(nano)materialssensors and liquid chromatography

Resumen

The research on materials and new strategies to improve sample pretreatment and/or instrumental techniques has attracted great attention in the current developments of Analytical Chemistry. This Thesis presents interesting uses of (nano)materials to improve or develop sensing, extraction and separation techniques. The recent goal in Analytical Chemistry is the development of ecofriendly methodologies. In order to achieve this aim, analytical strategies focused on green aspects have been carried out: (i) miniaturized sample pretreatment and separation techniques and (ii) in-situ sensors. The materials studied in this Thesis have been organized in silicon-based (PDMS, C18 and MCF), carbon-based (MWCNTs and SWCNTs) and metallic-based (MOF and AgNPs). The versatile properties and low cost of PDMS has promoted its use as extractive phase in SPME and support for sensing devices has grown in importance. PDMS has been studied as extractive phase in IT-SPME-Cap-LC for estimating DEHP, BAK and DPA at trace levels in several matrices of environmental, industrial and forensic interest. The potential use of CNTs as extractive phase has been widely reported. Thus, CNTs have been studied to functionalize capillary columns for IT-SPME. Due to the enhancement on extraction efficiency and chromatographic profiles, CNTs have proved to be a reliable alternative to conventional phases in IT-SPME for estimating amphetamines in oral fluids. The proposed IT-SPME approach coupled to CapLC integrates on-line extraction, preconcentration and separation, reducing the sample treatment steps. Another important application of PDMS is its use as embedding material of dyes for developing optical sensors for in-situ analysis. In this context, colorimetric sensors for on-site estimation of amino compounds such as casein, a biocide, amphetamine-like compounds and ketamine have been developed. Moreover, a sensor based on AgNPs has been also developed as clinical kit for the in-situ and real time detection of volatile sulfur compounds, which are related to oral malodour. AgNPs are highly sensitive materials for their application as plasmonic sensor. A new application of the material C18 has been carried out. Thanks to the retentive capacity for amphetamine compounds, and thus, the capacity of C18 to disrupt as well as to clean-up the sample, this material has been successfully evaluated as dispersant phase for MSPD. This approach integrates matrix disruption, clean-up and derivatization to simplify sample preparation for the determination of amphetamines in hair. A potential applicability of MCF silica as sensing layer for resonant piezoelectric microcantilevers has been tested. In addition, an alternative fabrication procedure by using a polymeric commercial material for the sacrificial layer has been developed. Thus, the fabrication procedure is simplified due to sacrificial layer is removed during the firing step. To our knowledge, the first example of a MOF capable of separating chiral polar drugs by using SPE has been studied in this Thesis. A chiral Cu(II) 3D MOF based on the tripeptide Gly-L-His-Gly has been used as extractive phase for the enantioselective separation of ephedrine. The potential applicability of the materials studied has been demonstrated by the determination of several target compounds in different matrices. The proposed methodologies have reported improvements in terms of cost, rapidity, simplicity and sensitivity, besides protecting the operator and the environment.