Polyurethane foam elution

Adsorption of lA of POMs with CV and Malachite Green (MG) on the polyurethane foams (PF) and some other adsorbents is investigated. While lA is fully adsorbed on the PF in wide pH range (0,4 M H SO - pH 4) extent of dye adsoi ption does not exceed 0,4%. lA are adsorbed faster then POMs. Extent of sorption of lA is 60-70% at 5 minutes and is complete after 15 minutes. lA can be eluted from PF most effectively by methylbutylketone, acetone or alcohols can be used too. 

Surface Adsorption Hater sample is passed through a column of the adsorbent and the adsorbed organic constituents subsequently eluted with a smaller volume of organic solvent. All sample types Adsorbents Include charcoal, macroretlcular resins, polyurethane foams, bonded phases and ion-exchangers. Generally have high capacity but sample discrimination may be a -problem. Sample modification and Incomplete recovery are further possible problems. 

Preconcentration of Mo from mineral and produced waters has been performed by Ferreira et al. [24], employing polyurethane foam as sorbent, prior to the determination by ET-AAS. The thiocyanate complex of Mo(VI) was adsorbed onto a minicolumn filled with the sorbent, followed by elution with a 3 M HNO3 solution. With an enrichment factor of 10, an LoD of 0.08 p,g l-1 was achieved. Good agreement in the analysis of mineral waters was found between the results of the proposed method and those obtained by ICP-MS. 

As regards fractionation methodologies for the selective determination of Pb and other metals compounds in wines, Lemos et al. [57] have developed a FIA method for the direct determination of available free Pb(II) and total Pb content in wine samples. Lead (II) was chemically retained on a packed polyurethane foam microcolumn, modified by immobilization of 2-(2-benzothiazolyazo)p-cresol (BTAC) and eluted with 0.1 M HC1. The eluate was determined on-line by FAAS. Total Pb was quantified after sample digestion with HN03 and H202, whereas free Pb was determined by direct sample on-line preconcentration and elution. No effect of ethanol on the enrichment procedures was observed. With a preconcentration factor of 26 an LoD of 1 xg l-1 was reached. Four red and three white wines of different origins were analyzed and the total Pb content varied from 8 to 42 p,g 1 1. 

Ultrasonic nebulizers have also been employed in continuous flow systems as interfaces between sample preparation steps in the analytical process and detection by virtue of their suitability for operating in a continuous mode. Thus, preconcentration devices have commonly been coupled to atomic spectrometers in order to increase the sensitivity of some analytical methods. An enhancement factor of 100 (10 due to USNn and 10 due to preconcentration) was obtained in the determination of platinum in water using a column packed with polyurethane foam loaded with thiocyanate to form a platinum-thiocyanate complex [51]. An enhancement factor of 216 (12 with USNn and 18 with preconcentration) was obtained in the determination of low cadmium concentrations in wine by sorption of metallic complexes with pyridylazo reagents on the inner walls of a PTFE knotted reactor [52]. One special example is the sequential determination of As(lll) and As(V) in water by coupling a preconcentration system to an ICP-AES instrument equipped with a USN. For this purpose, two columns packed with two different resins selective for each arsenic species were connected via a 16-port valve in order to concentrate them for their subsequent sequential elution to the spectrometer [53]. 

Solid-phase extraction (SPE) and elution with different mixtures of solvents are also very common [24,73,128,153]. XAD-2 [9,10,14—16,68,80,81,90-92,135,142], polyurethane foam [68,80], and C18-bonded silica [14,31,141] are the most widely used adsorbing resins. The adsorbing material is generally supported inside a column or fixed on a membrane disk. SPE has several advantages, in fact it can be used in field applications, it has easy automation, a low solvent consumption, and there is less critical cleanup of the eluate. 

Atmosphere adsorption on polyurethane foam (desorption by Soxhlet extraction with petroleum ether) alumina fractionation (elution with 2 1 MeOH/ CH2CI2) water. SPE on XAD-2 resin Matrix solid phase dispersion extraction with Cijj (MeOH elution) AI2O3 cleanup of MeOH eluate SPE on poly(styrene/divinylbenzene) disk (elution with acetone, MeCl2, hexane) NP-HPLC fractionation Water. SPE on Cig (acetone elution) sediment and algae Soxhlet extraction with hexane cleanup by SPE NH2 media (elution with 75 25 hexane/acetone)... 

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