Life is often about making a choice or the best possible compromise between two aspects that seem to stand diametrically opposed to each other. For example, staying out late for dinner with friends while planning a long hike the following day with an early start. Either of these activities provides great pleasure, but combining both on the same weekend may not be the best idea. I come across many similar challenges almost every week, and each time I need to make a choice that seems to be the most promising in a given situation.
The same is true in some cases for analysis using inductively coupled plasma mass spectrometry (ICP-MS). While many questions about removing interferences were answered by my colleague Simon Nelms in his blogs, I would like to state here that most laboratories performing applied analytical testing of, for example, water samples or foodstuffs, mostly rely on single quadrupole-based ICP-MS, such as the Thermo Scientific™ iCAP™ RQ ICP-MS, due to their robustness, ease of use and speed of analysis.
Single quadrupole-based instruments remove all interferences using inert helium as a collision gas and kinetic energy discrimination (KED). The QCell collision/reaction cell (CRC) has two important advantages for this setup: High ion transmission across the full mass range (so that light elements such as lithium and beryllium can also be measured with the lowest detection limits), and an automatically adjusted low mass cutoff to further suppress backgrounds. More information on how KED removes interferences can be found here. Using a single collision gas for all analytes means that the time required for fill/flush cycle in the CRC can be cut from the method, and sample turnover times as low as 45 seconds for a multi-element analysis are feasible.
In turn, triple quadrupole ICP-MS systems, like the Thermo Scientific™ iCAP™ TQ ICP-MS, may use a larger variety of gases for interference removal, among them helium, oxygen, hydrogen or ammonia. With dedicated measurement modes set up for specific analytes, superior interference removal is accomplished, allowing you to tackle challenging sample matrices and eliminating difficult interferences (such as doubly charged or isobaric interferences). However, each mode and each gas switch adds a few seconds to the method, so that a fully blown method using all available options may end up with extended sample turnover times, which may not be acceptable in a busy laboratory.
Thermo Scientific™ iCAP™ TQe ICP-MSWhile the inherent complexity of setting up a method has been reduced by innovative software tools, like the Reaction Finder method development assistant available in the Thermo Scientific™ Qtegra™ Intelligent Scientific Data Solution™ Software, complex installation requirements and analysis times have been a barrier for adoption of triple quadrupole ICP-MS systems in applied testing laboratories.
So is there again only a choice between two aspects of technology that seem to be incompatible with each other? Well, there is a new way to combine the superior interference removal of a triple quadrupole with the speed of a single quadrupole.
The application experts in the Thermo Fisher Scientific Center of Excellence for Mass Spectrometry in Bremen, Germany, have recently developed a new method based on the use of oxygen as the only reactive gas in a method designed for a triple quadrupole ICP-MS system. Oxygen provides a wealth of chemical reactions to fully eliminate all interferences on common contaminants (such as chromium, arsenic, cadmium and mercury), but also provides comparable performance for elements not immediately benefitting from this reactive gas (e.g., typical matrix elements such as sodium, potassium, calcium or iron).
At the same time, sample turnover times of just a little more than 1 minute are possible, so that several hundreds of samples can be analyzed during a shift, with no concerns about sample re-runs or data quality. The team has used a Thermo Scientific™ iCAP™ TQe ICP-MS, an instrument designed specifically for laboratories looking to improve both interference removal and productivity. Independent of the matrix, this instrument allows you to overcome all current challenges, for example in the analysis of foodstuffs, and sets the lab up for increased sample loads or new sets of analytes waiting to be taken on.
If you would like to know more about how to overcome the seemingly impregnable gap between superior interference removal and productivity in the busy laboratory, please check out the iCAP TQe ICP-MS.