This is a working overview of HPLC, written for readers who want more than a one-paragraph summary but less than a textbook.
This page was last updated on 2025-10-09 and is reviewed periodically as new material appears.
Regulatory and pharmacopeial texts shape how HPLC testing is performed and documented. The International Council for Harmonisation provides validation guidance, while pharmacopeias publish general chromatography chapters and monographs for specific materials. Accreditation standards such as ISO/IEC 17025 address laboratory competence and traceability. Inspectors may review instrument qualification, analyst training, reference material control, and electronic records. Open questions include how best to validate methods for new complex products and how to handle automated data processing. Laboratories generally resolve these issues through risk assessment, method lifecycle management, and documented scientific justification.
In quality control laboratories, HPLC testing supports batch release, raw material checks, stability studies, and impurity profiling. A validated method defines sample preparation, instrument settings, calibration, and acceptance criteria. Analysts compare results with specifications and investigate out-of-specification outcomes before a batch is approved. Documentation includes chromatograms, integration records, audit trails, and reagent details. Because results influence product decisions, laboratories follow formal quality systems and data integrity rules. The exact tests and limits depend on the material, its intended use, and the applicable regulatory framework.
Documentation and traceability are central to regulated HPLC testing. Records typically include instrument logs, column history, mobile-phase preparation, sample preparation, injection sequences, raw chromatograms, and audit trails. Electronic systems may require user access controls, time-stamped changes, and backup procedures. Training records show that analysts are qualified for assigned methods. Audits and inspections check whether written procedures match actual practice and whether deviations are documented. These controls support reproducibility and allow results to be reconstructed if questions arise later.
Method validation establishes that an HPLC procedure is suitable for its intended purpose. Typical parameters include accuracy, precision, specificity, linearity, range, limit of detection, limit of quantitation, robustness, and solution stability. Accuracy reflects closeness to a reference value, while precision reflects agreement among repeated measurements. Specificity shows whether the method can measure the analyte without interference from matrix components. Validation is documented through protocols and reports, and the required extent depends on the method's use and regulatory context.
| Property | Value | Notes |
|---|---|---|
| Primary guidance | ICH Q2(R2) | Analytical procedure validation |
| Compendial chapter | USP <621> | Chromatography general chapter |
| Validation parameter | Accuracy | Closeness to accepted true value |
| System suitability check | Peak resolution | Ensures separation between adjacent peaks |
| Data record | Audit trail | Supports data integrity and traceability |
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.
Separation performance depends on particle size, pore size, column length, and the chemistry of the stationary phase. Smaller particles generally improve efficiency but require higher pressure and suitable instrumentation. The mobile phase often contains buffers and organic solvents that influence retention and selectivity. Testing labs select conditions based on the analytes, sample matrix, and required sensitivity. Method development frequently involves screening several columns and solvent mixtures before a final set of conditions is chosen.
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.
=== Diving === Barotrauma may be caused when diving, either from being crushed, or squeezed, on descent or by stretching and bursting on ascent; both can be avoided by equalising the pressures. A negative, unbalanced pressure is known as a squeeze, crushing eardrums, dry suit, lungs or mask inwards and can be equalised by putting air into the squeezed space. A positive unbalanced pressure expands internal spaces rupturing tissue and can be equalised by letting air out, for example by exhaling. Both may cause barotrauma. There are a variety of techniques depending on the affected area and whether the pressure inequality is a squeeze or an expansion:
==== Protection from oxidative damage ==== Some MAAs protect cells from reactive oxygen species (i.e. singlet oxygen, superoxide anions, hydroperoxyl radicals, and hydroxyl radicals). Reactive oxygen species can be created during photosynthesis; further supporting the idea that MAAs provide protection from UV light. Mycosporine-glycine is a MAA that provides antioxidant protection even before Oxidative stress response genes and antioxidant enzymes are induced. MAA-glycine (mycosporine-glycine) is able to quench singlet oxygen and hydroxyl radicals very quickly and efficiently. Some oceanic microbial ecosystems are exposed to high concentrations of oxygen and intense light; these conditions are likely to generate high levels of reactive oxygen species. In these ecosystems, MAA-rich cyanobacteria may be providing antioxidant activity.
=== Use of methylene chloride === Merck & Co. once used methylene chloride, a "priority pollutant" on the United States Environmental Protection Agency's list of pollutants and an animal carcinogen. It was used as a solvent in the manufacturing process for imipenem, an ingredient of the antibiotic Primaxin. Merck chemists and engineers subsequently replaced the compound with others having fewer negative environmental effects. Merck has also modified its equipment to provide greater control over its manufacturing process. Biological oxygen demand was reduced by 75%.
Projections to areas caudal to the hypothalamus go through the medial forebrain bundle, the mammillotegmental tract and the dorsal longitudinal fasciculus. Projections to areas rostral to the hypothalamus are carried by the mammillothalamic tract, the fornix and terminal stria. Projections to areas of the sympathetic motor system (lateral horn spinal segments T1–L2/L3) are carried by the hypothalamospinal tract and they activate the sympathetic motor pathway.
The magnocellular cells in the PVN elaborate and secrete two peptide hormones: oxytocin and vasopressin. These hormones are packaged into large vesicles, which are then transported down the unmyelinated axons of the cells and released from neurosecretory nerve terminals residing in the posterior pituitary gland. Similar magnocellular neurons are found in the supraoptic nucleus which also secrete vasopressin and oxytocin.
Sources: en.wikipedia.org
==== Therapy ==== Breast augmentation via autologous fat grafts allows the oncological breast surgeon to consider conservative breast surgery procedures that usually are precluded by the presence of alloplastic breast implants, e.g. lumpectomy, if cancer is detected in an implant-augmented breast. In previously augmented patients, aesthetic outcomes cannot be ensured without removing the implant and performing mastectomy. Moreover, radiotherapy treatment is critical to reducing cancerous recurrence and to the maximal conservation of breast tissue; yet, radiotherapy of an implant-augmented breast much increases the incidence of medical complications – capsular contracture, infection, extrusion, and poor cosmetic outcome.
== Epidemiology == McLeod syndrome is present in 0.5 to 1 per 100,000 of the population. McLeod males have variable acanthocytosis due to a defect in the inner leaflet bilayer of the red blood cell, as well as mild hemolysis. McLeod females have only occasional acanthocytes and very mild hemolysis; the lesser severity is thought to be due to X chromosome inactivation via the Lyon effect. Some individuals with McLeod phenotype develop myopathy, neuropathy, or psychiatric symptoms, producing a syndrome that may mimic chorea.
The harm from smoking comes from the many toxic chemicals in the natural tobacco leaf and those formed in smoke from burning tobacco. A 2024 study estimated that each cigarette reduces life expectancy by 20 minutes, while other studies estimate that each one reduces life expectancy by about 11 minutes on average. Humans continue to smoke because nicotine, the primary psychoactive chemical in cigarettes, is highly addictive. Cigarettes, like narcotics, have been described as "strategically addictive", with their addictive properties being a core component of the business strategy. About half of smokers die from a smoking-related cause. Smoking harms nearly every organ of the body. Smoking leads most commonly to diseases affecting the heart, liver, and lungs, being a major risk factor for heart attacks, strokes, chronic obstructive pulmonary disease (COPD) (including emphysema and chronic bronchitis), and cancer (particularly lung cancer, cancers of the larynx and mouth, and pancreatic cancer). It also causes peripheral vascular disease and hypertension. The incidence of erectile dysfunction is approximately 85 percent higher in men who smoke compared to men who do not smoke. Children born to women who smoke during pregnancy are at higher risk of congenital disorders, cancer, respiratory disease, and sudden death. Starting smoking earlier in life and smoking cigarettes higher in tar content increases the risk of these diseases.
Vicine is an alkaloid glycoside found mainly in fava beans, which are also called broad beans (Vicia faba). Vicine is toxic in individuals who have a hereditary loss of the enzyme glucose-6-phosphate dehydrogenase. It causes haemolytic anaemia, called favism. The formation of vicine in Vicia faba has been studied, but this natural formation has not yet been found.
Sources: en.wikipedia.org
System suitability is a set of checks performed before and during an HPLC run to confirm that the instrument and method are working as expected. It may include retention time repeatability, resolution between peaks, peak symmetry, and signal intensity. Failing suitability criteria usually invalidates the run.
An HPLC method is typically validated before its routine use and revalidated in part when significant changes affect the method. Regulators do not set a universal calendar interval. The need for revalidation depends on the change, its risk, and the applicable guidance.
Validation establishes that a method is suitable for its intended purpose, often through a planned study. Verification confirms that a laboratory can reproduce a previously validated or compendial method under its own conditions. Verification is usually narrower than full validation.
Validation establishes suitability for a new method, while verification confirms that a method works in a specific laboratory. Verification is often used when a validated method is adopted with existing equipment and staff. Both rely on documented acceptance criteria.