The gains in sensitivity since 1975 for quadrupole mass spectrometers equipped with atmospheric pressure ionization (API), and in particular triple quadrupole mass spectrometers (QqQs) since 1981, have been driven by the needs of the environmental, biomedical, agricultural, and other scientific research, industrial, regulatory, legal, and sporting communities to continually achieve lower limits of quantitation and identification. QqQs have realized a one-million-fold improvement in sensitivity attempting to address these needs over the past two score years. It is the purpose of this article to describe how that came about, not through an exhaustive review of the literature, but rather by describing what general approaches were used across the industry to improve sensitivity and provide some examples to illustrate its evolution. The majority of the gains came from the ion source and its interface to the vacuum system. “Sampling efficiency” is a measurement of the losses in this area so will be a focus of this review. The discovery of the phenomenon of collisional focusing was key to improving sampling efficiency because it enabled designs that increased the ion-containing gas loads from the ion source, using staged differential pumping backed by increasingly larger pumps, and prevented the scattering losses of ions in the resulting gas expansion inside vacuum. Likewise, systems with smaller pumps and lower ion-containing gas loads could be designed with size and cost reduction in mind while maintaining reasonable sampling efficiencies. As a consequence, advancements in the designs of both larger and smaller turbomolecular vacuum pumps were accelerated by pump manufacturers to accommodate the explosive growth in the use of API-QqQ and API-ion trap mass spectrometers that occurred in the 1990s and continued into the new millennium. Sampling efficiency was further improved by increasing the ion yield from electrospray by increasing the rate of droplet desolvation. An estimate of the practical limit to further sensitivity improvements beyond what has been achieved to date is provided to shed light on what to expect in the future. Lastly, the implications and unforeseen consequences of the sensitivity gains are considered with a particular focus on how they have enabled a dramatic increase in daily sample throughput on triple quadrupole and other types of mass spectrometers.

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时间流逝，所有的离子都去哪儿了？自 20 世纪 70 年代中期以来，串联四极杆质谱仪的大气压电离灵敏度不断提高。一个视角


自 1975 年以来，配备常压电离 (API) 的四极杆质谱仪，特别是自 1981 年以来的三重四极杆质谱仪 (QqQs) 的灵敏度不断提高，这是由环境、生物医学、农业和其他科学研究的需求推动的、工业、监管、法律和体育界不断实现定量和鉴定的更低限度。在过去的两年里，QqQ 尝试满足这些需求的灵敏度已经提高了一百万倍。本文的目的是描述这是如何发生的，不是通过对文献进行详尽的回顾，而是通过描述整个行业使用哪些通用方法来提高灵敏度，并提供一些示例来说明其演变。大部分增益来自离子源及其与真空系统的接口。 “采样效率”是该领域损失的衡量标准，因此将成为本次审查的重点。碰撞聚焦现象的发现是提高采样效率的关键，因为它使得设计能够增加来自离子源的含离子气体负载，使用由越来越大的泵支持的分级差动泵，并防止离子在离子源中的散射损失。导致真空内气体膨胀。同样，具有较小泵和较低含离子气体负载的系统在设计时可以考虑减小尺寸和降低成本，同时保持合理的采样效率。 因此，泵制造商加速了较大和较小涡轮分子真空泵设计的进步，以适应 20 世纪 90 年代出现并持续到新世纪的 API-QqQ 和 API-离子阱质谱仪使用的爆炸性增长。千年。通过提高液滴去溶剂化速率来提高电喷雾的离子产量，进一步提高了采样效率。对进一步提高灵敏度的实际限制进行了估计，以阐明未来的预期。最后，考虑了灵敏度增益的影响和不可预见的后果，特别关注它们如何使三重四极杆和其他类型的质谱仪上的每日样品通量显着增加。