“…In recent years, several methods have been developed using ultra-high performance liquid chromatography (UHPLC) to improve separation of multi-class analytes in short run times (Aguilera-Luiz, Vidal, Romero-González, & Frenich, 2008;Frenich, Vidal, Romero-González, & Aguilera-Luiz, 2009;Peters, Bolck, Rutgers, Stolker, & Nielen, 2009;Ventura, Ramírez, Monfort, & Segura, 2009). Furthermore, the emergence of stable detector power sources allows the fast polarity switching with minimal delays as low as 20 ms to enable detection of both positively and negatively charged compounds in a single injection (Whelan et al, 2010).…”