Temperature-Programmed Packed Capillary Liquid Chromatography Coupled to Fourier-Transform Infrared Spectroscopy

Abstract

Temperature‐programmed packed capillary liquid chromatography has been coupled off‐line to Fourier‐transform infrared spectroscopy, utilizing a commercially available interface with a pneumatic nebulizer rebuilt to handle low flow rates at elevated temperatures. The modified interface showed excellent performance with regard to non‐aqueous reversed phase separations of polymer additives, resulting in constructed Gram‐Schmidt chromatograms comparable to chromatograms obtained using UV detection. The spray of the in‐house constructed nebulizer was not influenced by temperature changes of the column effluent, and hence temperature‐programmed gradient separations could be used successfully. The relative standard deviation of peak height was 4.4% (n = 5) and the mass limit of detection was determined to be about 40 ng, using a polymer antioxidant as model compound. The present instrumental coupling has been used for characterization of the antioxidant Irgafos P‐EPQ.

Analysis of polyolefin stabilizers and their degradation products

“…Irgafos 168 turned out to be easily oxidized 8, 10, 15–17, 52 and hydrolyzed (resulting in di‐ tert ‐butylphenol) 8. Irgafos P‐EPQ underwent oxidation 23, while Irgafos 126 was hydrolyzed 52. Oxidation of phosphite‐type stabilizers occurs – as already mentioned above – when they decompose a hydroperoxide.…”

“…In the recent publications (compare Tables 2(a) and (b)), HPLC under RP conditions is still dominating 7–9, 15, 19–22. The number of publications applying capillary chromatography 23–26, GC 14, 27, NP‐HPLC 10, TLC 28, and supercritical fluid chromatography (SFC) 12 is much lower. Also an electro‐driven separation of stabilizers was established 29; however, this approach was not pursued further.…”

“…The development of new ionization techniques promoted MS for highly sensitive and selective detection 10, 20–22, 24. Compared with MS, IR detection lost its importance 23. Evaporative light scattering detection (ELSD) is employed due to its advantage of being universal 8, 15, 24–26.…”

High-Temperature Liquid Chromatography and the Hyphenation with Mass Spectrometry Using High-Pressure Electrospray Ionization

“…54) For HTLC that uses pure water (without organic content) as the mobile phase, FID had been coupled to the FID directly. 23,55) For compounds that do not absorb UV light, other detection methods such as evaporative light scattering detection (ELSD), 56) nuclear magnetic resonance (NMR), 57) Fourier transform infrared spectroscopy (FTIR), 58) and IR absorbance and scattering detectors are also available. 59) Mass spectrometry e coupling of HTLC to MS had been performed using pneumatically-assisted ESI or APCI at >100 µL/min and with the use of ow restrictors of 50-64 µm.…”

Detection Modes with High Temperature Liquid Chromatography—A Review

“…The coupling between HTLC and FTIR was tested by Greibrokk et al (165). Their study of the separation of complex antioxidants demonstrates that temperature gradients did not influence the nebulizer spray performance or the solute deposition, making temperature programming preferable to solvent gradient elution.…”