Effect of pH and mobile phase additives on the chromatographic behaviour of an amide‐embedded stationary phase: Cyanocobalamin and its diaminemonochloro‐platinum(II) conjugate as a case study

Abstract

Several mobile phase additives (i.e., organic acids and their ammonium salts) were used to modulate the chromatographic retention of cyanocobalamin and its cis‐diaminemonochloroplatinum(II) conjugate, depending on the specific nature of the stationary phase. Regardless of the mobile phase additive, the positively charged cyanocobalamin‐cis‐diaminemonochloroplatinum(II) conjugate was systematically less retained than cyanocobalamin on a conventional octadecyl‐silica column. In contrast, the amide‐embedded C18 column exhibited a progressive increase in the conjugate retention time upon changing the mobile phase additive from organic (acetic, formic and trifluoroacetic) acids to ammonium salts, ultimately leading to an inversion of the elution order. This change of retention was interpreted by invoking the interplay between hydrophobic interactions, hydrogen bonding between the conjugate and the polar amide groups and the ion‐pairing ability of the lyophilic counterions, whereby the acetate anion was found to be the most suitable to control the solute retention.

Tandem mass spectrometry characterization of a conjugate between oleuropein and hydrated cis‐diammineplatinum(II)

“…CP ([Pt II (NH 3 ) 2 Cl 2 ]) exhibits a great affinity for cyano groups after aquation, which involves the facile loss of one or two chloride labile ligands, and the formation of monohydrated species (i.e., [Pt II (NH 3 ) 2 Cl(OH 2 )] + and Pt II (NH 3 ) 2 Cl(OH)) and a dihydroxylated complex ([Pt II (NH 3 ) 2 (OH) 2 ] + ) which are considered to be the active reaction intermediates . Methanol was used instead of acetonitrile as organic modifier of the mobile phase to separate the in vitro reaction mixture products, in combination with a reversed‐phase C18 amide‐embedded column . Figure shows the base peak chromatogram obtained in ESI positive ion mode by RPLC/ESI‐MS analysis.…”

“…26,24 Methanol was used instead of acetonitrile as organic modifier of the mobile phase to separate the in vitro reaction mixture products, in combination with a reversedphase C18 amide-embedded column. 26,32,33 Figure 2 shows the base peak chromatogram obtained in ESI positive ion mode by RPLC/ESI-MS analysis. Two main chromatographic peaks can be observed, with retention times 7.2 and 9.8 min, peaks 1 and 2, respectively; peak 2 was easily recognized as due to unreacted Ole, since a peak at the same retention time and an identical MS spectrum was obtained after injection of an Ole standard solution (data not shown).…”

Detection and quantification of Covid-19 antiviral drugs in biological fluids and tissues

“…Its quantification in plasma samples was carried out by using the peak signals at m/z 286.1 as precursor ion and at m/z 134.0 as product ion. The ionization efficiency of analytes undergoing quantification, can modulate well the selectivity of the LC-MS methods [ 149 ] and it can further be increased by promoting the ionization by proper desolvation temperature, gas flows and source settings [ 150 ]. When these strategies are not sufficient, the second easiest method to improve the selectivity of the method may be the replacement of the C18 phase with a different sort of stationary phase.…”

Analysis of Phospholipids, Lysophospholipids, and Their Linked Fatty Acyl Chains in Yellow Lupin Seeds (Lupinus luteus L.) by Liquid Chromatography and Tandem Mass Spectrometry

“…80% v/v) in the mobile phase. Thus, an efficient desolvation and ionization of compounds in the electrospray (ESI) source are guaranteed [19]. Moreover, a separation based on the head group polarity leads to simplified chromatograms of very complex mixtures with each peak/band almost corresponding to a specific PL class.…”