Analytical strategies for coupling separation and flow-injection techniques

• Coupling of flow and separation techniques improves their individual features.
• Coupling allows the whole analytical protocol in a single instrumental assembly.
• Automation simplifies execution and increases separation efficiency.
• Monolithic columns allowed low-pressure chromatographic techniques.

Flow techniques (FTs) are non-separative tools and high-performance separation techniques that require sample pretreatment. On-line combinations of flow sample-pretreatment units and discrete sample-introduction devices are very attractive, as they allow the whole analytical sequence to be developed in a single instrumental assembly. In this review, we present the state of the art and future trends in coupling separation techniques, such as chromatography and capillary electrophoresis, and FTs. FTs can be coupled as a front end to separation techniques or by integrating the separation column in the flow system, generating new low-pressure chromatographic techniques. We discuss different coupling strategies, highlighting their benefits and disadvantages. We also present an updated review of coupled systems applied to environmental and biological samples.