Selective solid phase extraction of platinum on an ion imprinted polymers for its electrothermal atomic absorption spectrometric determination in environmental samples

An ion-imprinted polymer (IIP) was obtained by copolymerization of methacrylic acid (as a functional monomer) and ethylene glycol dimethacrylate (as a crosslinking agent) in the presence of various chelators for Pt(II) ion and using 2,2??-azo-bis-isobutyronitrile as the initiator. Specifically, acetaldehyde thiosemicarbazone (AcTSn) and benzaldehyde thiosemicarbazone (BnTSn) were used as chelators. The IIPs were applied as sorbents for solid-phase extraction of Pt(II) and Pt(IV) ions from aqueous solutions. The effects of acidity and flow rate of the sample, of elution conditions and of potentially interfering ions were investigated. The imprinting effect of analyte is clearly demonstrated by the fact that only the IIP is capable of quantitative retention of Pt(II) and Pt(IV) ions. The method works best in the pH range from 0.5 to 1 and from 3.5 to 9.5. The ions can be recovered with an acidic solution of thiourea. The Pt-AcTSn polymer displays better sorption properties for the separation of analytes. The selectivity coefficients of the Pt-AcTSn and control polymers for Pt(IV) in the presence Pd(II), Rh(III), Ru(III), Al(III) and Cu(II) were calculated, and the sorbent capacity for Pt(IV) was found to be 4.56???g?g?^-1. The method was successfully applied to the determination of Pt(IV) by electrothermal atomic absorption spectrometry in tap water, tunnel dust and anode slime samples.

Carbamohydrazonothioate derivative—experimental and theoretical explorations of the crystal and molecular structure

Structural Chemistry - The structural studies of carbamohydrazonothioate derivative and its hydrochloride solvate are the aim of hereunder presented research. The combination of the...     

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.     

Unusual oxidation reactions of 7α-methyl- and 7α-phenylcholest-5-ene-3β,7β-diol

Summary Ozonation of 7-methyl (or 7-phenyl) cholest-5-ene-3,7-diol 3-TBDMS ether afforded the corresponding 5,6-epoxy derivatives. The same product was formed byMCPBA oxidation. The reaction of 7-phenylcholest-5-ene-3,7-diol with CrO₃ yielded 3,7-dioxo-6,7-seco-7-phenylcholest-4-ene-5-carboxaldehyde. An analogous B-seco aldehyde was obtained from 7-methylcholest-5-ene-3,7-diol in addition to 7-methylcholesta-4,6-dien-3-one.Jones oxidation of 7-phenylcholest-5-ene-3,7-diol or B-seco-aldehyde gave 3,7-dioxo-6,7-seco-7-phenylcholest-4-en-6-oic acid isolated as its methyl ester upon treatment with diazomethane.

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Ungewöhnliche Oxidation von 7-Methyl- und 7-Phenylcholest-3-en-3,7-diol

Zusammenfassung Ozonolyse von 7-Methyl- bzw. 7-Phenyl-cholest-3-en-3,7-diol-3-TBDMS-ether ergab die entsprechenden 5,6-Epoxy-Derivate.MCPBA-Oxidation führte zum gleichen Ergebnis. Bei der Reaktion von 7-Phenyl-cholest-5-en-3,7-diol mit CrO₃ wurde 3,7-Dioxo-6,7-seco-7-phenyl-cholest-4-en-5-carbaldehyd gebildet. Einen analogen B-seco-Aldehyd erhält man neben 7-Methyl-cholesta-4,6-dien-3-on auch aus 7-Methyl-cholest-5-en-3,7-diol. DurchJones-Oxidation von 7-Phenyl-cholest-5-en-3,7-diol oder B-seco-Aldehyd erhält man 3,7-Dioxo-6,7-seco-7-phenylcholest-4-en-6-carbonsäure, die nach Behandlung mit Diazomethan als ihr Methylester isoliert wurde.

     

Studies of ion-imprinted polymers for solid-phase extraction of ruthenium from environmental samples before its determination by electrothermal atomic absorption spectrometry

The examination of the effect of interfering ions on the analytical signal of ruthenium measured by electrothermal atomic absorption spectrometry was initially performed in this work. The complexes of ruthenium(III) with thiosemicarbazide (TSd) and acetaldehyde thiosemicarbazone (AcTSn) were prepared and imprinted in polymeric network. The ion-imprinted polymers were synthesized by copolymerization of methacrylic acid, as functional monomer and ethylene glycol dimethacrylate, as crosslinking agent in the presence of 2,2-azobisisobutyronitrile as initiator. The effects of sample volume, pH, and flow rate on the extraction of analyte were studied in dynamic mode. The optimum pH for quantitative retention of ruthenium on each of the studied sorbents was 7.5 ± 0.5. The elution of analyte was completed with 0.2 mol L⁻¹ thiourea in 0.2 mol L⁻¹ HCl. The effect of matrix ions on ruthenium(III) separation process was studied. The analytical performance of the Ru-TSd polymer in the presence of competing ions was better than Ru-AcTSn polymer, considering recovery of analyte, reproducibility of results, selectivity coefficients, and sorbent capacity. The detection limit of the proposed method (0.16 ng mL⁻¹ on Ru-TSd and 0.25 ng mL⁻¹ on Ru-AcTSn) is lower in comparison with the previously published methods. The developed separation method was successfully applied to the determination of trace amounts of ruthenium in spiked water samples, sludge, grass, and human hair.     

Direct Synthesis of Double Hydrophilic Statistical Di‐ and Triblock Copolymers Comprised of Acrylamide and Acrylic Acid Units via the MADIX Process

Double hydrophilic statistical, diblock and triblock copolymers comprised of acrylamide and acrylic acid units have been synthesized in aqueous medium using the MADIX process. Starting from an either monofunctional or difunctional xanthate, the resulting AB and ABA‐type double hydrophilic block copolymers (DHBC) exhibited molar masses predetermined by the initial monomer/xanthate precursor molar ratio and polydispersity indices in the range 1.2–1.5. Batch copolymerizations yielded well‐defined statistical copolymers that were chain‐extended for the synthesis of novel poly‐ (acrylic acid‐stat‐acrylamide)‐block‐polyacrylamide DHBC.