Determination of melamine in milk powder by capillary - Lietuvos ...

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234Žana Černova, Ina Razmislevičienė, Audrius Padarauskaswas not significantly different from zero. In addition, it waschecked whether at the lower limit of the linear range, definedas the method limit of quantification, the analyticalperformances were satisfactory. Consequently, for the firstconcentration (0.2 mg/l) of the linear range, the signal-tonoiseratio was measured and the RSD of the peak area wascalculated with five replicates. The signal-to-noise ratio was13 and the repeatability RSD 7.8%. The detection limit (threetimes the baseline noise) was 0.06 mg/l. These data confirmthe suitability of the proposed method for its application toreal samples.Method accuracy was determined by measuring repeatabilityand intermediate precision (between-day precision). Inorder to determine the repeatability of the method, six replicateinjections of the standards at three MEL concentrationlevels (0.2, 0.5 and 1 mg/l) were carried out. The intermediateaccuracy was evaluated over three days by performing sixsuccessive injections daily. A relatively little dispersion wasobserved for migration times because both repeatability andintermediate accuracy were less than 1.8%. For peak areas,the repeatability was in the range 2.3–4.8%, whereas intermediateprecision ranged from 3.9 to 6.3% depending on theconcentrations.To evaluate the proposed CE system for real samples, itwas used to determine MEL in milk powder samples. Amongthe 10 samples obtained from local supermarkets, nonewere found positive for MEL. Figure 5 shows the electropherogramsobtained for a non-fortified milk powder sample(a) and the same sample fortified at 2 mg/kg of MEL (b). Toevaluate the accuracy of the method, a recovery study wascarried out with two samples, and the results are summarizedin Table. As one can see, the concentrations found are generallyin good agreement with the added concentrations, withrecoveries between 93.5 and 104%. These results suggest thatinterferences by the other matrix components are not significantand the CE conditions are suitable to obtain an adequateaccuracy of the method.Table. MEL recovery test results for two milk powder samples (n = 3)Sample No Added, mg/kg Found, mg/kg Recovery, %12.00 1.87 93.55.00 4.83 96.622.00 2.08 1045.00 4.90 98.0In comparison with GC and HPLC techniques, the CEmethod has a minimal set-up time, a lower sample matrixdependence, needs lower costs and reagent consumptionand gives better separation efficiencies in a shorter time ofanalysis.Received 29 June 2009Accepted 7 August 2009ReferencesFig. 5. Electropherograms of milk powder sample (a) and milk powder samplefortified at 2 mg/kg of melamine standard (b)1. B. Bann, S. A. Miller, Chem. Rev., 58, 131 (1958).2. R. A. Yokley, L. C. Mayer, R. Rezaaiyan, M. E. Manuli,M. W. Cheung, J. Agric. Food Chem., 48, 3352 (2000).3. D. N. Heller, C. B. Nochetto, Rapid Commun. MassSpectrom., 22, 3624 (2008).4. J. V. Sancho, M. Ibánez, S. Grimalt, O. J. Pozo, F. Hernández,Anal. Chim. Acta, 530, 237 (2005).5. W. C. Andersen, S. B. Turnipseed, C. M. Karbiwnyk,S. B. Clark, M. R. Madson, C. M. Gieseker, R. A. Miller,N. G. Rummel, R. Reimschuessel, J. Agric. Food Chem., 56,4340 (2008).6. M. S. Filigenzi, B. Puschner, L. S. Aston, R. H. Poppenga, J.Agric. Food Chem., 56, 7593 (2008).7. M. C. Breadmore, P. R. Haddad, Electrophoresis, 22, 2464(2001).8. A. Padarauskas, Electrophoresis, 24, 2054 (2003).9. A. Padarauskas, Anal. Bioanal. Chem., 384, 132 (2006).10. Ch. W. Klamfl, L. Andersen, M. Haunschmidt,M. Himmelsbach, W. Buchberger, Electrophoresis, 30, 1(2009).11. W. Buchberger, S. A. Cousins, P. R. Haddad, Trends Anal.Chem., 13, 313 (1994).
Determination of melamine in milk powder by capillary electrophoresis23512. A. Padarauskas, V. Olsauskaite, V. Paliulionyte, Anal. Chim.Acta, 374, 159 (1998).13. Z. Daunoravicius, A. Padarauskas, Electrophoresis, 23, 2439(2002).14. E. Cordova, J. Gao, G. M. Whitesides, Anal. Chem., 69,1370 (1997).15. B. Pranaityte, A. Padarauskas, A. Dikcius, R. Ragauskas,Anal. Chim. Acta, 507, 185 (2004).16. B. Pranaityte, A. Padarauskas, J. Chromatogr. A, 1042, 197(2004).17. B. Pranaityte, A. Padarauskas, Electrophoresis, 27, 1915(2006).18. B. Pranaityte, S. Jermak, E. Naujalis, A. Padarauskas,Microchem. J., 86, 48 (2007).Žana Černova, Ina Razmislevičienė, Audrius PadarauskasMELAMINO NUSTATYMAS PIENO MILTELIUOSEKAPILIARINĖS ELEKTROFOREZĖS METODUSantraukaOptimizuotas kapiliarinės elektroforezės metodas melaminui nustatyti.Atskiriama dvigubu poli(dialildimetilamonio chlorido)/poli(natrio-4-stirensulfonato) sluoksniu padengtame kapiliare50 mmol/l tris(hidroksimetil)aminometano fosfato elektrolite(pH 2,5, 214 nm) detektuojant. Kalibracinė kreivė yra tiesinė0,2–10,0 mg/l melamino koncentracijų intervale, koreliacijos koeficientas≥0,9997, aptikimo riba – 0,06 mg/l. Metodas pritaikytasmelaminui nustatyti pieno milteliuose. Analičių išgavos iš realiųmėginių siekia 93,5–104 %.
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