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Performance evaluation of a high-pressure microwave-assisted flow digestion system for juice and milk sample preparation

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Abstract

Acid digestion is usually required for metal determination in food samples. However, this step is usually performed in batch mode which is time consuming, labor intensive, and may lead to sample contamination. Flow digestion can overcome these limitations. In this work, the performance of a high-pressure microwave-assisted flow digestion system with a large volume reactor was evaluated for liquid samples high in sugar and fat (fruit juice and milk). The digestions were carried out in a coiled perfluoroalkoxy (PFA) tube reactor (13.5 mL) installed inside an autoclave pressurized with 40 bar nitrogen. The system was operated at 500 W microwave power and 5.0 mL min−1 carrier flow rate. Digestion conditions were optimized with phenylalanine, as this substance is known to be difficult to digest completely. The combinations of HCl or H2O2 with HNO3 increased the digestion efficiency of phenylalanine, and the residual carbon content (RCC) was around 50% when 6.0% V/V HCl or H2O2 was used in combination with 32% V/V HNO3. Juice samples were digested with 3.7 mol L−1 HNO3 and 0.3 mol L−1 HCl, and the RCC was 16 and 29% for apple and mango juices, respectively. Concentrated HNO3 (10.5 mol L−1) was successfully applied for digesting milk samples, and the RCCs were 23 and 25% for partially skimmed and whole milk, respectively. Accuracy and precision of the flow digestion procedure were compared with reference digestions using batch mode closed vessel microwave-assisted digestion and no statistically significant differences were encountered at the 95% confidence level.

Application of a high-pressure microwave-assisted flow digestion system for fruit juice and milk sample preparation

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References

  1. Khan N, Jeong IS, Hwang IM, Kim JS, Choi SH, Nho EY, Choi JY, Park KS, Kim KS. Analysis of minor and trace elements in milk and yogurts by inductively coupled plasma-mass spectrometry (ICP-MS). Food Chem. 2014;147:220–4. Available from: http://dx.doi.org/10.1016/j.foodchem.2013.09.147

    Article  CAS  Google Scholar 

  2. Suturović Z, Kravić S, Milanović S, Đurović A, Brezo T. Determination of heavy metals in milk and fermented milk products by potentiometric stripping analysis with constant inverse current in the analytical step. Food Chem. 2014;155:120–5. Available from: http://linkinghub.elsevier.com/retrieve/pii/S030881461400051X

    Article  Google Scholar 

  3. Núñez-Sánchez N, Martínez-Marín AL, Polvillo O, Fernández-Cabanás VM, Carrizosa J, Urrutia B, Serradilla JM. Near infrared spectroscopy (NIRS) for the determination of the milk fat fatty acid profile of goats. Food Chem. 2016;190:244–52. Available from: http://linkinghub.elsevier.com/retrieve/pii/S0308814615008183

    Article  Google Scholar 

  4. Welna M, Szymczycha-Madeja A. Effect of sample preparation procedure for the determination of As, Sb and Se in fruit juices by HG-ICP-OES. Food Chem. 2014;159:414–9. Available from: http://dx.doi.org/10.1016/j.foodchem.2014.03.046

    Article  CAS  Google Scholar 

  5. Szymczycha-Madeja A, Welna M, Jedryczko D, Pohl P. Developments and strategies in the spectrochemical elemental analysis of fruit juices. Trends Anal Chem. 2014;55:68–80. Available from: http://dx.doi.org/10.1016/j.trac.2013.12.005

    Article  CAS  Google Scholar 

  6. McKinstry P, Indyk H, Kim N. The determination of major and minor elements in milk and infant formula by slurry nebulisation and inductively coupled plasma-optical emission spectrometry (ICP-OES). Food Chem. 1999;65(2):245–52. Available from: http://linkinghub.elsevier.com/retrieve/pii/S0308814698001836

    Article  CAS  Google Scholar 

  7. Sola-Larrañaga C, Navarro-Blasco I. Optimization of a slurry dispersion method for minerals and trace elements analysis in infant formulae by ICP OES and FAAS. Food Chem. 2009;115(3):1048–55. Available from: http://dx.doi.org/10.1016/j.foodchem.2008.12.037

    Article  Google Scholar 

  8. Nóbrega JA, Gélinas Y, Krushevska A, Barnes RM. Direct determination of major and trace elements in milk by inductively coupled plasma atomic emission and mass spectrometry. J Anal At Spectrom. 1997;12(10):1243–6.

    Article  Google Scholar 

  9. Froes RES, Borges Neto W, Silva NOCE, Naveira RLP, Nascentes CC, Silva JBB. Multivariate optimization by exploratory analysis applied to the determination of microelements in fruit juice by inductively coupled plasma optical emission spectrometry. Spectrochim Acta Part B At Spectrosc. 2009;64(6):619–22. Available from: http://dx.doi.org/10.1016/j.sab.2009.06.006

  10. Szymczycha-Madeja A, Welna M. Evaluation of a simple and fast method for the multi-elemental analysis in commercial fruit juice samples using atomic emission spectrometry. Food Chem. 2013;141(4):3466–72. Available from: http://dx.doi.org/10.1016/j.foodchem.2013.06.067

    Article  CAS  Google Scholar 

  11. Cindrić IJ, Zeiner M, Kröppl M, Stingeder G. Comparison of sample preparation methods for the ICP-AES determination of minor and major elements in clarified apple juices. Microchem J. 2011;99(2):364–9. Available from: http://linkinghub.elsevier.com/retrieve/pii/S0026265X11001214

    Article  Google Scholar 

  12. Wiltsche H, Winkler M, Tirk P. Matrix effects of carbon and bromine in inductively coupled plasma optical emission spectrometry. J Anal At Spectrom. 2015;30(10):2223–34. Available from: http://xlink.rsc.org/?DOI=C5JA00237K

    Article  CAS  Google Scholar 

  13. Potortì AG, Di Bella G, Lo Turco V, Rando R, Dugo G. Non-toxic and potentially toxic elements in Italian donkey milk by ICP-MS and multivariate analysis. J Food Compos Anal. 2013;31(1):161–72. Available from: http://linkinghub.elsevier.com/retrieve/pii/S0889157513000690

    Article  Google Scholar 

  14. Wiltsche H, Knapp G. Flow digestion systems with microwave and conductive heating. In: Flores EMM, editor. Microwave-assisted sample preparation for trace element analysis. 1st ed. Polonia: Elsevier; 2014. p. 253–80. Available from: http://linkinghub.elsevier.com/retrieve/pii/B978044459420400009X.

    Chapter  Google Scholar 

  15. Pichler U, Haase A, Knapp G, Michaelis M. Microwave-enhanced flow system for high-temperature digestion of resistant organic materials. Anal Chem. 1999;71(18):4050–5. Available from: http://pubs.acs.org/doi/abs/10.1021/ac9903048

    Article  CAS  Google Scholar 

  16. Wiltsche H, Tirk P, Motter H, Winkler M, Knapp G. A novel approach to high pressure flow digestion. J Anal At Spectrom. 2014;29(2):272–9. Available from: http://dx.doi.org/10.1039/C3JA50290B

    Article  CAS  Google Scholar 

  17. Marques TL, Wiltsche H, Motter H, Nóbrega JA, Knapp G. High pressure microwave-assisted flow digestion system using a large volume reactor-feasibility for further analysis by inductively coupled plasma-based techniques. J Anal At Spectrom. 2015;30(9):1898–905. Available from: http://xlink.rsc.org/?DOI=C5JA00194C

    Article  Google Scholar 

  18. Stewart LJM, Barnes RM. Flow-through, microwave-heated digestion chamber for automated sample preparation prior to inductively coupled plasma spectrochemical analysis. Analyst. 1994;119(5):1003–10. Available from: http://xlink.rsc.org/?DOI=an9941901003

    Article  CAS  Google Scholar 

  19. Oliveira CC, Sartini RP, Zagatto EAG. Microwave-assisted sample preparation in sequential injection: spectrophotometric determination of magnesium, calcium and iron in food. Anal Chim Acta. 2000;413(1–2):41–8. Available from: http://linkinghub.elsevier.com/retrieve/pii/S0003267000007996

    Article  CAS  Google Scholar 

  20. Pratt KW, Kingston HM, MacCrehan WA, Koch WF. Voltammetric and liquid chromatographic identification of organic products of microwave-assisted wet ashing of biological samples. Anal Chem. 1988;60(19):2024–7. Available from: http://dx.doi.org/10.1021/ac00170a008

    Article  CAS  Google Scholar 

  21. Daniel MM, Batchelor JD, Rhoades CB, Jones BT. The effect of digestion temperature on matrix decomposition using a high pressure asher. At Spectrosc. 1998;19(6):198–203.

    CAS  Google Scholar 

  22. Froes RES, Borges Neto W, Naveira RLP, Silva NC, Nascentes CC, Silva JBB. Exploratory analysis and inductively coupled plasma optical emission spectrometry (ICP OES) applied in the determination of metals in soft drinks. Microchem J. 2009;92(1):68–72. Available from: http://dx.doi.org/10.1016/j.microc.2008.12.008

    Article  CAS  Google Scholar 

  23. Silva JCJ, Cadore S, Nobrega JA, Baccan N. Dilute-and-shoot procedure for the determination of mineral constituents in vinegar samples by axially viewed inductively coupled plasma optical emission spectrometry (ICP OES). Food Addit Contam. 2007;24(2):130–9. Available from: http://www.tandfonline.com/doi/abs/10.1080/02652030600931970

    Article  Google Scholar 

  24. Carrilho ENVM, Nogueira ARA, Nóbrega JA, Souza GB, Cruz GM. An attempt to correlate fat and protein content of biological samples with residual carbon after microwave-assisted digestion. Fresenius J Anal Chem. 2001;371(4):536–40. Available from: http://link.springer.com/10.1007/s002160101029

    Article  CAS  Google Scholar 

  25. Brenner IBU, Zander AT. Axially and radially viewed inductively coupled plasmas—a critical review. Spectrochim Acta Part B At Spectrosc. 2000;55(8):1195–240.

    Article  Google Scholar 

Download references

Acknowledgements

The authors acknowledge the support from the Graz University of Technology, Federal University of São Carlos, and Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq, Brazil, Science without Borders Program, fellowships 249068/2013-3 and 140474/2013-7 PPGQ-UFSCar provided to T.L.M.).

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Authors and Affiliations

  1. Department of Chemistry, Federal University of São Carlos, Rodovia Washington Luiz, km 235, São Carlos, São Paulo, 13565-905, Brazil

    Thiago L. Marques & Joaquim A. Nóbrega

  2. Institute of Analytical Chemistry and Food Chemistry, Graz University of Technology, Stremayrgasse 9, 8010, Graz, Styria, Austria

    Helmar Wiltsche, Monika Winkler & Günter Knapp

Authors
  1. Thiago L. Marques
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  2. Helmar Wiltsche
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  3. Joaquim A. Nóbrega
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  4. Monika Winkler
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  5. Günter Knapp
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Correspondence to Thiago L. Marques.

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Marques, T.L., Wiltsche, H., Nóbrega, J.A. et al. Performance evaluation of a high-pressure microwave-assisted flow digestion system for juice and milk sample preparation. Anal Bioanal Chem 409, 4449–4458 (2017). https://doi.org/10.1007/s00216-017-0388-5

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  • DOI: https://doi.org/10.1007/s00216-017-0388-5

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