Supercritical fluid chromatography and two-dimensional supercritical fluid chromatography of polar car lubricant additives with neat CO2 as mobile phase

Columns in analytical-scale supercritical fluid chromatography: From traditional to unconventional chemistries

Within this review, we thoroughly explored supercritical fluid chromatography (SFC) columns used across > 3000 papers published from the first study carried out under SFC conditions in 1962 to the end of 2022. We focused on the open tubular capillary, packed capillary, and packed columns, their chemistries, dimensions, and trends in used stationary phases with correlation to their specific interactions, advantages, drawbacks, used instrumentation, and application field. Since the 1990s, packed columns with liquid chromatography and SFC-dedicated stationary phases for chiral and achiral separation are predominantly used. These stationary phases are based on silica support modified with a wide range of chemical moieties. Moreover, numerous unconventional stationary phases were evaluated, including porous graphitic carbon, titania, zirconia, alumina, liquid crystals, and ionic liquids. The applications of unconventional stationary phases are described in detail as they bring essential findings required for further development of the supercritical fluid chromatography technique.

Rapid analysis of lubricants by atmospheric solid analysis probe-ion mobility mass spectrometry

Formulated lubricants are complex mixtures composed of base oil(s) and additives with various functions (detergents, corrosion inhibiter, antioxidant, viscosity modifiers, etc.). Because of the aliphatic nature of base oil and the chemical diversity of additives, the characterization of lubricant is currently a long and complex process. The comprehensive analysis of lubricant samples involves several techniques such as nuclear magnetic resonance, mass spectrometry, chromatography and infrared spectroscopy. The coupling of atmospheric solid analysis probe (ASAP) with ion mobility-mass spectrometry (IM-MS) has been shown to be an efficient tool for the characterization of complex mixture containing vaporizable polar to non-polar compounds. This approach affords the coupling of a direct ionization technique that does not require sample preparation, with a bi-dimensional separation method with high peak capacity. In this work, we show that ASAP-IM-MS is a suitable method for rapid and direct characterization of lubricant samples. Indeed, base oil and additives yielded, by ASAP, ions series which could be separated by IM-MS. Molecular additives such as Zn-dithiocarbamate, phosphite, thiophosphate and Alkyl diphenylamine were ionized as molecular ions [M](+•) or protonated molecules [M + H](+), depending of their polarity. In some cases, fragment ions were observed, confirming the additive identification. In addition, high molecular weight polymeric additives such as poly(alkyl methacrylate) (PAM) were pyrolized in the ASAP source leading to characteristic fragment ions. ASAP-IM-MS is shown to be a powerful tool for studying complex mixtures, allowing the first comprehensive analysis of lubricants in just a few minutes.

High-throughput quantification of stabilizers in polymeric materials by flow injection tandem mass spectrometry

RATIONALE

High-throughput methods for identification and quantification of stabilizers in plastic materials are of significant importance in order to evaluate the suitability of materials of unknown origin for specific application areas, to clarify reasons for failure of materials, or for comparison of materials from different sources.

METHODS

In the present study, a highly sensitive and rapid flow injection method coupled to selected reaction monitoring mass spectrometry (MS) for comprehensive analysis of 21 polymer stabilizers in polyolefins is demonstrated. A critical factor for this approach is the choice of ionization mode, as no separation was performed prior to MS detection. Differences between several ionization techniques regarding matrix effects are reported.

RESULTS

Atmospheric pressure chemical ionization was found to be the most suitable ionization technique, with no significant matrix effects observed. The developed method has a linear dynamic range over two to three orders of magnitude with correlation coefficients better than 0.99 for all studied analytes. Following a multistep sample preparation protocol, the method allowed quantification down to minimum values of between 0.0001 and 0.04 wt% depending on the type of stabilizer. Results were compared to an established chromatographic approach and showed very good correlation (bias below 7.5%).

CONCLUSIONS

The applicability of the optimized method could be demonstrated for both the qualitative and quantitative determination of polymer stabilizers in polyolefins. Furthermore, the described approach yields a complete analysis in a much shorter time than can be achieved with commonly applied chromatographic methods.