NEW TRENDS IN SAMPLE PREPARATION FOR FOOD ANALYSIS 
"For me, everything related to the laboratory work is stimulating. It attracts me because it is creative. But probably one of the most gratifying aspects is teaching and working with PhD students. Probably because for me learning is the reward. An additional treat is meeting very interesting and nice people on the way."
Lourdes, what is your tutorial about?
"This tutorial gives an overview of modern analytical techniques in use for the analysis of organic components in (semi-)solid foodstuffs with special attention on the analysis of residual compounds regulated by current legislations. The feasibility of approaches based on miniaturisation and hyphenation of the several treatments involved in these determinations at the low levels typically found in real-life food samples will be demonstrated through representative examples."
"Foodstuffs are complex mixtures of volatile, inorganic and organic components at very different concentration levels. Food chemical characterisation consequently requires the analysis of a variety of macromolecules such as proteins, macronutrients like carbohydrates and lipids, natural bioactive components such as polyphenols, aroma and flavour components, inorganic micronutrients and organometalic compounds, as well as undesirable residues of other small molecules introduced during production, processing, storage and/or transport of food, including contaminants, i.e. plasticizers, pesticides, persistent organic pollutants, veterinary drugs, and toxins.
The different nature and volatility of these analytes determine the instrumentation used for final determination. However, unless the concentration level is high enough and the separation-plus-detection highly selective, analytical protocols in use for the analysis of all these food components typically involve several previous treatments for extraction, isolation and concentration of the target compounds before instrumental determination. In most instances, similar sample preparation techniques are used almost irrespective of the target analyte."
Why is sample preparation important in food analysis?
"Analytical procedures typically involve a number of equally relevant steps for sampling, sample preparation, isolation of the target compounds, identification, quantification and data handling. As in many other application fields, in most instances, extremely powerful separation-plus-detection techniques are used in food analysis for final instrumental determination of the target compounds. However, unless the matrix is simple enough, the concentration level of the investigated analyte(-s) relatively high and the technique selected for instrumental analysis highly selective, sample treatment is frequently mandatory, specially when dealing with complex matrices such as foodstuffs."
"Every single physico-chemical treatment carried out to isolate the analytes from other matrix components that can interfere during their instrumental determination or to increase their concentration in the extract subjected to analysis is considered as a step of the sample preparation protocol. According to this consideration, one can conclude that typical sample preparation methods in use for food analysis are long, tedious, and highly manipulative multi-step procedures prone to loose, degradation and/or contamination of the target analytes. Sample preparation is consequently a key part of the analytical process that, in many applications within this research area, has a profound effect on both the time required to complete the analytical process and the validity of the final results."
What is the most interesting aspect of in sample preparation?
"Food analysis has recently been re-defined as foodomics [J. Chromatogr. A (2009) 1216] and probably this –omic-based term is appropriate in this field in which many different aspects are involved. Foodstuffs are complex mixtures of volatile, inorganic and organic components at very different concentration levels. Food chemical characterisation requires the analysis of all a variety of macromolecules such as proteins, other macronutrients like carbohydrates and lipids, natural bioactive components such as polyphenols, aroma and flavour components, inorganic micronutrients and organometallic compounds, as well as undesirable residues of other small molecules introduced during production, processing, storage and/or transport of food, including contaminants, i.e. plasticizers, pesticides, persistent organic pollutants, veterinary drugs, and toxins. Sample preparation is, in one way or another, required almost in all these types of analyses."
What is the biggest challenge in food analysis?
"Because of the still rather traditional protocols used for many of these determinations, there are many opportunities for improvement and analytical development. The new analytical demands derived from current legislations concerning (and constantly affecting) food routine control and monitoring programs to ensure human health protection also contribute to promote new improvements and developments in the field, with increasing automation probably being one of the main requirements. Finally, as in many other application fields, the large amount of (frequently toxic) wastes generated during sample preparation of foodstuffs demands the development of alternative greener analytical procedure also in this research area."
Where do you see the future in food analysis methods?
"In my opinion, “miniaturisation”, “hyphenation” and “automation” should be considered as key words when considering future developments in food sample preparation with the nowadays available treatment techniques. Of course the ideal situation would be the on-site test based on a single and fast measurement. Despite the remarkable advances made during the last years in the field of sensors, and although some analyte and multi-analyte sensor kits have been developed, we must accept that today this option is far from being a realistic alternative for most food analytical determinations. But anyway, this type of tests would represent a green, convenient, fast and efficient analytical alternative also in this field."
Lourdes Ramos
Department of Instrumental Analysis and Environmental Chemistry, IQOG (CSIC), Juan de la Cierva 3, 28006 Madrid, Spain
l.ramos@iqog.csic.es
