Abstract: Alkylphenol polyethoxylates (APEs) are a widely used group of nonionic surfactants in commercial production. Characterization of the composition of APE mixtures can be exploited for the determination of their most effective uses. In this study sample mixtures contain nonylphenol polyethoxylates and octylphenol polyethoxylates. The separation of individual alkylphenols by ethoxylate units is performed by supercritical fluid chromatography (SFC)-UV as well as normal-phase high-performance liquid chromatographic (HPLC)-UV employing packed columns. The stationary phase and column length are varied in the SFC setup to produce the most favorable separation conditions. Additionally, combinations of packed columns of different stationary phases are tested. The combination of a diol and a cyano column is found to produce optimal results. An advantage of using packed columns instead of capillary columns is the ability to inject large amounts of sample and thus collect eluted fractions. In this regard, fractions from SFC runs are collected and analyzed by flow injection analysis-electrospray ionization-mass spectroscopy in order to positively identify the composition of the fractions. In comparing the separation of APE mixtures by SFC and HPLC, it is found that SFC provides shorter retention times with similar resolution. In addition, less solvent waste is produced using SFC.

Abstract: A supercritical fluid chromatography-chemiluminescence nitrogen detection (SFC-CLND) system for open tubular columns is described. The chemistry for the post-restrictor detector is based on the chemiluminescent reaction between ozone generated from oxygen and nitric oxide via high-temperature pyrolysis of nitrogen-containing compounds. The minimum detectable quantity is found to be 60 pg nitrogen of indole by flow injection analysis. Detector linearity was at least three orders of magnitude, and a selectivity of 10(5) was obtained. Several applications of SFC-CLND in the analysis of compounds containing nitrogen are presented.