EC‐MS Technical Note #12
Cleaning procedures
EC-MS Technical notes #12
- Last updated
Introduction
This technical note aims to equip Spectro Inlet’s EC‐MS users, and indeed anybody doing fundamental electrochemical studies, with an overview of appropriate cleaning procedures for various experimental applications.
We would like to stress that ”best practices” in terms of choosing the correct cleaning procedure depends strongly on the type of experiment being conducted [1], what level of cleanliness is required and to what extend the user are able to control the sample composition/uniformity [2]. Considering these aspects, several cleaning methods are outlined, including their benefits and downsides as well as hazards and user requirements. Cleaning electrochemical systems is an often overlooked aspect within electrocatalysis. However, just as standardized sample preparation, e.g. using the Clavilier method for Pt electrode investigations [3], standardizing the cell condition can be of equivalent importance. The methods mentioned herein are therefore suggestions and NOT requirements, i.e. any cleaning procedure should be chosen to match the users needs and ﴾cap﴿abilities. When initially receiving the EC‐MS system it arrives with at PCTFE EC‐MS cell, chips, U‐cups, luer‐ and Luggin adapters among others, see figure 1 for an overview.
Spectro Inlet recommend EC‐MS users to purchase appropriate syringes or alternative systems for electrolyte injection. Moreover, it is recommended to acquire a polycrystalline platinum ﴾PtPoly﴿ or glassy carbon ﴾GC﴿ electrode sample to benchmark the EC‐MS system prior intended use, see Benchmark Measurements EC‐MS Technical Note #2.
While the specific GC or PtPoly sample electrodes may have little relevance to the user, their response in the EC‐MS system are well suited to: i﴿ Benchmark the received EC‐MS system ii﴿ Train new EC‐MS users. Consequently, in the following we will list typical cleaning procedures for first time EC‐MS use, aimed towards enabling standard aqueous EC‐MS benchmarking experiments described in the Benchmark Measurements EC‐MS Technical Note #2, while in the second part general cleaning procedures will be discussed.
Cleaning procedure for first time users
Tuning of peak position and width is crucial to obtain reliable sensitivity when collecting MID data using the EC-MS. Zilien collects the signal intensity precisely at the chosen mass. Therefore, already a slight shift in peak position can potentially lead to a large difference in signal intensity, if a position on the side of the peak is probed instead of the maximum.
In this example, we will tune only with the masses available in air and with He carrier gas, i.e. M4, M28 and M40. Upon delivery of your instrument it will be pre-tuned using a calibration gas containing He (M4), N<sub>2</sub> (M28), Ar (M40) and Xe (M129). Note that it is necessary to always tune over the entire mass range of interest to get the best possible results. I.e. if some products have mass fragments above M40, we recommend also tuning a higher mass between 100-200 amu. While it is easy and reliable, it is not a necessity to use a calibration gas containing Xe; it is also possible to use e.g.: a volatile substance with known mass fragment at a higher mass. In this case, use a non-aqueous chip or a dilute aqueous solution to prevent chip breach.
For more information on different tuning procedures the user is referred to the PV MassSpec Manual (accessible via the “Help” tab in the software), in particular the section “Best Known Methods for Tuning” and related topics.