Determination of total iron in food samples after flow injection preconcentration on polyurethane foam functionalized with N,N-bis(salicylidene)-1,3-propanediamine.

A highly selective flow injection sorption system was developed for the fast determination of total iron in food samples. Iron (III) was reduced to iron (II) by ascorbic acid and preconcentrated on a mini-column packed with polyurethane foam (PUF) functionalized with N,N-bis(salicylidene)-1,3-propanediamine (SPDA). The retained Fe (II) was eluted with hydrochloric acid and subsequently reacted to 2,4,6-tri(2'-pyridyl)-1,3,5-triazine (TPTZ) then measured at 593 nm. The procedure has resulted preconcentration factor 36, sample frequency 20 h(-1) and detection limit 18 µg L(-1). The precision (RSD) was found to be 5.7% and 3.1% at concentration levels 0.1 and 5.0 µg mL(-1) iron (II), respectively. Finally, the method was successfully applied to determination of total iron in reference material and food samples.

Cationic polyelectrolyte copolymer modified polyurethane foam for flow injection preconcentration and separation of trace amounts of ß-lactam antibiotics.

A more sensitive flow injection preconcentration method has been developed for the determination of four ß-lactam antibiotics (BLAs) namely cefaclor, cefotaxime, amoxicillin and ampicillin in urine, pharmaceuticals and milk. A mini-column packed with PUF functionalized with the cationic polyelectrolyte, poly(N-chloranil N,N,N',N'-tetramethylethylene diammonium dichloride) PCTDD, was utilized for selective preconcentration. The detection limits with this method were 3.3, 3.8, 5.1 and 7.0 ng mL(-1) and enrichment factors were 38, 21, 39, and 36 for cefaclor, cefotaxime, amoxicillin and ampicillin, respectively with a sample throughput of 12 h(-1) for all BLAs. Moreover, the BLAs were successfully separated by isocratic elution using a micellar mobile phase. Application of the method developed has resulted in recovery values in the range 95%-109% (RSD≤8.7), 83%-99% (RSD≤9.7) and 91%-103% (RSD≤4.0) for urine, pharmaceuticals and milk samples, respectively.

Separation and determination of trace amounts of zinc, lead, cadmium and mercury in tap and Qaroun lake water using polyurethane foam functionalized with 4-hydroxytoluene and 4-hydroxyacetophenone.

A stable chelating sorbent was synthesized by covalently linking 4-hydroxytoluene or 4-hydroxyacetophenone with the polyurethane foam (PUF) through -N=N- group. The synthesized chelating sorbents were characterized by IR and UV/vis measurements. The modified foams show excellent stability towards various solvents. Factors influencing the extraction process of Zn(II), Pb(II), Cd(II) and Hg(II) were studied and evaluated as a function of pH of metal ion solution and equilibration shaking time. The values of sorption capacity of metal ions (microg g(-1)) were determined with the two types of bonded foams. The two phenolic bonded foams were studied comparatively. The potential applications of the two newly synthesized foams for the removal and separation of the examined metal ions from two natural water samples (drinking tap water and Qaroun lake water at Fayoum City, Egypt) were investigated. Precision (assessed as a relative standard deviation, R.S.D.) was also evaluated and found to be < or =7.3% (N=5) with a detection limit under 0.46 microg L(-1).