Grapes sampling

With fortification levels between 0.01 and 0.50 mg kg , average recoveries of M-1 and fenpyroximate from untreated apple and grape samples are 87 and 91% with the limits of determination being 0.01 and 0.05 mg kg respectively, for the apple and grape samples. 

Because they are important, the phenolics and their roles in wine have been studied considerably (I), but more needs to be known. Since different classes of phenols behave quite differently in the various roles as pigments, oxidation substrates, flavors, etc., separate consideration and analysis is essential to completely understand them. Every individual phenol should be separately determined precisely and quantitatively. Chromatography may solve these problems, but for now, chromatography and other detailed separatory methods have drawbacks, particularly for economical application to many individual wine or grape samples. 

Quantify peaks of interest (e.g., methyl anthranilate in Concord grape samples). 

SNIF-NMR and/or IRMS techniques were often combined with trace element analyses (ICP-MS, ICP-OES, FAAS, ETAAS, GFFA) and chemometrics for the geographical characterization of wines. In a relatively old paper, Day et ah (1995) analyzed 165 grape samples collected in 1990 in four different production areas of France (Alsace, Beaujolais, Burgundy, and the Loire Valley). The combined use of isotopic and trace element data allowed an excellent classification of wine samples corresponding to... 

Figure 3. Grape sampling station and grape sampler...

In studies of methoxypyrazines, a stable isotope labeled internal standard has not always been used. Calo et al. (6) used 5ec-butylmethoxypyrazine as an internal standard to quantify isobutylmethoxypyrazine in a comparison of grape varieties. Recently, Hashizume and Umeda have used 2-methyl-3-Ai-propylpyrazine as an internal standard to quantify methoxypyiazines in Japanese red wine and grape samples (7). However, the increased potential for lack of precision and accuracy needs to be recognized, and the natural occurrence of 5gc-butylmethoxypyrazine is a drawback to its use as an internal standard. 

GC analysis is performed by using an ion trap mass spectrometer (ITMS) equipped with a chemical liquid ionization system. Figure 6.4 shows the GC-MS chromatogram relative to THPI and captan analysis in a grape sample, analytical conditions are reported in Table 6.13. The... 

Figure 6.4 GC-MS chromatogram relative to analysis of THPI (0.13mg/kg) and captan (0.76mg/kg) in a grape sample. (Reproduced from J. Agric. Food Chem., 2003, 51, 6761-6766, Angioni et al., with permission of the American Chemical Society)...

The elemental composition of 36 grape samples harvested at technological ripeness from 10 varieties is reported in Figure 8.2. Concentration ranges agree with the other data reported in the literature (Cabanis, 1998 Sponholz, 1989). 

Figure 8.2 Box plots of the amounts of elements in 36 grape samples from 10 different varieties cultivated in northern Italy determined by ICP-MS...

Figure 8.4 Distribution of the contents of residual sulphur in 159 grape samples of the 2005 vintage in Trentino (northern Italy)...

A fast extraction of pesticides from 75 g of grape sample was performed using 200mL of ethyl acetate. After filtration, lOmL of extract was evaporated to dryness, taken up with 1.5mL of methanol, and analyzed by LC/MS without further clean up. A total of 57 different pesticides were reported with recoveries ranging between 70 and 100% (Jansson et al.,2004). 

Venkateswarlu, P., Mohan, K.R., Kumar, Ch.R., and Seshaiah, K. (2007). Monitoring of multi-class pesticide residues in fresh grape samples using liquid chromatography with electrospray tandem mass spectrometry, Food Chem.,105,1760-1766. 

The seeds peptide MALDI profile proved to be suitable in characterizing grape varieties. This result was confirmed excluding, or by evaluating as being of minor influence, the other factors that might contribute to the protein profile the harvest year, zone of production and vineyard treatments. To achieve it, seeds of Raboso Piave grape samples collected from different vineyards and harvested in different years were studied. The 3D plot of Fig. 10.3 shows that the profile is maintained in particular the species at m/z 6113, which is characteristic of this variety, is detected in the spectra of all samples. 

FIGURE 2.3 UHPLC-ESI-TOF chromatograms of a grape sample positive to indoxacarb. (a) Total ion chromatogram and (b) nw-XIC ( 10 mDa) and combined mass spectrum for the peak at 3.54 min. (c) Combined product ion spectra obtained by QTOF MS/MS experiments performed at different... 

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