Qilin Chan, a research specialist, spoke to SelectScience® about the technologies enabling his work in material characterization, within the corporate lab analytical group at 3M. 3M is a large manufacturer of many products including Post-ItTM notes, ScotchTM tapes, CommandTM strips, FiltreteTM filters and CubitronTM abrasives, all of which require rigorous impurity testing.
Dr Chan has extensive expertise in inorganic analyses and uses inductively coupled plasma mass spectrometry (ICP-MS) and inductively coupled plasma atomic emission spectroscopy (ICP-AES) to measure trace level impurities in 3M materials. 3M has many analytical labs and the corporate research lab is particularly involved in method development for customized preparation and analysis.
Effective detection of impurities
Impurities may be metal or semi-metal and are often foreign materials unintentionally introduced during production and residual traces of the catalysts used in production, particularly in polymers. Detection of these impurities requires very high sensitivity, down to parts per million (ppm), billion (ppb) or even trillion (ppt). The selection of ICP-MS or ICP-AES is dependent on the sample type and the level of detection required.
Elemental analyses are also performed using ICP-AES, x-ray fluorescence and scanning electron microscopy. ICP-AES has the required sensitivity for detection in the ppm range, which is ideal for residual catalysts in polymers. However, ICP-MS has far greater sensitivity to detect impurities in the ppb to ppt range. Dr Chan explains, “We use the Thermo Fisher Scientific Element 2™ ICP-MS, which provides the highest mass resolution we have been able to achieve.”
The Element 2 is fantastic and we have been using it for many years.
Dr Qilin Chan
This high-resolution approach enables the analytes to be separated from the interference peaks. For example, arsenic is a monoisotopic element (75As+) and this peak often interferes with the argon chloride ion (40Ar35Cl+) peak on a single quadrupole ICP-MS. While other ICP-MS techniques employ collision/reaction gases to reduce interferences, Element 2 has enough mass resolution to simply discriminate between these peaks, so the high sensitivity and resolution of Element2 make it an ideal tool for this challenge. In the words of Dr Chan, “The Element 2 is fantastic and we have been using it for many years.”
3M is a diversified company covering a variety of markets including healthcare businesses, where regulations on impurities are becoming tighter, with much lower detection limits required, so the Element 2 is also very useful for such analyses. In addition, the Element 2 is heavily employed at 3M for the electronics and semi-conductors sector, as these products are very sensitive to metal impurities and need reliable impurity testing.
Dr Chan believes that the mass resolution of the Element 2 is superior, however, he would like to see faster detection in the future. The lab often combines ICP-MS with other techniques, such as laser ablation, to do online analyses of transient signals. This requires faster detection, to get as many data points as possible and capture these transient signals, which are particularly important for elemental imaging and single particle analyses.