Evaluation of commercial C18 cartridges for trace elements solid phase extraction from seawater followed by inductively coupled plasma-optical emission spectrometry determination

Possibilities of the use of commercial C18 cartridges to separate and preconcentrate trace elements from seawater have been evaluated. Trace elements (Al, Cd, Cu, Fe, Mn, Ni, Pb, Sn, V and Zn) were previously complexed with 8-hydroxyquinoline, 8-HQ (5 × 10−4 M as final concentration) at alkaline pH (8.0 ± 0.1) and then they were eluted with 2.5 ml of 2.0 M nitric acid. Metals eluted from cartridges were measured by inductively coupled plasma-optical emission spectrometry (ICP-OES). Variables affecting the metal-8-HQ complexation such as pH and 8-HQ concentration, and affecting the metal-8-HQ complexes solid phase adsorption and elution (load and elution flow rates and concentration and volume of eluting solution) were studied in order to find compromise operating conditions for the simultaneous metals complexation, adsorption and elution. After studies of contamination of commercial C18 cartridges for trace metals, high reagent blanks were reached for Ti so that they are useless for the determination of this element. In addition, commercial C18 cartridges can be used at least seven times without loss of adsorption properties. Working with a seawater sample volume of 100 ml and using an optimum nitric acid volume of 2.5 ml for elution, a preconcentration factor of 40 was achieved, factor high enough to determine trace elements in unpolluted surface seawater samples by ICP-OES. Analytical performances, such as limits of detection and quantification, repeatability of the overall procedure and accuracy, by analyzing saline (CASS-3 and SLEW-3) and non-saline (TM-24) certified reference materials, were finally assessed.