Fused-core particle technology as an alternative to sub-2-μm particles to achieve high separation efficiency with low backpressure

Reversed-Phase Liquid Chromatography of Peptides for Bottom-Up Proteomics: A Tutorial

The performance of the current bottom-up liquid chromatography hyphenated with mass spectrometry (LC-MS) analyses has undoubtedly been fueled by spectacular progress in mass spectrometry. It is thus not surprising that the MS instrument attracts the most attention during LC-MS method development, whereas optimizing conditions for peptide separation using reversed-phase liquid chromatography (RPLC) remains somewhat in its shadow. Consequently, the wisdom of the fundaments of chromatography is slowly vanishing from some laboratories. However, the full potential of advanced MS instruments cannot be achieved without highly efficient RPLC. This is impossible to attain without understanding fundamental processes in the chromatographic system and the properties of peptides important for their chromatographic behavior. We wrote this tutorial intending to give practitioners an overview of critical aspects of peptide separation using RPLC to facilitate setting the LC parameters so that they can leverage the full capabilities of their MS instruments. After briefly introducing the gradient separation of peptides, we discuss their properties that affect the quality of LC-MS chromatograms the most. Next, we address the in-column and extra-column broadening. The last section is devoted to key parameters of LC-MS methods. We also extracted trends in practice from recent bottom-up proteomics studies and correlated them with the current knowledge on peptide RPLC separation.

Assessment of greenness for the determination of voriconazole in reported analytical methods

Analytical research with adverse environmental impact has caused a severe rise in concern about the ecological consequences of its strategies, most notably the use and emission of harmful solvents/reagents into the atmosphere. Nowadays, industries are searching for the best reproducible methods. Voriconazole is a second-generation azole derivative used effectively in the treatment of Candida and Aspergillus species infections and oropharyngeal candidiasis in AIDS patients. Recently it has become the drug of choice in treating mucormycosis in several countries, which raises the need for production in large quantities. The present review deals with various recent important analytical techniques used to estimate voriconazole and its combination in pharmaceutical formulations and biological fluids. The methods show their own unique way of analyzing voriconazole in different matrices with excellent linearity, detection, and quantification limits. Additionally, this article deals with methods and solvents analyzed for their impact on the environment. This is followed by estimating the degree of greenness of the methods using various available assessment tools like analytical eco-scale, national environmental method index, green analytical procedure index, and AGREE metrics to confirm the environmental impact. The scores obtained with the evaluation tools depict the quantum of greenness for the reported methods and provide an ideal approach adopted for VOR estimation. Very few methods are eco-friendly, which shows that there is a need for the budding analyst to develop methods based on green analytical principles to protect the environment.

Development and Validation of a Stability-Indicating Reversed-Phase High Performance Liquid Chromatography Method for Assay of Doramectin and Estimation of its Related Substances in Commercial Batches of Doramectin Drug Substance

BACKGROUND

Doramectin is a broad-spectrum antiparasitic drug used in veterinary medicine. It belongs to the family of avermectins which possess a macrocyclic lactone structure and is widely used for the treatment of parasites. Objective: This study was aimed to develop a stability-indicating reversed phase high performance liquid chromatography (RP-HPLC) method for assay and identification of doramectin including identification and estimation of its related substances in commercial batches of doramectin drug substance.

METHOD

Methanol (MeOH) was used to dissolve and prepare doramectin samples. Doramectin and its related substances were separated on a HALO C8 (100 mm × 4.6 mm i.d., 2.7 µm particle size) column maintained at 40 °C using an isocratic HPLC method with mobile phase composed of acetonitrile (ACN)-water (70 + 30, v/v). Analytes were detected with UV detection at 245 nm and quantitated against a single point external reference standard of doramectin. The quantitation limit (QL) of the method is 0.1% of target concentration as described in the method. Results: The HPLC method can separate all analytes of interest by an isocratic elution within 10 min. The method was validated according to the guidelines described in The International Conference on Harmonization (ICH) Q2(R1). Conclusions: The HPLC method for assay of doramectin and estimation of its related substances was successfully developed, validated, and demonstrated to be accurate, robust, specific, and stability-indicating. Highlights: This is the first known paper to report a HPLC method for assay of doramectin and estimation of its related substances in commercial batches of doramectin drug substance.

Fundamental to achieving fast separations with high efficiency: A review of chromatography with superficially porous particles

Types of particles have been fundamental to LC separation technology for many years. Originally, LC columns were packed with large-diameter (>100 μm) calcium carbonate, silica gel, or alumina particles that prohibited fast mobile-phase speeds because of the slow diffusion of sample molecules inside deep pores. During the birth of HPLC in the 1960s, superficially porous particles (SPP, ≥30 μm) were developed as the first high-speed stationary-phase support structures commercialized, which permitted faster mobile-phase flowrates due to the fast movement of sample molecules in/out of the thin shells. These initial SPPs were displaced by smaller totally porous particles (TPP) in the mid-1970s. But SPP history repeated when UHPLC emerged in the 2000s. Stationary-phase support structures made from sub-3-μm SPPs were introduced to chromatographers in 2006. The initial purpose of this modern SPP was to enable chromatographers to achieve fast separations with high efficiency using conventional HPLCs. Later, the introduction of sub-2-μm SPPs with UHPLC instruments pushed the separation speed and efficiency to a very fast zone. This review aims at providing readers a comprehensive and up-to-date view on the advantages of SPP materials over TPPs historically and theoretically from the material science angle.

Mass Spectrometry-Based Microbial Metabolomics: Techniques, Analysis, and Applications

The demand for understanding the roles genes play in biological systems has steered the biosciences into the direction the metabolome, as it closely reflects the metabolic activities within a cell. The importance of the metabolome is further highlighted by its ability to influence the genome, transcriptome, and proteome. Consequently, metabolomic information is being used to understand microbial metabolic networks. At the forefront of this work is mass spectrometry, the most popular metabolomics measurement technique. Mass spectrometry-based metabolomic analyses have made significant contributions to microbiological research in the environment and human disease. In this chapter, we break down the technical aspects of mass spectrometry-based metabolomics and discuss its application to microbiological research.

Mass spectrometry detection of basic drugs in fast chiral analyses with vancomycin stationary phases

Current trends in chiral analysis of pharmaceutical drugs are focused on faster separations and higher separation efficiencies. Core-shell or superficially porous particles (SPP) based chiral stationary phases (CSPs) provide reduced analysis times while maintaining high column efficiencies and sensitivity. In this study, mobile phase conditions suitable for chiral analyses with electrospray ionization LC-MS were systematically investigated using vancomycin as a representative CSP. The performance of a 2.7 µm SPP based vancomycin CSP (SPP-V) 10 cm × 0.21 cm column was compared to that of a corresponding 5 µm fully porous particles based analogue column. The results demonstrated that the SPP-V column provides higher efficiencies, 2-5 time greater sensitivity and shorter analysis time for a set of 22 basic pharmaceutical drugs. The SPP-V was successfully applied for the analysis of the degradation products of racemic citalopram whose enantiomers could be selectively identified by MS.

Novel comprehensive multidimensional liquid chromatography approach for elucidation of the microbosphere of shikimate-producing Escherichia coli SP1.1/pKD15.071 strain

Shikimic acid is a intermediate of aromatic amino acid biosynthesis and the preferred starting material for production of the most commonly prescribed anti-influenza drug, Tamiflu. Its six-membered carbocyclic ring is adorned with several chiral centers and various functionalities, making shikimic acid a valuable chiral synthon. When microbially-produced, in addition to shikimic acid, numerous other metabolites are exported out of the cytoplasm and accumulate in the culture medium. This extracellular matrix of metabolites is referred to as the microbosphere. Due to the high sample complexity, in this study, the microbosphere of shikimate-producing Escherichia coli SP1.1/pKD15.071 was analyzed by liquid chromatography and comprehensive two-dimensional liquid chromatography coupled to photodiode array and mass spectrometry detection. GC analysis of the trimethylsilyl derivatives was also carried out in order to support the elucidation of the selected metabolites in the microbosphere. The elucidation of the metabolic fraction of this bacterial strain might be of valid aid for improving, through genetic changes, the concentration and yield of shikimic acid synthesized from glucose. Graphical abstract.

Comparing monolithic and fused core HPLC columns for fast chromatographic analysis of fat-soluble vitamins

HPLC stationary phases of monolithic and fused core type can be used to achieve fast chromatographic separation as an alternative to UPLC. In this study, monolithic and fused core stationary phases are compared for fast separation of four fat-soluble vitamins. Three new methods on the first and second generation monolithic silica RP-18e columns and a fused core pentafluoro-phenyl propyl column were developed. Application of three fused core columns offered comparable separations of retinyl palmitate, DL-α-tocopheryl acetate, cholecalciferol and menadione in terms of elution speed and separation efficiency. Separation was achieved in approx. 5 min with good resolution (Rs > 5) and precision (RSD ≤ 0.6 %). Monolithic columns showed, however, a higher number of theoretical plates, better precision and lower column backpressure than the fused core column. The three developed methods were successfully applied to separate and quantitate fat-soluble vitamins in commercial products.

Separation of peptides on superficially porous particle based macrocyclic glycopeptide liquid chromatography stationary phases: consideration of fast separations

Macrocyclic glycopeptide based liquid chromatography stationary phases are known for their highly selective peptide separations. Fast and ultrafast (t _R < 1 min) high-efficiency separations were achieved with superficially porous particle (SPP)-based stationary phases. Separations of pharmaceutically important classes of peptides such as enkephalins and bradykinins have been achieved in less than 5 min in isocratic elution modes. Selectivity for peptides structurally similar to one another was increased with use of teicoplanin-based stationary phases compared with commercial C₁₈ stationary phases. Ultrafast isocratic separations of structurally related peptides were achieved with teicoplanin- and vancomycin-based short SPP columns. Acidic mobile phases produced better separations. Ammonium formate was the optimal mobile phase buffer additive. Use of an appropriate combination of a macrocyclic glycopeptide stationary phase and a mobile phase permits faster and more electrospray ionization mass spectrometry compatible isocratic separations than previous gradient approaches. The tryptic peptide separation characteristics of the teicoplanin stationary phase are demonstrated. Additionally, compared with commercial C₁₈ stationary phases, teicoplanin showed tryptic peptide separations with different selectivities. Graphical Abstract Ultrafast separation of enkephalin peptide epimers.

A new approach to the rapid separation of isomeric compounds in a Silybum marianum extract using UHPLC core-shell column with F5 stationary phase

In this paper, a new ultra-high performance liquid chromatography (UHPLC) method using a core-shell column with a pentafluorophenyl stationary phase for separation of seven active compounds of a Silybum marianum extract was developed and validated. Silymarin, an extract of Silybum marianum, is known for its abilities to protect the liver from toxic substances, hepatitis therapy, and anti-tumour activity. Silymarin is currently being widely used in commercial preparations and herbal teas. Separation of seven compounds contained in the Silybum marianum extract (taxifolin, silychristin, silydianin, silybin A, silybin B, isosilybin A, isosilybin B) and other substances occurring in real samples was performed on the Kinetex 1.7μ F5 100A (150×2.1mm), 1.7μm particle size core-shell column, with a mobile phase methanol/100mM phosphate buffer pH 2.0 according to the gradient program. A mobile phase 0.35mLmin-1 flow rate and 50°C temperature was used for the separation. The detection wavelength was set at 288nm. Under optimal chromatographic conditions, good linearity with a correlation coefficient of R2 >0.999 for all compounds was achieved. The available commercial samples of herbal teas and food supplements were extracted with methanol using an ultrasonic bath. After dilution with water and centrifugation, a 2μL sample of the filtered supernatant was directly injected into the UHPLC system. The use of a pentafluorophenyl stationary phase with methanol as the organic component of the mobile phase showed new ways to effectively separate isomeric compounds in herbal extracts, which could not be done with the conventional C18 stationary phase.

Quantification of Oxidized and Unsaturated Bile Alcohols in Sea Lamprey Tissues by Ultra-High Performance Liquid Chromatography-Tandem Mass Spectrometry

A sensitive and reliable method was developed and validated for the determination of unsaturated bile alcohols in sea lamprey tissues using liquid-liquid extraction and ultra-high performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS). The liver, kidney, and intestine samples were extracted with acetonitrile and defatted by n-hexane. Gradient UHPLC separation was performed using an Acquity BEH C18 column with a mobile phase of water and methanol containing 20 mM triethylamine. Multiple reaction monitoring modes of precursor-product ion transitions for each analyte was used. This method displayed good linearity, with correlation coefficients greater than 0.99, and was validated. Precision and accuracy (RSD %) were in the range of 0.31%-5.28%, while mean recoveries were between 84.3%-96.3%. With this technique, sea lamprey tissue samples were analyzed for unsaturated bile alcohol analytes. This method is practical and particularly suitable for widespread putative pheromone residue analysis.

Simultaneous analysis of 210 prohibited substances in human urine by ultrafast liquid chromatography/tandem mass spectrometry in doping control

RATIONALE

Doping analysis is a two-step process consisting of a screening step for prohibited substances and a confirmation step to verify the presence of specific substances found during the screening. The entire process must be performed within a limited time period, but traditional screening procedures commonly employ separate analytical methods for each class of prohibited substances being screened and thus require a great deal of human resources and instrumentation. A single simple and rapid multiresidue analytical method that could accommodate multiple classes of prohibited substances would be extraordinarily useful in doping analyses.

METHODS

Urine samples were extracted via two consecutive liquid-liquid extractions at different pH values following enzymatic hydrolysis. Analyses were performed by ultrafast liquid chromatography/triple-quadrupole mass spectrometry with polarity switching and time-dependent selected reaction monitoring.

RESULTS

We developed a rapid multiresidue screening and confirmation method for efficient high-throughput doping analyses. The present method was validated with regard to the limits of detection (0.01-100.0 ng/mL for screening analyses and 0.2-500.0 ng/mL for confirmation assays), matrix effects (48.9-118.9%), recovery (20.6-119.7%) and intra- (0.6-17.6%) and inter-day (4.0-20.0%) precision.

CONCLUSIONS

A multiresidue analytical method was developed and validated for screening and confirming the presence of performance-enhancing drugs. A total of 210 substances from diverse classes of prohibited substances were successfully identified with an analytical run time of 10 min.

High-throughput salting-out-assisted liquid-liquid extraction for the simultaneous determination of atorvastatin, ortho-hydroxyatorvastatin, and para-hydroxyatorvastatin in human plasma using ultrafast liquid chromatography with tandem mass spectrometry

A high-throughput, specific, and rapid liquid chromatography with tandem mass spectrometry method was established and validated for the simultaneous determination of atorvastatin and its two major metabolites, ortho-hydroxyatorvastatin and para-hydroxyatorvastatin, in human plasma. A simple salting-out-assisted liquid-liquid extraction using acetonitrile and a mass-spectrometry-friendly salt, ammonium acetate, was employed to extract the analytes from human plasma. A recovery of more than 81% for all analytes was achieved in 1 min extraction time. Chromatographic separation was performed on a Kinetex XB C18 column utilizing a gradient elution starting with a 60% of water solution (1% formic acid), followed by increasing percentages of acetonitrile. Analytes were detected on a tandem mass spectrometer equipped with an electrospray ionization source that was operated in the positive mode, using the transitions of m/z 559.3 → m/z 440.2 for atorvastatin, and m/z 575.3 → m/z 440.2 for both ortho- and para-hydroxyatorvastatin. Deuterium-labeled compounds were used as the internal standards. The method was validated over the concentration ranges of 0.0200-15.0 ng/mL for atorvastatin and ortho-hydroxyatorvastatin, and 0.0100-2.00 ng/mL for para-hydroxyatorvastatin with acceptable accuracy and precision. It was then successfully applied in a bioequivalence study of atorvastatin.

Off-line two dimensional isoelectrofocusing-liquid chromatography/mass spectrometry (time of flight) for the determination of the bioactive peptide lunasin

Progress in liquid chromatography and mass spectrometry technologies offers a great opportunity for the determination of bioactive peptides. Nevertheless, in many cases, the direct application of this technology does not enable the detection of the investigated peptides due to serious signal suppression. This is the case of lunasin, a cancer preventive, anti-inflammatory, and cholesterol-reducing peptide originally isolated from soybean and later found in some cereals. Most methods applied for the quantitation of this peptide were immunological and based on the detection of just a fragment of the lunasin sequence. At this regard, there is a peptide commercially available with a sequence similar to lunasin but differing in just one amino acid that has been wrongly used for the quantitation of lunasin. The use of high resolution mass spectrometry has enabled to be aware of this issue and of the need for new methods enabling the reliable identification and determination of lunasin. However, when different approaches were evaluated in this work for the reduction of the interferences originating signal suppression, such as matrix dilution, previous lunasin purification by reversed-phase or ion-exchange solid-phase extraction, and use of different chromatographic columns, no one resulted successful in the case of soybean. Just a one-dimensional separation of the soybean extract by isoelectrofocusing followed by a second dimension separation by reversed-phase liquid chromatography enabled a significant reduction of matrix interferences and the detection of lunasin in soybean products by high resolution mass spectrometry with a time of flight (TOF) analyzer. After method optimization, selectivity, linearity, accuracy, precision, and limits of detection and quantitation were evaluated, being possible to quantitate as low as 25ng/mL (1.5μg lunasin/g protein). Concentration of lunasin in the analyzed soybean flour and textured soybean ranged from 14.0 to 22.5mg lunasin/g protein.

Silica, hybrid silica, hydride silica and non-silica stationary phases for liquid chromatography

Free silanols on the surface of silica are the "villains", which are responsible for detrimental interactions of those compounds and the stationary phase (i.e., bad peak shape, low efficiency) as well as low thermal and chemical stability. For these reasons, we began this review describing new silica and hybrid silica stationary phases, which have reduced and/or shielded silanols. At present, in liquid chromatography for the majority of analyses, reversed-phase liquid chromatography is the separation mode of choice. However, the needs for increased selectivity and increased retention of hydrophilic bases have substantially increased the interest in hydrophilic interaction chromatography (HILIC). Therefore, stationary phases and this mode of separation are discussed. Then, non-silica stationary phases (i.e., zirconium oxide, titanium oxide, alumina and porous graphitized carbon), which afford increased thermal and chemical stability and also selectivity different from those obtained with silica and hybrid silica, are discussed. In addition, the use of these materials in HILIC is also reviewed.

HPLC column-switching technique for sample preparation and fluorescence determination of propranolol in urine using fused-core columns in both dimensions

A new and fast high-performance liquid chromatography (HPLC) column-switching method using fused-core columns in both dimensions for sample preconcentration and determination of propranolol in human urine has been developed. On-line sample pretreatment and propranolol preconcentration were performed on an Ascentis Express RP-C-18 guard column (5 × 4.6 mm), particle size, 2.7 μm, with mobile phase acetonitrile/water (5:95, v/v) at a flow rate of 2.0 mL min(-1) and at a temperature of 50 °C. Valve switch from pretreatment column to analytical column was set at 4.0 min in a back-flush mode. Separation of propranolol from other endogenous urine compounds was achieved on the fused-core column Ascentis Express RP-Amide (100 × 4.6 mm), particle size, 2.7 μm, with mobile phase acetonitrile/water solution of 0.5% triethylamine, pH adjusted to 4.5 by means of glacial acetic acid (25:75, v/v), at a flow rate of 1.0 mL min(-1) and at a temperature of 50 °C. Fluorescence excitation/emission detection wavelengths were set at 229/338 nm. A volume of 1,500 μL of filtered urine sample solution was injected directly into the column-switching HPLC system. The total analysis time including on-line sample pretreatment was less than 8 min. The experimentally determined limit of detection of the method was found to be 0.015 ng mL(-1).

LC-ESI-TOF MS method for the evaluation of the immunostimulating activity of soybeans via the determination of the functional peptide soymetide

Bioactive peptides content in foodstuffs can seriously vary with many factors such as crop variety, food processing, animal breeding, etc. Because of this variability, quantitative methodologies are required to evaluate the content of bioactive peptides in foodstuffs. Progress in liquid chromatography and mass spectrometry technologies offer a great opportunity for the quantitation of bioactive peptides. This study undertook the development of a liquid chromatography-electrospray ionization-time-of-flight mass spectrometry method using a fused-core technology column for the sensitive and unambiguous determination of the immunostimulating peptide soymetide in soybean varieties. Soymetide precursor protein (α' subunit of β-conglycinin) was extracted with a Tris-HCl buffer (pH 8.0) containing urea and digested with trypsin. Soymetide separation conditions by reversed phase liquid chromatography (ion-pairing reagent, organic modifier, separation column, and elution gradient) and detection by MS were optimized, and a study of soymetide stability was also conducted. The method selectivity having been demonstrated, the linearity, accuracy, precision, and limits of detection and quantitation were evaluated. The developed method enabled the detection and quantitation of soymetide concentrations in the ppb range (7.5 ng/mL and 25 ng/mL, respectively), and about 30 times lower than those detected and determined in a previous work by capillary liquid chromatography with UV detection. These values could allow the quantitation of only 17 μg of soymetide per gram of soybean. The developed methodology was applied to the quantitation of soymetide in different soybean varieties from Europe, Japan, and USA observing great differences in soymetide content that ranged from 40 to 600 μg per gram of soybean depending on the soybean variety.

Fused-core particle technology in high-performance liquid chromatography: An overview

The advent of superficially porous particles (SPPs) for packed HPLC columns has changed the way that many practitioners have approached the problem of developing needed separations. The very high efficiency of such columns, combined with convenient operating conditions, modest back pressures and the ability to use conventional HPLC instruments has resulted in intense basic studies of SPP technology, and widespread applications in many sciences. This report contains an overview of the SPP technology first developed in 2006 by Advanced Materials Technology, Inc., for sub-3-μm particles, then expanded into a family of SPP products with different particle sizes, pore sizes and other physical parameters. This approach was designed so that each particle of the family could be optimized for separating a particular group of compounds, usually based on solute size.

An improved approach to hydrophilic interaction chromatography of peptides: salt gradients in the presence of high isocratic acetonitrile concentrations

Hydrophilic interaction chromatography (HILIC) for separations of peptides has been employed infrequently, particularly considering that this technique was introduced over 20 years ago. The present manuscript describes a radical departure from the traditional HILIC elution approach, where separations are achieved via increasing salt (sodium perchlorate) gradients in the presence of high isocratic concentrations (>80%) of acetonitrile, denoted HILIC/SALT. This initial study compared to reversed-phase chromatography (RPC), HILIC and HILIC/SALT for the separation of mixtures of synthetic peptide standards varying in structure (amphipathic α-helix, random coil), length (10-26 residues), number of positively charged residues (+1 to +11) and hydrophilicity/hydrophobicity. Results showed a marked superiority of the HILIC/SALT approach compared to traditional HILIC and excellent complementarity to RPC for peptide separations. We believe these initial results offer a new dimension to HILIC, enabling it to transform from an occasional HPLC approach for peptide separations to a more generally applicable method.

Development of a high-performance liquid chromatography-electrospray ionization-quadrupole-time-of-flight-mass spectrometry methodology for the determination of three highly antihypertensive peptides in maize crops

The simultaneous quantification of three highly antihypertensive peptides (LRP, LSP, and LQP) in six maize crops using novel HPLC-ESI-Q-ToF methodology is presented. The method included the extraction of α-zein proteins from maize, their purification by acetone precipitation, digestion with thermolysin and HPLC separation in a fused-core column. Several MS parameters were optimized to increase sensitivity and reduce spontaneous fragmentation of peptide ions into the ESI source. The ions with m/z 193.1315, 385.2558 (for LRP), 316.1867 (for LSP), and 357.2132 (for LQP) were monitored in the optimization and characterization of the method. In order to improve the repeatability, sensitivity, and the stability of peptides in the sample, the removal of urea was required. The use of two solid-phase extraction methods to remove urea from digested extract was evaluated. For the first time filter-aided sample preparation approach for the study of bioactive peptides in foodstuffs has been proposed. The optimized HPLC-ESI-Q-ToF method was characterized by the evaluation of linearity, LOD, LOQ, precision, and recovery. A study on the existence of matrix interferences was also performed. The developed method was applied to the quantification of LRP, LQP, and LSP peptides in maize lines using the standard addition method. The results showed the highest yield of LSP peptide in EZ11A line and LRP and LQP peptides in A632 line.

Reversed-phase fused-core HPLC modeling of peptides

Different fused-core stationary phase chemistries (C18, Amide, Phenyl-hexyl and Peptide ES-C18) were used for the analysis of 21 structurally representative model peptides. In addition, the effects of the mobile phase composition (ACN or MeOH as organic modifier; formic acid or acetic acid, as acidifying component) on the column selectivity, peak shape and overall chromatographic performance were evaluated. The RP-amide column, combined with a formic acid–acetonitrile based gradient system, performed as best. A peptide reversed-phase retention model is proposed, consisting of 5 variables: log SumAA, log Sv, clog P, log nHDon and log nHAcc. Quantitative structure-retention relationship (QSRR) models were constructed for 16 different chromatographic systems. The accuracy of this peptide retention model was demonstrated by the comparison between predicted and experimentally obtained retention times, explaining on average 86% of the variability. Moreover, using an external set of 5 validation peptides, the predictive power of the model was also demonstrated. This peptide retention model includes the novel in-silico calculated amino acid descriptor, AA, which was calculated from log P, 3D-MoRSE, RDF and WHIM descriptors.