**Acknowledgements**

The author is appreciated of the support of Islamic Azad University, Shahr-e-Qods branch, Tehran, Iran.

**71**

Author details

Foujan Falaki

Tehran, Iran

provided the original work is properly cited.

*Sample Preparation Techniques for Gas Chromatography DOI: http://dx.doi.org/10.5772/intechopen.84259*

© 2019 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium,

Department of Chemistry, Shahr-e-Qods Branch, Islamic Azad University,

\*Address all correspondence to: foujanfalaki@gmail.com

*Sample Preparation Techniques for Gas Chromatography DOI: http://dx.doi.org/10.5772/intechopen.84259*

*Gas Chromatography - Derivatization, Sample Preparation, Application*

drop. The searches are shown that N-octane and toluene possess the best extraction efficiency for nonpolar substances, while chloroform is more favorable to extract polar alkaloids, and then they can be analyzed by GC techniques [37]. One limitation of direct immersion SDME is the instability of the droplet at high stirring rates. Although high stirring rates enhance the extraction efficiency, to avoid the problem caused by elevated stirring speeds, a 1-μl microsyringe (instead of a more common

Ionic liquids have been established as alternative to organic solvents because of their high boiling point and viscosity which allow production of larger and more reproducible extraction drops. HPLC is a preferred method for analyzing ionic liquid extract, but their nonvolatility causes them unsuitable for GC analysis. To couple ionic liquid-based SDME to GC instrument, the extract is introduced via a removable interface which prevents entering of ionic liquid into the GC column, while the analytes can be entered quantitatively into the capillary column [37]. HS-SDME in which the organic droplet is held above the aqueous sample solution is most suitable for the consideration of volatile or semivolatile analytes [39]. The advantages of HS-SDME include the following: (1) Headspace SDME permits quick stirring of the sample solution with no concerning on the droplet stability. (2) The effects of nonvolatile matrix interferences are reduced, even if they are not eliminated. (3) In this mode, the analytes are distributed between three phases: the aqueous sample, headspace, and organic droplet. Since an elevated stirring rate of the sample solution enhances the mass transfer between the three phases. (4) In comparison with HS-SPME, HS-SDME shows to have the same precision and rate of analysis as HS-SPME. However, HS-SDME procedure possesses two special advantages over HS-SPME. At first, the approach of choosing solvents is wider. Second, the solvent cost (on the basis of several microliters) is negligible in comparison with the cost of commercially available fibers in SPME [39]. Alternatively, the use of SDME for headspace analysis seems relatively difficult, because of the requirement of the higher boiling point solvents. Although the most suitable solvents for gas chromatography should have relatively high vapor pressures or low boiling points, the limit of these solvents is obvious: they would evaporate too quickly in the headspace during extraction. Therefore, the select of suitable solvents should be the

Many methods are available for the treatment of volatile substances prior to instrumental analysis. In this chapter, the major methods which are leading to GC analysis have been explained. It has been observed that yet the classical techniques such as purge and trap, static headspace extraction, and liquid-liquid extraction act as important roles in chemical analysis of all sample types. New methods, such as SPME and membrane extraction, possess some advantages like convenient in automation and field sampling and reduction of solvent consumption, as well. If the analyst may be confronted with every difficulty, there is an appropriate available method to solve and face it. As a consequence, the main and primary analytical

The author is appreciated of the support of Islamic Azad University, Shahr-e-

problem is to select the best sample preparation technique.

10-μl one) with some modification of its tip was used by Ahmadi et al. [38].

**70**

first decision in HS-SDME techniques.

**8. Conclusions**

**Acknowledgements**

Qods branch, Tehran, Iran.

Author details

Foujan Falaki Department of Chemistry, Shahr-e-Qods Branch, Islamic Azad University, Tehran, Iran

\*Address all correspondence to: foujanfalaki@gmail.com

© 2019 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
