Barbara Leśniewska

Ion-Exchange Preconcentration and Separation of Trace mounts of Platinum and Palladium

ABSTRACT The preconcentration and separation of platinum and palladium from weakly acidic solution (pH=4) were done on microcolumn packed with Cellex-T resin. Selective platinum elution from the column was performed with 0.01 mol/l glycine solution at pH=12, while for palladium elution 1.2 mol/l thiourea (pH=0.5) or 4.0 mol/l potassium thiocyanate (pH=1) may be used. As the detection technique was used either FAAS or GFAAS, depending on the concentration of studied metals in the eluate.

Separation of ruthenium from environmental samples on polymeric sorbent based on imprinted Ru(III)-allyl acetoacetate complex

A new ion imprinted polymer (IIP) for ruthenium recognition/pre-concentration was prepared via bulk polymerization using methacrylic acid as the functional monomer and ethylene glycol dimethacrylate as the cross-linking agent in the presence of Ru(III)-allyl acetoacetate complex as a template. The synthesized IIP was used as a new support for solid phase extraction (SPE) of ruthenium from environmental samples before electrothermal atomic absorption spectrometric determination. Variables affecting the SPE process, such as pH, load and elution flow rates, as well as concentration and volume of the eluting solution, were evaluated. The optimized procedure consists of a sample loading (sample pH of 6.5 ± 0.5) through IIP-SPE columns containing 200mg of the synthesized IIP at a flow rate of 1.0 mL min(-1). Elution was performed by passing 0.3 mol L(-1) thiourea in 0.1 mol L(-1) HCl at a flow rate of 1.0 mL min(-1). For 10 mL of sample pre-concentration factor of 20 was achieved. The limit of detection of the method was 0.32 ng mL(-1), while the relative standard deviation for six replicated separation processes was 2.5%. Good selectivity of the synthesized material for Ru(III) ions against other transition metal ions assures efficient removal of matrix of analyzed samples (tap and river water, municipal and road sewages, and grass) by the proposed IIP-SPE procedure.

Multi-commutation flow system with on-line solid phase extraction exploiting the ion-imprinted polymer and FAAS detection for chromium speciation analysis in sewage samples

A multi-commutation flow analysis system using on-line solid phase extraction and flame atomic absorption spectrometric detection (MCFA-FAAS) was developed for the study of chromium speciation in sewage samples. A new chromium imprinted polymer was prepared and applied as a selective sorbent for the separation and preconcentration of Cr(III) ions. The polymer was prepared using a Cr(III)-8-hydroxyquinoline complex as a template, styrene as a functional monomer, and divinylbenzene as a crosslinking monomer using 2,2′- azobisisobutyronitrile as an radical initiator for bulk polymerization. The chromium imprinted polymer exhibits good chemical and mechanical stability, sorption capacity and selectivity towards Cr(III) ions. The analyte, Cr(III) ions, was quantitatively retained on the sorbent at pH 9, eluted with 0.3 mL of 0.1 mol L−1 nitric acid and determined by FAAS with a detection limit of 2.1 ng mL−1 and a 33-fold preconcentration factor obtained with a 10 min loading time. The MCFA-FAAS system is fully automated and enables analysis of 1 mL of sample in 4.5 min, which gives a throughput of 12 samples per hour. The accuracy of the proposed method was proved by analysis of a reference material of wastewater RES 10.2 (ielab). The method was successfully applied to the determination of trace amounts of Cr(III) in municipal sewage samples.

Preconcentration of Trace Amounts of Platinum in Water on Different Sorbents

Abstract Three different sorbents for platinum preconcentration in water were investigated: alumina, silica gel with bonded aminopropyl groups and Cellex-T. The sorbents were tested in a microcolumn at the flow rate 3 ml/min. Elution was performed with 2.0 mol/l ammonia, 2.0 mol/l hydrochloric acid and 1.2 mol/l thiourea solution, respectively. The optimal enrichment factor was 400 for the alumina column, when the eluent volume was 25 μl. Satisfactory precision was obtained for all sorbents. As the detection technique was used either FAAS or GFAAS, depending on the concentration of platinum in the eluate.

A novel ion imprinted polymer as a highly selective sorbent for separation of ruthenium ions from environmental samples

A complex of Ru(III) with benzaldehyde thiosemicarbazone was used for the preparation of new ruthenium ion imprinted polymers. The polymers were synthesized using 4-vinylpyridine and styrene as functional monomers, divinylbenzene as a cross-linking agent, and ethanol or chloroform as a porogen in the presence of 2,2′-azobisisobutyronitrile as an initiator via the bulk polymerization technique. The polymers were used in dynamic mode as a selective sorbent for solid phase extraction of Ru(III) ions. The analyte was efficiently retained on the polymers at pH 8.0 ± 0.1 and eluted with 2 mL of 0.3 mol L−1 thiourea in 0.3 mol L−1 HCl. The influence of the type of porogen (ethanol and chloroform) and column size on the separation of analyte on the prepared material was also studied. The efficiency of retention and elution and sample flow rates were higher on columns of smaller diameter and the polymer prepared in ethanol. The analytical performance of the polymer prepared in ethanol such as the recovery of the Ru(III) ions, the reproducibility of the results (<3%), the limit of detection (0.26 ng mL−1), the selectivity in the presence of Pt(IV), Pd(II), Rh(III), Co(II) ions and the sorption capacity (237.4 μg g−1) was superior in comparison to other ruthenium imprinted polymers. The developed separation procedure was successfully applied to electrothermal atomic absorption spectrometric determination of trace amounts of ruthenium in tap and river water, municipal sewage, road runoff, and grass.

Evaluation of ion imprinted polymers for the solid phase extraction and electrothermal atomic absorption spectrometric determination of palladium in environmental samples

The complexes of Pd(II) with ammonium pyrrolidinedithiocarbamate (APDC), N,N′-diethylthiourea (DET) and dimethylglyoxime (DMG) were prepared and imprinted into a polymeric network. The ion-imprinted polymers (IIPs) were synthesized by copolymerization of 4-vinylpyridine (VP) and styrene as functional monomers and divinylbenzene as a cross-linking agent in the presence of 2,2-azo-bis-isobutyronitrile as an initiator. The influence of sample volume, pH and flow rate on the extraction efficiency of Pd was studied under dynamic conditions. Pd(II) could be quantitatively retained on each of the studied sorbents at the pH range of 0.5 to 1.0, and eluted with an acidic solution of thiourea. The polymer with the imprinted Pd-DET-VP complex offered the highest selectivity for Pd(II) over certain matrix components, such as Pt(IV), Ni(II) and Cu(II). The low sample pH is an important advantage of the separation procedure, as it allows an effective separation of Pd(II) from complex environmental matrices. The developed separation method was successfully applied to the electrothermal atomic absorption spectrometric (ETAAS) determination of trace amounts of Pd in tap and river water, grass, and certified platinum ore (CRM SARM 7 and SARM 76) samples with reproducibility below 6.5%. The detection limit for Pd(II) obtained by ETAAS after the pre-concentration on Pd-DET-VP polymer was 0.012 ng mL−1 for 75 mL sample volume.

Recent Advances in On-Line Methods Based on Extraction for Speciation Analysis of Chromium in Environmental Matrices.

The biological activity of Cr(III) and Cr(VI) species, their chemical behavior, and toxic effects are dissimilar. The speciation analysis of Cr(III) and Cr(VI) in environmental matrices is then of great importance and much research has been devoted to this area. This review presents recent developments in on-line speciation analysis of chromium in such samples. Flow systems have proved to be excellent tools for automation of sample pretreatment, separation/preconcentration of chromium species, and their detection by various instrumental techniques. Analytical strategies used in chromium speciation analysis discussed in this review are divided into categories based on selective extraction/separation of chromium species on solid sorbents and liquid-liquid extraction of chromium species. The most popular strategy is that based on solid-phase extraction. Therefore, this review shows the potential of novel materials designed and used for selective binding of chromium species. The progress in miniaturization of measurement systems is also presented.

Extraction of ranitidine and nizatidine with using imidazolium ionic liquids prior spectrophotometric and chromatographic detection.

A new extraction medium was proposed for liquid-liquid extraction of the histamine H2 receptor antagonists ranitidine (RNT) and nizatidine (NZT). The ionic liquids with low vapor pressure and favorable solvating properties for a range of compounds such as 1-butyl-3-methylimidazolium hexafluorophosphate [C4mim][PF6] and 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide [C4mim][Tf2N] were tested for isolation of analytes. The extraction parameters of RNT and NZT, namely, amount of ionic liquid, pH of sample solution, shaking and centrifugation time were optimized. The isolation processes were performed with 1 mL of the ionic liquids. The extracted samples (pH values near 4) were shaken at 1750 rpm. The influence of interfering substances on the efficiency of extraction process was also studied. Methods for the histamine H2 receptor antagonists (ranitidine and nizatidine) determination after their separation using imidazolium ionic liquids by high performance liquid chromatography (HPLC) combined with UV spectrophotometry were developed. The application of ionic liquids in extraction step allows for selective isolation of analytes from aqueous matrices and their preconcentration. The above methods were applied to the determination of RNT and NZT in environmental samples (river water and wastewater after treatment).

On the effect of hydrogen peroxide on the flow-injection determination of platinum based on luminol chemiluminescent reaction

Abstract A flow‐injection chemiluminescent (CL) method for the determination of trace amounts of Pt(IV) based on the oxidation reaction of luminol in alkaline solution is proposed. The effect of Pt(IV) on the oxidation of luminol was studied in the absence and in the presence of hydrogen peroxide. The positive effect of hydrogen peroxide as well as chloride ions on the sensitivity of measurements was observed. The developed method is characterized by a low limit of detection of Pt (LOD=0.06 ng mL−1) and good reproducibility (RSD=2.2%). The addition of hydrogen peroxide to the reaction medium resulted in decreasing of platinum detection limit to 0.03 ng mL−1.

On the Underestimated Factors Influencing the Accuracy of Determination of Pt and Pd by Electrothermal Atomic Absorption Spectrometry in Road Dust Samples

The accurate determination of Pt and Pd in environmental samples requires application of sensitive analytical technique as well as the separation/preconcentration of analytes from complex matrix of such samples. The careful optimization of sample pre-treatment procedure is also essential, but often certain steps of optimization process are neglected. The solid phase extraction procedure based on separation/preconcentration of Pt and Pd on immobilized biomass of fungi Aspergillus sp. and determination of analytes by ETAAS was chosen as an example for discussion. The most critical aspects of sample pre-treatment procedure, that affect the accuracy of determination of Pt and Pd in road dust, such as sample storage, sample digestion, transformation of analyte into adequate form, and separation of analytes from interfering matrix are discussed in this chapter. The optimized procedure was applied to the determination of Pt and Pd in road dust collected in Bialystok (Poland). The content of Pt in road dust increased from 93 µg kg−1 in 2000 to 263 µg kg−1 in 2011, while the content of Pd increased from 43 µg kg−1 in 2000 to 328 µg kg−1 in 2011.