Derivatization for LC-Electrospray Ionization-MS: A Tool for Improving Reversed-Phase Separation and ESI Responses of Bases, Ribosides, and Intact Nucleotides
作者:Anders Nordström、Petr Tarkowski、Danuse Tarkowska、Karel Dolezal、Crister Åstot、Göran Sandberg、Thomas Moritz
DOI:10.1021/ac0499017
日期:2004.5.1
We have developed a method for analyzing polar compounds by reversed-phase LC-ESI-MS following esterification of the analytes' free hydroxyl groups with propionyl or benzoyl acid anhydride. The method was applied to members of the plant hormone group cytokinins, which includes adenine bases, ribosides/glycosides, and nucleotides substituted at N-6 with an isoprenoid side chain, spanning a wide range of polarity. It was also used to analyze other compounds of biological importance, e.g., the nucleotides AMP, ADP, and ATP. The formation of more hydrophobic derivatives had a significant impact on two aspects of the analysis. The retention on a reversed-phase material was greatly increased without the use of any acetate/formate buffer or ion pairing reagent, and the ESI response was enhanced, due to the higher surface activities of the derivatives. Detection limits of propionylated cytokinins were in the high-attomole to low-femtomole range, an improvement by factors of 10−100 compared to previously reported figures. Using an automated SPE-based purification method, 12 endogenous cytokinins were quantified in extracts from 20- to 100-mg samples of leaves (from the plant Arabidopsis thaliana) with high accuracy and precision. Furthermore, the chromatographic properties of the benzoylated AMP, ADP, and ATP in the reversed-phase LC−MS system were much better in terms of retention, separation, and sensitivity than those of their underivatized counterparts, even without the use of any ion pairing reagent. Our data show that derivatization followed by LC-ESI-MS is an effective strategy for analyzing low molecular weight compounds, enabling compounds with a wide range of polarity to be determined in a single-injection LC−MS analysis.
我们已经开发了一种分析极性化合物的方法,即在分析物的自由羟基上进行丙酸酐或苯甲酸酐的酯化反应后,进行反相液相-电喷雾-质谱(LC-ESI-MS)分析。该方法应用于植物激素类细胞分裂素的成员,包括腺嘌呤碱基、核糖核苷/糖苷以及在N-6位带有异戊二烯侧链的核苷酸,这些物质的极性范围广泛。该方法还被用于分析其他具有生物学重要性的化合物,例如核苷酸 AMP、ADP 和 ATP。形成更具疏水性的衍生物对分析的两个方面产生了重大影响。在不使用任何乙酸盐/甲酸盐缓冲液或离子配对试剂的情况下,保留在反相材料上的时间大大增加,并且由于衍生物的较高表面活性,ESI响应性增强。丙酸酰化的细胞分裂素的检测限在高位阿托摩尔到低位飞摩尔范围,相较于先前报道的数据,有了10至100倍的改进。使用自动化的SPE基净化方法,从植物拟南芥叶子的20至100毫克样品中提取的12种内源性细胞分裂素,能够以高度的准确性和精确性进行定量。此外,在反相LC-MS系统中,苯甲酸酰化的AMP、ADP和ATP的色谱特性在保留、分离和灵敏度方面远优于未经衍生的对应物,即便没有使用任何离子配对试剂。我们的数据显示,衍生化后进行LC-ESI-MS分析是分析低分子量化合物的一种有效策略,能够在单次注射LC-MS分析中测定极性范围广泛的化合物。