“…Lobue et al (2019) have shown that for their method the ion‐pair method is more sensitive for three out of four oligonucleotides present, including a phosphorothioate. Another challenge is that HILIC may have greater difficulty achieving similar chromatographic resolution to ion‐pair chromatography since the mechanism of retention for different column chemistries is currently still under investigation (Gong & McCullagh, 2011; Li et al, 2012; Easter et al, 2013; Gong, 2017; Studzińska, Łobodziński, & Buszewski, 2017; Lobue et al, 2019). Studzinska provides the greatest insight into how column chemistries impact HILIC performance comparing several columns indirectly (Studzińska, Łobodziński, & Buszewski, 2017).…”