Everything below concerns method validation. We keep the language plain, cite what the science says, and separate well-supported claims from open questions.
Updated 2026-07-14. 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 of a liquid sample by passing it 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 interaction with the stationary phase cause analytes to migrate at different rates. Detectors record elution as peaks, and a data system converts signals into a chromatogram. The method is suited to compounds that dissolve in a liquid and are not volatile enough for gas chromatography.
Reversed-phase chromatography dominates modern HPLC testing, using a nonpolar stationary phase such as chemically bonded octadecyl groups and a polar mobile phase of water mixed with organic solvent. Analytes partition between the mobile and stationary phases according to hydrophobicity. Gradient elution changes the mobile phase composition over time to separate compounds with a wide range of retention. Isocratic elution keeps the composition constant and is simpler for routine assays. Column temperature, pH, and flow rate influence selectivity, peak shape, and retention time, so these parameters are controlled during a validated method.
Detection in HPLC testing commonly relies on ultraviolet-visible absorbance, fluorescence, refractive index, or mass spectrometry. A diode array detector records full spectra across a wavelength range, which helps identify co-eluting peaks. Mass spectrometry provides mass-to-charge ratios and can confirm molecular identity at low concentrations. The choice of detector depends on analyte structure, required sensitivity, and whether quantitation or identification is the goal. No single detector works for every compound, and method development often compares responses before selecting one.
| 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. |
Validation demonstrates that a method is suitable for its intended use. Typical performance characteristics include accuracy, precision, specificity, linearity, range, limit of detection, limit of quantitation, and robustness. Regulators and standards organizations provide frameworks, but specific requirements depend on the application and jurisdiction. System suitability tests are run before sample analysis to confirm resolution, peak symmetry, retention time repeatability, and sensitivity. A validated method is not permanently fixed; changes may require partial or full 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.
=== Medicine === Medical technicians may sequence genes (or, theoretically, full genomes) from patients to determine if there is risk of genetic diseases. This is a form of genetic testing, though not all genetic tests involve complete genome DNA sequencing. As of 2013 DNA sequencing was increasingly used to diagnose and treat rare diseases. As more and more genes are identified that cause rare genetic diseases, molecular diagnoses for patients become more mainstream. DNA sequencing allows clinicians to identify genetic diseases, improve disease management, provide reproductive counseling, and more effective therapies. Gene sequencing panels are used to identify multiple potential genetic causes of a suspected disorder. Also, DNA sequencing may be useful for determining a specific bacteria, to allow for more precise antibiotics treatments, hereby reducing the risk of creating antimicrobial resistance in bacteria populations.
=== Casting === In February 2024, it was announced that Jessica Green had joined the cast of The Librarians: The Next Chapter. In March, it was announced Christian Kane would reprise the role of Jacob Stone, and that British actors Callum McGowan, Olivia Morris, Bluey Robinson, and Caroline Loncq had also joined the cast of the series.
UPMC Harrisburg is a 409-bed urban, teaching hospital in Harrisburg, Pennsylvania, serving as the primary referral hospital for the UPMC Central PA system which comprises seven hospitals and additional clinics serving south central and southeastern Pennsylvania.
Sources: en.wikipedia.org
Access to transition care, mental care, and other issues affecting transgender people is very limited; there is only one comprehensive transgender health care clinic available in South Africa. Additionally, the typical lack of access to transition options that comes as a result of gatekeeping is compounded by the relatively limited knowledge of transgender topics among psychiatrists and psychologists in South Africa.
Endre Mester (1903–1984) was a Hungarian physician and pioneer of laser medicine, especially the use of low level laser therapy (LLLT). In 1967, only a few years after the first working laser was invented, he started his experiments with the effects of lasers on skin cancer. He is credited as the discoverer of positive biological effects of low power lasers, which have been advocated as alternative medicine for use in wound healing, smoking cessation, tuberculosis, temporomandibular joint disorders, and musculoskeletal conditions such as carpal tunnel syndrome, fibromyalgia, osteoarthritis, and rheumatoid arthritis. LLLT devices are popular and may bring about temporary relief of some types of pain. As of 2009, a summary from Quackwatch reported medical authorities found no reason to believe LLLT influence the course of any ailment or are more effective for pain control than other forms of heat delivery. Subsequent research has found LLLT may offer benefit in treating several health ailments, including rheumatoid arthritis, osteoarthritis, tendinopathy, and frozen shoulders.
== MrBayes software == MrBayes is a free software tool that performs Bayesian inference of phylogeny. It was originally written by John P. Huelsenbeck and Frederik Ronquist in 2001. As Bayesian methods increased in popularity, MrBayes became one of the software of choice for many molecular phylogeneticists. It is offered for Macintosh, Windows, and UNIX operating systems and it has a command-line interface. The program uses the standard MCMC algorithm as well as the Metropolis coupled MCMC variant. MrBayes reads aligned matrices of sequences (DNA or amino acids) in the standard NEXUS format. MrBayes uses MCMC to approximate the posterior probabilities of trees. The user can change assumptions of the substitution model, priors and the details of the MC³ analysis. It also allows the user to remove and add taxa and characters to the analysis. The program includes, among several nucleotide models, the most standard model of DNA substitution, the 4x4 also called JC69, which assumes that changes across nucleotides occur with equal probability. It also implements a number of 20x20 models of amino acid substitution, and codon models of DNA substitution. It offers different methods for relaxing the assumption of equal substitutions rates across nucleotide sites. MrBayes is also able to infer ancestral states accommodating uncertainty to the phylogenetic tree and model parameters. MrBayes 3 was a completely reorganized and restructured version of the original MrBayes. The main novelty was the ability of the software to accommodate heterogeneity of data sets.
=== Political activism === In 2018, she became spokesperson of the On est prêt collective. She spoke at the European Parliament, notably alongside Greta Thunberg, Belgians Adélaïde Charlier and Anuna De Wever and the German Luisa Neubauer. It was at Sciences Po Paris that Camille turned her attention to the climate crisis. She became president of the student branch of Amnesty International. She was also elected, in 2018, to the student organisation NOVA. During lockdown, she created the collective 'Avant l'orage' (Before the Storm) which aims to bring together art and environmentalism. On 28 May 2020 the collective's YouTube channel released a video titled Wake Up. The video, filmed in the mountains, features the activist with a dancer and engineering graduate, Léa Durand. Camille speaks about the climate emergency and reminds viewers, particularly those from Generation Z, on the need to act. Her words are accompanied by movements from the dancer. The video was a success, gaining 15 million views on various platforms and has been translated into Spanish, English, German and Portuguese. In August 2020, while speaking at the Medef summer school, she suggested "working less, but maybe with more meaning" to "reinvent" the world of business. She also questions the economic growth model, which, according to her, pushes us to "produce too much", "exceed planetary limits" and so "directly endangers our lives".
Sources: en.wikipedia.org
== I == Sir Christopher Kelk Ingold (1893–1970), English chemist known for introducing concepts such as nucleophile, electrophile, inductive and resonance effects Vladimir Ipatieff (1867–1952), Russian-American chemist who worked in petroleum chemistry and catalysts
As with cocaine in Coca-Cola, lithium was widely marketed as one of several patent medicine products popular in the late 19th and early 20th centuries and was claimed to be included in many drinks including lithia water and 7 Up. Charles Leiper Grigg, who launched his St. Louis-based company The Howdy Corporation, invented a formula for a lemon-lime soft drink in 1920. The product, at one point named "7Up Lithiated Lemon Soda", was launched two weeks before the Wall Street Crash of 1929. It claimed to contain the mood stabilizer lithium citrate, and was one of many patent medicine products popular in the late-19th and early-20th centuries. All references to lithium were removed in 1937 after it became clear that 7Up contains no lithium. Many sources written by scientists (instead of historians) incorrectly report that 7 Up was forced to remove lithium in 1948, with an FDA action that supposedly banned lithium from beverages. Despite the supposed ban, in 1950, the Painesville Telegraph still carried an advertisement for a lithiated lemon beverage.
== Medical uses == Both corticotropin and tetracosactide have been used for diagnostic purposes to determine adrenocortical insufficiency, particularly in Addison's disease, via the ACTH stimulation test. However, as of 2015 the US label for corticotropin does not include diagnostic use. Both corticotropin and tetracosactide have been used for therapeutic purposes. In the US the tetracosactide label is limited to diagnosis but the UK label provides for therapeutic uses. In the US corticotropin is used to treat epileptic spasms in infants, acute exacerbations of multiple sclerosis in adults; acute episodes of psoriatic arthritis and rheumatoid arthritis and ankylosing spondylitis; in acute exacerbations or as maintenance therapy for collagen disorders like systemic lupus erythematosus and systemic dermatomyositis; for skin conditions like severe erythema multiforme and Stevens–Johnson syndrome; for serum sickness; for severe acute and chronic allergic and inflammatory processes involving the eye such as keratitis, iritis and iridocyclitis, diffuse posterior uveitis, choroiditis, optic neuritis, chorioretinitis, and anterior segment inflammation; sarcoidosis in the lungs; and to treat edema in certain nephrotic syndromes. In the UK tetracosactide is used for short-term therapy in conditions for which glucocorticoids are usually used but for some reason should not be; some uses include use for people who do not respond to glucocorticoids or cannot tolerate them who have ulcerative colitis, Crohn's disease, juvenile rheumatoid arthritis, rheumatoid arthritis, or osteoarthrosis.
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 testing separates and quantifies components in a liquid sample. It is used to check identity, purity, concentration, or stability. The technique works best for compounds that dissolve and are not easily vaporized.