High peak capacity separations of peptides in reversed-phase gradient elution liquid chromatography on columns packed with porous shell particles

A flexible metal–organic framework with adaptive pores for high column-capacity gas chromatographic separation

A new zinc pyrazolyl-carboxylate framework with multi-mode and adaptive flexibility has been synthesized for efficient gas chromatographic separations.

Future perspectives in high efficient and ultrafast chiral liquid chromatography through zwitterionic teicoplanin-based 2-μm superficially porous particles

With the aim of pushing forward the limits of high efficient and ultrafast chiral liquid chromatography, a new Chiral Stationary Phase (CSP) has been prepared by covalently bonding the teicoplanin selector on 2.0μm Superficially Porous Particles (SPPs). An already validated bonding protocol, which permits to achieve teicoplanin-based CSPs exhibiting zwitterionic behaviour, has been employed to prepare not only the 2.0μm version of the CSP but also two other analogous CSPs based, respectively, on 2.7μm SPPs and 1.9μm Fully Porous Particles (FPPs). The kinetic performance of these CSPs has been compared through the analysis of both van Deemter curves and kinetic plots by employing in-house packed columns of 4.6mm internal diameter and different lengths (20, 50 and 100mm). In particular on the columns packed with 2.0μm SPPs, extremely large efficiencies were observed for both achiral (>310,000 theoretical plates/meter, N/m; h_r: 1.61) and chiral compounds (>290,000 N/m; h_r: 1.72) in HILIC conditions. Thanks to their efficiency and enantioselectivity, these CSPs were successfully employed in ultrafast chiral separations. As an example, the enantiomers of haloxyfop were baseline resolved in about 3s, with a resolution higher than 2.0, (flow rate: 8mL/min) on a 2cm long column packed with the 2.0μm chiral SPPs.

Recent advancements and future directions of superficially porous chiral stationary phases for ultrafast high-performance enantioseparations

This review focuses on the use of superficially porous particles (SPPs) as chiral stationary phases for ultra-high performance liquid enantioseparations.

The use of ammonium formate as a mobile-phase modifier for LC-MS/MS analysis of tryptic digests

A major challenge facing current mass spectrometry (MS)-based proteomics research is the large concentration range displayed in biological systems, which far exceeds the dynamic range of commonly available mass spectrometers. One approach to overcome this limitation is to improve online reversed-phase liquid chromatography (RP-LC) separation methodologies. LC mobile-phase modifiers are used to improve peak shape and increase sample load tolerance. Trifluoroacetic acid (TFA) is a commonly used mobile-phase modifier, as it produces peptide separations that are far superior to other additives. However, TFA leads to signal suppression when incorporated with electrospray ionization (ESI), and thus, other modifiers, such as formic acid (FA), are used for LC-MS applications. FA exhibits significantly less signal suppression, but is not as effective of a modifier as TFA. An alternative mobile-phase modifier is the combination of FA and ammonium formate (AF), which has been shown to improve peptide separations. The ESI-MS compatibility of this modifier has not been investigated, particularly for proteomic applications. This work compares the separation metrics of mobile phases modified with FA and FA/AF and explores the use of FA/AF for the LC-MS analysis of tryptic digests. Standard tryptic-digest peptides were used for comparative analysis of peak capacity and sample load tolerance. The compatibility of FA/AF in proteomic applications was examined with the analysis of soluble proteins from canine prostate carcinoma tissue. Overall, the use of FA/AF improved online RP-LC separations and led to significant increases in peptide identifications with improved protein sequence coverage.

Optimization of data-dependent acquisition parameters for coupling high-speed separations with LC-MS/MS for protein identifications

Recent developments in chromatography, such as ultra-HPLC and superficially porous particles, offer significantly improved peptide separation. The narrow peak widths, often only several seconds, can permit a 15-min liquid chromatography run to have a similar peak capacity as a 60-min run using traditional HPLC approaches. In theory, these larger peak capacities should provide higher protein coverage and/or more protein identifications when incorporated into a proteomic workflow. We initially observed a decrease in protein coverage when implementing these faster chromatographic approaches, due to data-dependent acquisition (DDA) settings that were not properly set to match the narrow peak widths resulting from newly implemented, fast separation techniques. Oversampling of high-intensity peptides lead to low protein-sequence coverage, and tandem mass spectra (MS/MS) from lower-intensity peptides were of poor quality, as automated MS/MS events were occurring late on chromatographic peaks. These observations led us to optimize DDA settings to use these fast separations. Optimized DDA settings were applied to the analysis of Trypanosome brucei peptides, yielding peptide identifications at a rate almost five times faster than previously used methodologies. The described approach significantly improves protein identification workflows that use typical available instrumentation.

On-line comprehensive two dimensional separations of charged compounds using reversed-phase high performance liquid chromatography and hydrophilic interaction chromatography. Part II: application to the separation of peptides

In this second paper of a two-part series, on-line RPLC×HILIC is compared to on-line RPLC×RPLC through the separation of peptides. Our choices regarding the conditions are discussed. Injection effects and overloading effects are evaluated in both configurations. It is shown that whereas large volumes can be injected in the second dimension in RPLC×RPLC under HT-UHPLC conditions (>20% of the column dead volume), even small injection volumes (8% of the column the dead volume) have a detrimental effect on peak shapes in RPLC×HILIC. Advantages and limits of the two 2D-systems are compared through the 2D-separation of a tryptic digest of three proteins. A ten-fold gain in analysis time along with a significant gain in peak capacity are obtained with both systems compared to the most efficient one-dimensional separation of peptides recently published.

Optimization of gradient reversed phase chromatographic peak capacity for low molecular weight solutes

A general protocol for optimizing peak capacity for the separation of low molecular weight molecules under gradient elution conditions has not yet been developed. By studying the effects of gradient time, flow rate, temperature, final eluent composition, and column length on peak capacity, a protocol has been developed for the optimization of a separation of small molecules such as those seen in metabolomic studies. The strategy developed employs the Linear-Solvent-Strength Theory (LSS Theory) to predict retention, building on an approach for the optimization of the peak capacity of large molecules (peptides) in fixed column format separations.

Advanced proteomic liquid chromatography

Liquid chromatography coupled with mass spectrometry is the predominant platform used to analyze proteomics samples consisting of large numbers of proteins and their proteolytic products (e.g., truncated polypeptides) and spanning a wide range of relative concentrations. This review provides an overview of advanced capillary liquid chromatography techniques and methodologies that greatly improve separation resolving power and proteomics analysis coverage, sensitivity, and throughput.

Comparison of columns packed with porous sub-2 microm particles and superficially porous sub-3 microm particles for peptide analysis at ambient and high temperature

The objective of this study was to evaluate various chromatographic approaches for peptide analysis. Initially, the ultra-HPLC (UHPLC) strategy, which consists of using columns packed with sub-2 microm particles at a maximal pressure of 1000 bar, was tested. To limit the backpressure generated by small particles, columns packed with superficially porous sub-3 microm particles (fused-core technology) that should theoretically improve mass transfer, particularly beneficial for large biomolecules, were investigated. To evaluate these claims, kinetic plots were constructed in both isocratic and gradient modes at ambient and elevated temperature (up to 90 degrees C). For peptide analysis, both UHPLC and fused-core technologies showed a significant gain in peak capacity when compared with conventional HPLC using 5 mum particles and monolithic supports. Additionally, it has been shown that high temperature was of utmost interest to further improve kinetic performance and peak shape due to the improvement of secondary interaction kinetics. Finally, the best conditions developed for UHPLC using the gradient kinetic plot methodology were applied to the analysis of a complex tryptic digest of various proteins. The expected and experimental peak capacity values obtained were similar. In addition, the resolving power of UHPLC at 60 degrees C was appropriate for resolving complex mixtures of peptides.

Fast and sensitive determination of Polysorbate 80 in solutions containing proteins

A fast and sensitive method has been developed for the specific determination of Polysorbate 80 (Tween 80) in liquid formulations in the presence of proteins and excipients. The quantitative determination is based on a fast liquid chromatographic (HPLC) separation and charged aerosol detection (CAD). The method was validated using a Poroshell 300SB-C18 column packed with 5 microm shell particles (75 mm x 2.1 mm) and acetonitrile-methanol-water-trifluoroacetic acid mobile phase at a flow rate of 0.65 ml/min. The rapid LC-CAD method is suitable for quantifying Polysorbate 80 in the range of 10-60 microg/ml in protein solutions within good manufacturing practices (GMPs) of the pharmaceutical industry.

Approaches to comprehensive multidimensional liquid chromatography systems

This work compares the performance of the three different schemes implementing two-dimensional liquid chromatography (2D-LC) in terms of the peak capacity that they can generate and of the time that they need to complete a two-dimensional analysis. We discuss in detail how time is spent in these two-dimensional liquid chromatography x liquid chromatography (LC x LC) schemes and how to compare them. Keeping constant the characteristics of the first-dimension separation, we systematically varied those of the second-dimension separation and of its coupling to the first-dimension. In the process, five systems were created, based on the principles of the three known implementations of comprehensive 2D-LC. This work demonstrates an original method for the selection of the best comprehensive 2D-LC approach, depending on the desired peak capacity and on time constraints. The decision to use a 2D-LC method arises from the need to achieve a given resolution (i.e., a target peak capacity) within as short a time as possible or to reach the highest possible resolution in a given analysis time. Using the most appropriate schemes, we suggest how it is realistically possible to generate peak capacities ranging from 266 in just over 20 min or about 2800 in 2.3 h. When the time available for a two-dimensional separation is very short and the desired peak capacity cannot be achieved in 1D-LC, an on-line 2D-LC approach is unquestionably best. However, if a longer analysis time is acceptable, a 10-fold increase in the peak capacity can be obtained at the cost of a mere 7-fold increase in total analysis time.