Evaluation of an ion mobility detector for supercritical fluid chromatography with solvent-modified carbon dioxide mobile phases

Process Development for the Instant Quantification of Lycopene from Agricultural Produces Using Supercritical Fluid Chromatography-Diode Array Detector (SFC-DAD)

A quick, simple, and reliable isocratic ultra-performance supercritical fluid chromatography-photodiode array detector (UPSFC-DAD) method was developed and validated to determine lycopene in different horticultural products. The effects of stationary phase, co-solvent, pressure, temperature, flow rate, and mobile phase additive on the separation of lycopene were evaluated. The developed method involved BEH-2EP—2.1 × 150 mm, 5 µm as the stationary phase, and CO2/MeOH 85:15 (v/v) with formic acid as the additive at 0.10% as the mobile phase. The column temperature was maintained at 45 °C, ABPR at 1800 psi, and the mobile phase’s flow rate was maintained at 1 mL/min. Under the optimized conditions, lycopene was successfully separated within 0.722 ± 0.001 min. The standard curve assayed over a range of 10 to 100 µg/mL resulted in a correlation coefficient of 0.998. The mean recoveries between 97.38% and 102.67% at different spiking levels with RSD < 2.5% were achieved. The intra and inter-day precision expressed as relative standard deviations (RSD) were found to range from 1.27% to 3.28% and from 1.57% to 4.18%, respectively. Robustness in terms of retention time (tR) and RSD were found to be 0.93 ± 0.23 min and less <2.80%, respectively. The limits of detection and quantification were 0.14 µg/mL and 0.37 µg/mL, respectively. This method was successfully applied to determine lycopene extracted from papaya, grapefruit, and bitter melon.

Ion mobility spectrometry-mass spectrometry (IMS-MS) of small molecules: separating and assigning structures to ions

The phenomenon of ion mobility (IM), the movement/transport of charged particles under the influence of an electric field, was first observed in the early 20th Century and harnessed later in ion mobility spectrometry (IMS). There have been rapid advances in instrumental design, experimental methods, and theory together with contributions from computational chemistry and gas-phase ion chemistry, which have diversified the range of potential applications of contemporary IMS techniques. Whilst IMS-mass spectrometry (IMS-MS) has recently been recognized for having significant research/applied industrial potential and encompasses multi-/cross-disciplinary areas of science, the applications and impact from decades of research are only now beginning to be utilized for "small molecule" species. This review focuses on the application of IMS-MS to "small molecule" species typically used in drug discovery (100-500 Da) including an assessment of the limitations and possibilities of the technique. Potential future developments in instrumental design, experimental methods, and applications are addressed. The typical application of IMS-MS in relation to small molecules has been to separate species in fairly uniform molecular classes such as mixture analysis, including metabolites. Separation of similar species has historically been challenging using IMS as the resolving power, R, has been low (3-100) and the differences in collision cross-sections that could be measured have been relatively small, so instrument and method development has often focused on increasing resolving power. However, IMS-MS has a range of other potential applications that are examined in this review where it displays unique advantages, including: determination of small molecule structure from drift time, "small molecule" separation in achiral and chiral mixtures, improvement in selectivity, identification of carbohydrate isomers, metabonomics, and for understanding the size and shape of small molecules. This review provides a broad but selective overview of current literature, concentrating on IMS-MS, not solely IMS, and small molecule applications.

Evaluation of capillary liquid chromatography-electrospray ionization ion mobility spectrometry with mass spectrometry detection

Due to the proteomics revolution, multi-dimensional separation and detection instruments are required to evaluate many peptides and proteins in single samples. In this study, electrospray ionization (ESI) ion mobility spectrometry (IMS) was evaluated as an additional separation after HPLC separations. Common HPLC mobile phase compositions (solvents, acid modifiers, and buffers) were assessed for the effect on ESI-IMS response. Up to 5 mM sodium phosphate, a non-volatile buffer, was able to be electrosprayed into the IMS without degradation of the instrumental performance. Due to the rapid separation times of IMS, multiple IMS spectra were obtained within a single HPLC peak. A five-peptide mixture was separated in a capillary HPLC column under isocratic conditions within 3 min. Coelution of two peaks due to non-optimal HPLC conditions occurred and these two peaks could not be distinguished by HPLC with UV detection. In contrast, the single ion mobility chromatograms provided separation of each peptide as well as providing a second degree of analyte identification (HPLC retention time and IMS mobility). Furthermore, IMS-MS analysis of the five peptides and comparison with HPLC retention times showed that each peptide had a unique retention time-ion mobility-mass to charge value. This work showed that IMS could be employed for direct separation and detection of HPLC eluents and also could be combined with HPLC-MS for three unique dimensions of separation.