Everything below concerns stationary phase. We keep the language plain, cite what the science says, and separate well-supported claims from open questions.
Last reviewed on 2026-02-27. Where a claim depends on a specific study, the study is described rather than over-claimed.
Most routine HPLC testing uses reversed-phase columns, where the stationary phase is nonpolar and the mobile phase is a polar mixture such as water with an organic solvent. Analytes partition between the two phases according to polarity, size, and charge. Gradients that change solvent composition over time can separate compounds with broad retention ranges. Isocratic conditions keep solvent composition constant and suit simpler mixtures. The choice of column chemistry, pH, and temperature affects selectivity and peak shape.
Detection in HPLC testing commonly relies on ultraviolet-visible absorbance, fluorescence, refractive index, or mass spectrometry. UV detection is widely used because many organic compounds absorb light, but it requires a chromophore. Mass spectrometry provides mass-based identification and high sensitivity for trace analytes. Each detector has trade-offs in selectivity, cost, and compatibility with mobile phases. Quantification typically uses calibration curves prepared from reference standards. Results are reported as concentration, purity, or presence above a limit.
High-performance liquid chromatography is an analytical technique that separates components of a liquid sample by passing it through a packed column under pressure. A pump delivers a mobile phase at a controlled flow rate, and an injector introduces the sample into the stream. Differences in interaction with the stationary phase cause analytes to migrate at different rates. Detectors record elution as peaks, and a data system converts signals into a chromatogram. The method is suited to compounds that dissolve in a liquid and are not volatile enough for gas chromatography.
Reversed-phase chromatography dominates modern HPLC testing, using a nonpolar stationary phase such as chemically bonded octadecyl groups and a polar mobile phase of water mixed with organic solvent. Analytes partition between the mobile and stationary phases according to hydrophobicity. Gradient elution changes the mobile phase composition over time to separate compounds with a wide range of retention. Isocratic elution keeps the composition constant and is simpler for routine assays. Column temperature, pH, and flow rate influence selectivity, peak shape, and retention time, so these parameters are controlled during a validated method.
Detection in HPLC testing commonly relies on ultraviolet-visible absorbance, fluorescence, refractive index, or mass spectrometry. A diode array detector records full spectra across a wavelength range, which helps identify co-eluting peaks. Mass spectrometry provides mass-to-charge ratios and can confirm molecular identity at low concentrations. The choice of detector depends on analyte structure, required sensitivity, and whether quantitation or identification is the goal. No single detector works for every compound, and method development often compares responses before selecting one.
| Property | Value | Notes |
|---|---|---|
| Separation mode | Reversed-phase | Nonpolar stationary phase with polar mobile phase |
| Typical column particle size | 3–5 µm | Smaller particles improve resolution but raise pressure |
| Typical flow rate | 0.5–2.0 mL/min | Depends on column dimensions and pressure limits |
| Common detection | UV-Vis absorbance | Requires analytes with chromophores |
| Typical run time | 5–30 min | Varies with method, gradient, and sample complexity |
Method validation evaluates accuracy, precision, specificity, linearity, range, detection limit, quantitation limit, and robustness. Regulatory guidance for pharmaceuticals, foods, and environmental testing defines expected documentation and acceptance criteria. Verification confirms that a validated method works in a specific laboratory with its own instruments and reagents. Calibration curves use reference standards with known purity and traceability, while measurement uncertainty is estimated from validation data, control charts, and collaborative studies. The scope of validation depends on the method's intended use.
Routine quality control monitors retention time shifts, baseline noise, system pressure, and peak shape. Trends can reveal column aging, mobile phase preparation errors, detector drift, or sample degradation. Corrective actions may include replacing the column, preparing fresh mobile phase, or recalibrating the detector. Stability testing often uses HPLC to measure parent compound loss and degradation product formation. Open questions remain about how accelerated stability results extrapolate to long-term storage under varied conditions.
Quality control for HPLC testing combines scheduled checks, documented procedures, and review of results. Before sample analysis, system suitability testing confirms that the instrument, column, and method meet predefined criteria. Common criteria include resolution between critical peaks, retention time precision, peak tailing, and theoretical plate count. Failure triggers investigation before results are reported. Records link raw data, calculations, instrument logs, and analyst identity to each batch, supporting audits and repeat analysis.
Developing an HPLC test begins with defining the analytes, matrix, and required reporting limits. Chemists select a separation mode, column chemistry, mobile phase composition, flow rate, and detection wavelength or mass transition. Experiments then adjust these variables to achieve adequate retention, resolution, and peak shape. System suitability tests confirm that the instrument and method perform consistently before sample analysis. Without suitable resolution, quantitative results may be unreliable. Preliminary runs often use scouting gradients to locate retention windows.
Validation establishes that a method is suitable for its intended purpose. Typical parameters include accuracy, precision, specificity, linearity, range, limit of detection, limit of quantification, robustness, and stability of standards and samples. Acceptance criteria are defined in advance, and results are documented in a validation report. Regulatory guidance for pharmaceuticals, foods, and environmental testing differs, so the applicable framework must be identified. Ongoing verification uses control samples and trend charts after validation. Method transfer to another laboratory may require partial revalidation.
Routine quality control includes blanks, duplicates, spiked samples, and certified reference materials. Calibration curves are prepared with standards at several concentrations, and the detector response is checked for linearity. Carryover, column aging, mobile phase evaporation, and temperature drift can shift retention times or peak areas. Maintenance such as replacing seals, filters, and columns helps prevent failures. Records of injections, integration, and deviations support traceability. Audits may request raw data and instrument logs for each batch.
β-pleated sheet structures are made from extended β-strand polypeptide chains, with strands linked to their neighbours by hydrogen bonds. Due to this extended backbone conformation, β-sheets resist stretching. β-sheets in proteins may carry out low-frequency accordion-like motion as observed by the Raman spectroscopy and analyzed with the quasi-continuum model. A β-helix is formed from repeating structural units consisting of two or three short β-strands linked by short loops. These units "stack" atop one another in a helical fashion so that successive repetitions of the same strand hydrogen-bond with each other in a parallel orientation. See the β-helix article for further information. In lefthanded β-helices, the strands themselves are quite straight and untwisted; the resulting helical surfaces are nearly flat, forming a regular triangular prism shape, as shown for the 1QRE archaeal carbonic anhydrase at right. Other examples are the lipid A synthesis enzyme LpxA and insect antifreeze proteins with a regular array of Thr sidechains on one face that mimic the structure of ice.
Cotadutide is an experimental drug for the treatment of type 2 diabetes mellitus. It lowers blood glucose levels by mimicking the human hormones glucagon-like peptide 1 and glucagon, which play a role in blood sugar regulation. The drug is a peptide that is injected under the skin. Cotadutide is in Phase II clinical trials as of February 2021. Cotadutide, a therapeutic agent, was undergoing Phase II clinical trials. This stage of trials typically involves evaluating the drug's effectiveness and further assessing its safety in a larger group of participants, compared to earlier phases. Glucagon (medication)
Pharmaceutical engineering is an interdisciplinary science that includes drug engineering, novel drug delivery and targeting, pharmaceutical technology, unit operations of chemical engineering, and pharmaceutical analysis. It may be deemed as a part of pharmacy due to its focus on the use of technology on chemical agents in providing better medicinal treatment. This is an extremely broad category—essentially covering all health care products that do not achieve their intended results through predominantly chemical (e.g., pharmaceuticals) or biological (e.g., vaccines) means, and do not involve metabolism. A medical device is intended for use in: the diagnosis of disease or other conditions in the cure, mitigation, treatment, or prevention of disease. Some examples include pacemakers, infusion pumps, the heart-lung machine, dialysis machines, artificial organs, implants, artificial limbs, corrective lenses, cochlear implants, ocular prosthetics, facial prosthetics, somato prosthetics, and dental implants.
Sources: en.wikipedia.org
Ethane-1,2-dithiol, also known as EDT, is a colorless liquid with the formula C2H4(SH)2. It has a very characteristic odor which is compared by many people to rotten cabbage. It is a common building block in organic synthesis and an excellent ligand for metal ions. Ethane-1,2-dithiol is made commercially by the reaction of 1,2-dichloroethane with aqueous sodium bisulfide. In the laboratory, it can also be prepared by the action of 1,2-dibromoethane on thiourea followed by hydrolysis. 1,2-Ethanedithiol is a weak acid, typical of alkyl thiols. In the presence of base and an alkylating agent, 1,2-ethanedithiol converts to thioethers: HS(CH2)2SH + 2 NR3 + 2 R'I → R'S(CH2)2SR' + 2 [R3NH]I Oxidation of 1,2-ethanedithiol gives a series of oligomers, including the cyclic bis(disulfide). As a 1,2-dithiol, this compound reacts with aldehydes and ketones to give 1,3-dithiolanes, which can be useful intermediates.
Anne S. Ulrich (born December 31, 1966) is a German chemist. She is the director of the Institute of Biological Interfaces (IBG-2) and Chair of Biochemistry at the Karlsruhe Institute of Technology. She studied chemistry at the University of Oxford - continued her doctoral work in the laboratory of Anthony Watts - held subsequent research positions as an EMBO-Fellow with Hartmut Oschkinat at the European Molecular Biology Laboratory in Heidelberg and as a Liebig-Fellow with Felix Wieland at the University of Heidelberg - became Associate Professor at the University of Jena - until she moved her group in 2002 to the Karlsruhe Institute of Technology. Her research focuses on the structural and functional analysis of biomembranes by solid state NMR. The main systems of interest are:
Human uses of AGPs include the use of Gum arabic in the food and pharmaceutical industries because of natural properties in thickening and emulsification. AGPs in cereal grains have potential applications in biofortification, as sources of dietary fibre to support gut bacteria and protective agents against ethanol toxicity. Arabinogalactan Proteoglycan This article was adapted from the following source under a CC BY 4.0 license (2021) (reviewer reports): Yingxuan Ma; Kim Johnson (2021). "Arabinogalactan-proteins" (PDF). WikiJournal of Science. 4 (1): 2. doi:10.15347/wjs/2021.002. Wikidata Q99557488.
Vasoactive intestinal peptide (VIP) is a 28-residue amino acid peptide first characterized in 1970 that was initially isolated from porcine duodenum. A member of the secretin/glucagon hormone superfamily, VIP was initially discovered owing to its potent vasodilatory effects (as its name implies). VIP is widely distributed in the central and peripheral nervous system as well as in the digestive, respiratory, reproductive, and cardiovascular systems as a neurotransmitter and neuroendocrine releasing factor. These effects contribute to an extensive range of physiological and pathological processes related to development, growth, and the control of neuronal, epithelial, and endocrine cell function. VIP acts on two receptors - VPAC1 and VPAC2, which are class B of G-protein-coupled receptors (GPCRs).VPAC1 is mainly present in the lung and T-lymphocytes, whereas VPAC2 is mainly seen in the smooth muscle, mast cells and the basal parts of the lung mucosa.
Sources: en.wikipedia.org
These cyclic dipeptides incorporate both donor and acceptor groups for hydrogen bonding. They are conformationally constrained nearly planar scaffolds. Diversity can be introduced at up to six positions and stereochemistry controlled at up to four positions. They are stable to proteolysis. These characteristics underpin theis biologically activity and utility in medicinal chemistry. As a consequence of their predominant biosynthetic origin from L-α-amino acids most naturally occurring 2,5-DKPs are cis configured as the cyclo(L-Xaa-L-Yaa) isomers. 2,5-DKPs epimerize under basic, acidic and thermal conditions. The composition of the cis and trans isomers in the equilibrium state varies widely depending on the bulk of the side chains, if a ring (e.g. proline) is present, or if the nitrogen atoms are alkylated . Although epimerization was historically an issue in the synthesis of 2,5-DKPs, several mild methods have been developed recently that avoid epimerization.
With ring-opening polymerization, automated synthesis has been used for rapid screening and optimization, including with catalyst + initiator systems and their polymerization conditions. For example, Hoogenboom et al. determined the optimal temperature for the polymerization of 2-ethyl-2-oxazoline in dimethylacetamide (DMAc), allowing for individual heating of the parallel reactors, which shortened the time needed for preparation and analysis. To aid with the catalyst research for polyolefins, Symyx Technologies Inc. used automated synthesis to create a library of palladium and nickel catalysts, which were screened for ethylene polymerization. This process found that the largest polyethylene polymers were created by the complexes with the highest steric hindrance for the ortho-positions of the aryl rings, while electronic factors did not influence yield or molecular weight. In addition, Tuchbreiter and Mülhaupt used automated synthesis to demonstrate the improvements of minireactors for the polymerization of olefins, with quality improving as compared to utilizing simple arrays.
2,5-Diketopiperazine is an organic compound with the formula (NHCH2C(O))2. The compound features a six-membered ring containing two amide groups at opposite positions in the ring. It was first compound containing a peptide bond to be characterized by X-ray crystallography in 1938. It is the parent of a large class of 2,5-Diketopiperazines (2,5-DKPs) with the formula (NHCH2(R)C(O))2 (R = H, CH3, etc.). They are ubiquitous peptides in nature. They are often found in fermentation broths and yeast cultures as well as embedded in larger more complex architectures in a variety of natural products as well as several drugs. In addition, they are often produced as degradation products of polypeptides, especially in foods and beverages. They have also been found in extraterrestrial objects such as comets and asteroids.
Sources: en.wikipedia.org
It separates components in a liquid sample and measures their amounts using a detector. Results can indicate concentration, purity, or identity based on retention time and detector response. The technique works for mixtures that can be dissolved and filtered.
It offers high resolution, reproducibility, and compatibility with many sample types. A single run can separate and quantify multiple analytes. It is common in pharmaceutical, food, environmental, and industrial laboratories.
Samples must be soluble in a suitable mobile phase and free of particles that can block the column. Detector response depends on analyte structure, so some compounds need derivatization or alternative detection. Complex matrices may require extensive sample preparation.
HPLC testing separates and quantifies components in a liquid sample. It is used to check identity, purity, concentration, or stability. The technique works best for compounds that dissolve and are not easily vaporized.