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Stacking and analysis of melamine in milk products with acetonitrile-salt stacking technique in capillary electrophoresis.

Kong Y, Wei C, Hou Z, Wang Z, Yuan J, Yu J, Zhao Y, Tang Y, Gao M - J Anal Methods Chem (2014)

Bottom Line: The optimized buffer contains 80.0 mmol/L pH 2.8 phosphates.Melamine could be detected within 20.0 min at +10 kV with a low limit of detection (LOD) of 0.03 μmol/L.Satisfactory reproducibility (inter- and intraday RSD% both for migration time and peak area was lower than 5.0%) and a wide linearity range of 0.05 μmol/L ~ 10.0 μmol/L were achieved.

View Article: PubMed Central - PubMed

Affiliation: Institute of Mitochondrial Biology and Medicine, The Key Laboratory of Biomedical Information Engineering of Ministry of Education, Department of Bioengineering, School of Life Science and Technology, Xi'an Jiaotong University, Xi'an 710049, China.

ABSTRACT
Melamine was measured in real milk products with capillary electrophoresis (CE) based on acetonitrile-salt stacking (ASS) method. Real milk samples were deproteinized with acetonitrile at a final concentration of 60% (v/v) and then injected hydrodynamically at 50 mBar for 40.0 s. The optimized buffer contains 80.0 mmol/L pH 2.8 phosphates. Melamine could be detected within 20.0 min at +10 kV with a low limit of detection (LOD) of 0.03 μmol/L. Satisfactory reproducibility (inter- and intraday RSD% both for migration time and peak area was lower than 5.0%) and a wide linearity range of 0.05 μmol/L ~ 10.0 μmol/L were achieved. The proposed method was suitable for routine assay of MEL in real milk samples that was subjected to a simple treatment step.

No MeSH data available.


Influence of pH on migration times and Rs values.
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Related In: Results  -  Collection


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fig1: Influence of pH on migration times and Rs values.

Mentions: Buffer pH was one of most important factors that would influence separation and stacking. In this section, a pH range of 2.0~5.0 was firstly studied, as the pKa values of MEL were about 5.0; it could only be positively charged when buffer pH was lower than 5.0. There was an interferent compound in blank milk sample (contained no MEL, data not shown) which had similar migration time as MEL. Regarding this, the optimization of pH was mainly based on the resolution (Rs) between MEL and interferent as well as their migration times. The influence of pH on Rs and migration times were shown in Figure 1. It indicated that, at the lower pH (<2.5), the electroosmotic flow (EOF) was nearly zero, and MEL was strongly and positively charged and migrated to the detecting window by itself; when the pH became higher, the silanol started to dissociate and, as a result, the EOF slightly increased and migration times dropped; pH 3.5 had the slight longer migration time compared with pH 3.0, which may be caused by the faster decreasement of effective positive charges of MEL compared with the slower increasement of EOF. In addition, a peak order change was also observed in pH range of 2.0~2.5, which was similar to our CZE separation works (data not shown). Finally, based on the curve of Rs in Figure 1, pH 2.8, which had the best Rs value and relative shorter migration time, was chosen for further usage.


Stacking and analysis of melamine in milk products with acetonitrile-salt stacking technique in capillary electrophoresis.

Kong Y, Wei C, Hou Z, Wang Z, Yuan J, Yu J, Zhao Y, Tang Y, Gao M - J Anal Methods Chem (2014)

Influence of pH on migration times and Rs values.
© Copyright Policy - open-access
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC4150491&req=5

fig1: Influence of pH on migration times and Rs values.
Mentions: Buffer pH was one of most important factors that would influence separation and stacking. In this section, a pH range of 2.0~5.0 was firstly studied, as the pKa values of MEL were about 5.0; it could only be positively charged when buffer pH was lower than 5.0. There was an interferent compound in blank milk sample (contained no MEL, data not shown) which had similar migration time as MEL. Regarding this, the optimization of pH was mainly based on the resolution (Rs) between MEL and interferent as well as their migration times. The influence of pH on Rs and migration times were shown in Figure 1. It indicated that, at the lower pH (<2.5), the electroosmotic flow (EOF) was nearly zero, and MEL was strongly and positively charged and migrated to the detecting window by itself; when the pH became higher, the silanol started to dissociate and, as a result, the EOF slightly increased and migration times dropped; pH 3.5 had the slight longer migration time compared with pH 3.0, which may be caused by the faster decreasement of effective positive charges of MEL compared with the slower increasement of EOF. In addition, a peak order change was also observed in pH range of 2.0~2.5, which was similar to our CZE separation works (data not shown). Finally, based on the curve of Rs in Figure 1, pH 2.8, which had the best Rs value and relative shorter migration time, was chosen for further usage.

Bottom Line: The optimized buffer contains 80.0 mmol/L pH 2.8 phosphates.Melamine could be detected within 20.0 min at +10 kV with a low limit of detection (LOD) of 0.03 μmol/L.Satisfactory reproducibility (inter- and intraday RSD% both for migration time and peak area was lower than 5.0%) and a wide linearity range of 0.05 μmol/L ~ 10.0 μmol/L were achieved.

View Article: PubMed Central - PubMed

Affiliation: Institute of Mitochondrial Biology and Medicine, The Key Laboratory of Biomedical Information Engineering of Ministry of Education, Department of Bioengineering, School of Life Science and Technology, Xi'an Jiaotong University, Xi'an 710049, China.

ABSTRACT
Melamine was measured in real milk products with capillary electrophoresis (CE) based on acetonitrile-salt stacking (ASS) method. Real milk samples were deproteinized with acetonitrile at a final concentration of 60% (v/v) and then injected hydrodynamically at 50 mBar for 40.0 s. The optimized buffer contains 80.0 mmol/L pH 2.8 phosphates. Melamine could be detected within 20.0 min at +10 kV with a low limit of detection (LOD) of 0.03 μmol/L. Satisfactory reproducibility (inter- and intraday RSD% both for migration time and peak area was lower than 5.0%) and a wide linearity range of 0.05 μmol/L ~ 10.0 μmol/L were achieved. The proposed method was suitable for routine assay of MEL in real milk samples that was subjected to a simple treatment step.

No MeSH data available.