Calibration curve comes up often in conversation and rarely with the context attached. Here we lay out the basics in order, then work through the practical considerations.
Updated 2025-09-04. Numbers and descriptions here follow the published literature rather than marketing material.
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.
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.
System suitability testing is performed before and during analytical runs to confirm that the instrument and method are working as expected. Typical checks include retention time, peak area precision, resolution between critical pairs, tailing factor, and theoretical plate count. Acceptance criteria are set in the method or pharmacopeial monograph. If a suitability check fails, the run may be rejected and the instrument or sample preparation may need investigation. This practice helps prevent release of data from a system that has drifted out of control.
Quality control samples are inserted at intervals to monitor accuracy and precision throughout a batch. Blank samples detect contamination, while spiked samples assess recovery from the sample matrix. Calibration standards establish the relationship between detector response and concentration, and control samples are prepared independently from them whenever possible. Laboratories also participate in proficiency testing and maintain audit trails, instrument logs, and reagent records. Ongoing review of control charts can reveal trends before they cause out-of-specification results.
| Property | Value | Notes |
|---|---|---|
| Retention time RSD | ≤1% for five replicate injections | Typical criterion; method-specific limits apply. |
| Resolution | ≥1.5 between critical pair | Baseline separation is generally desired. |
| Tailing factor | ≤2.0 | Measures peak symmetry. |
| Theoretical plates | ≥2000 per column | Method-dependent; higher values indicate greater efficiency. |
| Peak area RSD | ≤2% for replicate injections | Reflects autosampler and detector precision. |
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.
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 HPLC testing depends on controlled reagents, calibrated instruments, and documented procedures. Columns degrade over time, so retention times and peak shapes are monitored for drift. Mobile phases are filtered and degassed to prevent pump damage and detector noise. Reference standards must be traceable and stored under suitable conditions. Data handling systems record injections, calculations, and audit trails. Quality control samples interspersed with unknowns help detect errors during a run.
Developing an HPLC method begins with defining the purpose, such as quantifying a main component, measuring impurities, or confirming identity. Analysts select separation mode, column, mobile phase, detection, and sample preparation based on analyte properties and matrix. Experiments vary solvent strength, pH, buffer type, and temperature to achieve resolution between critical peaks. The goal is a robust method that produces reliable results across instruments and operators. Method development often involves trial runs and statistical optimization.
== External links == alpha-Fetoproteins at the U.S. National Library of Medicine Medical Subject Headings (MeSH) Overview of all the structural information available in the PDB for UniProt: P02771 (Alpha-fetoprotein) at the PDBe-KB.
In immunology, an antigen (Ag) is a molecule, or portion thereof, that can bind to a specific antibody or T-cell receptor. The presence of antigens in the body may trigger an immune response. Antigens can be proteins, peptides (amino acid chains), polysaccharides (chains of simple sugars), lipids, or nucleic acids. Antigens exist on normal cells, cancer cells, parasites, viruses, fungi, and bacteria. Antigens are recognized by antigen receptors, including antibodies and T-cell receptors. Diverse antigen receptors are made by cells of the immune system so that each cell has a specificity for a single antigen. Upon exposure to an antigen, only the lymphocytes that recognize that antigen are activated and expanded, a process known as clonal selection. In most cases, antibodies are antigen-specific, meaning that an antibody can only react to and bind one specific antigen; in some instances, however, antibodies may cross-react to bind more than one antigen. The reaction between an antigen and an antibody is called the antigen-antibody reaction. Antigen can originate either from within the body ("self-protein" or "self antigens") or from the external environment ("non-self"). The immune system identifies and attacks "non-self" external antigens. Antibodies usually do not react with self-antigens due to negative selection of T cells in the thymus and B cells in the bone marrow. The diseases in which antibodies react with self antigens and damage the body's own cells are called autoimmune diseases.
Climate change is projected to raise average temperatures in Portugal by as much as 3–4 °C (37.4–39.2 °F) by 2100 relative to the 1990s–2010s average, with impacts in water, ecosystem, agriculture, health, and security.
Some hemoglobinopathies seem to have given an evolutionary benefit, especially to heterozygotes, in areas where malaria is endemic. Having a mild form of alpha thalassemia has been demonstrated to protect against malaria and thus can be an advantage in malaria endemic areas, thus conferring a selective survival advantage on carriers (known as heterozygous advantage), and perpetuating the mutation. Alpha thalassemia genes have a high prevalence in populations originating in sub-Saharan Africa, Mediterranean, Middle East, and southeast and east Asia; all areas which historically have been malaria endemic. The prevalence of these genes has increased in previously non-endemic areas as a consequence of migration flows, slave-trade, and colonization. A number of mechanisms have been proposed to explain the increased chance of survival for the carrier of an abnormal hemoglobin trait.
Sources: en.wikipedia.org
1993/453) National Rivers Authority (Anglian Region) (Reconstitution of the North Level Internal Drainage Board) Order 1992 S.I. 1993/454) Environmentally Sensitive Areas (Breckland) Designation Order 1993 (S.I. 1993/455) Environmentally Sensitive Areas (Clun) Designation Order 1993 (S.I. 1993/456) Environmentally Sensitive Areas (North Peak) Designation Order 1993 (S.I. 1993/457) Environmentally Sensitive Areas (Suffolk River Valleys) Designation Order 1993 (S.I. 1993/458) Environmentally Sensitive Areas (Test Valley) Designation Order 1993 (S.I. 1993/459) Environmentally Sensitive Areas (Pennine Dales) Designation (Amendment) Order 1993 (S.I. 1993/460) National Assistance (Sums for Personal Requirements) Regulations 1993 (S.I. 1993/462) Education (Further Education Corporations) (Designated Staff) Order 1993 (S.I. 1993/465) Bradford, Kirklees and Leeds (City and Metropolitan Borough Boundaries) Order 1993 (S.I. 1993/473) Warwickshire and West Midlands (County and District Boundaries) Order 1993 (S.I. 1993/474) Merchant Shipping (Light Dues) (Amendment) Regulations 1993 (S.I. 1993/475) Wireless Telegraphy (Television Licence Fees) (Amendment) Regulations 1993 (S.I. 1993/476) Residential Accommodation (Relevant Premises, Ordinary Residence and Exemptions) Regulations 1993 (S.I. 1993/477) Social Security (Claims and Payments) Amendment Regulations 1993 (S.I. 1993/478) Social Fund Maternity and Funeral Expenses (General) Amendment Regulations 1993 (S.I. 1993/479) Personal Injuries (Civilians) Amendment Scheme 1993 (S.I.
=== In development === Several new drugs and treatments are under development for snakebite. For instance, the metal chelator dimercaprol has recently been shown to potently antagonize the activity of Zn2+-dependent snake venom metalloproteinases in vitro. New monoclonal antibodies, polymer gels and a small molecule inhibitor called Varespladib are in development. A core outcome set (minimal list of consensus outcomes that should be used in future intervention research) for snakebite in South Asia is being developed. In an article published in Nature in October 2025, a group led by researchers from the Technical University of Denmark has presented the possibility of a broad-spectrum antivenom that can work against the bites of many different snakes. They have developed an experimental polyvalent recombinant anti-venom that the authors claim to be capable of neutralising seven toxin families or subfamilies. A study conducted by Jacob Glanville used two antibodies taken from the memory B cells of blood from a "hyperimmune" donor, who had been deliberately bitten by many species of snake, to develop an antivenom "cocktail". Elapidae were the focus of the study, of which nineteen are classified as being the deadliest on Earth by the World Health Organization. Tested on mice, the antivenom cocktail prevented death from thirteen of the nineteen species, with partial protection observed from the other six.
=== International organizations === United Nations: UN Secretary General Antonio Guterres said Gaza was an integral part of a future Palestinian state. Amnesty International's Agnès Callamard condemned Trump's plan to take over Gaza and forcibly relocate Palestinians, calling it "outrageous and shameful." She said it would be a war crime and urged the global community to reject it and uphold Palestinian rights. International Coordination of Revolutionary Parties and Organizations: The ICOR released a statement condemning Trump's Gaza plan saying that it would be tantamount to a new Nakba. Holy See: The Catholic Patriarch of Jerusalem, Pierbattista Pizzaballa, on July 21, 2025, stated that the majority in Gaza will remain there: “First of all, they don’t know where to go, but they also don’t want to leave, because their roots are there, their home is there—or rather, they had their home there—and they want to rebuild it there. The Pope has been very clear on this: no population transfers; there will be no 'rivieras' in Gaza”.
== Prolactin == Agonists: Growth hormone Human placental lactogen Placental growth hormone (growth hormone variant) Prolactin S179D-hPRL Somatotropin Antagonists: Δ1–9-G129R-hPRL Δ1–14-G129R-hPRL G120K-hGH G129R-hPRL Prolactin modulators: Prolactin inhibitors: D2 receptor agonists (e.g., bromocriptine, cabergoline); Prolactin releasers: D2 receptor antagonists (e.g., domperidone, metoclopramide, risperidone) Estrogens (e.g., estradiol) Progestogens (e.g., progesterone)
== Legislation == Orphan drugs generally follow the same regulatory development path as any other pharmaceutical product, in which testing focuses on pharmacokinetics and pharmacodynamics, dosing, stability, safety and efficacy. However, some statistical burdens are lessened to maintain development momentum. For example, orphan drug regulations generally acknowledge the fact that it may not be possible to test 1,000 patients in a phase III clinical trial if fewer than that number are affected by the disease. Government intervention on behalf of orphan drug development takes several forms:
Sources: en.wikipedia.org
=== Neurodegeneration === Pathological protein aggregation is a major hallmark of multiple neurodegenerative diseases. O-GlcNAc on various proteins has been found to play roles in suppressing protein aggregation, motivating clinical efforts to inhibit OGA and elevate cellular O-GlcNAc levels. This strategy is being evaluated by companies for Alzheimer's disease, Parkinson's disease, progressive supranuclear palsy, and amyotrophic lateral sclerosis (ALS). Multiple companies have advanced OGA inhibitors into the clinic including Alectos Therapeutics, Asceneuron, Biogen, Eli Lilly, and Merck.
=== MMPs regulation === Under physiological conditions, MMPs are regulated at five levels: transcription; activation of zymogen precursors; interaction with ECM components; inhibition by TIMPs; and regulated absorption/elimination of active proteases from the extracellular environment. The majority of the literature is based on an investigation of transcriptional level (level 1) modifications, which lacks information on the physiologically relevant actions and control of secreted and post-translationally activated proteases. Future study could focus on the post-transcriptional regulation of MMP activity, especially in vivo.
== Dietary sources == Good sources of phenylalanine are eggs, chicken, liver, beef, milk, and soybeans. Another common source of phenylalanine is anything sweetened with the artificial sweetener aspartame, such as diet drinks, diet foods and medication; the metabolism of aspartame produces phenylalanine as one of the compound's metabolites.
=== Others === Blood: Pentamidine frequently causes leukopenia and less often thrombopenia, which may cause symptomatic bleeding. Some cases of anemia, possibly related to folic acid deficiency, have been described. Cardiovascular: Hypotension, which may be severe. Severe or fatal arrhythmias and heart failure are quite frequent. Kidney: 25 percent develop signs of nephrotoxicity ranging from mild, asymptomatic azotemia (increased serum creatinine and urea) to irreversible renal failure. Ample fluids or intravenous hydration may prevent some nephrotoxicity. Liver: Elevated liver enzymes are associated with intravenous use of pentamidine. Hepatomegaly and hepatitis have been encountered with long term prophylactic use of pentamidine inhalation. Neurological: Dizziness, drowsiness, neuralgia, confusion, hallucinations, seizures and other central side effects are reported. Pancreas: Hypoglycemia that requires symptomatic treatment is frequently seen. On the other hand, pentamidine may cause or worsen diabetes mellitus. Respiratory: Cough and bronchospasm, most frequently seen with inhalation. Skin: Severe local reactions after extravasculation of intravenous solutions or following intramuscular injection treatment have been seen. Pentamidine itself may cause rash, or rarely Stevens–Johnson syndrome or Lyell syndrome. Eye discomfort, conjunctivitis, throat irritation, splenomegaly, Herxheimer reaction, electrolyte imbalances (e.g. hypocalcemia).
Pd-catalyzed Tyr O-alkylation By using a pre-formed electrophilic π-allylpalladium(II) reagent derived from allylic acetate or carbamate precursors, selective allylic alkylation of tyrosines can be achieved in aqueous solution at room temperature and in the presence of cysteines.
Sources: en.wikipedia.org
System suitability is typically performed before each batch or according to the validated method and laboratory procedure. Some long runs include periodic checks during analysis. The required frequency depends on regulatory expectations and method performance.
Retention time drift can result from changes in mobile phase composition, column temperature, pump flow, or column age. A gradual shift often points to column degradation. A sudden shift may indicate a leak, mixing error, or incorrect mobile phase.
Retention time alone cannot confirm identity because different compounds may elute at similar times. Coupling HPLC with mass spectrometry or comparing against authenticated standards increases confidence. Confirmation usually requires orthogonal data.
Method validation is the documented process of showing that an HPLC procedure produces reliable results for a defined purpose. It examines parameters such as accuracy, precision, specificity, linearity, and robustness. Regulators and quality systems often require validation before routine use.