The short version of HPLC fits in a sentence. The long version — which is the one that helps — is below.
Reviewed 2026-08-01. Anything still debated is marked as such rather than presented as settled.
Routine quality control uses system suitability, blank injections, check standards, and control samples to detect drift or contamination. System suitability criteria may specify minimum resolution, maximum tailing factor, and a permitted range for repeated injections. Blank injections reveal carryover or solvent contamination, while check standards confirm calibration accuracy over a batch. Control samples with known analyte levels can show whether results remain within statistical limits. When a control result falls outside limits, the analyst investigates the cause and may invalidate affected results before repeating the batch.
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.
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.
| Property | Value | Notes |
|---|---|---|
| Accuracy | Recovery near 100% | Depends on acceptance criteria and matrix |
| Precision | Relative standard deviation | Often at or below 2% for replicate injections |
| Limit of detection | Signal-to-noise ratio 3:1 | Approximate and method-specific |
| Limit of quantitation | Signal-to-noise ratio 10:1 | Confirmed by precision and accuracy |
| Resolution | 1.5 or greater | Typical system suitability target |
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, 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.
Data handling and documentation are central to HPLC quality control. Electronic systems should have audit trails that record changes to methods, sequences, and results. Integration parameters, such as peak baseline and threshold, can affect reported areas and must be defined in advance. Out-of-specification results trigger a structured investigation that may include reanalysis, instrument checks, and review of sample preparation. Regulatory inspections often examine raw data, audit trails, and training records to verify that reported results are traceable and reliable.
Method validation establishes that an HPLC procedure is suitable for its intended use. Key parameters include accuracy, precision, specificity, linearity, range, limit of detection, limit of quantitation, and robustness. Accuracy measures agreement with a true or accepted value, while precision describes repeatability and intermediate precision. Specificity confirms that the method measures the analyte without interference from impurities, degradants, or excipients. Validation is documented in a protocol and report, and acceptance criteria are set before experiments begin. Regulatory guidance varies by region, but the general principles are widely harmonized.
System suitability testing is performed before and during analytical runs to confirm that the instrument and method are working as expected. Common checks include retention time, peak area, resolution between critical pairs, tailing factor, and theoretical plate count. Results are compared with predefined limits, and a failed check requires investigation before sample results are reported. Quality control samples at low, middle, and high concentrations are injected at intervals to monitor accuracy and precision. Blank injections detect carryover and contamination, while control charts track performance over time.
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.
Architectural propaganda is the use of architecture for the purpose of propaganda. Throughout history, significant architectural works have been used to convey ideas, including many intended to command respect and obedience.
== Side effects == Prucalopride has been given orally to ~2700 patients with chronic constipation in controlled clinical trials. The most frequently reported side effects are headache and gastrointestinal symptoms (abdominal pain, nausea or diarrhea) and suicidal ideation. Such reactions occur predominantly at the start of therapy and usually disappear within a few days with continued treatment.
Cider has also been popular in the Basque Country for centuries. While Txakoli and Rioja wines became more popular in Biscay, Álava, and Navarre during the 19th century, there is still a strong Basque cider culture in Gipuzkoa. From the 1980s, government and gastronomic associations have worked to revive this culture in all Basque regions. Known as sagardoa (IPA: /s̺a'gardoa/), it is drunk either bottled or in a cider house (called a sagardotegi), where it is poured from barrels. Most of "sagardotegis" are in the north of Gipuzkoa (Astigarraga, Hernani, Urnieta, and Usurbil), but they can be found everywhere in Gipuzkoa, the northwest of Navarre and the northern Basque country. Cider tasting events are popular in the Basque province of Gipuzkoa, where stalls are set up on the street selling the drink from several producers at cheap prices and served until stock runs out.
Sources: en.wikipedia.org
The ants plant the seeds and the domatia of young seedling are immediately occupied and the ant faeces in them contribute to rapid growth. Similar dispersal associations are found with other dolichoderines in the region as well. Another example of this type of ectosymbiosis comes from the Macaranga tree, which has stems adapted to house colonies of Crematogaster ants. Many plant species have seeds that are adapted for dispersal by ants. Seed dispersal by ants or myrmecochory is widespread, and new estimates suggest that nearly 9% of all plant species may have such ant associations. Often, seed-dispersing ants perform directed dispersal, depositing the seeds in locations that increase the likelihood of seed survival to reproduction. Some plants in arid, fire-prone systems are particularly dependent on ants for their survival and dispersal as the seeds are transported to safety below the ground. Many ant-dispersed seeds have special external structures, elaiosomes, that are sought after by ants as food. Ants can substantially alter rate of decomposition and nutrient cycling in their nest. By myrmecochory and modification of soil conditions they substantially alter vegetation and nutrient cycling in surrounding ecosystem. A convergence, possibly a form of mimicry, is seen in the eggs of stick insects. They have an edible elaiosome-like structure and are taken into the ant nest where the young hatch.
Glucagon-like peptide-2 (GLP-2) is a 33 amino acid peptide with the sequence HADGSFSDEMNTILDNLAARDFINWLIQTKITD (see Proteinogenic amino acid) in humans. GLP-2 is created by specific post-translational proteolytic cleavage of proglucagon in a process that also liberates the related glucagon-like peptide-1 (GLP-1). GLP-2 is produced by the intestinal endocrine L cell and by various neurons in the central nervous system. Intestinal GLP-2 is co-secreted along with GLP-1 upon nutrient ingestion. When externally administered, GLP-2 produces a number of effects in humans and rodents, including intestinal growth, enhancement of intestinal function, reduction in bone breakdown and neuroprotection. GLP-2 may act in an endocrine fashion to link intestinal growth and metabolism with nutrient intake. GLP-2 and related analogs (such as Teduglutide) may be treatments for short bowel syndrome, Crohn's disease, osteoporosis and as adjuvant therapy during cancer chemotherapy. GLP-2 has an antidepressant effect in a mouse model of depression when delivered via intracerebroventricular injection. However, a GLP-2 derivative (PAS-CPP-GLP-2) was shown to be efficiently delivered to the brain intranasally, with similar efficacy.
Acral persistent papular mucinosis Atypical lichen myxedematosus (intermediate lichen myxedematosus) Atypical tuberous myxedema (Jadassohn–Dosseker syndrome) Cutaneous focal mucinosis Cutaneous lupus mucinosis (papular and nodular mucinosis in lupus erythematosus, papular and nodular mucinosis of Gold, papulonodular mucinosis in lupus erythematosus) Discrete papular lichen myxedematosus Eccrine mucinosis Follicular mucinosis (alopecia mucinosa, mucinosis follicularis, Pinkus' follicular mucinosis, Pinkus' follicular mucinosis–benign primary form) Localized lichen myxedematosus Myxoid cyst (digital mucous cyst, mucous cyst) Myxoid lipoblastoma Neuropathia mucinosa cutanea Nodular lichen myxedematosus Papular mucinosis (generalized lichen myxedematosus, sclerodermoid lichen myxedematosus, scleromyxedema) Papular mucinosis of infancy (cutaneous mucinosis of infancy) Perifollicular mucinosis Reticular erythematous mucinosis (midline mucinosis, plaque-like cutaneous mucinosis, REM syndrome) Scleroderma Self-healing juvenile cutaneous mucinosis Self-healing papular mucinosis Stiff skin syndrome (congenital fascial dystrophy)
==== Long-term ==== There is consistent evidence of structural and functional deficits in MDMA users with high lifetime exposure. These structural or functional changes appear to be dose dependent and may be less prominent in MDMA users with a lifetime exposure of less than 50 doses used and less than 100 tablets consumed. Nonetheless, moderate MDMA use may still result in neurotoxicity and what constitutes moderate use is not clearly established. Furthermore, it is not clear yet whether "typical" recreational users of MDMA (1 to 2 pills of 75 to 125 mg MDMA or analogue every 1 to 4 weeks) will develop neurotoxic brain lesions. Long-term exposure to MDMA in humans has been shown to produce marked neurodegeneration in striatal, hippocampal, prefrontal, and occipital serotonergic axon terminals. Neurotoxic damage to serotonergic axon terminals has been shown to persist for more than two years. Elevations in brain temperature from MDMA use are positively correlated with MDMA-induced neurotoxicity. However, most studies on MDMA and serotonergic neurotoxicity in humans focus more on heavy users who consume as much as seven times or more the amount that most users report taking. The evidence for the presence of serotonergic neurotoxicity in casual users who take lower doses less frequently is not conclusive. However, adverse neuroplastic changes to brain microvasculature and white matter have been observed to occur in humans using low doses of MDMA. Reduced gray matter density in certain brain structures has also been noted in human MDMA users.
Sources: en.wikipedia.org
Since June 20, 1979, the FDA has received many questions about Good Laboratory Practice (GLP) regulations (21 CFR 58). The responses to these inquiries are stored in the Dockets Management Branch (HFA-305) and shared with the Agency's Bioresearch Monitoring (BIMO) program managers and district offices to ensure consistency. Consequently, the US FDA published the 1981 Questions & Answers - Good Laboratory Practice Regulations document to consolidate and clarify these responses. This Q&A document categorizes responses by specific GLP provisions to make them more useful for both the FDA headquarters and field offices. The FDA has signed a memorandum of understanding (MOU) with Canada, France, Germany, Italy, Japan, The Netherlands, Sweden, and Switzerland to enhance cooperation on good laboratory practice (GLP) for nonclinical laboratory studies supporting product approvals, aiming to facilitate information exchange and inspections for regulatory oversight. Proposed amendments were published in the Federal Register on August 24, 2016, which aimed to require a comprehensive quality system approach known as a GLP Quality System to enhance the current quality system approach for nonclinical laboratory studies. This system would be mandatory for safety and toxicity studies that support or are intended to support applications or submissions for products regulated by the FDA.
=== Performance-enhancing use === Because they promote lower heart rates and reduce tremors, beta blockers have been used in professional sports where high accuracy is required, including archery, shooting, golf and snooker. Beta blockers are banned in some sports by the International Olympic Committee. In the 2008 Summer Olympics, 50-metre pistol silver medalist and 10-metre air pistol bronze medalist Kim Jong-su tested positive for propranolol and was stripped of his medals. For similar reasons, beta blockers have also been used by surgeons. Classical musicians have commonly used beta blockers since the 1970s to reduce stage fright.
=== Lung toxicity === Pulmonary toxicity, or toxicity to lungs, is a serious complication associated with sirolimus therapy, especially in the case of lung transplants. The mechanism of the interstitial pneumonitis caused by sirolimus and other macrolide mTOR inhibitors is unclear, and may have nothing to do with the mTOR pathway. The interstitial pneumonitis is not dose-dependent, but is more common in patients with underlying lung disease.
Sex reassignment operations (gender-affirming surgery) have been performed in Thailand since 1975, and Thailand is among the most popular destinations globally for patients seeking such operations. Puberty blockers and cross sex hormones are also available to minors in Thailand. Transgender people are quite common in Thai popular entertainment, television shows and nightclub performances, however, transgender people lack various legal rights compared to the rest of the population, and may face discrimination from society. Transgender women, known as kathoeys, have access to hormones through non-prescription sources. This kind of access is a result of the low availability and expense of transgender health care clinics. However, transgender men have difficulty gaining access to hormones such as testosterone in Thailand because it is not as readily available as hormones for kathoeys. As a result, just a third of all trans men surveyed are taking hormones to transition whereas almost three quarters of kathoeys surveyed are taking hormones.
Madecassic acid is a pentacyclic triterpenoid compound that occurs naturally in several plant species. Madecassic acid is a member of the ursane-type triterpenoids and is structurally similar to Asiatic acid, differing by the presence of a hydroxyl group at the C-2 position.
Sources: en.wikipedia.org
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.
Quantification usually compares detector response to a standard curve made from reference standards. The curve may be external, internal, or based on standard addition depending on matrix effects. Results are reported with units and, when required, uncertainty.
Carryover occurs when analyte from a previous injection remains in the system and appears in a later chromatogram. It can come from the injector, column, or tubing. Blank injections and needle washes help detect and reduce it.
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.