Everything below concerns mobile phase. We keep the language plain, cite what the science says, and separate well-supported claims from open questions.
Updated 2026-01-20. Numbers and descriptions here follow the published literature rather than marketing material.
High-performance liquid chromatography, or HPLC, separates dissolved compounds by passing a liquid mobile phase through a packed column. Components distribute differently between the stationary phase and the moving liquid, so they travel at different speeds and exit at different times. A detector records these eluting bands as peaks, and peak area or height relates to amount. The technique supports testing in pharmaceuticals, foods, environmental samples, and industrial chemicals. Quantification usually depends on calibration with known standards.
Several separation modes exist, including reversed-phase, normal-phase, ion-exchange, size-exclusion, and hydrophilic interaction liquid chromatography. Reversed-phase uses a nonpolar stationary phase with a polar mobile phase and is widely applied to small organic molecules. Gradient elution changes mobile phase composition during the run, while isocratic elution keeps it constant. Column chemistry, particle size, temperature, flow rate, and mobile phase pH all influence retention and resolution. Method development selects conditions that separate analytes from matrix components and from each other.
Detection commonly uses ultraviolet-visible absorbance, fluorescence, refractive index, or mass spectrometry. Ultraviolet detection depends on molecular chromophores that absorb light at specific wavelengths. Mass spectrometry provides mass information and sensitive quantification, often after electrospray ionization. Before sample batches, performance checks examine resolution, elution time repeatability, peak symmetry, and plate count. Matrix effects and co-elution remain recognized uncertainties; formal validation studies and orthogonal detection help address them. Detector choice depends on analyte properties and required sensitivity.
High-performance liquid chromatography is an analytical technique that separates components in a liquid sample by passing them 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 how analytes partition between the mobile phase and the stationary phase cause them to exit the column at different times. Detection then records a signal proportional to the amount of each separated substance. The resulting chromatogram provides retention times and peak areas for identification and quantification.
Instrumentation includes a solvent delivery system, an autosampler, a column oven, and one or more detectors. Reversed-phase columns with chemically modified silica are widely used, but normal-phase, ion-exchange, size-exclusion, and affinity modes exist for specific separations. Detectors may rely on ultraviolet absorbance, fluorescence, refractive index, or mass spectrometry. Column temperature, mobile phase composition, and flow rate are adjusted to improve resolution. System pressure is monitored because rising pressure can indicate column blockage or deteriorating packing.
| Property | Value | Notes |
|---|---|---|
| Column particle size | 3–5 µm for conventional HPLC; sub-2 µm for UHPLC | Smaller particles increase backpressure and efficiency. |
| Typical flow rate | 0.5–2.0 mL/min for a 4.6 mm internal diameter column | Flow scales with column diameter and particle size. |
| UV detection wavelength | 190–400 nm | Selection depends on analyte chromophore. |
| Column temperature | 25–40 °C | Temperature affects retention, selectivity, and pressure. |
| Injection volume | 1–20 µL | Larger volumes may distort early-eluting peaks. |
Laboratories apply HPLC testing across pharmaceutical, food, environmental, and industrial chemistry. The method can measure active ingredients, impurities, additives, preservatives, and degradation products. Sample preparation often includes dilution, filtration, and sometimes extraction or derivatization. The choice of column, mobile phase, pH, temperature, and detector depends on the analytes and matrix. Results are compared with reference standards to assign identity and concentration. Method suitability is judged by resolution, precision, and accuracy.
HPLC testing is not a single fixed procedure; it is a family of separation modes. Reversed-phase, normal-phase, ion-exchange, size-exclusion, and affinity chromatography each suit different analyte properties. Reversed-phase methods dominate because they handle many neutral and moderately polar compounds. Detection can be optical, electrochemical, or mass spectrometric, and the detector dictates what information is available. Coupling with mass spectrometry increases selectivity and enables identification when standards are unavailable. The technique cannot separate every mixture without adjustment.
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.
HPLC testing separates dissolved compounds by passing a liquid sample through a column packed with stationary phase. A pump delivers mobile phase at controlled flow, and the sample components interact differently with stationary and mobile phases. Compounds that spend more time in mobile phase elute earlier; those retained by stationary phase elute later. Detectors record elution as peaks, and peak area or height relates to amount. This mechanism underpins quantitative analysis of mixtures.
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.
Routine HPLC testing compares a sample result with a calibration curve prepared from known reference standards. Peak area or peak height is plotted against concentration, and the curve is used to estimate unknown amounts. Retention time supports tentative identification when compared with a standard, though mass spectrometry or another confirmatory method may be needed for definitive identification. Pre-run checks verify repeatability, resolution, and peak symmetry before sample analysis. Limits of detection and quantification describe the smallest amounts that can be reliably observed or measured. Sample preparation, filtration, and degassing help prevent column damage and inconsistent results.
High-performance liquid chromatography is an analytical technique that separates components in a liquid sample. A pump moves a liquid mobile phase through a column packed with a solid stationary phase. Compounds interact differently with both phases and travel at different rates, leaving the column at distinct retention times. A detector records these arrivals as peaks on a chromatogram. The resulting pattern supports identification and quantification of substances in mixtures. Modern instruments use high pressure to force solvent through small particles, which improves speed and resolution compared with older low-pressure liquid chromatography methods.
Smashburger IP Holder LLC, doing business as Smashburger (stylized SmashBURGER), is an American multinational fast-casual hamburger restaurant chain founded in Denver, Colorado. As of 2022, it has more than 227 corporate and franchise-owned restaurants in 35 U.S. states, the District of Columbia and 2 Canadian provinces. Founded in 2007 by Rick Schaden and Tom Ryan, the chain serves "smashed" burgers using a specialized process of cooking them on a flattop grill at a high heat. This technique originated in the Great Lakes region at pressed-chuck burger restaurants, and has been a staple there for decades. The method sears the burger for flavor. These are then topped with additional ingredients and can be customized. At one time, the chain offered unique burgers in each city where its restaurants were located. The menu also includes chicken, turkey and portobello sandwiches as well as french fries, sweet potato fries, fried pickles and other items. Some locations offer the Udi's gluten-free bun. The restaurant saw rapid growth after its first location opened in 2007 and it added several hundred locations within a few years, although a larger slowdown of the "better burger" industry saw it slow its size and expansion plans. Company leaders initially considered an IPO, but Philippine-based quick-service operator Jollibee Group bought a 40 percent stake in the company in 2015, at which time it was valued at $335 million. As of December 2018, Jollibee owns 100% of Smashburger.
=== Persistent infection === Most often, SeV infection initiates an apoptotic program in the host cells, which leads to the death of target cells without interrupting the life cycle of the virus. However, paramyxoviruses, including SeV, can cause persistent infection in primary cell cultures that does not kill cells or turn off cellular RNA transcription and translation. It has been demonstrated that mouse connective tissues cells (L-929) and hamster kidney fibroblasts (BHK-21) can become infected with Sendai virus and the infection can be persistent. The possibility of establishing a persistent viral infection was demonstrated in SeV-infected ovine fibroblasts.
Surgical pathology is one of the primary areas of practice for most anatomical pathologists. Surgical pathology involves the gross and microscopic examination of surgical specimens, as well as biopsies submitted by surgeons and non-surgeons such as general internists, medical subspecialists, dermatologists, and interventional radiologists. Often an excised tissue sample is the best and most definitive evidence of disease (or lack thereof) in cases where tissue is surgically removed from a patient. These determinations are usually accomplished by a combination of gross (i.e., macroscopic) and histologic (i.e., microscopic) examination of the tissue, and may involve evaluations of molecular properties of the tissue by immunohistochemistry or other laboratory tests. There are two major types of specimens submitted for surgical pathology analysis: biopsies and surgical resections. A biopsy is a small piece of tissue removed primarily for surgical pathology analysis, most often in order to render a definitive diagnosis. Types of biopsies include core biopsies, which are obtained through the use of large-bore needles, sometimes under the guidance of radiological techniques such as ultrasound, CT scan, or magnetic resonance imaging. Incisional biopsies are obtained through diagnostic surgical procedures that remove part of a suspicious lesion, whereas excisional biopsies remove the entire lesion, and are similar to therapeutic surgical resections. Excisional biopsies of skin lesions and gastrointestinal polyps are very common.
Sources: en.wikipedia.org
== Further reading == Serafini M, Cargnin S, Massarotti A, Pirali T, Genazzani AA (September 2020). "Essential Medicinal Chemistry of Essential Medicines". Journal of Medicinal Chemistry. 63 (18): 10170–10187. doi:10.1021/acs.jmedchem.0c00415. PMC 8007110. PMID 32352778. Stuart MC, Kouimtzi M, Hill SR, eds. (2009). WHO Model Formulary 2008. World Health Organization. hdl:10665/44053. ISBN 978-92-4-154765-9. The selection and use of essential medicines. Twentieth report of the WHO Expert Committee 2015 (including 19th WHO Model List of Essential Medicines and 5th WHO Model List of Essential Medicines for Children). Geneva: World Health Organization. 2015. hdl:10665/189763. ISBN 978-92-4-069494-1. ISSN 0512-3054. WHO technical report series; no. 994. The selection and use of essential medicines: report of the WHO Expert Committee, 2017 (including the 20th WHO Model List of Essential Medicines and the 6th Model List of Essential Medicines for Children). Geneva: World Health Organization. 2017. hdl:10665/259481. ISBN 978-92-4-121015-7. ISSN 0512-3054. WHO technical report series; no. 1006. The selection and use of essential medicines: report of the WHO Expert Committee on Selection and Use of Essential Medicines, 2019 (including the 21st WHO Model List of Essential Medicines and the 7th WHO Model List of Essential Medicines for Children). Geneva: World Health Organization. 2019. hdl:10665/330668. ISBN 978-92-4-121030-0. ISSN 0512-3054. WHO technical report series;1021. Organization WH (2019).
== Terms == Analyte – the substance to be separated during chromatography. It is also normally what is needed from the mixture. Analytical chromatography – the use of chromatography to determine the existence and possibly also the concentration of analyte(s) in a sample. Bonded phase – a stationary phase that is covalently bonded to the support particles or to the inside wall of the column tubing. Chromatogram – the visual output of the chromatograph. In the case of an optimal separation, different peaks or patterns on the chromatogram correspond to different components of the separated mixture. Plotted on the x-axis is the retention time and plotted on the y-axis a signal (for example obtained by a spectrophotometer, mass spectrometer, or a variety of other detectors) corresponding to the response created by the analytes exiting the system. In the case of an optimal system the signal is proportional to the concentration of the specific analyte separated. Chromatograph – an instrument that enables a sophisticated separation, e.g. gas chromatographic or liquid chromatographic separation. Chromatography – a physical method of separation that distributes components to separate between two phases, one stationary (stationary phase), the other (the mobile phase) moving in a definite direction. Eluent (sometimes spelled eluant) – the solvent or solvent fixture used in elution chromatography and is synonymous with mobile phase. Eluate – the mixture of solute (see Eluite) and solvent (see Eluent) exiting the column. Effluent – the stream flowing out of a chromatographic column.
The history of the U.S. legislation on AAS goes back to the late 1980s, when the U.S. Congress considered placing AAS under the Controlled Substances Act following the controversy over Ben Johnson's victory at the 1988 Summer Olympics in Seoul. AAS were added to Schedule III of the Controlled Substances Act in the Anabolic Steroids Control Act of 1990. The same act also introduced more stringent controls with higher criminal penalties for offenses involving the illegal distribution of AAS and human growth hormone. By the early 1990s, after AAS were scheduled in the U.S., several pharmaceutical companies stopped manufacturing or marketing the products in the U.S., including Ciba, Searle, Syntex, and others. In the Controlled Substances Act, AAS are defined to be any drug or hormonal substance chemically and pharmacologically related to testosterone (other than estrogens, progestins, and corticosteroids) that promote muscle growth. The act was amended by the Anabolic Steroid Control Act of 2004, which added prohormones to the list of controlled substances, with effect from 20 January 2005. Even though they can still be prescribed by a medical doctor in the U.S., the use of anabolic steroids for injury recovery purposes has been a taboo subject, even amongst the majority of sports medicine doctors and endocrinologists.
=== MSNovelist: De novo structure prediction === MSNovelist is a computational method for the de novo generation of small molecule structures. It addresses a key limitation of database search tools, which can only identify compounds already present in reference structure databases. This makes it particularly useful for analyzing poorly represented analyte classes and novel compounds. It is not intended to replace database searches altogether, but generates structures which can serve as a great starting point for elucidation of specific unknowns. MSNovelist functions by generating novel molecular structures based on the molecular formula (identified by SIRIUS) and the molecular fingerprint (predicted by CSI:FingerID) of the unknown compound. An encoder–decoder recurrent neural network (RNN) model is trained to translate the input fingerprint into a structure, represented as a SMILES sequence, under the constraints of the predicted molecular formula. MSNovelist generates multiple candidate structures from the predicted molecular fingerprint. Once the candidate structures are generated, they are ranked using CSI:FingerID.
Sources: en.wikipedia.org
HPLC separates and quantifies compounds in a liquid sample. Detectors produce a response proportional to the amount of a compound passing through the flow cell. Identification by retention time requires comparison with a known standard.
UHPLC uses columns with smaller particles and operates at higher pressures than conventional HPLC. These conditions can improve speed, resolution, and sensitivity. Both techniques use the same fundamental separation principles.
Validation shows that a method performs reliably for its intended purpose across a defined range. It assesses accuracy, precision, specificity, linearity, and robustness. Regulated testing often requires documented validation before routine use.
HPLC separates and detects individual compounds in a liquid sample, producing peaks at characteristic retention times. Peak area or height can be used to estimate concentration when calibrated with known standards. It does not identify unknown compounds with certainty unless additional detectors or reference materials are used.