Sze Kwan-Lok, Yeung William Shu-Biu, Fung Ying-Sing
Department of Chemistry, The University of Hong Kong, Hong Kong SAR, China.
Electrophoresis. 2007 Nov;28(22):4156-63. doi: 10.1002/elps.200700541.
To prevent casein adsorption and improve between-run repeatability, a CE procedure is developed for cation analysis in milk using a modified imidazole/alpha-hydroxyisobutyric acid (HIBA) BGE system to operate at pH 6 to match the pH of milk and elevate imidazole concentration to enhance its buffer action. The procedure is shown to produce a fast, economic and efficient method for cation separation in milk with only simple dilution. Upon direct hydrodynamic injection of diluted milk sample at 8 cm for 30 s in an uncoated column with a BGE consisting of 10 mM imidazole, 10 mM HIBA and 10% methanol at pH 6.0 under +18 kV, baseline separation was achieved for K(+), Na(+), Ca(2+), Mg(2+), Mn(2+), Cd(2+), Co(2+), Ni(2+)and Zn(2+). Agreeable results at 95% confidence level were obtained using CE and inductively coupled plasma-atomic emission spectrometry (ICP-AES) for milk samples after protein removal. Baseline-resolved peaks for essential minerals were obtained for fresh and non-refrigerated reconstituted milks. Long-term stability was demonstrated by repeated determinations without rinsing and improvement in repeatability was shown by rinsing with 60 mM SDS in BGE. Information on metal speciation useful for nutritional assessment was obtained from CE to complement the ICP methods.
为防止酪蛋白吸附并提高批间重复性，开发了一种毛细管电泳（CE）方法，用于牛奶中的阳离子分析。该方法采用改良的咪唑/α-羟基异丁酸（HIBA）背景电解质（BGE）系统，在pH 6下运行以匹配牛奶的pH值，并提高咪唑浓度以增强其缓冲作用。结果表明，该方法只需简单稀释，就能快速、经济且高效地分离牛奶中的阳离子。在未涂层柱中，以由10 mM咪唑、10 mM HIBA和10%甲醇组成的BGE为背景电解质，在pH 6.0、+18 kV电压下，将稀释后的牛奶样品直接进行8 cm、30 s的流体动力学进样，实现了K(+)、Na(+)、Ca(2+)、Mg(2+)、Mn(2+)、Cd(2+)、Co(2+)、Ni(2+)和Zn(2+)的基线分离。去除蛋白质后的牛奶样品，采用CE和电感耦合等离子体原子发射光谱法（ICP-AES）在95%置信水平下获得了一致的结果。新鲜牛奶和非冷藏复原乳均获得了必需矿物质的基线分离峰。通过不冲洗的重复测定证明了长期稳定性，用含60 mM SDS的BGE冲洗显示了重复性的提高。从CE获得了有助于营养评估的金属形态信息，以补充ICP方法。
