Ion selective sensor with modulated ionization

根据正在进行的项目的研究结果，该项目旨在开发一种新型传感器，用于快速、灵敏地检测空气中的挥发性有机痕量化合物，更新提案旨在提高传感器的选择性。传感器原理基于待检测物质的脉冲大气压化学电离。在电离之后，离子特异性离子-离子复合以及电荷转移反应导致存在于电离区域中的离子种类的离子特异性寿命。随着电离结束和测量电离区域中剩余的总离子电荷之间的延迟增加，具有较短寿命的离子种类越来越多地被区分。因此，选择性基于离子特定的离子-离子复合速率和电荷转移速率，这允许通过其特征衰变曲线来识别不同的气体混合物。此外，限定在特定浓度下的剩余离子电荷的阈值，可以以高可靠性识别和检测长寿命离子。然而，为了获得更好的选择性，将在更新提案中研究离子比离子生成速率及其对衰变曲线的影响。短时间电离将主要导致具有快速产生速率的离子种类，并因此改变初始离子分布，从而影响离子-离子复合和电荷转移反应。该概念也可用于离子迁移谱法中，以将离子产生导向低质子仿射和电子仿射物质，其在高质子仿射和电子仿射物质存在下通常难以分离，因此难以检测。然而，离子特定离子形成的研究及其在离子迁移谱和气体传感中的应用需要脉冲电离源，其脉冲宽度为0.1 µs至10 ms，离子产生速率恒定。最小脉冲宽度约为10 µs且离子产生速率相当不受控制的市售电子源（Optimare Analytik）不适用于研究离子形成过程。因此，一个自己的非放射性电子源和一个改进的电晕放电源与脉冲UV-LED将在更新项目中开发，既提供合适的脉冲宽度和受控的离子产生率，操纵离子分布在电离区域通过简单地改变电离的持续时间。这可以以两种方式采用：第一，通过使用短电离脉冲来区分具有低离子形成速率的离子种类，以及第二，当改变电离的持续时间时，由于电离区域中的不同初始离子分布而产生气体混合物的衰减曲线的特征集合。这两种效应都可用于显著提高离子迁移谱的选择性和灵敏度。此外，离子选择性传感器将通过调制电离来改进。

On the basis of the research results of the ongoing project towards a new sensor for fast and sensitive detection of volatile organic trace compounds in air the renewal proposal aims for an increased sensor selectivity. The sensor principle is based on a pulsed atmospheric pressure chemical ionization of the substances to be detected. After ionization ion specific ion-ion-recombination as well as charge transfer reactions lead to an ion specific life time of the ion species present in the ionization region. With an increasing delay between the end of the ionization and measuring the remaining total ion charge in the ionization region ion species with shorter life time are increasingly discriminated. Thus, selectivity is based on the ion specific ion-ion-recombination rate and charge transfer rate, which allows identifying different gas mixtures by their characteristic decay curves. Furthermore, defining a threshold of the remaining ion charge long living ions at a certain concentration can be identified and detected with high reliability. However, for better selectivity the ion specific ion generation rate and its effect on the decay curve will be investigated in the renewal proposal. Short ionization will mainly lead to ion species with fast generation rates and therefore change the initial ion distribution affecting the ion-ion recombination and charge transfer reactions. This concept can be also used in ion mobility spectrometry to direct ion generation towards low proton affine and electron affine substances, which are usually hard to ionize in the presence of high proton affine and electron affine substances and therefore difficult to detect. However, the investigation of the ion specific ion formation and its application in ion mobility spectrometry and gas sensing requires a pulsed ionization source with pulse widths from 0.1 µs to 10 ms at constant ion generation rates. The commercially available electron source (Optimare Analytik) with a minimum pulse width of about 10 µs and a rather uncontrolled ion generation rate is not feasible to investigate the ion formation processes. Thus, an own non-radioactive electron source and a modified corona discharge source with pulsed UV-LED will be developed in the renewal project, both providing suitable pulse widths and controlled ion generation rates to manipulate the ion distribution in the ionization region by simply varying the duration of ionization. This can be employed in two ways: First, to discriminate ion species with low ion formation rates by using short ionization pluses, and second, to generate a characteristic set of decay curves of a gas mixture due varying initial ion distributions in the ionization region when varying the duration of ionization. Both effects can be used to significantly improve selectivity and sensitivity in ion mobility spectrometry. Furthermore, the ion selective sensor will be improved by modulating the ionization.