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Total-reflection X-ray fluorescence analysis of Austrian wine
Spectrochimica Acta Part B 61 (2006) 1214 – 1218 www.elsevier.com/locate/sab
Analytical note
Total-reflection X-ray fluorescence analysis of Austrian wine☆ X. Gruber, P. Kregsamer, P. Wobrauschek, C. Streli ⁎ Atominstitut der Österreichischen Universitäten, 1020 Vienna, Austria Received 13 December 2005; accepted 22 August 2006 Available online 11 October 2006
Abstract The concentration of major, minor and trace elements in Austrian wine was determined by total-reflection X-ray fluorescence using gallium as internal standard. A multi-elemental analysis was possible by pipetting 6 μl of wine directly on the reflector and drying. Total-reflection X-ray fluorescence analysis was performed with Atomika EXTRA II A (Cameca) X-rays from a Mo tube with a high-energy cut-off at 20 keV in totalreflection geometry. The results showed that it was possible to identify only by the elemental analysis as fingerprint the vineyards and year of vintage among 11 different wines. © 2006 Elsevier B.V. All rights reserved. Keywords: Total-reflection X-ray fluorescence (TXRF); Wine analysis; Trace element analysis
1. Introduction Total-reflection X-ray fluorescence analysis (TXRF) is a well-established method to analyze liquid samples [1–3]. The first study of wine with TXRF deals with Madeira wine [4], which differs from table wines in sugar and alcohol content. As a consequence of the complex matrix of the Madeira wine, a time intensive sample preparation (digestion with concentrated HNO3 in a Teflon beaker) had to be chosen. In a further study [5], the elemental concentrations in wines from different countries (New Zealand, Australia, Bulgaria, France, South Africa and Chile) were determined. In two researches done on table wine using X-ray fluorescence analysis [6,7], wines from different types of grapes (up to 6 white and 4 red wines) and different countries (Brazil, Portugal, Chile) were compared to each other. In none of the previous analyses of table wines, samples from the same type of grape had been compared. Furthermore, due to the geographical distance between the viticulture regions of the
☆
This paper was presented at the 11th International Conference on Total Reflection X-ray Fluorescence Spectrometry and Related Methods (TXRF2005), held in Budapest, Hungary, 18-22 September 2005, and is published in the special issue of Spectrochimica Acta Part B, dedicated to that conference. ⁎ Corresponding author. Tel.: + 43 1 58801 14130; fax: +43 1 58801 14199. E-mail address: [email protected] (C. Streli). 0584-8547/$ - see front matter © 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.sab.2006.08.006
analyzed samples, the grapes were growing under different climatic and geological conditions. The major aim of the present experimentation was to investigate whether differences of elemental concentrations existed in table wines from the same type and provide sufficient significance, to allow clear recognition of the sample. The initial part of the work deals with wines from the same type of grape but from different wine growing areas in Lower Austria. For fulfilment of the research purpose, two bottles of the identical grape of the same year of vintage but from different wine growers and areas were analyzed by TXRF. One bottle of “Blauer Portugieser 2003” originating from the viticulturist Traxler in Langenlois (abbreviation bpt) and one from the viticulturists Grabner and Schierer in Sooss (bpg). The second part deals with difference in the elemental concentrations as a consequence of the barrel in use for fermentation. During the maturing process, especially of red wine, the use of either high-grade steel barrels or barriques made out of oak wood is common. From the producer in Sooss, a bottle of “cuvée privat” (cvg), barrique matured, was analyzed and the concentrations of the elements (especially the metallic elements of high-grade steel) were compared with concentrations found in the “Blauer Portugieser” matured in steel barrels. The main part of this work deals with the analysis of eight wines picked from the wine growing area of Langenlois and produced by Nastl in order to establish the influence of the vintage year on the concentration of
X. Gruber et al. / Spectrochimica Acta Part B 61 (2006) 1214–1218
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Table 1 Comparison of elemental concentrations (in μg/l) in NIST 1643c and the obtained values
NIST 1643c This work
K
Ca
V
Cr
Mn
Fe
Co
Ni
Cu
Zn
As
Se
Rb
Sr
Pb
2300 1510
36 800 25 530
31.4 32.5
19.0 22.4
35.1 32.1
106.9 115.9
23.5 20.3
60.6 59.2
22.3 22.0
73.9 76.3
82.1 83.5
12.7 12.5
11.4 12.5
263.6 256.1
35.3 33.6
elements. Thanks to the support of the winegrower, it was possible to perform measurements on wines from the type Green Veltliner, vintages 1999, 2001, 2002 and 2003; cultivated in vineyards located at “Kittmannsberg” (v9k, v1k, v2k, v3k) and “Steinhaus” (v9s, v1s, v2s, v3s) with a distance from each other of approximately 900 m. Only the grapes from the own vineyards were used for the production of this wine. Because of the small distance between the two vineyards, differences in the elemental concentrations in wines cannot be explained by the sheer result of different climatic conditions. The grapes were treated individually but with the same equipment (wine press, high-grade steel barrels, etc.) and along the same procedures. Another aim of this work was to show, that TXRF is a suitable routine method to observe the concentration of selected elements. The International Organisation of Vine and Wine (OIV) set maximum permissible concentrations for the elements Cd (0.01 mg/l), Cu (1 mg/l), Pb (0.20 mg/l), Zn (5 mg/l) and Fe (100 mg/l) [8,9]. Ni is also on the list, although the limit of the maximum concentration has not been decided yet.
3. Sample collection and preparation
2. Experimental set-up
The accuracy of measurements of this TXRF spectrometer was checked through the analysis of a standard reference material (Trace Elements in Water 1643c from the National Institute for Standards and Technology). As for the measurements of the wine samples, Ga was used as internal standard. Table 1 reflects the results obtained in this work. A typical spectrum obtained for a wine sample is shown in Fig. 1.
Measurements were done while using the energy-dispersive spectrometer Extra II A from ATOMIKA (Cameca), equipped with two separated 2 kW X-ray tubes with anodes of Mo and W. For this work, the Mo anode X-ray tube was operated with an attenuation filter (50 μm Mo and 1 mm Al) at 50 kV and a varying current from 5 to 12 mA. The spectra were acquired for 1000 s (live time) and the dead time was approximately 40%. The Si(Li) detector crystal was 3 mm thick and of 80 mm2 area of nominal 168 eV resolution at 5.9 keV (Mn Kα) and had a 25 μm thick Be window. The cut-off energy of the quartz reflector was adjusted to 20 keV. Quantification was made by adding a known concentration of an element absent in the wine as internal standard. The concentrations were obtained using the equation Ni SGa Ci ¼ CGa NGa Si
Wine samples were provided directly by the winegrowers Traxler and Nastl in Langenlois and from Grabner and Schierer in Sooss (both in the region of Lower Austria). The bottles were cleaned from outside dust, shaken, opened cautiously and 30 ml was transferred in a Sarstedt-bottle. For each bottle of wine, the mixture of 1.2 ml wine and 0.3 ml of a 50 mg/l Ga standard was prepared three times and stored in 1.8 ml bottles. The final Ga concentration was 10 mg/l. Due to the high scattering of the radiation by the sugar in dried wine, only 6 μl of sample could be pipetted in the center of a previously cleaned and siliconized (Silicone solution, Serva) Si reflector. In order to keep the droplet small, the sample was pipetted in two steps of 3 μl each and dried on a heat plate (Schott) in a laminar flow hood (Interflow). From each bottle of wine, 20 samples were prepared and analyzed in order to provide reliable statistics. 4. Results and discussion
ð1Þ
where C is the concentration of a given element, N the integrated net peak area in the spectrum, S the relative sensitivity, the subscript i denotes each element analyzed and the subscript Ga is the element selected as internal standard. The relative sensitivities from the calibration files presently available for this spectrometer EXTRA II A were used to quantify the elemental concentrations.
Fig. 1. TXRF spectrum of 6 μl of Green Veltliner 2002 Kittmannsberg with 10 mg/l Ga as internal standard. Excitation with Mo tube at 50 kV, 5 mA for 1000 s (live time).
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X. Gruber et al. / Spectrochimica Acta Part B 61 (2006) 1214–1218
Table 2 Comparison of three bottles of Green Veltliner 2002 Kittmannsberg (n = 20, mean value ± standard deviation of the concentration in mg/l)
Bottle #1 Bottle #2 Bottle #3
K
Ca
Mn
Fe
Cu
Rb
Sr
522 ± 22 534 ± 28 546 ± 32
60.1 ± 1.7 63.5 ± 2.2 62.8 ± 2.8
0.793 ± 0.031 0.786 ± 0.038 0.799 ± 0.019
1.851 ± 0.075 1.827 ± ± 0.030 1.860 ± 0.027
0.062 ± 0.008 0.064 ± 0.009 0.061 ± 0.014
0.551 ± 0.015 0.553 ± 0.013 0.555 ± 0.017
0.346 ± 0.014 0.340 ± 0.010 0.346 ± 0.013
Verification had to be done before the start of the research work to ensure that measured values are representative for the produced wine. For this purpose, three bottles of identical wine (Green Veltliner 2002 from the vintage Kittmannsberg) were opened and measured 20 times. The results shown in Table 2 proved that bottles of the same production have similar concentrations in major elements (K, Ca) as well as in trace elements like Cu. A particular difference between red and white wine was detected in the concentration of K. The concentration of potassium in the grape reveals a maximum in the outer layers of the individual grape [10]. Peels are used in the production of red wine, and consequently the concentration of K in red wines could be expected to be higher than in white wines. This effect was measured and confirmed in this work (see Fig. 2). 4.1. Results for the “Blauer Portugieser” The range of concentration for two bottles of “Blauer Portugieser” overlapped, except of four elements. The differences in S (volatile) and Cu (near the detection limit) are not very significant. The concentrations of Fe (see Fig. 3 and Table 3) and Rb differed between the two analyzed samples. Therefore it was possible to differentiate the two samples. 4.2. Results for the fermentation in barrique or steel barrels The sample of barrique grown wine showed no difference in iron concentration compared to the “Blauer Portugieser” origi-
nating from the same producer (see cvg and bpg in Fig. 3 and in Table 3). Cu could not be detected in this sample (below detection limit of 0.037 mg/l) whereas a concentration of 0.046 mg/l could be found in bpg. A second difference was found in the Zn concentrations (0.492 ± 0.020 mg/l in cvg and 0.258 ± 0.014 mg/l in bpg). Ni was in both samples below the detection limit. The differences in the elemental concentrations were also delivered by the different row materials (different year of vintage and different grapes). 4.3. Results for wines from the vintages “Steinhaus” and “Kittmannsberg” The eight bottles of white wine could be distinguished due to the different concentrations of the major, minor and trace elements. Separation could not only be executed between samples from the same year and different vineyards but also between the samples from the same vineyard but consecutive years. The samples were separable, if the bandwidth of the elemental concentrations (defined by the highest and lowest measured values) did not overlap (see Figs. 2 and 3 and Table 3). 4.4. General remarks for the results From the selected elements mentioned by the OIV, only Cu, Fe and Zn could be detected with sufficient intensities. The K lines from Cd could not be excited because of the high-energy cut-off at 20 keV of the primary radiation of the Mo tube. The L lines were overlapped by elements
Fig. 2. Mean value ± standard deviation, highest and lowest measured value (n = 20) of potassium in different wines.
X. Gruber et al. / Spectrochimica Acta Part B 61 (2006) 1214–1218
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Fig. 3. Mean value ± standard deviation, highest and lowest measured value (n = 20) of iron in different wines.
with a high concentration in the wine (K and Ca) or the presence of the Ar peak in the spectrum. Because of the choice of Ga as internal standard, the detection limits for Pb were poor (overlapping from the Ga Kβ line with the Pb Lα lines). Ni was in the analyzed wines below or near the detection limit. Each analyzed wine had a specific concentration pattern of the determined elements. As shown in Table 3, a test measurement with one selected wine (measurement number 425) was clearly identified as a sample of v1s and had significant differences in the elemental concentrations compared to the other wines. This can be considered as the fundamental output of this work. A distinct clear identification of a particular wine according to grape and year of vintage by the analyzed elemental composition is feasible. 5. Conclusions The results obtained establish that TXRF is a suitable method for the determination of a wide range of elements at
different magnitudes of concentration in wine samples. Due to the easy preparation of the samples, the method can be used for routine control of the concentration of selected elements like Cu, Fe, Zn. A distinct goal of the work was to analyze wine with a minimum of sample preparation. The values of the concentrations are not only determined by the type of the grapes, but also by the soil of the wine-growing area, by the producer and mainly by the year of vintage as a consequence of the climatic conditions. Finally, the measurement proved that the concentration of elements do not vary between bottles of the same year and from one single producer. Fluctuations in the concentrations were measured in samples from the same vineyards but having different vintage years and between samples of the same year but grown on slightly different soil. Because of the large number of permitted treatments of the wine during the production, it was not possible to separate the influence of raw material, fertilization, pest control or maturing processes on the final concentration of elements in the wine.
Table 3 Comparison of the concentrations (in mg/l) of the measurement number 425 with the measured concentrations (highest and lowest value in mg/l) of the other 11 analyzed wines White wines
K Ca Mn Fe Rb Sr
Red wines
#425
v9s
v1s
v2s
v3s
v9k
v1k
v2k
v3k
cvg
bpg
bpt
265 317 29.9 38.9 0.377 0.623 1.971 2.248 0.359 0.432 0.159 0.231
356 406 37.1 42.1 0.480 0.722 0.743 0.929 0.576 0.655 0.189 0.271
388 468 44.5 52.0 0.418 0.678 1.105 1.375 0.517 0.640 0.235 0.309
270 304 45.9 55.7 0.450 0.671 1.427 1.658 0.583 0.698 0.209 0.302
296 361 33.7 40.3 0.401 0.629 2.282 2.689 0.206 0.272 0.151 0.220
391 457 45.9 53.2 0.389 0.673 0.586 0.814 0.455 0.550 0.219 0.301
494 570 55.9 64.6 0.628 0.949 1.683 2.112 0.490 0.603 0.292 0.402
362 429 48.7 53.9 0.645 0.903 0.562 0.761 0.443 0.537 0.246 0.331
497 578 32.0 44.9 0.385 0.774 0.907 1.197 0.304 0.419 0.160 0.264
668 820 32.2 41.6 0.247 0.515 0.817 1.055 0.219 0.297 0.135 0.224
799 1008 38.7 48.5 0.269 0.574 1.167 1.460 0.626 0.758 0.136 0.260
Possible overlaps in concentration are emphasized with bold and italic characters.
376 39.7 0.617 0.826 0.601 0.240
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References [1] R. Klockenkämper, Total Reflection X-ray Fluorescence Analysis, John Wiley & Sons Inc., 1997. [2] U. Reus, B. Markert, C. Hoffmeister, D. Spott, H. Guhr, Determination of trace-metals in river water and suspended-solids by TXRF spectrometry — a methodical study on analytical performance and sample homogeneity, Fresenius Z. Anal. Chem. 347 (1993) 430–435. [3] M.A. Barreiros, M.L. Carvalho, M.M. Costa, M.I. Marques, M.T. Ramos, Application of total reflection XRF to elemental studies of drinking water, X-ray Spectrom. 26 (1997) 165–168. [4] M.L. Carvalho, M.A. Barreiros, M.M. Costa, M.T. Ramos, M.I. Marques, Study of heavy metals in Madeira wine by total reflection X-ray fluorescence analysis, X-ray Spectrom. 25 (1996) 29–32.
[5] S.J. Haswell, A.D. Walmsley, Multivariante data visualisation methods based on multi-elemental analysis of wines and coffees using total reflection X-ray fluorescence analysis, J. Anal. At. Spectrom. 13 (1998) 131–134. [6] M.J. Anjos, R.T. Lopes, E.F.O. de Jesus, S. Moreira, R.C. Barroso, C.R.F. Castro, Trace elements in red and white wines using total-reflection X-ray fluorescence, Spectrochim. Acta Part B 58 (2003) 2227–2332. [7] M.J. Anjos, R.C. Barroso, R.T. Lopes, E.F.O. de Jesus, S.M. Simabuco, C.R.F. Castro, EDXRF analysis of red and white wines from Brazil, X-ray Spectrom. 33 (2004) 407–409. [8] Résolution oenologique 25/2000, Organisation Internationale de la Vigne et du Vin, 2000. [9] Receuil international des méthodes d'analyse des vins et des mouts, Organisation Internationale de la Vigne et du Vin, 2005. [10] K. Bauer, Weinbau, Österreichischer Agrarverlag, Wien, 2002.
Analytical note
Total-reflection X-ray fluorescence analysis of Austrian wine☆ X. Gruber, P. Kregsamer, P. Wobrauschek, C. Streli ⁎ Atominstitut der Österreichischen Universitäten, 1020 Vienna, Austria Received 13 December 2005; accepted 22 August 2006 Available online 11 October 2006
Abstract The concentration of major, minor and trace elements in Austrian wine was determined by total-reflection X-ray fluorescence using gallium as internal standard. A multi-elemental analysis was possible by pipetting 6 μl of wine directly on the reflector and drying. Total-reflection X-ray fluorescence analysis was performed with Atomika EXTRA II A (Cameca) X-rays from a Mo tube with a high-energy cut-off at 20 keV in totalreflection geometry. The results showed that it was possible to identify only by the elemental analysis as fingerprint the vineyards and year of vintage among 11 different wines. © 2006 Elsevier B.V. All rights reserved. Keywords: Total-reflection X-ray fluorescence (TXRF); Wine analysis; Trace element analysis
1. Introduction Total-reflection X-ray fluorescence analysis (TXRF) is a well-established method to analyze liquid samples [1–3]. The first study of wine with TXRF deals with Madeira wine [4], which differs from table wines in sugar and alcohol content. As a consequence of the complex matrix of the Madeira wine, a time intensive sample preparation (digestion with concentrated HNO3 in a Teflon beaker) had to be chosen. In a further study [5], the elemental concentrations in wines from different countries (New Zealand, Australia, Bulgaria, France, South Africa and Chile) were determined. In two researches done on table wine using X-ray fluorescence analysis [6,7], wines from different types of grapes (up to 6 white and 4 red wines) and different countries (Brazil, Portugal, Chile) were compared to each other. In none of the previous analyses of table wines, samples from the same type of grape had been compared. Furthermore, due to the geographical distance between the viticulture regions of the
☆
This paper was presented at the 11th International Conference on Total Reflection X-ray Fluorescence Spectrometry and Related Methods (TXRF2005), held in Budapest, Hungary, 18-22 September 2005, and is published in the special issue of Spectrochimica Acta Part B, dedicated to that conference. ⁎ Corresponding author. Tel.: + 43 1 58801 14130; fax: +43 1 58801 14199. E-mail address: [email protected] (C. Streli). 0584-8547/$ - see front matter © 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.sab.2006.08.006
analyzed samples, the grapes were growing under different climatic and geological conditions. The major aim of the present experimentation was to investigate whether differences of elemental concentrations existed in table wines from the same type and provide sufficient significance, to allow clear recognition of the sample. The initial part of the work deals with wines from the same type of grape but from different wine growing areas in Lower Austria. For fulfilment of the research purpose, two bottles of the identical grape of the same year of vintage but from different wine growers and areas were analyzed by TXRF. One bottle of “Blauer Portugieser 2003” originating from the viticulturist Traxler in Langenlois (abbreviation bpt) and one from the viticulturists Grabner and Schierer in Sooss (bpg). The second part deals with difference in the elemental concentrations as a consequence of the barrel in use for fermentation. During the maturing process, especially of red wine, the use of either high-grade steel barrels or barriques made out of oak wood is common. From the producer in Sooss, a bottle of “cuvée privat” (cvg), barrique matured, was analyzed and the concentrations of the elements (especially the metallic elements of high-grade steel) were compared with concentrations found in the “Blauer Portugieser” matured in steel barrels. The main part of this work deals with the analysis of eight wines picked from the wine growing area of Langenlois and produced by Nastl in order to establish the influence of the vintage year on the concentration of
X. Gruber et al. / Spectrochimica Acta Part B 61 (2006) 1214–1218
1215
Table 1 Comparison of elemental concentrations (in μg/l) in NIST 1643c and the obtained values
NIST 1643c This work
K
Ca
V
Cr
Mn
Fe
Co
Ni
Cu
Zn
As
Se
Rb
Sr
Pb
2300 1510
36 800 25 530
31.4 32.5
19.0 22.4
35.1 32.1
106.9 115.9
23.5 20.3
60.6 59.2
22.3 22.0
73.9 76.3
82.1 83.5
12.7 12.5
11.4 12.5
263.6 256.1
35.3 33.6
elements. Thanks to the support of the winegrower, it was possible to perform measurements on wines from the type Green Veltliner, vintages 1999, 2001, 2002 and 2003; cultivated in vineyards located at “Kittmannsberg” (v9k, v1k, v2k, v3k) and “Steinhaus” (v9s, v1s, v2s, v3s) with a distance from each other of approximately 900 m. Only the grapes from the own vineyards were used for the production of this wine. Because of the small distance between the two vineyards, differences in the elemental concentrations in wines cannot be explained by the sheer result of different climatic conditions. The grapes were treated individually but with the same equipment (wine press, high-grade steel barrels, etc.) and along the same procedures. Another aim of this work was to show, that TXRF is a suitable routine method to observe the concentration of selected elements. The International Organisation of Vine and Wine (OIV) set maximum permissible concentrations for the elements Cd (0.01 mg/l), Cu (1 mg/l), Pb (0.20 mg/l), Zn (5 mg/l) and Fe (100 mg/l) [8,9]. Ni is also on the list, although the limit of the maximum concentration has not been decided yet.
3. Sample collection and preparation
2. Experimental set-up
The accuracy of measurements of this TXRF spectrometer was checked through the analysis of a standard reference material (Trace Elements in Water 1643c from the National Institute for Standards and Technology). As for the measurements of the wine samples, Ga was used as internal standard. Table 1 reflects the results obtained in this work. A typical spectrum obtained for a wine sample is shown in Fig. 1.
Measurements were done while using the energy-dispersive spectrometer Extra II A from ATOMIKA (Cameca), equipped with two separated 2 kW X-ray tubes with anodes of Mo and W. For this work, the Mo anode X-ray tube was operated with an attenuation filter (50 μm Mo and 1 mm Al) at 50 kV and a varying current from 5 to 12 mA. The spectra were acquired for 1000 s (live time) and the dead time was approximately 40%. The Si(Li) detector crystal was 3 mm thick and of 80 mm2 area of nominal 168 eV resolution at 5.9 keV (Mn Kα) and had a 25 μm thick Be window. The cut-off energy of the quartz reflector was adjusted to 20 keV. Quantification was made by adding a known concentration of an element absent in the wine as internal standard. The concentrations were obtained using the equation Ni SGa Ci ¼ CGa NGa Si
Wine samples were provided directly by the winegrowers Traxler and Nastl in Langenlois and from Grabner and Schierer in Sooss (both in the region of Lower Austria). The bottles were cleaned from outside dust, shaken, opened cautiously and 30 ml was transferred in a Sarstedt-bottle. For each bottle of wine, the mixture of 1.2 ml wine and 0.3 ml of a 50 mg/l Ga standard was prepared three times and stored in 1.8 ml bottles. The final Ga concentration was 10 mg/l. Due to the high scattering of the radiation by the sugar in dried wine, only 6 μl of sample could be pipetted in the center of a previously cleaned and siliconized (Silicone solution, Serva) Si reflector. In order to keep the droplet small, the sample was pipetted in two steps of 3 μl each and dried on a heat plate (Schott) in a laminar flow hood (Interflow). From each bottle of wine, 20 samples were prepared and analyzed in order to provide reliable statistics. 4. Results and discussion
ð1Þ
where C is the concentration of a given element, N the integrated net peak area in the spectrum, S the relative sensitivity, the subscript i denotes each element analyzed and the subscript Ga is the element selected as internal standard. The relative sensitivities from the calibration files presently available for this spectrometer EXTRA II A were used to quantify the elemental concentrations.
Fig. 1. TXRF spectrum of 6 μl of Green Veltliner 2002 Kittmannsberg with 10 mg/l Ga as internal standard. Excitation with Mo tube at 50 kV, 5 mA for 1000 s (live time).
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X. Gruber et al. / Spectrochimica Acta Part B 61 (2006) 1214–1218
Table 2 Comparison of three bottles of Green Veltliner 2002 Kittmannsberg (n = 20, mean value ± standard deviation of the concentration in mg/l)
Bottle #1 Bottle #2 Bottle #3
K
Ca
Mn
Fe
Cu
Rb
Sr
522 ± 22 534 ± 28 546 ± 32
60.1 ± 1.7 63.5 ± 2.2 62.8 ± 2.8
0.793 ± 0.031 0.786 ± 0.038 0.799 ± 0.019
1.851 ± 0.075 1.827 ± ± 0.030 1.860 ± 0.027
0.062 ± 0.008 0.064 ± 0.009 0.061 ± 0.014
0.551 ± 0.015 0.553 ± 0.013 0.555 ± 0.017
0.346 ± 0.014 0.340 ± 0.010 0.346 ± 0.013
Verification had to be done before the start of the research work to ensure that measured values are representative for the produced wine. For this purpose, three bottles of identical wine (Green Veltliner 2002 from the vintage Kittmannsberg) were opened and measured 20 times. The results shown in Table 2 proved that bottles of the same production have similar concentrations in major elements (K, Ca) as well as in trace elements like Cu. A particular difference between red and white wine was detected in the concentration of K. The concentration of potassium in the grape reveals a maximum in the outer layers of the individual grape [10]. Peels are used in the production of red wine, and consequently the concentration of K in red wines could be expected to be higher than in white wines. This effect was measured and confirmed in this work (see Fig. 2). 4.1. Results for the “Blauer Portugieser” The range of concentration for two bottles of “Blauer Portugieser” overlapped, except of four elements. The differences in S (volatile) and Cu (near the detection limit) are not very significant. The concentrations of Fe (see Fig. 3 and Table 3) and Rb differed between the two analyzed samples. Therefore it was possible to differentiate the two samples. 4.2. Results for the fermentation in barrique or steel barrels The sample of barrique grown wine showed no difference in iron concentration compared to the “Blauer Portugieser” origi-
nating from the same producer (see cvg and bpg in Fig. 3 and in Table 3). Cu could not be detected in this sample (below detection limit of 0.037 mg/l) whereas a concentration of 0.046 mg/l could be found in bpg. A second difference was found in the Zn concentrations (0.492 ± 0.020 mg/l in cvg and 0.258 ± 0.014 mg/l in bpg). Ni was in both samples below the detection limit. The differences in the elemental concentrations were also delivered by the different row materials (different year of vintage and different grapes). 4.3. Results for wines from the vintages “Steinhaus” and “Kittmannsberg” The eight bottles of white wine could be distinguished due to the different concentrations of the major, minor and trace elements. Separation could not only be executed between samples from the same year and different vineyards but also between the samples from the same vineyard but consecutive years. The samples were separable, if the bandwidth of the elemental concentrations (defined by the highest and lowest measured values) did not overlap (see Figs. 2 and 3 and Table 3). 4.4. General remarks for the results From the selected elements mentioned by the OIV, only Cu, Fe and Zn could be detected with sufficient intensities. The K lines from Cd could not be excited because of the high-energy cut-off at 20 keV of the primary radiation of the Mo tube. The L lines were overlapped by elements
Fig. 2. Mean value ± standard deviation, highest and lowest measured value (n = 20) of potassium in different wines.
X. Gruber et al. / Spectrochimica Acta Part B 61 (2006) 1214–1218
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Fig. 3. Mean value ± standard deviation, highest and lowest measured value (n = 20) of iron in different wines.
with a high concentration in the wine (K and Ca) or the presence of the Ar peak in the spectrum. Because of the choice of Ga as internal standard, the detection limits for Pb were poor (overlapping from the Ga Kβ line with the Pb Lα lines). Ni was in the analyzed wines below or near the detection limit. Each analyzed wine had a specific concentration pattern of the determined elements. As shown in Table 3, a test measurement with one selected wine (measurement number 425) was clearly identified as a sample of v1s and had significant differences in the elemental concentrations compared to the other wines. This can be considered as the fundamental output of this work. A distinct clear identification of a particular wine according to grape and year of vintage by the analyzed elemental composition is feasible. 5. Conclusions The results obtained establish that TXRF is a suitable method for the determination of a wide range of elements at
different magnitudes of concentration in wine samples. Due to the easy preparation of the samples, the method can be used for routine control of the concentration of selected elements like Cu, Fe, Zn. A distinct goal of the work was to analyze wine with a minimum of sample preparation. The values of the concentrations are not only determined by the type of the grapes, but also by the soil of the wine-growing area, by the producer and mainly by the year of vintage as a consequence of the climatic conditions. Finally, the measurement proved that the concentration of elements do not vary between bottles of the same year and from one single producer. Fluctuations in the concentrations were measured in samples from the same vineyards but having different vintage years and between samples of the same year but grown on slightly different soil. Because of the large number of permitted treatments of the wine during the production, it was not possible to separate the influence of raw material, fertilization, pest control or maturing processes on the final concentration of elements in the wine.
Table 3 Comparison of the concentrations (in mg/l) of the measurement number 425 with the measured concentrations (highest and lowest value in mg/l) of the other 11 analyzed wines White wines
K Ca Mn Fe Rb Sr
Red wines
#425
v9s
v1s
v2s
v3s
v9k
v1k
v2k
v3k
cvg
bpg
bpt
265 317 29.9 38.9 0.377 0.623 1.971 2.248 0.359 0.432 0.159 0.231
356 406 37.1 42.1 0.480 0.722 0.743 0.929 0.576 0.655 0.189 0.271
388 468 44.5 52.0 0.418 0.678 1.105 1.375 0.517 0.640 0.235 0.309
270 304 45.9 55.7 0.450 0.671 1.427 1.658 0.583 0.698 0.209 0.302
296 361 33.7 40.3 0.401 0.629 2.282 2.689 0.206 0.272 0.151 0.220
391 457 45.9 53.2 0.389 0.673 0.586 0.814 0.455 0.550 0.219 0.301
494 570 55.9 64.6 0.628 0.949 1.683 2.112 0.490 0.603 0.292 0.402
362 429 48.7 53.9 0.645 0.903 0.562 0.761 0.443 0.537 0.246 0.331
497 578 32.0 44.9 0.385 0.774 0.907 1.197 0.304 0.419 0.160 0.264
668 820 32.2 41.6 0.247 0.515 0.817 1.055 0.219 0.297 0.135 0.224
799 1008 38.7 48.5 0.269 0.574 1.167 1.460 0.626 0.758 0.136 0.260
Possible overlaps in concentration are emphasized with bold and italic characters.
376 39.7 0.617 0.826 0.601 0.240
1218
X. Gruber et al. / Spectrochimica Acta Part B 61 (2006) 1214–1218
References [1] R. Klockenkämper, Total Reflection X-ray Fluorescence Analysis, John Wiley & Sons Inc., 1997. [2] U. Reus, B. Markert, C. Hoffmeister, D. Spott, H. Guhr, Determination of trace-metals in river water and suspended-solids by TXRF spectrometry — a methodical study on analytical performance and sample homogeneity, Fresenius Z. Anal. Chem. 347 (1993) 430–435. [3] M.A. Barreiros, M.L. Carvalho, M.M. Costa, M.I. Marques, M.T. Ramos, Application of total reflection XRF to elemental studies of drinking water, X-ray Spectrom. 26 (1997) 165–168. [4] M.L. Carvalho, M.A. Barreiros, M.M. Costa, M.T. Ramos, M.I. Marques, Study of heavy metals in Madeira wine by total reflection X-ray fluorescence analysis, X-ray Spectrom. 25 (1996) 29–32.
[5] S.J. Haswell, A.D. Walmsley, Multivariante data visualisation methods based on multi-elemental analysis of wines and coffees using total reflection X-ray fluorescence analysis, J. Anal. At. Spectrom. 13 (1998) 131–134. [6] M.J. Anjos, R.T. Lopes, E.F.O. de Jesus, S. Moreira, R.C. Barroso, C.R.F. Castro, Trace elements in red and white wines using total-reflection X-ray fluorescence, Spectrochim. Acta Part B 58 (2003) 2227–2332. [7] M.J. Anjos, R.C. Barroso, R.T. Lopes, E.F.O. de Jesus, S.M. Simabuco, C.R.F. Castro, EDXRF analysis of red and white wines from Brazil, X-ray Spectrom. 33 (2004) 407–409. [8] Résolution oenologique 25/2000, Organisation Internationale de la Vigne et du Vin, 2000. [9] Receuil international des méthodes d'analyse des vins et des mouts, Organisation Internationale de la Vigne et du Vin, 2005. [10] K. Bauer, Weinbau, Österreichischer Agrarverlag, Wien, 2002.