Headspace strategiesstate of the art and development of novel applications to address current issues in environmental, agro-industrial and forensic fields

Resumen

The aim of this doctoral thesis is to develop different headspace methods for the determination of diverse volatile and semivolatile organic compounds applied to different fields such as environmental, agro-industrial or forensic.The methods proposed are based on static headspace (SHS) and headspace solid-phase microextraction (HS-SPME) coupled to gas chromatography-mass spectrometry (GC/MS). Depending on the objective of each individual work included in this thesis, different method optimization steps were taken. Since not only qualitative analysis but, also quantitative analysis was carried out, the approaches used were different. Multiple headspace extraction (MHE) analysis and corresponding calibration for quantitative purposes, qualitative and quantitative analysis of solid samples, matrix effect in headspace extraction, degradation reaction monitoring and volatile profile monitoring are some of the points discussed throughout this thesis. Taking into account the popularity and the interest that headspace techniques have gained worldwide, a review of headspace methods and their potential industrial applications is also included. This thesis is composed of five individual scientific research papers. Article I reviews the most recent and significant advances in static and dynamic headspace (DHS), as well as HS-SPME techniques coupled to GC. The evolution and potential application of headspace techniques in the last five years are reviewed and discussed, covering food chemistry, pharmaceutical chemistry, process monitoring, fuel industry and quality control. Additionally, two practical SHS and HS-SPME analytical methods developed for industrial application are presented.In Article II the evaluation of the process of lindane degradation using different iron nanoparticles is reported. Lindane degradation process was monitored by analyzing water samples after being treated with iron nanoparticles; this way, lindane remaining in the solution was measured over time using solid-phase extraction (SPE). HS-SPME-GC/MS was also used to extract and detect the gas by-products generated at different times during the degradation. In Article III a HS-SPME procedure for the qualitative analysis of walnut volatile compounds over a typical growing season is presented. Volatile natural products have played a large role in efforts to control or monitor different insect pests. Therefore, in this work, mechanically damaged and intact walnuts were characterized and compared with the aim of identifying candidate volatiles for future use in host plant-based attractants. The basic background volatile profile of walnut was also obtained, which could provide useful information about the volatile bouquet that insect pests encounter in walnut orchards.Article IV describes the development and optimization of a method for simultaneous quantitation of volatile compounds in mushroom samples based on multiple headspace extractions (MHE). The results obtained using three sample treatment methodologies, HS with two different injection techniques (pressure-loop system and gas-tight syringe autosampling system) and HS-SPME, were compared and validated. The three developed methods were then applied to the quantitative analysis of volatile compounds present in mushroom samples.Another application of the MHE methodology was researched in Article V. The aim of this work is to develop an ink dating procedure, named DATINK, for documents written with ballpoint pens characterized by the disappearance of volatile solvents from the ink entry. For this purpose, multiple headspace solid-phase microextraction (MHS-SPME) coupled to GC/MS was used to measure different solvents from ink entries made with different BIC® ballpoint pens. In this case, the multiple extractions were not carried out with a quantitative purpose. Instead, the A1 (area of the first extraction), AT (total area) and ßß parameter (a constant that describes how fast the extraction process proceeds) calculated from the MHE procedure were studied and evaluated as a function of time.