A capillary electrophoresis–tandem mass spectrometry methodology for the determination of non-protein amino acids in vegetable oils as novel markers for the detection of adulterations in olive oils

Abstract

A new analytical methodology based on capillary electrophoresis-mass spectrometry (CE-MS(2)) is presented in this work, enabling the identification and determination of six non-protein amino acids (ornithine, β-alanine, GABA, alloisoleucine, citrulline and pyroglutamic acid) in vegetable oils. This methodology is based on a previous derivatization with butanol and subsequent separation using acidic conditions followed by on-line coupling to an ion trap analyzer for MS(2) detection established through an electrospray-coaxial sheath flow interface. The electrophoretic and interface parameters were optimized obtaining the separation of all compounds in less than 15 min and with resolutions higher than 5. The proposed method was validated by assessing its accuracy, precision (RSD<7% for corrected peak areas), LODs and LOQs (between 0.04-0.19 ng/g and 0.06-0.31 ng/g, respectively) and linearity range (R(2)>0.99), and it was used in order to identify the selected non-protein amino acids in soybean oils, sunflower oils, corn oils and extra virgin olive oils. MS(2) experiments performed the fingerprint fragmentation of these compounds allowing to corroborate ornithine and alloisoleucine in seed oils but not in olive oils. The method was applied to identify and quantify olive oil adulterations with soybean oil detecting in a single run the amino acids in mixtures up to 2% (w/w). The results showed a high potential in using these compounds as novel markers for the detection of adulterations of extra virgin olive oils with seed oils. Thus, the developed method could be considered a simple, rapid and reliable method for the quality evaluation of extra virgin olive oil permitting its authentication.

Effects of sprint training combined with vegetarian or mixed diet on muscle carnosine content and buffering capacity

“…Since beta-alanine is the rate limiting precursor of carnosine synthesis (Bakardjiev and Bauer 1994;Dunnett and Harris 1999;Hill et al 2007) and since it is a natural constituent of meat, fish and poultry (Abe 2000;Boldyrev 2007), this training effect will probably occur only if sufficient substrate for carnosine synthesis is present. Except from the minimal traces of beta-alanine recently found in vegetable oils (Sanchez-Hernandez et al 2011), beta-alanine containing dipeptides are virtually absent in plants and therefore, chronic vegetarians have lower muscle carnosine content than omnivorous subjects Everaert et al 2010). It can thus be expected that a combination of the above-mentioned training program with a vegetarian diet will probably not lead to an increase in muscle carnosine.…”

Determination of betaines in vegetable oils by capillary electrophoresis tandem mass spectrometry – application to the detection of olive oil adulteration with seed oils

“…However, most of these methodologies need sophisticated chemometric tools to interpret the data and differentiate the adulterated samples from pure olive oils. Recently, our research group proposed for the first time the use of non-protein amino acids as novel markers for the detection of adulterations of olive oils with seed oils [18]. In fact, the development of a CE-MS 2 methodology enabling the identification and determination of six non-protein amino acids in vegetable oils allowed to propose ornithine and alloisoleucine as markers for the detection of adulterations of olive oils.…”

Capillary electrophoresis determination of non-protein amino acids as quality markers in foods

“…5(A)) [8]. Following the same sample treatment described for the determination of ornithine in olive and seed oils [7] and using a derivatization with butanol to improve not only the analytical sensitivity but also the selectivity (by improving mass differentiation among analytes) the separation was achieved within 10 min using a 0.1 M formic acid (pH 2.0) as running buffer. The LOD obtained using MS detection (1 ng/g) was 20 times lower than that obtained previously with UV detection.…”

“…An interesting CE-MS 2 methodology was developed enabling the determination of non-protein amino acids in vegetable oils [7]. The simultaneous separation of ornithine, ␤-alanine, GABA, alloisoleucine, citrulline, and pyroglutamic acid, previously derivatized with butanol, was achieved in only 15 min with a 0.1 M formic acid buffer (pH 2.0).…”

“…Even though non-protein amino acids have been studied to a lesser extent, they have also shown to play an important role in the quality and safety of foods. Thus, different research works have demonstrated the relevance of determining non-protein amino acids to detect food adulterations, to investigate fermentation, storage and thermal treatments, to evaluate the nutritional quality of foods or to determine their toxic effects [7][8][9][10][11][12].…”