Speciation Approaches Direct Methods or Hyphenated Techniques

SPECIATION APPROACHES DIRECT METHODS OR HYPHENATED TECHNIQUES 

The predominant techniques for element speciation are hyphenated systems. Here, the analytes are separated and the species are selectively detected via their element content. For complementary information and improved quality control, molecule selective-detection is also hyphenated to separation devices. 

Combined systems provide extended variability and applicability but suffer from increased complexity and thus from increased risk of error. Species equilibria can be altered during separation by dilution or by 

In SEC, the retention of a solute depends on its hydrodynamic volume, which is related to molecular size. If the chromatographic system is suitably calibrated, a size characterization of elemental species is possible. Moreover, SEC is a gentle method and—provided, parameters are optimized—minimises the loss of element species or on-column alterations. It plays a predominant role when separating biopolymers with labile or weak metal binding. 

One of the most important advantages of lEC in speciation analysis is its high separation efficiency and wide applicability. Solutions for many speciation problems are provided. Frocesses involved in lEC are based on the utilization of exchange equilibria between charged solute ions and the oppositely charged surface of the stationary phase. The equilibrium is determined by three variables pH, ionic strength of the mobile phase, and nature of the ion exchanger. 

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