Advances in HPLC Stationary phases: Zirconia HPLC columns

基于二氧化硅的HPLCcolumns have remained workhorses in HPLC laboratories. Over the years with advances in particle technologies size reduction has been possible from 5μm to sub- 2μm which led to development of UHPLC. Further introduction of核 - 壳技术和单片色谱柱扩展了应用范围，并促进了更大的样本吞吐量。

Properties of Zirconia supports

二氧化硅柱的主要限制是在2至8之间的pH范围和温度到环境的可用性。另一方面，氧化锆支持在整个pH范围内表现出运行稳定性，工作温度高达200°C。

路易斯酸

Zirconia or ZrO2 is an oxide in which the Zr atom acts as a Lewis acid i.e. – it accepts electron pair due to prescence of empty orbital. This feature provides enhanced selectivity over conventional silica columns.

Adsorption capacity

与二氧化硅包装相比，吸附容量更大

耐化学性

High resistance to acidic and basic solutions. Retention of basic and acidic analytes can be finely controlled by changing the pH of medium over the entire available range.

Types of phases

Four surface chemistries based on surface activities are available which greatly extend selectivity and retention of for improved separations

聚丁二烯涂层氧化锆

该阶段类似于使用C18二氧化硅的反相，但具有以下优点：

• Available pH range 1 – 13
• 温度稳定性高达200°C
• Less hydrophobic than C18 and is suitable for separations involving amines and bases

Zirconia-C18

• 多孔碳包层氧化锆颗粒用C18基团共价修饰。
• Selectivity is rather different from conventional C18 columns
• Can be used over the entire pH range (1 – 14) alongwith high temperature capabilities (up to 200°C)

Zirconia – polystyrene

• 多孔氧化锆颗粒用交联聚苯乙烯改性。
• Tolerate strongly aqueous solutions up (up to 100% pure water)
• Operational pH range 1 – 13
• Useful for separation of hydrophobic compounds and amines
• No requirement for离子配对要求
• 与二氧化硅的包装相比，碱性化合物的尾尾减少
• Provides mixed mode Reverse phase and Ion exchange separations

氧化锆 - 碳

• Porous carbon clad Zirconia particles provide enhanced retention of polar compounds
• Highly hydrophilic surface
• Useful for separation of isomers and diastereomers
• Good retention of fused – ring aromatic compounds

柱护理

Contaminated columns can deteriorate the peak shape, effect retention times, lead to high backpressure and increase baseline noise. Use of concentrations above 25 mM phosphate, acetate, carbonate/bicarbonate buffers and salts should be avoided. Anions such as carboxylic acids, fluoride and phosphate strongly absorb on Zirconia columns. The recommended steps for column regeneration are

1. 用20:80的乙腈和pH10氢氧化铵的混合物冲洗50柱，其次是10柱水
2. Repeat with 20:80 mixture of acetonitrile and 0.1 M nitric acid for same column volumes
3. Flush with pure methanol, acetonitrile, isopropanol or tetrahydrofuran for 20 column volumes. Zirconia HPLC columns will require the same solvents with at least 20% THF

Storage

• Zirconia HPLC columns should not be stored in phosphate buffer. The recommended storage procedure is
• 过夜 - 10卷有机改性剂/水
• Long-term storage – 10 volumes of pH 10 ammonium hydroxide followed by 10 volumes of 50: 50 organic modifier/water

We have seen that zirconia-based reverse phases offer a great choice of selectivity and retention. Additional benefits of column chemistries, pH and temperature extremes contribute to versatility of applications. A subsequent article on monolith stationary phase packing will introduce you to further advances in stationary phases.

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