During the past year, Spectroscopy examined current trends in various atomic and molecular spectroscopy techniques, such as single-particle inductively coupled
plasma–mass spectrometry, laser-induced breakdown spectroscopy, infrared spectroscopic imaging, and Raman spectroscopy, and
in applications such as nanoparticle analysis and the determination of metals in pharmaceuticals. This article presents highlights
of that coverage and offers insight into current trends in each area.
Through interviews and technical articles, Spectroscopy has provided readers with insight into important developments in a wide range of techniques and applications. Below, we have
excerpted recent interviews and one technical article on developments and trends in Raman spectroscopy, laser-induced breakdown
spectroscopy (LIBS), single-particle inductively coupled plasma–mass spectrometry (spICP-MS), and infrared (IR) imaging, as
well as in the application of spectroscopic techniques for nanoparticle analysis and the determination of metals in pharmaceuticals.
Measuring Nanoparticles in the Environment
Nanomaterials often possess physicochemical properties that are distinct from their dissolved and bulk analogues, and this
quality presents challenges for their measurement. spICP-MS is one of the few analytical methods capable of detecting, counting,
and sizing metal-containing nanoparticles at ultratrace levels in real-world samples. Here, Martin Hassellöv of the University
of Gothenburg, in Sweden, talks about the current state of spICP-MS for nanoparticle measurements.
Could you describe briefly how spICP-MS works?
Hassellöv: Basically, compared to normal ICP-MS, where one strives to obtain as steady a signal as possible, in spICP-MS one utilizes
the fact that bursts of ions are generated as metal nanoparticles pass through the plasma. By collecting data at much faster
acquisition rates than in normal ICP-MS it is possible to probe such ion bursts as individual particle events for dilute samples,
and analyze the frequency of events (directly proportional to the particle number concentration) as well as the signal intensity
of particle events, which is proportional to the mass of element in each particle (related to size).
What is the new "fast spICP-MS" method and how is it different from conventional spICP-MS?
Hassellöv: In "conventional" spICP-MS one applies a dwell time that is a bit longer (typically 5 ms) than the extent of a nanoparticle
event to avoid having many incomplete particle events (fronts or tails of events). In the new "fast" method that we recently
demonstrated (1), we applied a much faster acquisition rate (0.1 ms) so that a true real-time capture of the events with 4–6
data points across the peak is obtained. That improves the smallest detectable size, and increases the dynamic range in terms
of particle concentration because the probability of multiple particle events is drastically reduced.
How accurate is spICP-MS or fast spICP-MS when measuring nanoparticles in real-world samples?
Hassellöv: The accuracy in real world samples still need to be investigated because there are no reference materials or suitable reference
methods for environmental samples. But we have started to investigate the accuracy of the conventional spICP-MS in simple
solutions (2). In terms of size determinations, if nebulization efficiency has been thoroughly determined then spICP-MS is
comparable to reference methods such as electron microscopy. We have started to compare the accuracy of concentration measurements,
but improved reference methods are needed to make final conclusions.