5 Table 1. Dilution factors for the ‘off-the-shelf’ samples studied. Sample preparation
All samples were purchased locally. The juice samples assessed included orange, apple, pineapple, pomegranate, and grape. The alcoholic beverages assessed included five beers, three lagers (one non-alcoholic), a lemon flavoured beer, one hard cider, one sherry, one red wine, and four whiskeys. The beer samples were sonicated to remove carbonation. All of the samples were filtered through a 0.22 µm PVDF syringe filter and diluted in 1:1 acetonitrile- water. The dilution factors are listed in Table 1.
Figure 3. Calibration curves for the nine saccharide standards analysed showing R2
values obtained for each analyte.
RESULTS AND DISCUSSION
Figure 1. SIR chromatograms of the nine saccharide standards used in the study. The annnotated m/z represent the [M+Cl]-
adducts.
Figure 1 shows the SIR chromatograms for a mixed standard at 100 mg/L for fructose, glucose, arabinose, inositol, sorbitol, mannitol, sucrose, maltotriose, and maltose. Excellent separation of all of the standards was achieved. Initially, using isocratic conditions, the lower mass saccharides were separated, including the difficult pair sorbitol and mannitol. After 4.5 minutes a gradient was started that allowed timely separation of the larger molecular weight saccharides in the mix.
The mass spectra extracted from the SIR of each standard is shown in Figure 2. The use of guanidine chloride in the mobile phase ensured that the compounds were driven to their chloride adduct ([M+Cl]-
ion). The smaller 37 Cl adduct response was also present.
Figure 3 shows the SIR chromatograms for a mixed standard at 100 mg/L for each of the analytes listed in the Experimental above. An R2
value >0.995 was achieved for all of the analytes.
Figure 2. Mass spectra information extracted from SIRs of the nine saccharide standards. The annotated m/z represents the [M+ Cl]-
adducts. Standard preparation
A 100 mg/L stock of the nine saccharides listed above was prepared in 1:1 acetonitrile-water. This stock was further diluted to produce nine individual levels (1, 2, 4, 5, 10, 20, 40, 50, and 100 mg/L).
Figure 4 (A–E) shows the SIR profiles of a lager beer. In Figure 4A (m/z 185) arabinose is present. Other peaks are also apparent, suggesting the presence of other pentose saccharides. In Figure 6B (m/z 215) traces of fructose and glucose can be seen. The enhanced sensitivity of the ACQUITY QDa allows improved detection of these compounds, as opposed to less sensitive methods such as Refractive Index [1]. In Figure 6C (m/z 217) traces of sorbitol and mannitol are
present. We also saw small peaks representing the extraction of the 37
Cl adducts of fructose and glucose, which have the same molecular weight as sorbitol and mannitol. In Figure 5D and 5E (m/z 377 and 539 respectively), we observed the DP2 and DP3 compounds maltose and maltotriose, along with isomers of the same mass, which would be expected for a beverage derived from grain.
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54 |
Page 55 |
Page 56
