Electrospray ionization mass spectrometry fingerprinting of beer.
ABSTRACT After just simple degassing, dilution, pH adjustment and direct flow injection, characteristic fingerprint spectra of beer samples have been obtained by fast (few seconds) electrospray ionization mass spectrometry (ESI-MS) analysis in both the negative and positive ion modes. A total of 29 samples belonging to the two main beer types (lagers and ales) and several beer subtypes from USA, Europe and Brazil could be clearly divided into three groups both by simple visual inspection of their ESI(+)-MS and ESI(-)-MS fingerprints as well as by chemometric treatment of the MS data. Diagnostic ions with contrasting relative abundances in both the positive and negative ion modes allow classification of beers into three major types: P = pale (light) colored (pilsener, pale ale), D = dark colored (bock, stout, porter, mild ale) and M = malt beer. For M beers, samples of a dark and artificially sweetened caramel beer produced in Brazil and known as Malzbiers were used. ESI-MS/MS on these diagnostic beer cations and anions, most of which are characterized as arising from ionization of simple sugars, oligosaccharides, and iso-alpha-acids, yield characteristic tandem mass spectra adding a second and optional MS dimension for improved selectivity for beer characterization by fingerprinting. Direct ESI-MS or ESI-MS/MS analysis can therefore provide fast and reliable fingerprinting characterization of beers, distinguishing between types with different chemical compositions. Other unusual polar components, impurities or additives, as well as fermentation defects or degradation products, could eventually be detected, making the technique promising for beer quality control.
- SourceAvailable from: Fedor Macasek[Show abstract] [Hide abstract]
ABSTRACT: Electrospray ionization (ESI) mass spectra of hexoses, pentoses, and 2-deoxy-2-fluoro-d-glucose (FDG) were investigated and compared using liquid chromatography/mass spectroscopy (LC/MS). 18F-FDG is one of the most widely used radiopharmaceuticals. This work is aimed at the possible interpretations of ESI mass spectra and at the comparison of various pentoses (arabinose, ribose, xylose), and hexoses (glucose, fructose, galactose, mannose) which can be formed during the 18F-FDG’s synthesis or decomposition. As a result, nine major associates were found in the positive and four in the negative mass spectra of all examined saccharides of which intensities and mass can be used with their retention times to determine the saccharide. M · NH4+ and M · COOH− were identified as the most stable associates.Chemical Papers- Slovak Academy of Sciences 11/2008; 62(6):547-552. · 0.88 Impact Factor
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ABSTRACT: Stingless bees are found in many tropical and subtropical regions of the word. The knowledge of the composition of their propolis as well as the plants that are visited as sources of resins is therefore of prime importance. Here the negative ion mode electrospray ionization mass spectrometry [ESI(-)-MS] fingerprints of propolis from various species of native stingless bees from different regions in Brazil are compared to determine their composition patterns. The correlation among the propolis samples was investigated via chemometric analysis. Stachellose Bienen kommen in vielen tropischen und subtropischen Regionen der Welt vor und sind in diesen Regionen wichtige Bestäuber. Nichtsdestotrotz ist die Haltungstechnologie für die meisten Arten Stachelloser Bienen noch auf einem relativ niedrigen Niveau. Obwohl für Brasilien bereits verschiedene Studien zur Nischenüberlappung von einheimischen Bienen mit den eingeführten Honigbienen vorliegen, gibt es nur wenig Informationen zu Pflanzen, die von Stachellosen Bienen als Harzquelle für die Herstellung von Propolis genutzt werden. Propolisproben, die von Imkern in verschiedenen Regionen Brasiliens gewonnen wurden (zusammengestellt in Tab. 1), wurden eingefroren und für die Extraktion zermahlen. Die mazerierten Proben wurden auf einem Schüttler während sieben Tagen in Alkohol extrahiert und anschliessend im negativen Ionenmodus per Elektrospray-Ionisations-Massenspektrometrie [ESI(-)-MS] in einem Q-TOF-Massenspektrometer (Micromass) analysiert. Mittels einer chemometrischen Hauptkomponentenanalyse (PCA) wurden statistisch signifikante Korrelationen in diesen Fingerabdrucksanalysen der Propolisproben aufgedeckt. Abbildung 1 zeigt die PCA-Ergebnisse der ESI(-)-MS Fingerabdrücke von Propolisproben Stachelloser Bienen und von Honigbienen. Die Proben teilen sich anhand ihrer charakteristischen Ionen klar in drei Gruppen auf (Abb. 1 A, B). Abbildung 2 zeigt ESI(-)-MS-Spektren typischer Proben aus jeder dieser Gruppen. Gruppe 1 besteht aus neun Propolisproben, für die die Ionen m/z 371, 373, 401, 453, 455, 469 und 471 für die Gruppierung verantwortlich sind. Diese Ionen sind charakteristisch für Tetragonisca angustula Propolis, die diese Bienen in ganz Brasilien überwiegend von Schinus terebenthifolius sammeln. Gruppe 2 besteht ebenfalls aus neun Propolisproben, mit den Gruppierungsionen m/z 301, 315, 317, 319, 333, and 361. Diese sind für die braune A. mellifera Propolis charakteristisch, die vor allem aus Südbrasilien stammt und in der die Bienen Harze der Araucaria Tanne verarbeiten. Zwei Propolisproben (P. droryana aus São Paulo und P. remota aus Paraná) lagen zwischen diesen beiden Gruppen (Abb. 1A), was darauf hinweist, dass diese Bienen sowohl S. terebenthifolius als auch Araucaria Harze sammelten. Gruppe 3 besteht aus sechs Propolisproben, für die das Hauption (m/z 271) für die Gruppierung verantwortlich zeigt. Dieses ist charakteristisch für rote Robinienpropolis von A. mellifera aus dem Nordosten Brasiliens. Die meisten Fingerabdrücke von Propolisproben der einheimischen Stachellosen Bienen zeigten die für S. terebenthifolius charakteristischen Ionen. Diese in ganz Brasilien vorkommende Pflanze enthält medizinisch wirksame Substanzen und wird häufig von Stachellosen Bienen besucht. Unsere Ergebnisse zeigen, dass S. terebenthifolius eine wichtige Quelle für die Propolisgewinnung darstellt, dass Stachellose Bienen aber auch andere Pflanzen, insbesondere Aurakarien nutzen können. ESI-MS fingerprint–propolis–native stingless bees–Brazilpropolis–spectrométrie de masse par ionization avec électronébulisation–abeille sans aiguillon–Apidae–Meliponini–Brésil– Schinus therebentifolius ESI-MS Fingerabdruck–Propolis–Stachellose Bienen–BrazilApidologie 01/2007; 38(1):93-103. · 2.16 Impact Factor
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ABSTRACT: Extra virgin (EV), the finest and most expensive among all the olive oil grades, is often adulterated by the cheapest and lowest quality ordinary (ON) olive oil. A new methodology is described herein that provides a simple, rapid, and accurate way not only to detect such type of adulteration, but also to distinguish between these olive oil grades (EV and ON). This approach is based on the application of direct infusion electrospray ionization mass spectrometry in the positive ion mode, ESI(+)-MS, followed by the treatment of the MS data via exploratory statistical approaches, PCA (principal component analysis) and HCA (hierarchical clustering analysis). Ten distinct brands of each EV and ON olive oil, acquired at local stores, were analyzed by ESI(+)-MS and the results from HCA and PCA clearly indicated the formation of two distinct groups related to these two categories. For the adulteration study, one brand of each olive oil grade (EV and ON) was selected. The counterfeit samples (a total of 20) were then prepared by adding assorted proportions, from 1 to 20% w/w, with increments of 1% w/w, of the ON to the EV olive oil. The PCA and HCA methodologies, applied to the ESI(+)-MS data from the counterfeit (20) and authentic (10) EV samples, were able to readily detect adulteration, even at levels as low as 1% w/w.Rapid Communications in Mass Spectrometry 07/2010; 24(13):1875-80. · 2.51 Impact Factor
Concours d'ingénieur de laboratoire
du ministère de l’économie, de l’industrie et de l’emploi
et du ministère du budget,
des comptes publics et de la fonction publique
des 16 et 17 septembre 2008
SPECIALITE CHIMIE ANALYTIQUE
ÉPREUVE N° 3
Traduction d’un document technique rédigé en langue anglaise ;réponses en langue anglaise à
des questions portant sur les documents..
(durée 2 h - coefficient 2)
Cette épreuve comporte 5 pages.
1 - Traduire les deux premiers paragraphes de l’introduction figurant dans l’encadré.
2 - Questions
Give a concise summary of the main idea of the text – no more than a hundred words.
Give one of the advantages of electrospray ionization mass spectrometry.
What are the characteristics of an ESI(+) mass spectrum representative of malt “Malzbier” beer?
Electrospray ionization mass spectrometry fingerprinting of beer
Alexssander S. Araújo, Lilian L. da Rocha, Daniela M. Tomazela, Alexandra C. H. F. Sawaya,
Reinaldo R. Almeida, Rodrigo R. Catharino and Marcos N. Eberlin
First published as an Advance Article on the web 11th April 2005
Electrospray (ESI) is a soft and wide-ranging ionization technique that has revolutionized the way molecules are ionized and
transferred to mass spectrometers for mass measurement and structural characterization. ESI has greatly expanded the applicability
of mass spectrometry to a variety of new classes of molecules with thermal instability, high polarity and mass. Direct injection ESI-
MS has also been shown to be suitable for fast fingerprinting of complex mixtures such as plant extracts, propolis, wine and whisky.
ESI, with direct sample introduction, is likely therefore to be a convenient technique for fingerprinting and fast quality control of beer
with very little, simple sample manipulation and direct injection into a mass spectrometer. This is so because key components of the
blend of beer organic compounds bear acidic or basic sites that are therefore likely to be detected by direct injection ESI-MS as
either protonated or deprotonated molecules and form a set of diagnostic beer ions. Tandem MS/MS with collision-induced
dissociation (CID) of such diagnostic ions could also be used to add a second MS dimension in very selective beer fingerprinting,
allowing for the structural characterization of the precursor molecules.
Sensory properties such as taste, smell and sight are unique characteristics of food and drinks. These properties are
multivariate for they involve a combination of sensations, which are useful for classification, but are also subjective and can lead to
evaluation and classification errors. Fast and objective instrumental analytical measurements, such as the ESI-MS fingerprinting
method exemplified herein for beer, represent an attractive alternative for quality control of foods and drinks, particularly when
associated with multivariate statistics. These statistics provide a set of tools that help deal with the complexities and subtleties
confronted in the characterization and sensory classification process. Treating two or more variables simultaneously requires the
use of the mathematical apparatus of matrix algebra. Techniques such as principal component analysis (PCA) can serve to order
known samples and have been applied to MS data to classify unknown samples.
In this work, ESI-MS with direct flow injection is tested as a fast method (a few seconds) for the fingerprint characterization and
quality control of beer samples. Samples of internationally famous brands belonging to the two main types (ales and lagers) and of
several subtypes of beers from USA, Europe and Brazil were analyzed. These beer samples produce characteristic ESI-MS data in
both the positive and negative ion modes. Both simple visual inspection and chemometric treatment of data place the samples in
three distinct groups owing to very diagnostic (marker) ions.
Twenty-nine samples of beer (Table 1) belonging to the two main types (ales and lagers) and several beer subtypes (pilsener, pale
ales, bock, stout, porter, mild ale, malt) from USA, Europe, and Brazil were analyzed by ESI-MS in both positive and negative ion
modes. For malt beer, samples of a dark and artificially sweetened malt (caramel) Brazilian beer known as Malzbiers were used.
General experimental procedures
A Q-TOF mass spectrometer (Micromass, Manchester, UK) was used for fingerprint ESI-MS analysis. Typical ESI-MS conditions
were: source temperature 100 ° C, desolvation temper ature 120 ° C, capillary voltage 3.0 kV and cone vol tage 40 V. The beer
samples (250.0 µL) were degassed in order to eliminate CO2, and diluted in a flask with a 1:1 solution of water: methanol up to a
final volume of 1.0 mL. Formic acid (2 µL) was added to each sample for the positive ion mode ESI(+)-MS analysis whereas 2 µL of
ammonium hydroxide were added for the negative ion mode ESI(–)-MS analysis. The samples were injected at a flow rate of 15 µL
min-1 using a syringe pump (Harvard Apparatus). Mass spectra were acquired over a 50–1000 m/z range.
Statistical data treatment
To classify the beer samples after ESI-MS fingerprint analysis, principal component analysis (PCA) was performed on the respective
ESI-MS results. Data matrixes were constructed using the information of the mass spectra obtained in both ESI(+)-MS and ESI(–)-
MS modes. Ions producing the 20 major peaks in the MS of each of the 29 samples analyzed were selected as the variables.
Exploratory data analysis was applied to the data matrix constituted of the 29 samples (as rows) and this group of variables (as
columns). Einsight and Pirouette, both from Infometrix (Seattle, WA), were used to perform the Principal Component Analysis (PCA)
using Mean Centering as data pre-treatment.
Results and discussion
As exemplified by the mass spectra shown in Figs. 1 and 2, simple visual inspection of all 29 mass spectra obtained in both the
positive and negative ESI ion modes reveals 3 very characteristic groups that directly correspond to the three major types of beers:
P = pale (light) colored (pilsener, lager, pale ales),
M = malt ‘‘Malzbier’’ beers. Principal component chemometric analysis of both the ESI(+)-MS and ESI(–)-MS data
(Fig. 3A and B) also clearly divide the samples into the same P, D, and M groups, confirming the clear but subjective visual
interpretation of the ESI-MS fingerprints.
D = dark colored (bock, stout, mild ale) and
Fig. 1A shows an ESI(+) mass spectrum very typical of P beers, with intense ‘‘beer cations’’ in the m/z range of 70 to 705
corresponding to sodium [M + Na]+ and potassium [M + K]+ adducts. Since these adducts are known to be quite resistant towards
dissociation, each ion is likely to represent a single component of the mixture and not fragments of other heavier ions. A series of
major cations correspond to [M + Na]+ and [M + K]+ adducts of maltose (m/z 365 and 381), maltotriose (m/z 527 and 543) and
maltotetrose (m/z 689 and 705), as indicated by their tandem MS spectra and comparison with reported data. Therefore, as these
oligosaccharides are not totally consumed during fermentation, they form diagnostic cationized molecules for ESI-MS typification of
P beers. The [M + K]+ adduct of glucose of m/z 219 constitutes, however, a very minor ion which corresponds to the expectation that
most glucose is consumed during fermentation of P beers with their characteristic bitter taste. Another diagnostic and major cation
for P beers is that of m/z 325, and ESI-MS/MS shows this is likely the [M + K]+ adduct of a dimer of anhydrohexose.
Fig. 1B shows an ESI(+) mass spectrum typical of M beers. As the result of artificial sweetening, by far the most diagnostic
cations for the M beers are clearly the ones corresponding to the [M + Na]+ and [M + K]+ adducts of glucose of m/z 203 and 219, and
the [M + K]+ adduct of sucrose of m/z 399. These intense and diagnostic cationized glucose molecules indicate a beer additive, that
is, caramel malt responsible for the pronounced sweet taste and some of the dark color characteristic of Brazilian caramel
‘‘Malzbier’’ types of beer.
Fig. 1C shows a ESI(+) mass spectrum typical of D beers. Their fingerprint mass spectra is, in general, rather similar to that of
P beers, except mainly for the considerably more intense ion of m/z 219 that is clearly seen in such a spectrum. As for the M beers,
this cation is likely the [M + K]+ adduct of glucose indicating some degree of caramel coloring and sweetening, as normally observed
for dark beers. Another interesting and characteristic feature of the D beers is that only the [M + K]+ of the oligosaccharides (and not
the [M + Na]+ adducts of m/z 365, 527 and 689 as seen in Fig. 1A) are clearly seen as the cations of m/z 381, 543 and 705 (Fig.
1C). Direct infusion ESI(+)-MS seems therefore to be able to reveal, by comparison, distinct [K+]/[Na+] concentration ratios in P and
D beers. Also diagnostic but not so abundant for the D beers are the cations of m/z 165 and 179.
Fig. 2A shows an ESI(–) mass spectrum typical of P beers. Relatively intense and characteristic ‘‘beer anions’’ are seen in the m/z
range from 79 to 925 corresponding to deprotonated [M – H]– molecules. Since such ions were accelerated from the ESI source to
the MS using relatively low kinetic energies to avoid dissociation, the ion current is expected to represent intact molecules in their
deprotonated forms rather than fragment ions. Anions of m/z 161, 179, 341, 503, 665 and 827 are likely the [M – H]– forms of
anhydrohexose, glucose, maltose, maltotriose, maltotetrose and maltopentose, respectively, as also indicated by ESI-MS/MS and
comparison with reported data. Pairs of anions of m/z 377 and 379, 539 and 541, 701 and 703 are likely the chloride adducts (typical
isotopic pattern for the 35Cl and 37Cl isotologues) of maltose, maltotriose, and maltotetrose, as previously suggested. Other
characteristic and intense anions of P beers are those of m/z 79, 97, 128, 191, 259, 439, 601 and 763. The ions of m/z 439, 601,
763, and 925 most likely indicate the presence of unfermentable higher oligosaccharides with a ∆m/z of 162 (C6H10O5)n. The
concentrations of these oligosaccharides vary from beer to beer. Lower kiln temperatures during malting produce more dextrins and
less sugar, whereas higher temperatures produce less dextrins and more sugars.
Also noteworthy in the ESI(–) mass spectrum of Fig. 2A is the detection of the minor but relevant anions of m/z 347 and 361.
These anions correspond to the deprotonated forms of two major iso-alpha-acids responsible for the bitter taste of beer, also playing
an essential role in foam stability. Direct infusion ESI(–)-MS analysis, particularly when using selective ion monitoring (SIM), may
therefore also serve as a very fast method to control, compare or roughly quantitate levels of these important components in beer
Fig. 2B shows an ESI(–)-MS spectrum representative of M beers. Similarly to what is revealed by ESI(+)-MS (sodium adduct of
m/z 219 in Fig. 1B), deprotonated glucose of m/z 179 is by far the major anion detected (base peak) followed by the pair of
isotopologue chloride adducts of glucose of m/z 215 and 217. As in the positive ion mode, caramel malt addition is the most likely
source of glucose molecules. Other diagnostic anions for M beers are those of m/z 89 and 359.
Fig. 2C shows an ESI(–)-MS spectrum representative of the D beers. Many of the major anions seen for the P beers are also
present in the fingerprint spectra of the D beers, but the two anions of m/z 161 and 179 are clearly distinguishing. As for the P beers,
the anion of m/z 161 is likely the deprotonated molecule of anhydroxexose. As for the M beers, the ion of m/z 179 is the
deprotonated molecule of glucose again indicating some degree of artificial sweetening by caramel malt addition. Another rather
characteristic anion for D beers is that of m/z 255.
PCA data treatment was also performed for the ESI-MS fingerprint mass spectra, to test its performance for statistical beer
classification and quality control.
Fig. 3A shows a scatter plot of PC1 versus PC2 from the data matrix obtained from ESI(+)-MS data. The three types of beers
are very clearly grouped. P beers are placed on the upper right side whereas the D (upper) and M beers (bottom) are grouped on
the left side. Similarly for the ESI(–)-MS data (Fig. 3B), PCA analysis also clearly places the three types of beers in very well-defined
groups. In the PC1 versus PC2 plot for the ESI(–)-MS data, the P beers are again on the upper right side whereas the D beers
(upper) and M beers (bottom) are on the left side.