OnLine Coupling of a Flow Injection System to TS‐FF‐AAS for Preconcentration and Determination of Lead in Water and Vegetables

Abstract

An online solid phase preconcentration system coupled to thermospray flame furnace atomic absorption spectrometry (TS-FF-AAS) for Pb(II) ions determination is described. In the preconcentration system, Pb(II) ions complexed with ammonium O,O-diethyl-dithiophosphate (DDTP) in an acidic medium are preconcentrated as a neutral complex onto 20 mg of polyurethane foam (PUF) packed into a mini-column. The complex retained in the PUF is then released to TS-FF-AAS by using an 80% (v/v) ethanol solution. Chemical and flow variables associated with the preconcentration, such as the pH dependence of the Pb-DDTP complex, the DDTP concentration, and preconcentration and elution flow rates were optimized by the univariate method. The best sample pH value and DDTP concentration achieved are 2.0 and 0.5% (w/v), respectively, while the best preconcentration and elution flow rates are 2.4 and 1.0 mL min 21 , respectively. Under the optimized conditions, the present method, which is operated in volume mode (only 2 mL), makes possible the determination of Pb(II) ions within a linear range from 5.2 to 300.0 mg L 21 with a detection limit of 1.5 mg L 21 and analytical frequency of 16 h 21 . The precision (n ¼ 10) assessed as relative standard deviation (RSD) is, respectively, 7.3 and 4.8% for 6 and 200 mg L 21 solutions of Pb(II). The preconcentration system provides an enrichment factor of 6.4 and consumption index of 310 mL. Hence, the coupling of the preconcentration system to TS-FF-AAS is proven to be an efficient strategy to enhance TS-FF-AAS detectability. The applicability of the method was verified by analyses of spiked water samples as well as with certified and reference vegetable materials.

Lead Assays with Smartphone Detection Using a Monolithic Rod with 4-(2-Pyridylazo) Resorcinol

“…The resulting characteristics of the obtained PUF monolithic rods offer advantages over the PUF in powder form that was used in previous works [ 20 , 30 , 31 , 34 , 35 , 36 , 38 , 40 , 42 , 45 , 51 ].…”

“…Polyurethane foam (PUF) has gained interest for use as a sorbent for lead [ 20 , 30 , 31 , 32 , 33 , 34 , 35 , 36 , 37 , 38 , 39 , 40 , 41 , 42 , 43 , 44 , 45 , 46 , 47 ]. Many previous works have been devoted to pretreatment for the determination of lead by atomic absorption spectrometry.…”

A Glimpse of Recent Developments in Brazilian Analytical Chemistry

“…Some researchers have used common sorbents such as cellulose paper , activated carbon (Quinaia et al 2006), naphthalene (Anjos et al 2007), silica modified with zirconium oxide (Macarovscha et al 2007), silica gel chemically modified with niobium(V) oxide (Dutra et al 2006), polyurethane foam (Tarley et al 2005;Santos et al 2004;Santos et al 2006b), silica gel loaded with 1,3-diaminepropane-3-propyl (de Moraes et al 2005) and Amberlite resins (Silva et al 2005a;Amorim and Bezerra 2007 (Matos and Arruda 2006), and rice husks ). Other researchers have worked with functionalization of resins, and excellent results were obtained (Cassela et al 2005;Silva et al 2004a;Lemos et al 2005).…”

Grafting 3-mercaptopropyl trimethoxysilane on multi-walled carbon nanotubes surface for improving on-line cadmium(II) preconcentration from water samples

“…The preconcentration method precision, assessed as the relative standard deviation (n = 10) for 1.0 and 55.0 g L −1 Cd 2+ solutions, was found to be 4.04% and 2.34%, respectively. Some other parameters, such as concentration efficiency (CE) of 9.46 min −1 , consumptive index (CI) of 0.635 mL and sample throughput of 14 h −1 were determined as described in the literature [27]. The present method, when compared to previous preconcentration procedures based on solid phase extraction using MWCNT for Cd 2+ determination by FAAS (Table 3), provides low detection limit, low sample consumption and high sample throughput.…”