Solid-phase microextraction methodology

In recent decades the development of preconcentration steps to be implemented prior to analytical determinations of trace level compounds has been explored in considerable depth. With a view to eliminating or at least minimising the use of organic solvents used in conventional liquid-liquid extraction, other methodologies have been developed, such as membrane extraction, solid-phase extraction, solid-phase microextraction, etc. 

Abstract A relatively small number of mammalian pheromones has been identified, in contrast to a plethora of known insect pheromones, but two remarkable Asian elephant/insect pheromonal linkages have been elucidated, namely, (Z)-7-dodecen-1-yl acetate and frontalin. In addition, behavioral bioassays have demonstrated the presence of a chemical signal in the urine of female African elephants around the time of ovulation. Our search for possible ovulatory pheromones in the headspace over female African elephant urine has revealed for the first time the presence of a number of known insect pheromones. This search has been facilitated by the use of a powerful new analytical technique, automated solid phase dynamic extraction (SPDE)/GC-MS, as well as by novel macros for enhanced and rapid comparison of multiple mass spectral data files from Agilent ChemStation . This chapter will focus on our methodologies and results, as well as on a comparison of SPDE and the more established techniques of solid phase microextraction (SPME) and stir bar sorptive extraction (SBSE). 

Camara, J. S., Alves, M. A., and Marques, J. C. (2006c). Development of headspace solid-phase microextraction-gas chromatography-mass spectrometry methodology for analysis of terpenoids in Madeira wines. Anal. Chim. Acta 555,191-200. 

Godelmann, R., Limmert, S., and Kuballa, T. (2008). Implementation of head-space solid-phase-microextraction-GC-MS/MS methodology for determination of 3-alkyl-2-methoxypyrazines in wine, Eur. Food Res. Technol., 227(2), 449-461. 

Aguilar, C., Penalver, A., PocumU, E., Ferre, J., Borrull, F., and Marce, R. M., Optimization of solid-phase microextraction conditions using a response surface methodology to determine OCPs in water hy GC and electron-capture detection, J. Chromatogr. A, 844, 425-432, 1999. 

The procedure to be used to extract carbamate pesticides from environmental samples depends on their polarity and on the type of sample matrix involved. Various choices exist for the extraction of pesticides ranging from conventional procedures (e.g., Soxhlet extraction, liquid-liquid extraction (LLE), evaporation, steam distillation) to new methodologies including solid-phase extraction (SPE), solid-phase microextraction (SPME), supercritical fluid extraction (SEE), matrix solid-phase dispersion (MSPD), accelerated solvent extraction (ASE) and microwave-assisted extraction. " ... 

The search of adequate extraction techniques allowing the identification and quantification of wine volatile compounds has attracted the attention of many scientists. This has resulted in the availability of a wide range of analytical tools for the extraction of these compounds from wine. These methodologies are mainly based on the solubility of the compounds in organic solvents (liquid-liquid extraction LLE, simultaneous distillation liquid extraction SDE), on their volatility (static and dynamic headspace techniques), or based on their sorptive/adsorptive capacity on polymeric phases (solid phase extraction SPE, solid phase microextraction SPME, stir bar sorptive extraction SBSE). In addition, volatile compounds can be extracted by methods based on combinations of some of these properties (headspace solid phase microextraction HS-SPME, solid phase dynamic extraction SPDE). 

As described earlier (4,5), we have studied nestmate recognition by examining the differences of cuticular hydrocarbons between species, colonies, and castes. Briefly, we developed a methodology for the extraction of termite cuticular hydrocarbons by solid phase microextraction (SPME). Both headspace SPME, where the termites were heated in a vial to 120 °C with the fiber 1 cm above the termites, and direct contact SPME, where live termites walked on the SPME fiber for a certain time period, were studied. As shown in Figure 1, both methods were comparable to the normal hexane extraction method in the types of cuticular hydrocarbons that were extracted. Since SPME requires less manipulation of the sample and may use living termites, it may have advantages. 

Although most official methods for pesticide analysis in water samples use liquid-liquid extraction (LLE) on account of its simplicity and consolidated status, solid-phase extraction (SEE) techniques have gained increasing popularity lately. Other methodologies including solid-phase microextraction (SEME), liquid-phase microextraction (LFME), supercritical fluid extraction (SEE), and microwave-assisted extraction (MAE) have been used to determine pesticides in water [5,28,30]. 

Samples were placed in 20-mL vials and allowed to equilibrate at 25°C. A solid-phase microextraction (SPME) fiber, polydimethyl siloxane/divinyl-benzene, (PDMS/DVB) 65 pm (Supelco Park, Bellefonte, PA), was used for sampling volatile compounds, using the methodology already described [18]. 

Standard methods of analysis employ schemes to capture volatile compounds, concentrate them, separate them, and quantify them. Recent reviews of sample preparation for volatiles analysis include foods in general (1), cereals (2), and dairy products (3). Recent advances in analytical instrumentation and methodology have approached the threshold of selectivity and sensitivity demonstrated by the human nose. In this chapter, we describe new methodology employed to measure some of the key odorants in rice. The effective collection and analysis of volatile compounds can now be accomplished using solid-phase microextraction (SPME). A pictorial outline of the procedure is depicted in Fig. 1. 

Most methodologies for analysis of polycyclic aromatic hydrocarbons (PAHs) in food systems are laborious, time consuming and need organic solvents, specially for complex matrixes in which PAHs are strongly trapped due to their interaction with different components of the sample (Moret and Conte, 2000). Moreover, the sampling step may deteriorate the quality of several solid foods. Solid-phase microextraction (SPME) is an alternative technique that ean overeome some of these disadvantages. SPME integrates... 

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