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Liquid Chromatography Separation and Mass Spectrometry Detection of Silver-Lipoate Ag29(LA)12 Nanoclusters: Evidence of Isomerism in the Solution Phase
Analytical Chemistry ( IF 6.7 ) Pub Date : 2018-01-10 00:00:00 , DOI: 10.1021/acs.analchem.7b04104 David M. Black 1 , Geronimo Robles 1 , Priscilla Lopez 1 , Stephan B. H. Bach 1 , Marcos Alvarez 1 , Robert L. Whetten 1
Analytical Chemistry ( IF 6.7 ) Pub Date : 2018-01-10 00:00:00 , DOI: 10.1021/acs.analchem.7b04104 David M. Black 1 , Geronimo Robles 1 , Priscilla Lopez 1 , Stephan B. H. Bach 1 , Marcos Alvarez 1 , Robert L. Whetten 1
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Evidence for the existence of condensed-phase isomers of silver-lipoate clusters, Ag29(LA)12, where LA = (R)-α lipoic acid, was obtained by reversed-phase ion-pair liquid chromatography with in-line UV–vis and electrospray ionization (ESI)-MS detection. All components of a raw mixture were separated according to surface chemistry and increasing size via reversed-phase gradient HPLC methods and identified by their corresponding m/z ratio by ESI in the negative ionization mode. Aqueous and methanol mobile-phase mixtures, each containing 400 mM hexafluoroisopropanol (HFIP)–15 mM triethylamine (TEA), were employed to facilitate the interaction between the clusters and stationary phase via formation of ion-pairs. TEA-HFIP (triethylammonium-hexafluoroisopropoxide) had been shown to provide superior chromatographic peak shape and mass spectral signal compared with alternative modifiers such as TEAA (triethylammonium-acetate) for analysis of oligonucleotide samples. Liquid chromatographic separation prior to mass spectrometry detection facilitated sample analysis by production of simplified mass spectra for each eluting cluster species and provided insight into the existence of at least two major solution-phase isomers of Ag29(LA)12. UV–vis detection in-line with ESI analysis provided independent confirmation of the existence of the isomers and their similar electronic structure as judged from their identical optical spectra in the 300–500 nm range. [Diastereomerism provides a possible interpretation for the near-equal abundance of the two forms, based on a structurally defined nonaqueous homologue.]
中文翻译：
硫辛酸银Ag 29（LA）12纳米团簇的液相色谱分离和质谱检测：溶液相中的异构现象
通过反相离子对液相色谱和在线UV-分析获得了硫辛酸银团簇Ag 29（LA）12的冷凝相异构体的证据，其中LA =（R）-α硫辛酸。可见和电喷雾电离（ESI）-MS检测。原料混合物的所有成分均根据表面化学性质和通过反相梯度HPLC方法增加粒径而分离，并通过其相应的m / z进行鉴定在负电离模式下通过ESI测得的比率 使用含水和甲醇流动相混合物，每种混合物均包含400 mM六氟异丙醇（HFIP）–15 mM三乙胺（TEA），以通过形成离子对促进簇与固定相之间的相互作用。与替代的修饰剂如TEAA（乙酸三乙基铵）相比，TEA-HFIP（六乙基异丙醇三乙基铵）具有更好的色谱峰形和质谱信号。）分析寡核苷酸样品。质谱检测之前的液相色谱分离通过为每种洗脱的簇物质生成简化的质谱图促进了样品分析，并提供了对至少两种主要的Ag 29（LA）12溶液相异构体的存在的了解。通过ESI分析进行的紫外可见检测可独立确认异构体的存在及其相似的电子结构，这些异构体是根据它们在300-500 nm范围内的相同光谱判断的。[基于结构定义的非水同源物，非对映异构体为两种形式的近乎相等的丰度提供了一种可能的解释。]
更新日期：2018-01-10
中文翻译：
硫辛酸银Ag 29（LA）12纳米团簇的液相色谱分离和质谱检测：溶液相中的异构现象
通过反相离子对液相色谱和在线UV-分析获得了硫辛酸银团簇Ag 29（LA）12的冷凝相异构体的证据，其中LA =（R）-α硫辛酸。可见和电喷雾电离（ESI）-MS检测。原料混合物的所有成分均根据表面化学性质和通过反相梯度HPLC方法增加粒径而分离，并通过其相应的m / z进行鉴定在负电离模式下通过ESI测得的比率 使用含水和甲醇流动相混合物，每种混合物均包含400 mM六氟异丙醇（HFIP）–15 mM三乙胺（TEA），以通过形成离子对促进簇与固定相之间的相互作用。与替代的修饰剂如TEAA（乙酸三乙基铵）相比，TEA-HFIP（六乙基异丙醇三乙基铵）具有更好的色谱峰形和质谱信号。）分析寡核苷酸样品。质谱检测之前的液相色谱分离通过为每种洗脱的簇物质生成简化的质谱图促进了样品分析，并提供了对至少两种主要的Ag 29（LA）12溶液相异构体的存在的了解。通过ESI分析进行的紫外可见检测可独立确认异构体的存在及其相似的电子结构，这些异构体是根据它们在300-500 nm范围内的相同光谱判断的。[基于结构定义的非水同源物，非对映异构体为两种形式的近乎相等的丰度提供了一种可能的解释。]
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