Injection of eluites in solvents stronger than the mobile phase in reversed-phase liquid chromatography

Influence of a strong sample solvent on analyte dispersion in chromatographic columns

“…2) is observed. The concentration distribution c a,m is thus found to be bimodal, a property which is seen in practice in RPLC [1][2][3][5][6][7]9,48,49]. As time goes by, the analyte spreads to a larger region with peak tailing increasing towards the upstream direction.…”

“…This occurs in isocratic elution [1][2][3][4][5][6][7][8] as well as in gradient elution [9,10], and can also happen in hydrophilic interaction liquid chromatography [11]. This is detrimental to the separation performance.…”

Using strong injection solvents with 100% aqueous mobile phase in RP-LC

“…Since analyte D was migrating at the slowest rate, it spent the longest amount of time traversing the rear boundary of the solvent plug and thus the focusing effect is most noticeable for peak D, with the effect becoming less noticeable for the faster migrating analytes A-C. It appears that in a previous study, the same phenomenon may have occurred for the case of a polar compound (phenylalanine) which was dissolved in the relatively strong solvent n-propanol [3]. The investigators observed that the phenylalanine peak had become somewhat sharper and eluted slightly faster, in contrast to the deteriorated peak shape of a more strongly retained analyte which showed typical fragmentation due to injection solvent effects.…”

“…Instead, the peak fragmented into two major bands, one remaining within the region of the ACN peak tail, and the other eluting significantly later as a severely broadened peak approaching the normal retention time. This type of peak splitting behavior is well known in the case where the injection solvent is less retained than the analyte [3][4][5]8]. Peak A, which eluted before the solvent front (as for MeOH), remained as a single, well-defined peak.…”

Determination of Pesticides in Complex Samples by One Dimensional (1D-), Two-Dimensional (2D-) and Multidimensional Chromatography

“…An important issue in comprehensive LC is the compatibility of the mobile phases in the two dimensions. The mobile phase eluting from the primary column is preferably consisting of a weak solvent constituent of the second dimension mobile phase in order to create a focusing effect (Hoffman et al, 1989 These incompatibility problems were already observed in 1D LC in the past when sample solvents were significantly different than the initial conditions of the mobile phase. When the first-dimension separation is 'undersampled', for example when the resolution obtained in the first-dimension is partially lost by the fraction collecting rate, the first dimension peak capacity ( 1 n c ) cannot be higher than the number of fractions taken and is defined as (Eeltink et al, 2009):…”