Sequential injection system incorporating a micro-extraction column for automatic fractionation of metal ions in solid samples: Comparison of the extraction profiles when employing uni-, bi-, and multi-bi-directional flow plus stopped-flow sequential extr

Recently a novel approach to perform sequential extractions (SE) of elements in solid samples was developed by this group, based upon the use of a sequential injection (SI) system incorporating a specially designed extraction microcolumn. Entailing a number of distinct advantages as compared to conventional batch methods, this fully automated approach furthermore offers the potentials of a variety of operational extraction protocols. Employing the three-step sequential extraction BCR scheme to a certified homogeneous soil reference material (NIST, SRM 2710), this communication investigates four operating modes, namely uni-, bi- and multi-bi-directional flow and stopped-flow, allowing comparison of the metal fractionation profiles. Apart from demonstrating the versatility of the novel approach, the data obtained on the metal distribution in the various soil phases might offer valuable information as to the kinetics of the leaching processes and chemical associations in different soil geological phases. Special attention is also paid to the potentials of the microcolumn flowing technique for automatic processing of solid materials with variable homogeneity, as demonstrated with the sewage amended CRM483 soil which exhibits inhomogeneity in the particle size distribution.