Gae Ho Lee

Identification of tackifying resins and reinforcing resins in cured rubber

Abstract On-line thermogravimetic analysis/Fourier transform-infrared spectroscopy (TGA/FT-IR) and pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) were employed to identify the tackifying...

ANALYSIS OF LECITHIN IN COSMETICS BY REVERSED-PHASE LIQUID CHROMATOGRAPHY/ELECTROSPRAY TANDEM MASS SPECTROMETRY

A rapid, sensitive and selective method by reversed-phase liquid chromatography (LC) with electrospray ionization (ESI) mass spectrometry (MS) was employed for the determination of lecithin in a cosmetic raw material for quality control of the product formulation. The mixture of the phosphatidylcholine, phosphatidyl-ethanolamine, and phosphatidylinositol in lecithin was separated using aqueous methanol–acetonitrile solvent with a reversed-phase LC column, and detected as forms of pseudomolecular ions. Using this LC/ESI-MS technique, simultaneous separation and detection of phospholipid classes and molecular species within each class were achieved for the first time. Additionally informative fragmentation patterns were obtained by employing LC/ESI-MS/MS in both positive and negative ionization modes to identify these fatty acid chains and polar head groups in each molecular species of the phospholipids.

Analysis of t-butylphenol acetylene condensed resin with methyl-methine linkages in vulcanized rubber by pyrolysis-gas chromatography/mass spectrometry

Methyl-methine linkages of Novolac, a commercially available t-butylphenol acetylene condensed (TBPA) resin, have been identified by recognition of pyrolysis pathways using pyrolysis-gas chromatography/mass spectrometry (Py-GC/mS) in vulcanized rubber. The diagnostic mass spectrum of t-butylphenol with methyl-methine linkages between phenolic rings was observed at m/z 192, corresponding to 4-t-butyl-2-ethyl-6-methylphenol. Other molecular ions were observed at m/z 178, 164, and 150 in the characteristic pyrolyzates. The ion at m/z 192 in the TBPA resin was observed to be characteristic for methyl-methine linkages between the phenolic groups, and the analytical pyrolysis-GC/mS method was thus able to identify the resin at low levels in vulcanized rubber. Copyright 1999 John Wiley & Sons, Ltd.

Heavy Metal Determination by Inductively Coupled Plasma – Mass Spectrometry (ICP-MS) and Direct Mercury Analysis (DMA) and Arsenic Mapping by Femtosecond (fs) – Laser Ablation (LA) ICP-MS in Cereals

Abstract A study of the lead (Pb), cadmium (Cd), arsenic (As), and mercury (Hg) contents in popular cereals was conducted using inductively coupled plasma – mass spectrometry (ICP-MS), direct mercury analysis (DMA), and femtosecond laser ablation – inductively coupled plasma – mass spectrometry (fs-LA-ICP-MS). For Pb, Cd, and As determination, the samples were prepared using microwave digestion, while for Hg, the samples were homogenized and measured by DMA without additional pretreatment. Satisfactory values for all of the quality parameters that include the SD, limit of detection (LOD), limit of quantitation (LOQ), accuracy, and recovery were obtained, clearly validating the analytical techniques used in the current study. Recovery and accuracy measurements were done using rice flour CRM 108-01-002 from Korea Research Institute of Standards and Science (KRISS). All measured concentrations for these elements were lower than the national regulatory guideline values provided by the CODEX Alimentarius and Ministry of Food and Drug Safety. A sample from each group was also selected for an As distribution study within a grain using fs-LA-ICP-MS. As is classified as a first-class carcinogen by the International Agency for Research on Cancer (IARC). For adlay, oats, and barley, As was determined to be primarily distributed in the area where the grain splits, while for foxtail millet, sorghum and corn, As was concentrated in the grain embryo. Also, it was confirmed that the exposure of heavy metals in the diet was negligible due to the low metal concentrations consumed daily in these foods.