Preparation of mixed-mode stationary phase for separation of peptides and proteins in high performance liquid chromatography

One-stop solution for wide polar range compounds: Preparation and application of quaternary ammonium salt molecular cage stationary phase

The separation and analysis of complex samples with wide polar range on a singular column is always a difficult problem in separation and analysis science. In this study, the RCC3-R molecular cage modified with the quaternary ammonium salt stationary phase (RCC3-GQ@silica) was successfully prepared and applicated in the separation of wide polar range compounds. In the Reverse Phase Liquid Chromatography (RPLC) mode, due to the hydrophobicity and π-π interactions provided by the cyclohexane and benzene rings in the molecular cage structure, this stationary phase demonstrated effective separation capabilities for alkylbenzenes, polycyclic aromatic hydrocarbons, phenols, and anilines. In the Hydrophilic Interaction Liquid Chromatography (HILIC) mode, the study explored the separation performance of this stationary phase for sugars and inorganic salts. Utilizing a mixed mode of HILIC/RPLC/Ion Exchange Chromatography (IEC), effective separation was achieved for sulfonamides, nucleosides, acids, and amino acids, indicating good separation effects for medium to strongly polar compounds as well as various hydrophilic compounds. Combining various separation modes, the RCC3-GQ@silica stationary phase successfully separated 91 compounds across 15 categories. These results not only demonstrate the potential of the stationary phase in expanding the range of polarities of analyzable compounds and achieving multipurpose use on a single column, but also confirm its effective separation of nucleosides in pure water systems, further emphasizing the significant application potential of RCC3-GQ@silica stationary phase in the field of green chemistry.

Preparation of halloysite nanotube-based monolithic column for small molecules and protein analysis

s: This study aimed to prepare a new separation medium, silane coupling agent KH570- modified halloysite nanotube (MPS-HNT) monolithic column, with excellent separation performance for small molecular compounds and macromolecular proteins. This was prepared using the principle of redox polymerization with modified HNTs as monomers. The optimal monomer proportion was obtained by optimizing the ratio of monomer, cross-linker, and pore-forming agent, which was evaluated using scanning electron microscopy, nitrogen adsorption, and mercury intrusion. The monolithic column exhibited a relatively homogeneous pore structure and good separation performance and permeability. As a high-performance liquid chromatography stationary phase, six small aromatic molecules were successfully separated in 6 min with a theoretical plate count of 35, 640 plates m-1 for benzene. Twenty-one peaks were separated from the fermentation mattress extract containing lipopeptide antibiotics on the MPS-HNT column. The separated chromatographic peaks further identified three lipopeptide antibiotics using matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF-MS) analysis. Twelve chromatographic peaks were isolated from chicken egg whites, and the eighth peak was identified as the lysozyme. The methodological validation of the lysozyme in chicken egg white showed that the linear correlation coefficient was 0.9996. The intraday and inter-day relative standard deviations were 3.1-4.0 % and 1.9-3.4 %, respectively. The spike recovery rate of lysozyme was 94.20-103.31 %. The overall column displayed good stability: the relative standard deviations of the peak area of six aromatic compounds and retention time were < 3.28 %.

Insight into Protein Engineering: From In silico Modelling to In vitro Synthesis

Protein engineering alters the polypeptide chain to obtain a novel protein with improved functional properties. This field constantly evolves with advanced in silico tools and techniques to design novel proteins and peptides. Rational incorporating mutations, unnatural amino acids, and post-translational modifications increases the applications of engineered proteins and peptides. It aids in developing drugs with maximum efficacy and minimum side effects. Currently, the engineering of peptides is gaining attention due to their high stability, binding specificity, less immunogenic, and reduced toxicity properties. Engineered peptides are potent candidates for drug development due to their high specificity and low cost of production compared with other biologics, including proteins and antibodies. Therefore, understanding the current perception of designing and engineering peptides with the help of currently available in silico tools is crucial. This review extensively studies various in silico tools available for protein engineering in the prospect of designing peptides as therapeutics, followed by in vitro aspects. Moreover, a discussion on the chemical synthesis and purification of peptides, a case study, and challenges are also incorporated.

Retention behavior of nucleosides and nucleobases on a 3 μm undecylenic acid-functionalized silica column in per aqueous liquid chromatography and hydrophilic interaction liquid chromatography separation modes

A 3 μm undecylenic acid-functionalized stationary phase (UAS) was prepared for the separation of nucleosides and nucleobases using per aqueous liquid chromatography (PALC) and hydrophilic interaction liquid chromatography (HILIC). The retention behaviors of nucleosides and nucleobases in PALC and HILIC modes were explored by adjusting parameters such as water content, buffer concentration, pH of the mobile phase and column temperature. The experimental data and separation chromatogram demonstrated that PALC could provide retention comparable to that of HILIC for nucleosides and nucleobases. Comparative studies using diluted adenosine solutions evaluated theoretical plates and peak shape for the same retention factors (between 0.25 and 5.0) in PALC and HILIC. There was no buffer component in the mobile phases used to operate the comparisons. HILIC mode is more efficient for adenosine than PALC mode at low retention factors. It's the exact opposite phenomenon for high retention factors. It is proposed that the mass transfer of adenosine between the UAS, the water-rich layer and the ACN-rich mobile phase in HILIC is relatively slow. Given the significant use of toxic ACN in HILIC, PALC emerges as a safer and more effective alternative for separating nucleosides and nucleobases.

A review of analytical parameters in 'rapid' liquid chromatographic methods for bioanalysis: Can we do better?

Rapid bioanalysis is beneficial to many applications. However, how 'rapid' a method is, or could be, is often an unanswered question. In this statistical review, the authors have assessed multiple pre-analytical (i.e. sample preparation), and analytical method parameters specifically for liquid chromatography to assist researchers in developing and validating 'rapid' bioanalytical methods. We restricted the search to urine and plasma matrices only. Data were extracted from over 2,000 recent studies and evaluated to assess how these parameters affected the 'on-instrument' analysis time. In addition to methods using ultra-violet (UV) detection, there were a large number of mass spectrometric (MS) methods, allowing additional review of the differences between high- and low-resolution MS on analysis time. We observed that most (N = 922, 70 %) methods used 5 or 10 cm columns, and that whilst uptake of ultra-high performance (U)HPLC columns was good, the use of sub-5 cm columns and/or flow rates in excess of 1 mL/min was incredibly rare (N = 25, 3 %). The detector of choice for quantitative (U)HPLC-MS remains the triple quadrupole, although a number of groups report the use of high-resolution MS for such methods.

Development and Validation of Novel HPLC Methods for Quantitative Determination of Vitamin D3 in Tablet Dosage Form

In the present work, an efficient isocratic HPLC method was developed for the precise and accurate estimation of vitamin D3 in tablet form. The chromatographic conditions comprised an L3 silica column (5 µm in particle size, 4.6 mm × 250 mm) with a mobile phase n-hexane/ethyl acetate (85:15 v/v) with a flow rate of 2.0 mL/min and a detection wavelength of 292 nm. The new methodology was validated for accuracy, precision, specificity, robustness, and quantification limits according to an official monograph of USP/BP and ICH guidelines. The peak areas of the six replicates of the homogeneous sample were recorded. The mean value obtained was 67,301, and the relative standard deviation (RSD) was 0.1741. The linearity and range were in the acceptable bounds, i.e., 0.999, which was calculated using regression line analysis. The results show that the method is truly acceptable as the RSD, as the flow rate was 0.81%, while for the mobile phase composition, it was 0.72%, which lies in the acceptable range. The limit of detection (LOD) and the limit of quantification (LOQ) values were 0.0539 µg/mL and 0.1633 µg/mL, respectively. The % RSD of the intra and inter-day precision of the method was deemed acceptable according to the international commission for harmonization guidelines. The developed method has potential to be used for the detection and quantification of vitamin D3 during routine analysis for tablets in dosage form.

Development of Narrow-Bore C18 Column for Fast Separation of Peptides and Proteins in High-Performance Liquid Chromatography

Separation with high efficiency and good resolution is constantly in demand in the pharmaceutical industry. The fast and efficient separation of complex samples such as peptides and proteins is a challenging task. To achieve high efficiency with good resolution, chromatographers are moving towards small particles packed into narrow-bore columns. Silica monolith particles (sub-2 µm) were derivatized with chlorodimethyl octadecyl silane (C18) and packed into stainless steel columns (100 mm × 1.8 mm i.d) by a slurry-packing method. The developed columns were used for the separation of peptides and proteins. A separation efficiency (N) of 40,000 plates/column (400,000 plates/m) was achieved for the mixture of five peptides. Similarly, the fast separation of the peptides was carried out using a high flow rate, and the separation of the five peptides was achieved in one minute with high efficiency (N ≅ 240,000 plates/m). The limit of detection (DL) and the limit of quantification (QL) for each analyte were determined by developing a linear regression curve with relatively very low concentrations of the target compound. The average values of the QL for the peptide and proteins were 0.55 ng and 0.48 ng, respectively, using short C18 column (1.8 mm × 100 mm) UV (at 214 nm). The fast analysis of peptides and proteins with such high efficiency and good resolution has not been reported in the literature yet. Owing to high efficiency, these home-made columns could be used as an alternative to the expensive commercial columns for peptide and protein separation.