Analytical strategy for rapid identification and quantification of lubricant additives in mineral oil by high-performance thin-layer chromatography with UV absorption and fluorescence detection combined with mass spectrometry and infrared spectroscopy.
A simple strategy for identification and quantification of lubricant additives in mineral oil was demonstrated by high-performance thin-layer chromatography with UV absorption and fluorescence detection using various coupling options, e.g., with attenuated total reflectance infrared (ATR-IR) spectroscopy, Fourier transform infrared (FTIR) spectroscopy, electrospray ionization mass spectrometry (ESI-MS), and direct analysis in real-time mass spectrometry (DART-MS). For the additives zinc bis(O,O'-diisobutyl dithiophosphate), zinc bis(O,O'-didodecyl dithiophosphate), and Anglamol 99, 2 chromatographic systems were developed, i.e., a reversed-phase (RP) system on RP2 plates using an acetonitrile-based mobile phase and a normal-phase system on silica gel 60 plates using a toluene-based gradient. Densitometry was performed by absorption measurement at 220 nm. Repeatabilities (relative standard deviation, n = 6) between 2.2 and 5.5% and correlation coefficients >0.9973 were highly satisfactory for the analysis of these additives in the mineral oil. Primuline reagent was used to improve the detection limit of the lipophilic additives by a factor of 2, followed by fluorescence measurement at UV 366/>400 nm. For rapid identification by ATR-IR and FTIR, the respective additive zones on the plate were online extracted by an interface called ChromeXtract, concentrated, and directly applied for measurements in the wave number range of 4000-400 cm(-1). Identification was confirmed by online ESI-MS within a minute using ChromeXtract and by DART-MS within seconds.
Dytkiewitz
Elisabeth
E
University of Hohenheim, Institute of Food Chemistry, Stuttgart, Germany.
Morlock
Gertrud E
GE
D002855:Chromatography, Thin Layer; D007202:Indicators and Reagents; D054327:Lubricants / Q000032:analysis*; D013058:Mass Spectrometry; D008899:Mineral Oil / Q000032:analysis*; D012015:Reference Standards; D012996:Solutions; D013050:Spectrometry, Fluorescence; D013055:Spectrophotometry, Infrared; D013056:Spectrophotometry, Ultraviolet; D017550:Spectroscopy, Fourier Transform Infrared
D007202:Indicators and Reagents; D054327:Lubricants; D012996:Solutions; D008899:Mineral Oil