption spectrometry (FAAS). Effects of pH, concentration, and volume of elution solution; flow rate of elution; and sample solution, sample volume, and interfering ions for the recovery of the analytes were investigated. These metal ions can be desorbed with 0.5-M HNO3 (recovery, 98%-101%). The sorption capacity was found between 1.38×10(-1) and 3.58×10(-1) mmol/g. In order to evaluate the accuracy of the proposed procedure, the certified reference materials, BCR-032 (Moroccan phosphate rock) and BCR-715 (industrial effluent wastewater), were analyzed. The detection limits of the method were found to be 0.11, 1.91, and 0.43 μg/L for Cu(II), Pb(II), and Ni(II), respectively. The method was applied to the extraction and the recovery of copper, lead, and nickel in wastewater and other water samples.

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.

Solid phase selective separation and green preconcentration of Cu, Zn, Pb and Cd in drinking water by using novel functionalized resin

A new solid — phase extraction sorbent was developed based on stepwise anchoring of two ligand molecules for the determination of copper, zinc, lead and cadmium in drinking water by flame AAS. Amberlite XAD-2 functionalized with 4′-(2-hydroxyphenylazo)-3′-methyl-1′-phenyl-2′-pyrazolin-5′-one (HPAPyr) was utilized for preconcentration/separation of these elements. The sorbent was prepared by two successive azo coupling reactions. First, 2-aminophenol was anchored to the amino groups in the resin resulted from nitration followed by reduction. Then, the resulted 2-aminophenol functionalized resin was further diazotized and coupled to the pyrazolone compound and the final product HPAPyr-XAD-2 was characterized by IR and elemental analysis. The optimum pH range for sorption, shaking time, exchange capacity, sample flow rate, preconcentration factor and interference from co-existing ions were investigated. All metal ions were quantitatively desorbed from the resin by 4.5 mol L−1 nitric acid solution. The sorbent provides limit of detection within the range 0.9–3.3 µg L−1 and concentration factor up to 250. The procedure was validated by analysis of certified material NIST-SRM 1577b. Application to drinking water showed satisfactory results with relative standard deviation RSD ≤ 8.5%.

Development of a cloud-point extraction method for copper and nickel determination in food samples

A new, simple and versatile cloud-point extraction (CPE) methodology has been developed for the separation and preconcentration of copper and nickel. The metals in the initial aqueous solution were complexed with 2-(2'-benzothiazolylazo)-5-(N,N-diethyl)aminophenol (BDAP) and Triton X-114 was added as surfactant. Dilution of the surfactant-rich phase with acidified methanol was performed after phase separation, and the copper and nickel contents were measured by flame atomic absorption spectrometry. The variables affecting the cloud-point extraction were optimized using a Box-Behnken design. Under the optimum experimental conditions, enrichment factors of 29 and 25 were achieved for copper and nickel, respectively. The accuracy of the method was evaluated and confirmed by analysis of the followings certified reference materials: Apple Leaves, Spinach Leaves and Tomato Leaves. The limits of detection expressed to solid sample analysis were 0.1 microg g(-1) (Cu) and 0.4 microg g(-1) (Ni). The precision for 10 replicate measurements of 75 microg L(-1) Cu or Ni was 6.4 and 1.0, respectively. The method has been successfully applied to the analysis of food samples.

A solid phase extraction procedure for Fe3+, Cu2+ and Zn2+ ions on 2-phenyl-1H-benzo[d] imidazole loaded on Triton X-100-coated polyvinyl chloride

A new and efficient solid phase extraction method is described for the preconcentration of trace heavy metal ions. The method is based on the adsorption of Fe(3+), Cu(2+) and Zn(2+) on 2-phenyl-1H-benzo[d] imidazole (PHBI) loaded on Triton X-100-coated polyvinyl chloride (PVC). The influences of the analytical parameters including pH and sample volume were investigated. Common coexisting ions did not interfere on the separation and determination of analytes under study. The adsorbed analytes were desorbed by using 5 mL of 4 mol L(-1) nitric acid. The preconcentration factor is 90. The detection limits (3 sigma) were in the range of 0.95-1 microg L(-1). The sorbent exhibited excellent stability and its sorption capacity under optimum conditions has been found to be more than 2.7 mg of ions per gram of sorbent. The recoveries of analytes were generally higher than 95%. The relative standard deviations (R.S.D.s) were generally lower than 4%. The method has been successfully applied to some real samples.