**1. Introduction**

126 Chromatography – The Most Versatile Method of Chemical Analysis

Commun Mass Spectrom. 2009 Jul;23[14]:2125-38.

not? Rapid Commun Mass Spectrom. 2005;19[3]:401-7.

biological matrices. Bioanalysis. 2009 Apr;1[1]:205-20.

2006 Jan 18;830[2]:293-300.

Feb;25[1]:1-16.

Feb;25[1-2]:258-77.

Mass Spectrom. 1999;13[11]:1003-15.

[105] Matuszewski BK. Standard line slopes as a measure of a relative matrix effect in quantitative HPLC-MS bioanalysis. J Chromatogr B Analyt Technol Biomed Life Sci.

[106] Xia YQ, Jemal M. Phospholipids in liquid chromatography/mass spectrometry bioanalysis: comparison of three tandem mass spectrometric techniques for monitoring plasma phospholipids, the effect of mobile phase composition on phospholipids elution and the association of phospholipids with matrix effects. Rapid

[107] Kloepfer A, Quintana JB, Reemtsma T. Operational options to reduce matrix effects in liquid chromatography-electrospray ionization-mass spectrometry analysis of aqueous

[108] Stokvis E, Rosing H, Beijnen JH. Stable isotopically labeled internal standards in quantitative bioanalysis using liquid chromatography/mass spectrometry: necessity or

[109] Volkel W, Bittner N, Dekant W. Quantitation of bisphenol A and bisphenol A glucuronide in biological samples by high performance liquid chromatography-

[110] Briscoe CJ, Hage DS. Factors affecting the stability of drugs and drug metabolites in

[111] Shipkova M, Armstrong VW, Oellerich M, Wieland E. Acyl glucuronide drug metabolites: toxicological and analytical implications. Ther Drug Monit. 2003

[112] Li WK, Zhang J, Tse FLS. Strategies in quantitative LC-MS/MS analysis of unstable small molecules in biological matrices. Biomed Chromatogr. [Review]. 2011 Jan-

[113] Jemal M, Ouyang Z, Chen BC, Teitz D. Quantitation of the acid and lactone forms of atorvastatin and its biotransformation products in human serum by high-performance liquid chromatography with electrospray tandem mass spectrometry. Rapid Commun

tandem mass spectrometry. Drug Metab Dispos. 2005 Nov;33[11]:1748-57.

environmental samples. J Chromatogr A. 2005 Mar 4;1067[1-2]:153-60.

Nowadays, there is a growing need for applications in food and environmental areas able to cope with the analysis of a large number of analytes in very complex matrices [1]. The new analytical procedures demand sensitivity, robustness, effectiveness and high resolution with reduced analysis time. Many of these requirements may be met to a certain extent by the total or partial automation of the conventional analytical methods, including sample preparation or sample pre-treatment coupled on-line to the analytical system. Furthermore, the recent use of ultra-high-performance liquid chromatography (UHPLC) for environmental and food chemical analysis has increased the overall sample throughput and laboratory efficiency without loss (and even with an improvement) of resolution obtained by conventional HPLC systems.

Nonetheless, despite the advances in chromatographic separations and mass spectrometry techniques, sample treatment is still one of the most important parts of the analytical process and effective sample preparation is essential for achieving good analytical results [1]. Ideal sample preparation methods should be fast, accurate, precise and must keep sample integrity. Therefore, over the last years, considerable efforts have been made to develop modern approaches in sample treatment techniques that enable the reduction of the analysis time without compromising the integrity of the extraction process. The use of on-line solidphase extraction (SPE), which minimizes sample manipulation and provides both high preconcentration factors and recoveries [2-5], is an increasingly powerful and rapid technique used to improve the sample throughput and overcome many of the limitations associated with the classical off-line SPE procedure. However, in most of the cases, matrix related compounds may also be co-extracted and could interfere in the analysis. Consequently, in order to minimize the effect of all these possible interferences a selective clean-up step may be required. Higher specificity and selectivity together with satisfactory extraction efficiency can be obtained using sorbents based on molecularly imprinted polymers (MIPs) [6-8].

© 2012 Lucci et al., licensee InTech. This is an open access chapter 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. © 2012 Lucci et al., licensee InTech. This is a paper 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.

Solid-phase extraction (SPE) based on MIPs is a highly attractive and promising approach for matrix clean-up, enrichment and selective extraction of analytes in such kind of complex samples. Another modern trend in sample preparation for multi-residue applications is the use of the QuEChERS (*Quick, Easy, Cheap, Effective, Rugged and Safe*) method. The QuEChERS method is a recent and fascinating alternative procedure that has become particularly popular for the multi-residue analysis of pesticides in various food matrices [9,10], although this methodology is also being successfully employed for the extraction of other families of compounds [11,12]. Recently, the use of turbulent-flow chromatography (TFC) has also been reported for direct analysis of complex matrices such as honey, milk and animal tissues with reduced or without any sample manipulation [13-15].

Current Trends in Sample Treatment Techniques for Environmental and Food Analysis 129

on the sorbent bed: the impurities will be rinsed through with wash solutions that are strong enough to remove them, but weak enough to leave the analytes behind. Differently, selective elution consists in the elution of the adsorbed compounds of interest by a solvent that leaves the strongly retained impurities behind. The elution of target analytes could require different solvents, when SPE is applied in order to perform the class compound

To achieve optimal SPE extraction conditions, the choice of sorbent is a key factor because this can control parameters of primary importance such as selectivity, affinity and capacity [18]. This choice depends strongly on the nature of the analytes and their physical and chemical properties, which should define the interaction with the chosen sorbent. However, results can also depend heavily on the sample matrix and its interactions with both sorbent

After the sorbent choice, the eluotropic strength of adsorption on silica and the polarity index will be helpful in order to select a suitable solvent. The polarity index is an accurate measure of solvent's ability to interact as proton donator, proton acceptor or dipole whereas eluotropic series arranges solvents in order of decreasing elution strength for solutes from a

The sorbent selectivity depends on the attractive forces between the analytes and the functional groups on the sorbent surface. The sorbent can interact with analytes by hydrophobic (non polar-non polar, van der Waals), hydrophilic (polar-polar, hydrogen bonding, dipole-dipole, dipole-induced dipole), cationic-anionic and selective antigen-

fractionation.

and analytes.

particular sorbent.

**2.1. SPE sorbents** 

antibody interactions.

**Figure 1.** Schematic representation of SPE clean-up procedure.

The aim of this chapter is to discuss new trends in sample preparation techniques applied into food and environmental analysis. It includes a selection of the most interesting and promising sample treatment procedures such as on-line SPE methods, MIPs, QuEChERS, and turbulent flow chromatography. The applicability of each technique in food and environmental analysis will be discussed through the analysis of the most relevant papers recently published.
