Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California, USA.
Department of Chemistry, Dartmouth College, Hanover, New Hampshire, USA.
Astrobiology. 2021 May;21(5):575-586. doi: 10.1089/ast.2020.2298. Epub 2021 Feb 2.
instrumentation that can detect amino acids at parts-per-billion concentration levels and distinguish an enantiomeric excess of either d- or l-amino acids is vital for future robotic life-detection missions to promising targets in our solar system. In this article, a novel chiral amino acid analysis method is described, which reduces the risk of organic contamination and spurious signals from by-products by avoiding organic solvents and organic additives. Online solid-phase extraction, chiral liquid chromatography, and mass spectrometry were used for automated analysis of amino acids from solid and aqueous environmental samples. Carbonated water (pH ∼3, ∼5 wt % CO achieved at 6 MPa) was used as the extraction solvent for solid samples at 150°C and as the mobile phase at ambient temperature for chiral chromatographic separation. Of 18 enantiomeric amino acids, 5 enantiomeric pairs were separated with a chromatographic resolution >1.5 and 12 pairs with a resolution >0.7. The median lower limit of detection of amino acids was 2.5 μg/L, with the lowest experimentally verified as low as 0.25 μg/L. Samples from a geyser site (Great Fountain Geyser) and a geothermal spring site (Lemon Spring) in Yellowstone National Park were analyzed to demonstrate the viability of the method for future missions to Ocean Worlds.
能够检测到十亿分之一浓度水平的氨基酸，并区分 d-或 l-氨基酸的对映体过量的仪器对于未来在太阳系中对有前途的目标进行机器人生命探测任务至关重要。本文描述了一种新的手性氨基酸分析方法，该方法通过避免有机溶剂和有机添加剂，降低了有机污染和副产物虚假信号的风险。在线固相萃取、手性液相色谱和质谱用于自动分析来自固体和水基环境样品中的氨基酸。碳酸水（pH ∼3，在 6 MPa 下实现 ∼5 wt % CO）在 150°C 下用作固体样品的萃取溶剂，并在环境温度下用作手性色谱分离的流动相。在 18 种对映体氨基酸中，有 5 对对映体的分离度>1.5，12 对对映体的分离度>0.7。氨基酸的中值检测下限为 2.5μg/L，最低的实验验证值低至 0.25μg/L。对黄石国家公园间歇泉区（大喷泉间歇泉）和温泉区（柠檬泉）的样本进行了分析，以证明该方法对于未来海洋世界任务的可行性。
