Chromatographic studies of unusual on-column degradations of aniline compounds on XBridge Shield RP18 column in high pH aqueous mobile phase

Observation and confirmation of oxidation reactions occurring on ultra-high-performance liquid chromatography columns

“…). If the oxidization reaction occurred on the inlet frit, the oxidation products would be chromatographically separable from their parent compounds with independent peaks, as observed by Wang et al . and Myers et al .…”

“…The majority of the research concerning degradation of compounds on HPLC and UPLC columns has focused on degradation of macromolecules such as proteins, DNA, and polymers . Only two studies have, so far, reported on‐column (HPLC) degradation of small molecules . Wang et al .…”

“…Only two studies have, so far, reported on‐column (HPLC) degradation of small molecules . Wang et al . considered that the on‐column dimerization of anilines was a surface reaction caused by oxidation agents that were generated during complexation between unknown elements on the stationary phase surface of the X‐Bridge LC columns and ammonia in the high‐pH mobile phase.…”

“…This chelation was possibly in association with the stainless steel frits . Dimerization and nitrosation of amines occurring on HPLC columns have been reported when using high‐pH mobile phases containing ammonium hydroxide and acetonitrile (ACN) for separation …”

“…[26,27] Dimerization and nitrosation of amines occurring on HPLC columns have been reported when using high-pH mobile phases containing ammonium hydroxide and acetonitrile (ACN) for separation. [28,29] A redox (oxidation) reaction occurring on UPLC columns may negatively affect analysis of compounds that are susceptible to oxidation, such as polyphenolic compounds. Thus, it is necessary to ascertain the redox (oxidation) reaction occurring on UPLC columns and consequently find effective treatment to eliminate the negative effects.…”