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A preconcentration procedure is presented for the dispersive micro solid-phase extraction (DMSPE) of trace amounts of Pb(II), Cd(II), Zn(II), Cr(III), Mn(II), and Fe(III) as their batophenanthroline chelate complexes on the graphene oxide (GO) nanosheets prior to their determination by inductively coupled plasma optical emission spectrometry (ICP-OES) technique. The influence of analytical parameters including pH, type and concentration of eluent, amount of complexing reagent, sorption time and sample volume on the quantitative recoveries of analytes were investigated in order to obtain the optimum conditions. The experiment shows that metal ions can be simultaneously preconcentrated at pH of 8 with high recoveries (in the range of 90–97%) and excellent precision (RSDs within 1.6–3.0%). The detection limits are 0.25, 0.06, 0.16, 0.06, 0.12 and 0.21 ng mL−1 for Pb(II), Cd(II), Zn(II), Cr(III), Mn(II), and Fe(III), respectively. The method was successfully applied for the determination trace amounts of analytes in food and water samples. Unlabelled Image • Sorption of batophenanthroline - metal chelates on graphene oxide • Graphene oxide using as adsorbent in DMSPE • Using ICP-OES for the detection of Pb, Cd, Zn, Cr, Mn and Fe • Detection limit suitable for food and environmental analysis • Simple, fast, sensitive and environmental friendly method [ABSTRACT FROM AUTHOR]

Highlights: [•] Graphene oxide (GO) covalently bonded to the spherical silica. [•] Very stable sorbent for SPE of metal ions. [•] Excellent contact with solution due to the softness and flexibility of GO nanosheets. [•] Several adsorption–elution cycles without any loss of adsorptive properties. [•] High adsorption capacity due to the wrinkled structure of GO nanosheets. [Copyright &y& Elsevier]

Abstract: In this paper, the adsorptive properties of graphene nanosheets were used for simultaneous preconcentration of cobalt, nickel, copper and lead ions from water samples. The developed methodology is based on dispersive micro-solid phase extraction (DMSPE) which is miniaturized and a simplified version of classical solid phase extraction technique. In proposed procedure only 200μL of suspension containing graphene (0.2mg), ammonium pyrrolidine dithiocarbamate (APDC) (0.8mg) and Triton-X-100 (0.1mg) is rapidly injected to 50mL of water sample. Then, graphene nanosheets with adsorbed metal-APDC chelates are collected on membrane filter and measured using energy-dispersive X-ray fluorescence (EDXRF) spectrometry. The various parameters including pH, amount of APDC, sample volume, amount of Triton-X-100 and sorption time were optimized in order to obtain the best recoveries. The experiment shows that Co, Ni, Cu and Pb can be simultaneously preconcentrated at pH of 5 with high recoveries (97%, 96%, 99% and 96% for Co, Ni, Cu and Pb, respectively) and very good precision (RSDs within 2.6–3.4%). Due to the excellent enrichment factors ranging from 400 to 2500 the proposed DMSPE–EDXRF procedure offers low detection limits. For optimized measurement conditions (voltage and current of X-ray tube, primary beam filter) the detection limits are even 0.08, 0.07, 0.08 and 0.20ngmL−1 for Co, Ni, Cu and Pb, respectively. [Copyright &y& Elsevier]

Highlights: [•] Application of graphene (G) and graphene oxide (GO) in analytical chemistry. [•] Adsorption capacity of G and GO towards organic compounds and metal ions. [•] Application of G and GO in SPE, magnetic-SPE and SPME. [ABSTRACT FROM AUTHOR]

Ultrasound-assisted solid-phase extraction (SPE) with multiwalled carbon nanotubes (MWCNTs) as a solid sorbent and 1-(2-pyridylazo)-2-naphthol (PAN) as a chelating agent was developed for the determination of trace and ultratrace amounts of Cd(ii) ions in aqueous samples. The solution containing Cd(ii) complexed with PAN was passed through the syringe filter with a PVDF membrane loaded with 25 mg of MWCNTs. The elution process was performed with 2.0 mL of 2.0 mol L−1 HNO3 with assistance of sonication. In order to obtain the high recovery of the Cd(ii) ions, the proposed procedure was optimized for various analytical parameters such as pH, amounts of PAN, sample volume, and elution conditions such as volume and concentration of eluent and influence of sonication and temperature. The investigation shows that sonication considerably improves the recovery, whereas temperature does not influence the elution process. Under optimized conditions Cd(ii) ions can be determined with very good recovery (99 ± 3%), precision (RSD = 3.2%) and detection limit (0.3 ng mL−1) for an enrichment factor of 50. The effect of common coexisting ions was also investigated. Cd(ii) can be determined in the presence of heavy metal ions and alkali metals. The proposed ultrasound-assisted SPE was applied for the determination of Cd(ii) in water samples and biological samples (Lobster Hepatopancreas). [ABSTRACT FROM AUTHOR]

Abstract: Dispersive liquid–liquid microextraction (DLLME) using sodium diethyldithiocarbamate (DDTC) as a chelating agent was investigated for the simultaneous determination of iron, cobalt, nickel, copper, zinc, selenium and lead ions in water samples. The procedure was performed using 5mL of the sample, 100μL of a 0.5% solution of DDTC, 30μL of carbon tetrachloride (extraction phase) and 500μL of methanol (disperser solvent). The experiments showed that Fe, Co, Ni, Cu, Zn and Pb can be simultaneously extracted at a pH of 5 and that Se can be extracted at a pH of 2–3. The results were compared with those obtained using ammonium pyrrolidine dithiocarbamate as a chelating agent. For all analytes, a linear range was observed up to 0.4μgmL−1. If Fe and Zn are present in concentrations 10 times higher than those of the other analytes, then the linearity is observed up to 0.2μgmL−1. In the present study, the organic phase that contained preconcentrated elements was deposited onto a Millipore filter and measured using energy-dispersive X-ray fluorescence spectrometry. The obtained detection limits were 2.9, 1.5, 2.0, 2.3, 2.5, 2.0 and 3.9ngmL−1 for Fe, Co, Ni, Cu, Zn, Se and Pb, respectively. This combination of DLLME and the dried-spot technique is promising for multielement analyses using other spectroscopy techniques, such as laser ablation‐inductively coupled plasma‐mass spectrometry, laser-induced breakdown spectroscopy or total-reflection X-ray fluorescence spectrometry. [Copyright &y& Elsevier]

A methodology based on dispersive micro solid-phase extraction (DMSPE) using multiwalled carbon nanotubes (MWCNTs) as solid sorbent prior to measurement with energy-dispersive X-ray fluorescence (EDXRF) spectrometry is proposed. The procedure consists of chelating of nickel, cobalt, copper, and lead ions with ammonium pyrrolidinedithiocarbamate (APDC) and posterior adsorption of metal chelates on MWCNTs (1 mg) dispersed in the aqueous samples (100 mL). DMSPE promotes immediate interaction between the metal chelates and MWCNTs and shortens time of sample preparation in comparison with classical solid-phase extraction. After microextraction process, MWCNTs are collected onto filter and directly measured by EDXRF. With this technique, the direct quantification of metal species held in solid materials is possible and, therefore, the elution step can be avoided. The effects of various experimental parameters such as pH of the solution, amounts of MWCNTs and APDC, sample volume, and time of stirring were investigated. With the best analytical conditions (1 mg of MWCNTs, 2 mg of APDC, 100 mL sample volume, pH = 7, and 5 min time of stirring), Co(II), Ni(II), Cu(II), and Pb(II) can be simultaneously determined with very good recoveries (101%, 98%, 96%, 99%, respectively) and detection limits (0.43, 0.11, 0.46, 0.15 ng mL−1, respectively). The method was applied in determination of trace metal ions in tap water and wastewater samples. [ABSTRACT FROM AUTHOR]