Provenance determination of rooibos tea using strontium isotope ratio measured by inductively coupled plasma mass spectrometry
- Authors: Fouda Mbanga, Bienvenu Gael
- Date: 2016
- Subjects: Strontium compounds - Analysis , Strontium - Isotopes , Provenance trials , Inductively coupled plasma mass spectrometry , Rooibos tea
- Language: English
- Type: Masters (Thesis)
- Identifier: http://ujcontent.uj.ac.za8080/10210/367403 , http://hdl.handle.net/10210/251099 , uj:26177
- Description: M.Sc. (Chemistry) , Abstract: Rooibos tea is gaining importance as an herbal drink and product enhancer in the beverage, food, nutraceutical and cosmetic markets. Popular food products such as rooibos tea can be a target of fraudulent scheme, which consists of deliberate misrepresentation with the aim to mislead buyers with regard to the true product or any of its ingredients. Determination of the provenance of rooibos tea (fingerprinting) may play a key role in ensuring consumer safety, decreasing damage to producers and in creating awareness about potential use of such tool as deterrent to misleading traders. Among the fingerprinting techniques, inorganic mass spectrometry based on stable isotope ratios such as 87Sr/86Sr is used for determining the origin of various agricultural products. The purpose of this work was to evaluate the potential use of 87Sr/86Sr isotope ratio as a tool for determining the origin of the South African Rooibois tea. The ratio was determined by single quadrupole inductively coupled plasma mass spectrometry. Rooibos tea leaves and soil samples collected from seven tea growing farms in Clanwilliam district and the neighboring Northern Cape region were mineralized and total concentrations of the isotopes determined using internal standardization and external calibration. It was found that scandium (Sc) cannot be used as internal standard since it is present in tea leaves. Hence, throughout this work 69Ga, 115In, and 175Lu were used for instrument drift correction. The evaluation of 87Sr/86Sr ratio was difficult due to isobaric interference of 87Rb on 87Sr. To overcome this challenge, the two isotopes were separated successfully on Dowex 50W-X8 resin by metal-EDTA and metal-DCTA complex elution prior to isotopes ratio determination. Accuracy of the method was checked using tea leaves and sandy soil certified reference materials INCT-TL-1 and CRM-SA-C, respectively. The limits of detection (LOD) and of quantification (LOQ) were between 0.13-0.82 μg L-1 and 0.44-2.75 μg L-1, respectively. The lowness of the LOD and LOQ showed that analysis could be repeated. It was found that DCTA elution method was more efficient than the EDTA one because it complexes metal ions more strongly. The results obtained for 87Sr/86Sr isotope ratio in all the seven farms showed lack of a good correlation between the soil and the tea leaf samples.
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- Authors: Fouda Mbanga, Bienvenu Gael
- Date: 2016
- Subjects: Strontium compounds - Analysis , Strontium - Isotopes , Provenance trials , Inductively coupled plasma mass spectrometry , Rooibos tea
- Language: English
- Type: Masters (Thesis)
- Identifier: http://ujcontent.uj.ac.za8080/10210/367403 , http://hdl.handle.net/10210/251099 , uj:26177
- Description: M.Sc. (Chemistry) , Abstract: Rooibos tea is gaining importance as an herbal drink and product enhancer in the beverage, food, nutraceutical and cosmetic markets. Popular food products such as rooibos tea can be a target of fraudulent scheme, which consists of deliberate misrepresentation with the aim to mislead buyers with regard to the true product or any of its ingredients. Determination of the provenance of rooibos tea (fingerprinting) may play a key role in ensuring consumer safety, decreasing damage to producers and in creating awareness about potential use of such tool as deterrent to misleading traders. Among the fingerprinting techniques, inorganic mass spectrometry based on stable isotope ratios such as 87Sr/86Sr is used for determining the origin of various agricultural products. The purpose of this work was to evaluate the potential use of 87Sr/86Sr isotope ratio as a tool for determining the origin of the South African Rooibois tea. The ratio was determined by single quadrupole inductively coupled plasma mass spectrometry. Rooibos tea leaves and soil samples collected from seven tea growing farms in Clanwilliam district and the neighboring Northern Cape region were mineralized and total concentrations of the isotopes determined using internal standardization and external calibration. It was found that scandium (Sc) cannot be used as internal standard since it is present in tea leaves. Hence, throughout this work 69Ga, 115In, and 175Lu were used for instrument drift correction. The evaluation of 87Sr/86Sr ratio was difficult due to isobaric interference of 87Rb on 87Sr. To overcome this challenge, the two isotopes were separated successfully on Dowex 50W-X8 resin by metal-EDTA and metal-DCTA complex elution prior to isotopes ratio determination. Accuracy of the method was checked using tea leaves and sandy soil certified reference materials INCT-TL-1 and CRM-SA-C, respectively. The limits of detection (LOD) and of quantification (LOQ) were between 0.13-0.82 μg L-1 and 0.44-2.75 μg L-1, respectively. The lowness of the LOD and LOQ showed that analysis could be repeated. It was found that DCTA elution method was more efficient than the EDTA one because it complexes metal ions more strongly. The results obtained for 87Sr/86Sr isotope ratio in all the seven farms showed lack of a good correlation between the soil and the tea leaf samples.
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The classification of agricultural products according to geographical origin by means of quadrupole-based ICP-mass spectrometry for the determination of ¹¹B/¹°B isotope ratios, and the study of boron isotope fractionation
- Authors: Greeff, Liezl
- Date: 2010-04-01T05:32:05Z
- Subjects: Wine and wine making , Boron isotopes , Inductively coupled plasma mass spectrometry , Provenance trials
- Type: Thesis
- Identifier: uj:6740 , http://hdl.handle.net/10210/3148
- Description: M.Sc. , The 11B/10B stable isotope ratio in wine- and provenance soil samples of four South African wine regions was determined by means of quadrupole inductively coupled plasma mass spectrometry (ICP-MS). The data obtained was combined with multi-element results for the same samples. Discriminant analysis and ANOVA statistics were utilized to create a footprint of wines compared to their provenance soil. The results showed that the stable boron isotope ratio was a distinguishable characteristic in wine and soil samples for the Stellenbosch, Robertson, Swartland, and Walker Bay wine regions. The potential improvement of precision and accuracy was investigated specifically for ICP-QMS (quadrupole mass spectrometry) analysis of boron isotope ratios. Sample preparation methods for the matrices used in this work were developed and applied. The influence of the matrix components was investigated. Ion exchange separation procedures were developed for the separation of total B from the wine and soil matrices. Results were treated mathematically to minimize mass bias effects. It was found that combined matrix effects and TDS (total dissolved solids) deposition did have a pronounced effect on the 11B/10B isotope ratios of the samples. The possibility of boron isotope fractionation was investigated in vine plants. Hydroponic experiments were set up with test plants of two cultivars. A 10B enriched nutrient solution or growth solution with natural 11B/10B ratio was supplied to the plants during alternating periods of 5 weeks each. New growth leaves were harvested once every week during each of these time periods. All samples were carefully prepared and analyzed to determine the relationship of the 11B/10B ratio in the leaves compared to that of the supplied nutrient solution. It was observed that the 11B/10B isotope ratio of the growth solution had an influence on the 11B/10B stable isotope ratio in new growth leaves of vine plants.
- Full Text:
- Authors: Greeff, Liezl
- Date: 2010-04-01T05:32:05Z
- Subjects: Wine and wine making , Boron isotopes , Inductively coupled plasma mass spectrometry , Provenance trials
- Type: Thesis
- Identifier: uj:6740 , http://hdl.handle.net/10210/3148
- Description: M.Sc. , The 11B/10B stable isotope ratio in wine- and provenance soil samples of four South African wine regions was determined by means of quadrupole inductively coupled plasma mass spectrometry (ICP-MS). The data obtained was combined with multi-element results for the same samples. Discriminant analysis and ANOVA statistics were utilized to create a footprint of wines compared to their provenance soil. The results showed that the stable boron isotope ratio was a distinguishable characteristic in wine and soil samples for the Stellenbosch, Robertson, Swartland, and Walker Bay wine regions. The potential improvement of precision and accuracy was investigated specifically for ICP-QMS (quadrupole mass spectrometry) analysis of boron isotope ratios. Sample preparation methods for the matrices used in this work were developed and applied. The influence of the matrix components was investigated. Ion exchange separation procedures were developed for the separation of total B from the wine and soil matrices. Results were treated mathematically to minimize mass bias effects. It was found that combined matrix effects and TDS (total dissolved solids) deposition did have a pronounced effect on the 11B/10B isotope ratios of the samples. The possibility of boron isotope fractionation was investigated in vine plants. Hydroponic experiments were set up with test plants of two cultivars. A 10B enriched nutrient solution or growth solution with natural 11B/10B ratio was supplied to the plants during alternating periods of 5 weeks each. New growth leaves were harvested once every week during each of these time periods. All samples were carefully prepared and analyzed to determine the relationship of the 11B/10B ratio in the leaves compared to that of the supplied nutrient solution. It was observed that the 11B/10B isotope ratio of the growth solution had an influence on the 11B/10B stable isotope ratio in new growth leaves of vine plants.
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Multi-element analysis of South African wines and their provenance soils by ICP-MS and their classification according to geographical origin using multivariate statistics
- Authors: Van der Linde, Gert
- Date: 2010-04-08T08:45:39Z
- Subjects: Wine and wine making , Inductively coupled plasma mass spectrometry , Provenance trials , Trace elements
- Type: Thesis
- Identifier: uj:6766 , http://hdl.handle.net/10210/3172
- Description: M.Sc. , The South African wine industry is well respected internationally for producing high quality wines. The possible adulteration of these wines can lead to loss of reputation and a loss of sales and could also be dangerous to consumer’s health. Multi-element analysis of wines is one way of implementing quality control and the same multi-element data can also be used to prove the point of origin. The metal content of the fruit (grapes) should represent the metal content of the soil in which the plants (vineyards) were grown. An Inductively Coupled Plasma Mass Spectrometer (ICP-MS) was used with correct internal standard and interference correction to obtain reliable concentrations for 27 elements (Li, B, Al, Sc, V, Cr, Mn, Co, Ni, Cu, Zn, Se, Rb, Sr, Zr, Nb, Mo, Cd, Sn, Sb, Ba, Ce, Nd, W, Tl, Pb and U) of 1:1 diluted wines and microwave digested vineyard soil from four South-African wine-producing regions: Stellenbosch, Swartland, Robertson and Walker Bay. This multi-element data was then interpreted using multivariate statistical analysis in order to determine which elements have the ability to discriminate between the four regions. Li, B, Sc, Ni, Mn, Co, Cu, and Rb were the elements that were identified to have discrimination ability. 96% of wines and 100% of vineyard soils were correctly classified. Indirectly it has been proven that the metal content of the soil can be correlated to the metal content of the wine. This methodology can be reliably used in industry for quality control and routine provenance determination
- Full Text:
- Authors: Van der Linde, Gert
- Date: 2010-04-08T08:45:39Z
- Subjects: Wine and wine making , Inductively coupled plasma mass spectrometry , Provenance trials , Trace elements
- Type: Thesis
- Identifier: uj:6766 , http://hdl.handle.net/10210/3172
- Description: M.Sc. , The South African wine industry is well respected internationally for producing high quality wines. The possible adulteration of these wines can lead to loss of reputation and a loss of sales and could also be dangerous to consumer’s health. Multi-element analysis of wines is one way of implementing quality control and the same multi-element data can also be used to prove the point of origin. The metal content of the fruit (grapes) should represent the metal content of the soil in which the plants (vineyards) were grown. An Inductively Coupled Plasma Mass Spectrometer (ICP-MS) was used with correct internal standard and interference correction to obtain reliable concentrations for 27 elements (Li, B, Al, Sc, V, Cr, Mn, Co, Ni, Cu, Zn, Se, Rb, Sr, Zr, Nb, Mo, Cd, Sn, Sb, Ba, Ce, Nd, W, Tl, Pb and U) of 1:1 diluted wines and microwave digested vineyard soil from four South-African wine-producing regions: Stellenbosch, Swartland, Robertson and Walker Bay. This multi-element data was then interpreted using multivariate statistical analysis in order to determine which elements have the ability to discriminate between the four regions. Li, B, Sc, Ni, Mn, Co, Cu, and Rb were the elements that were identified to have discrimination ability. 96% of wines and 100% of vineyard soils were correctly classified. Indirectly it has been proven that the metal content of the soil can be correlated to the metal content of the wine. This methodology can be reliably used in industry for quality control and routine provenance determination
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Precise 87Sr/86Sr isotope ratio measurement by quadrupole based ICP-MS after ion exchange separation of Rb for provenance determination of agricultural products
- Authors: Vorster, Clarisa
- Date: 2010-04-08T08:33:41Z
- Subjects: Wine and wine making , Strontium isotopes , Inductively coupled plasma mass spectrometry , Ion exchange chromatography , Provenance trials
- Type: Thesis
- Identifier: uj:6750 , http://hdl.handle.net/10210/3158
- Description: M.Sc. , The strontium isotope ratio 87Sr/86Sr in the wine and soil of four wine-producing regions in South Africa has been determined using quadrupole ICP-MS. Isotope ratio measurements with fairly good precision had been obtained and 87Sr/86Sr ratio values in wine and soil samples were statistically evaluated to determine whether the regions investigated could be distinguished. Statistical interpretation of data revealed that the Robertson wine-producing region could be distinguished from Stellenbosch, Swartland and Walker Bay wine regions on the basis of their 87Sr/86Sr ratio. By using a combination of 87Sr/86Sr and multielement data, canonical discriminant functions with very good classification abilities could be obtained to correctly distinguish between wine and soil samples originating from a specific production region. Due to the isobaric overlap of strontium and rubidium at mass 87, a very good strontium-rubidium separation method had to be developed. The chelating properties of EDTA and DCTA in combination with ion exchange chromatography were explored in order to achieve such a separation. Due to the advanced rubidium separation ability of the developed DCTA elution method, it has been employed in all wine and soil sample preparations. Since chromatographic ion exchange procedures are not capable of removing all the rubidium from the sample matrices, 87Sr/86Sr ratio values were mathematically corrected for residual rubidium using an 88Sr correction. Since strontium isotope ratio measurements require very good precision, it is traditionally determined using TIMS. However, due to the ease of operation, shorter analysis time and widespread availability of quadrupole ICP-MS, the technique was evaluated for its merit for determining strontium isotope ratios. The optimization of acquisition parameters for the determination of the 87Sr/86Sr ratio in wine and soil samples with good precision of below 0.1% RSD has been conducted. Furthermore, selected sample matrix components were assessed as possible matrix interferences as well as for their ability to affect the precision of measurements. It was concluded that with adequate optimization of acquisition parameters, proper sample preparation and reliable mathematical correction of data, 87Sr/86Sr ratio measurements with reasonable precision could be obtained using quadrupole ICP-MS.
- Full Text:
- Authors: Vorster, Clarisa
- Date: 2010-04-08T08:33:41Z
- Subjects: Wine and wine making , Strontium isotopes , Inductively coupled plasma mass spectrometry , Ion exchange chromatography , Provenance trials
- Type: Thesis
- Identifier: uj:6750 , http://hdl.handle.net/10210/3158
- Description: M.Sc. , The strontium isotope ratio 87Sr/86Sr in the wine and soil of four wine-producing regions in South Africa has been determined using quadrupole ICP-MS. Isotope ratio measurements with fairly good precision had been obtained and 87Sr/86Sr ratio values in wine and soil samples were statistically evaluated to determine whether the regions investigated could be distinguished. Statistical interpretation of data revealed that the Robertson wine-producing region could be distinguished from Stellenbosch, Swartland and Walker Bay wine regions on the basis of their 87Sr/86Sr ratio. By using a combination of 87Sr/86Sr and multielement data, canonical discriminant functions with very good classification abilities could be obtained to correctly distinguish between wine and soil samples originating from a specific production region. Due to the isobaric overlap of strontium and rubidium at mass 87, a very good strontium-rubidium separation method had to be developed. The chelating properties of EDTA and DCTA in combination with ion exchange chromatography were explored in order to achieve such a separation. Due to the advanced rubidium separation ability of the developed DCTA elution method, it has been employed in all wine and soil sample preparations. Since chromatographic ion exchange procedures are not capable of removing all the rubidium from the sample matrices, 87Sr/86Sr ratio values were mathematically corrected for residual rubidium using an 88Sr correction. Since strontium isotope ratio measurements require very good precision, it is traditionally determined using TIMS. However, due to the ease of operation, shorter analysis time and widespread availability of quadrupole ICP-MS, the technique was evaluated for its merit for determining strontium isotope ratios. The optimization of acquisition parameters for the determination of the 87Sr/86Sr ratio in wine and soil samples with good precision of below 0.1% RSD has been conducted. Furthermore, selected sample matrix components were assessed as possible matrix interferences as well as for their ability to affect the precision of measurements. It was concluded that with adequate optimization of acquisition parameters, proper sample preparation and reliable mathematical correction of data, 87Sr/86Sr ratio measurements with reasonable precision could be obtained using quadrupole ICP-MS.
- Full Text:
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