This is a working overview of Calibration curve, written for readers who want more than a one-paragraph summary but less than a textbook.
This page was last updated on 2026-08-01 and is reviewed periodically as new material appears.
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.
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.
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.
| Property | Value | Notes |
|---|---|---|
| Accuracy | Closeness to true value | Often assessed by recovery of spiked samples |
| Precision | Agreement among repeated measurements | Often reported as relative standard deviation |
| Specificity | Ability to measure analyte without interference | Must separate analyte from impurities and matrix |
| Linearity | Proportional detector response | Evaluated across a defined concentration range |
| Robustness | Resistance to small method changes | Tests flow rate, pH, temperature, and mobile phase composition |
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.
Method validation demonstrates that an HPLC procedure is suitable for its intended purpose. Common validation parameters include accuracy, precision, specificity, linearity, range, limit of detection, limit of quantification, and robustness. Accuracy reflects agreement with a reference value, while precision describes repeatability under defined conditions. Specificity shows whether the method can measure the analyte in the presence of impurities or matrix components. Validation documents are reviewed before a method is used for routine testing or regulatory submissions.
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.
S-tag is the name of an oligopeptide derived from pancreatic ribonuclease A (RNase A). If RNase A is digested with subtilisin, a single peptide bond is cleaved, but the resulting two products remain weakly bound to each other and the protein, called ribonuclease S, remains active although each of the two products alone shows no enzymatic activity. The N-terminus of the original RNase A, also called S-peptide, consists of 20 amino acid residues, of which only the first 15 are required for ribonuclease activity. This 15 amino acids long peptide is called S15 or S-tag. The amino acid sequence of the S-tag is: Lys-Glu-Thr-Ala-Ala-Ala-Lys-Phe-Glu-Arg-Gln-His-Met-Asp-Ser. It is believed that the peptide with its abundance of charged and polar residues could improve solubility of proteins it is attached to. Moreover, the peptide alone is thought not to fold into a distinct structure. On DNA-level the S-tag can be attached to the N- or C-terminus of any protein. After gene expression, such a tagged protein can be detected by commercially available antibodies.
=== Management of insulin resistance === The main methods of management involve exercise and diet change, in addition to treatment of PPID. The primary goal is reduction of weight in an obese animal. Diet changes include limiting pasture access and reducing or eliminating grain. Obese animals are often best maintained on a diet consisting of ration balancer and hay, fed at 1.5% body weight and decreased if needed. Feed should be selected based on low nonstructural carbohydrate (NSC) levels. Hay NSC levels may be reduced by soaking it in cold water for 30 minutes. Exercise is increased in nonlaminitic horses. Animals resistant to weight loss, despite diet and exercise changes, can be placed on levothyroxine to increase metabolism. Metformin can also be used to reduce glucose absorption through the intestinal tract.
Thomas Aquinas claimed that X's soul was X's only substantial form, although X also had numerous accidental forms that accounted for X's nonessential features. Aquinas defined a substantial form as that which makes X's matter constitute X, which in the case of a human being is also able to transcend the limitations of matter and establish both the rational capacity and natural immortality of human beings. Nevertheless, Aquinas did not claim that human persons were their disembodied souls because the human soul is essentially a substantial form activating matter into the body. He held that a proper human being is a composite of the rational soul and matter (both prime matter and individualized matter). So a soul separated from its body does not become an angel but retains its orientation to animate matter, while a corpse from which the soul has departed is not actually or potentially a human being. Eleonore Stump describes Aquinas' theory of the soul in terms of "configuration". The body is matter that is "configured", i.e. structured, while the soul is a "configured configurer". In other words, the soul is itself a configured thing, but it also configures the body. A dead body is merely matter that was once configured by the soul. It does not possess the configuring capacity of a human being. Aquinas believed that rational capacity was a property of the soul alone, not of any bodily organ. However, he did believe that the brain had some basic cognitive function.
Sources: en.wikipedia.org
== Faculty Positions == On the faculty of Indiana University, Bloomington, since 1971. 1978 – Professor of Chemistry. 1980 – Visiting Scientist, Department of Immunogenetics, Max Planck Institute for Biology, Tübingen, Germany. 1988 – James H. Rudy Professor of Chemistry. 1999 – Distinguished Professor of Chemistry. 1999 – Director of the Institute for Pheromone Research. 2000–2015 – Lilly Chemistry Alumni Chair. 2004 – Adjunct Professor of Medicine, Indiana University School of Medicine. 2004–2009 – Director of the National Center for Glycomics and Glycoproteomics. 2010 – Director of the Novotny Glycoscience Laboratory. 2011 – Distinguished Professor Emeritus of Chemistry.
== Background == There is a debate on the composition, and the subsequent health burden, of tobacco smoke compared with electronic cigarette vapor. Tobacco smoke is a complex, dynamic and reactive mixture containing around 5,000 chemicals. In 2021, researchers at Johns Hopkins University analyzed the vape aerosols of popular brands such as Juul and Vuse, and found "nearly 2,000 chemicals, the vast majority of which are unidentified." E-cigarette vapor contains many of the known harmful toxicants found in traditional cigarette smoke, such as formaldehyde, cadmium, and lead, though usually at a reduced percentage. There are substances in e-cigarette vapor that are not found in tobacco smoke. Researchers are part of the conflict, with some opposing and others supporting of e-cigarette use. The public health community is divided, even polarized, over how the use of these devices will impact the tobacco epidemic. Some proponents of e-cigarettes think that these devices contain merely "water vapour" in the e-cigarette aerosols, but this view is refuted by the evidence.
People with Becker's muscular dystrophy, which is milder than DMD, have a form of dystrophin that is functional even though it is shorter than normal dystrophin. In 1990 England et al. noticed that a patient with mild Becker muscular dystrophy was lacking 46% of his coding region for dystrophin. This functional, yet truncated, form of dystrophin gave rise to the notion that shorter dystrophin can still be therapeutically beneficial. Concurrently, Kole et al. had modified splicing by targeting pre-mRNA with antisense oligonucleotides (AONs). Kole demonstrated success using splice-targeted AONs to correct missplicing in cells removed from beta-thalassemia patients Wilton's group tested exon skipping for muscular dystrophy.
1993/1223) Value Added Tax (General) (Amendment) (No. 4) Regulations 1993 (S.I. 1993/1224) Bromley and Greenwich (London Borough Boundaries) Order 1993 (S.I. 1993/1225) Medicines (Veterinary Drugs) (Renewal Applications for Licences and Animal Test Certificates) Regulations 1993 (S.I. 1993/1227) Beer Regulations 1993 (S.I. 1993/1228) Financial Services (Designated Countries and Territories) (Overseas Insurance Companies) Order 1993 (S.I. 1993/1237) Scottish Hospital Endowments Research Trust (Amendment) Regulations 1993 (S.I. 1993/1238) National Savings Bank (Investment Deposits) (Limits) (Amendment) Order 1993 (S.I. 1993/1239) Soft Drinks (Amendment) Regulations 1993 (S.I. 1993/1240) South West Regional Flood Defence Committee Order 1993 (S.I. 1993/1241) Social Security (Widow's Benefit and Retirement Pensions) Amendment Regulations 1993 (S.I. 1993/1242) Child Abduction and Custody (Parties to Conventions) (Amendment) Order 1993 (S.I. 1993/1243) Iraq (United Nations) (Sequestration of Assets) Order 1993 (S.I. 1993/1244) Iraq (United Nations) (Sequestration of Assets) (Dependent Territories) Order 1993 (S.I. 1993/1245) Treaty on Open Skies (Privileges and Immunities) Order 1993 (S.I. 1993/1246) Treaty on Open Skies (Privileges and Immunities) (Overseas Territories) Order 1993 (S.I. 1993/1247) Turks and Caicos Islands Constitution (Amendment) Order 1993 (S.I. 1993/1248) Income-related Benefits Schemes and Social Security (Recoupment) Amendment Regulations 1993 (S.I. 1993/1249) Access to Health Records (Northern Ireland) Order 1993 (S.I.
Sources: en.wikipedia.org
Midtown Raleigh is a relatively new term used to describe the residential and commercial area lying on the northside of the I-440 Beltline and is part of North Raleigh. It is roughly framed by Glenwood/Six Forks Road to the West, Wake Forest Road to the East, and Millbrook Road to the North. It includes shopping centers such as North Hills and Crabtree Valley Mall. It also includes North Hills Park and part of the Raleigh Greenway System. The term was coined by the Greater Raleigh Chamber of Commerce, developer John Kane and planning director Mitchell Silver. The News & Observer newspaper started using the term for marketing purposes only. The Midtown Raleigh Alliance was founded on July 25, 2011, as a way for community leaders to promote the area. The center of the area, especially around the North Hills development at the junction of Six Forks Road and the Beltline, is experiencing rapid urbanization as several high-rise buildings have been built since 2010.
Long-term informal caregiving is associated with wide-ranging impacts on physical and mental health and on financial circumstances, collectively described as caregiver burden. A range of interventions can help alleviate burden and improve caregiver wellbeing. Effective measures include complementary formal services, training and psychoeducation, psychological therapies such as cognitive behavioural therapy, and support groups.
Zidesamtinib, sold under the brand name Jideytro, is an anti-cancer medication used for the treatment of non-small cell lung cancer. Zidesamtinib is a kinase inhibitor. It is taken by mouth. Zidesamtinib was approved for medical use in the United States in July 2026.
Sources: en.wikipedia.org
System suitability is a set of checks performed before and during a run to confirm that the instrument, column, and method work as expected. Common checks include resolution, tailing factor, theoretical plates, and relative standard deviation of replicate injections. Failure triggers troubleshooting or method adjustment.
Validation demonstrates that a method produces reliable results for a defined purpose. It documents performance limits and acceptance criteria. Regulated industries require validation before routine testing of products or samples.
Retention time shifts can arise from changes in mobile phase composition, pH, temperature, column age, or flow rate. Contamination or worn seals may also alter pressure and delivery. Systematic checks of these factors help identify the cause.
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.