Yunhui Zhai

Solid-phase extraction of iron(III) with an ion-imprinted functionalized silica gel sorbent prepared by a surface imprinting technique

A new Fe(III)-imprinted amino-functionalized silica gel sorbent was prepared by a surface imprinting technique for selective solid-phase extraction (SPE) of Fe(III) prior to its determination by inductively coupled plasma atomic emission spectrometry (ICP-AES). Compared with non-imprinted polymer particles, the ion-imprinted polymers (IIPs) had higher selectivity and adsorption capacity for Fe(III). The maximum static adsorption capacity of the ion-imprinted and non-imprinted sorbent for Fe(III) was 25.21 and 5.10mg g(-1), respectively. The largest selectivity coefficient of the Fe(III)-imprinted sorbent for Fe(III) in the presence of Cr(III) was over 450. The relatively selective factor (alpha(r)) values of Fe(III)/Cr(III) were 49.9 and 42.4, which were greater than 1. The distribution ratio (D) values of Fe(III)-imprinted polymers for Fe(III) were greatly larger than that for Cr(III). The detection limit (3sigma) was 0.34microg L(-1). The relative standard deviation of the method was 1.50% for eight replicate determinations. The method was validated by analyzing two certified reference materials (GBW 08301 and GBW 08303), the results obtained is in good agreement with standard values. The developed method was also successfully applied to the determination of trace iron in plants and water samples with satisfactory results.

Tris(2-aminoethyl) amine functionalized silica gel for solid-phase extraction and preconcentration of Cr(III), Cd(II) and Pb(II) from waters

A new tris(2-aminoethyl) amine (TREN) functionalized silica gel (SG-TREN) was prepared and investigated for selective solid-phase extraction (SPE) of trace Cr(III), Cd(II) and Pb(II) prior to its determination by inductively coupled plasma atomic emission spectrometry (ICP-AES). Identification of the surface modification was characterized and performed on the basis of FT-IR. The separation/preconcentration conditions of analytes were investigated, including effects of pH, the shaking time, the sample flow rate and volume, the elution condition and the interfering ions. At pH 4, the maximum adsorption capacity of Cr(III), Cd(II) and Pb(II) onto the SG-TREN were 32.72, 36.42 and 64.61 mg g(-1), respectively. The adsorbed metal ions were quantitatively eluted by 5 mL of 0.1 mol L(-1) HCl. Common coexisting ions did not interfere with the separation. According to the definition of International Union of Pure and Applied Chemistry, the detection limits (3sigma) of this method for Cr(III), Cd(II) and Pb(II) were 0.61, 0.14 and 0.55 ng mL(-1), respectively. The relative standard deviation under optimum conditions is less than 4.0% (n=11). The application of this modified silica gel to preconcentration trace Cr(III), Cd(II) and Pb(II) of two water samples gave high accurate and precise results.

Preparation, characterization and application of N-2-Pyridylsuccinamic acid-functionalized halloysite nanotubes for solid-phase extraction of Pb(II)

Halloysite nanotubes (HNTs) were chemically modified with N-2-Pyridylsuccinamic acid (PSA) to produce a new nano-adsorbent (HNTs-PSA) for selective solid-phase extraction of Pb(II). The new adsorbent was characterized by Fourier transform infrared spectroscopy (FT-IR), transmission electron microscope (TEM), thermogravimetric analysis (TGA), and elemental analysis to evaluate the surface modification. Under the optimized conditions (pH 5, flow rate 1.5 mL min(-1)), Pb(II) was retained on the column packed with HNTs-PSA, and then was quantitatively eluted by 1.5 mL 0.5 mol L(-1) HCl and determined by inductively coupled plasma-optical emission spectrometry. An enrichment factor of 67 was obtained using 30 mg of HNTs-PSA. The maximum adsorption capacity for Pb(II) was found to be 23.58 mg g(-1). The detection limits of this method for Pb(II) was 0.32 μg L(-1). The relative standard deviation under optimum conditions was 3.4% (n = 11). The developed method was validated by analyzing a certified reference material, and then successfully applied to the determination of Pb(II) in actual samples.

Selective solid phase extraction of trace Sc(III) from environmental samples using silica gel modified with 4-(2-morinyldiazenyl)-N-(3-(trimethylsilyl)propyl)benzamide

In this study, a new 4-(2-morinyldiazenyl)-N-(3-(trimethylsilyl)propyl)benzamide modified silica gel (SG-MTPB) sorbent was prepared and characterized by FT-IR spectroscopy and studied for separation and preconcentration of Sc(III) prior to its determination by inductively coupled plasma atomic emission spectrometry (ICP-AES). Experimental conditions for effective adsorption of trace Sc(III) were optimized using both batch and column procedures. At pH 3, Sc(III) could be quantitatively adsorbed on the new sorbent. And the adsorbed Sc(III) could be completely eluted by using 2 mL of 6 mol L(-1) of HCl+2% CS(NH(2))(2). Most common coexisting ions did not interfere with the separation and preconcentration of Sc(III) at optimal conditions. The maximum static adsorption capacity of the sorbent for Sc(III) was 600 micaromol g(-1) while the time of 95% adsorption was less than 2 min. The detection limit of present method was found to be 0.085 micarog g(-1), and the relative standard deviation (R.S.D.) was lower than 1.3%. The method was also successfully applied to the preconcentration of trace Sc(III) in the environmental samples with satisfactory results.

A pre-enrichment procedure using diethyldithiocarbamate-modified TiO2 nanoparticles for the analysis of biological and natural water samples by ICP-AES

In this article, a new method that utilizes a diethyldithiocarbamate-modified nanometre TiO2 (TiO2–DDTC) as solid-phase extractant has been developed for simultaneous preconcentration of trace Cu(II), Pb(II), Zn(II), and Cd(II) prior to measurement by inductively coupled plasma atomic emission spectrometry (ICP-AES). The separation/preconcentration conditions of analytes, which include the effects of pH, sample flow rate and volume, elution conditions, and interfering ions on the recovery of the analytes, were investigated. At pH 5, the adsorption capacity of modified nanometre TiO2–DDTC was found to be 6.2, 19, 4.7, and 6.0 mg/g for Cu(II), Pb(II), Zn(II), and Cd(II), respectively. According to the definition of IUPAC, the detection limits (3σ) of this method for Cu(II), Pb(II), Zn(II), and Cd(II) were 0.41, 1.7, 0.39, and 0.52 ng/mL, respectively. The proposed method achieved satisfied results when applied to the determinations of trace Cu(II), Pb(II), Zn(II), and Cd(II) in biological and natural water samples.

Silica gel modified with diaminothiourea as selective solid-phase extractant for determination of Hg(II) in biological and natural water samples

In this paper, a new method that utilizes diaminothiourea-modified silica gel as solid-phase extractant has been developed for preconcentration of trace Hg(II) prior to the measurement by cold-vapour atomic absorption spectrometry. The separation/preconcentration conditions of the analyte, which include the effects of the pH, sample flow rate and volume, elution conditions, shaking time, and interfering ions on the recovery of the analyte were investigated. At pH 2, the adsorption capacity of modified silica gel for Hg(II) was found to be 36.3 mg/g. According to the definition of IUPAC, the detection limits (3σ) of this method for Hg(II) was 0.28 ng/mL. The proposed method yielded satisfactory results when it was applied to the determination of trace Hg(II) in biological and natural water samples.