Pressurized sample infusion (PSI) is a simple and effective means of continuously introducing a solution to an electrospray ionization mass spectrometry (ESI‐MS) source. It allows for acquisition of real‐time data in an air‐ and moisture‐free environment and requires minimal additional infrastructure. It is applicable for use for any reaction in which one or more components are detectable by ESI‐MS and for which time‐course information is desired over a time scale of seconds to minutes. The strengths and weaknesses of the method are critically examined, and technique tips and tricks are provided to enable maximal effectiveness when employing this approach to continuous monitoring of complex reaction mixtures.

The cover art blends together some experimental details -the pressurized, modified Schlenk flask used in the PSI experiments, and the tubing that leads out into the mass spectrometer -with the reaction traces generated while performing the experiment. The design was constructed using 3D modelling software and superimposed on a background of a lake bed for some added visual interest before rendering. What time-consuming dead-ends delayed the results before this breakthrough?Clogging of the PEEK tubing when working with heterogeneous solutions would often result in flow restrictions, causing delays in getting timely reaction monitoring results. Luckily our work with simple filter attachments has helped to streamline the data acquisition process. What do you consider the exciting developments in the field?The ability to acquire data online and in real time. This provides a unique perspective of reactions as information can be inferred Invited for this month's cover is the group of Scott McIndoe at the University of Victoria (Canada). The cover picture shows a pressurized reaction vessel with tubing leading out of the flask. That tubing normally leads directly into an electrospray ionization mass spectrometer, where the mass-to-charge ratio and relative abundance of the solution phase ions are measured. These data can be used to generate chronograms for each solution species, shown here in the form of a reactant diminishing with first order kinetics, accompanied by the formation of a product ion. Read the full text of their Review at 10.1002/ cmtd.202100068. Chemistry-Methods www.chemistrymethods.org

Mass spectrometric approaches to polymer analysis become increasingly ineffective as average molecular weight increases. This perspective explains these fundamental limits of MS for determining molecular weight distribution of high polymers.

Understanding catalytic reactions is inherently difficult because not only is the catalyst the least abundant component in the mixture, but it also takes many different forms as the reaction proceeds....

<p>Understanding catalytic reactions is inherently difficult because not only is the catalyst the least abundant component in the mixture, but it also takes many different forms as the reaction proceeds. Precatalyst is converted into active catalyst, short-lived intermediates, resting states, and decomposition products. Polymerization catalysis is harder yet to study, because as the polymer grows the identities of these species change with every turnover as monomers are added to the chain. Modern mass spectrometric methods have proved to be up to the challenge, with multiple reaction monitoring (MRM) in conjunction with pressurized sample infusion (PSI) used to continuously probe all stages of the Suzuki polycondensation (SPC) reaction. Initiation, propagation, and termination steps were tracked in real time, and the outstanding sensitivity and low signal-to-noise of the approach has real promise with respect to the depth with which this reaction and others like it can be studied.</p>