This is a working overview of Resolution, written for readers who want more than a one-paragraph summary but less than a textbook.
This page was last updated on 2025-12-31 and is reviewed periodically as new material appears.
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.
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.
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.
| Property | Value | Notes |
|---|---|---|
| Separation principle | Differential partitioning | Analytes distribute between mobile and stationary phases. |
| Mobile phase | Liquid solvent mixture | Composition controls retention and selectivity. |
| Stationary phase | Packed column particles | Often chemically bonded silica. |
| Typical detector | UV-Vis or photodiode array | Mass spectrometry is also common. |
| Common synonym | High-performance liquid chromatography | Abbreviated as HPLC. |
High-performance liquid chromatography is an analytical technique that separates components in a liquid sample. A pump moves a liquid mobile phase through a column packed with a solid stationary phase. Compounds interact differently with both phases and travel at different rates, leaving the column at distinct retention times. A detector records these arrivals as peaks on a chromatogram. The resulting pattern supports identification and quantification of substances in mixtures. Modern instruments use high pressure to force solvent through small particles, which improves speed and resolution compared with older low-pressure liquid chromatography methods.
Separation in HPLC depends on the chemistry of the stationary phase, the composition of the mobile phase, and the physical properties of the column. Reverse-phase separations use a nonpolar stationary phase and a polar mobile phase, and they are common for many organic compounds. Ion-exchange, size-exclusion, and normal-phase modes serve other classes of analytes. Gradient elution changes solvent strength over time, while isocratic elution holds it constant. Flow rate, temperature, particle size, and column length all influence peak shape and resolution. Detection may use ultraviolet absorbance, fluorescence, refractive index, or mass spectrometry, depending on the analyte and the required sensitivity.
Routine HPLC testing compares a sample result with a calibration curve prepared from known reference standards. Peak area or peak height is plotted against concentration, and the curve is used to estimate unknown amounts. Retention time supports tentative identification when compared with a standard, though mass spectrometry or another confirmatory method may be needed for definitive identification. Pre-run checks verify repeatability, resolution, and peak symmetry before sample analysis. Limits of detection and quantification describe the smallest amounts that can be reliably observed or measured. Sample preparation, filtration, and degassing help prevent column damage and inconsistent results.
Method validation demonstrates that an analytical procedure is suitable for its intended purpose. Typical validation characteristics include accuracy, precision, specificity, linearity, range, limit of detection, limit of quantitation, and robustness. Regulatory guidance from bodies such as the International Council for Harmonisation and the United States Pharmacopeia outlines expectations, though specific criteria depend on the product and method. System suitability tests are run before sample analysis to confirm resolution, peak symmetry, column efficiency, and injection repeatability. Failure of these checks can invalidate a batch of measurements.
Practical HPLC testing depends on careful sample preparation and instrument maintenance. Samples may require filtration, dilution, pH adjustment, or extraction to avoid column damage and matrix interference. Mobile phases are degassed and filtered, and columns are equilibrated before injection. Common problems include peak tailing, baseline drift, ghost peaks, carryover, and co-elution of analytes. Documentation of instrument logs, calibration records, and electronic audit trails supports data integrity and traceability. Ongoing training and routine maintenance help reduce variability between analysts and laboratories.
Quality control laboratories use HPLC to check identity, purity, concentration, and stability of raw materials and finished products. A validated method specifies the column, mobile phase, flow rate, detection wavelength, injection volume, and run time. Samples are prepared and compared against reference standards of known concentration. The resulting chromatogram provides quantitative data, such as assay values and impurity levels. This approach is common in pharmaceutical, food, environmental, and industrial testing where consistent measurements are required.
Amylin, or islet amyloid polypeptide (IAPP), is a 37-residue peptide hormone. It is co-secreted with insulin from the pancreatic β-cells in the ratio of approximately 100:1 (insulin:amylin). Amylin plays a role in glycemic regulation by slowing gastric emptying and promoting satiety, thereby preventing spikes in blood glucose levels after a meal. IAPP is processed from an 89-residue coding sequence. Proislet amyloid polypeptide (proIAPP, proamylin, proislet protein) is produced in the pancreatic beta cells (β-cells) as a 67 amino acid, 7404 Dalton pro-peptide and undergoes post-translational modifications including protease cleavage to produce amylin.
=== Trim weights in aircraft === Aircraft that contain depleted uranium trim weights for stabilizing wings and control surfaces (such as the Boeing 747–100) may contain between 652 and 1,059 pounds (296 and 480 kg) of DU. This application is controversial because the DU might enter the environment if the aircraft crashes. The metal can also oxidize to a fine powder in a fire. Its use has been phased out in many newer aircraft. Boeing and McDonnell-Douglas discontinued using DU counterweights in the 1980s. Depleted uranium was released during the crash of El Al Flight 1862 on 4 October 1992, in which 152 kilograms (335 lb) was lost, but a case study concluded that there was no evidence to link depleted uranium from the plane to any health problems. DU counterweights manufactured with cadmium plating are considered non-hazardous as long as the plating is intact.
=== Diabetes === Empagliflozin is indicated in adults with type 2 diabetes and established cardiovascular disease to reduce the risk of cardiovascular death; and as an adjunct to diet and exercise to improve glycemic control in adults with type 2 diabetes. In June 2023, the US Food and Drug Administration (FDA) expanded the indication, as an addition to diet and exercise, to improve blood sugar control in children 10 years and older with type 2 diabetes. Empagliflozin has shown beneficial effects on cardiovascular morbidity and mortality in patients with type 2 diabetes. Additionally, large-scale randomised controlled trials have demonstrated that empagliflozin decreases heart failure hospitalisations and cardiovascular mortality in adults with heart failure, whether they have reduced, mid-range, or preserved left ventricular ejection fraction and regardless of type 2 diabetes status. There is evidence from high quality studies that empagliflozin can also help to slow the rate of kidney function decline. Irrespective of diabetes status, benefit was observed in those with mild, moderate or severe loss of kidney function. People started on empagliflozin may first see a decrease in kidney function before their glomerular filtration rate stabilises. Greatest benefit was demonstrated in those who had severe loss of kidney function, higher risk of kidney function worsening and background of diabetes. Empagliflozin is also available as the fixed-dose combinations empagliflozin/linagliptin, empagliflozin/metformin, and empagliflozin/linagliptin/metformin.
Bolivia, however, was seeking additional funds from the United States and Western Europe to proceed with an eradication plan that was supposed to provide peasants US$2,000 per hectare eradicated. With the 1988 passage of Law 1008, coca growing became technically illegal outside a specially mandated 12,000- hectare area in the Yungas. A four-year government eradication campaign begun in 1989 sought to convert 55 percent of coca areas into legal crops. Coffee and citrus fruits were offered as alternative crops to coca despite the fact that their return was a fraction of that of coca. These crops were also harder to sell and transport. Coca has a much longer shelf-life than that of fruit crops, which require rapid transportation. The cocaine industry had a generally deleterious effect on the Bolivian economy. The cocaine trade greatly accelerated the predominance of the United States dollar in the economy and the large black market for currency, thereby helping to fuel inflation in the 1980s. The escalation of coca cultivation also damaged the output of fruits and coffee, which were mostly destined for local consumption. Coca's high prices, besides being generally inflationary, also distorted other sectors, especially labor markets. Manufacturers in the Cochabamba area during the 1980s found it impossible to match the wages workers could gain in coca, making their supply of labor unreliable and thus hurting the formal economy. In an example of the balloon effect, dramatic falls in coca cultivation in the late 1990s saw some cultivation move to Colombia.
Sources: en.wikipedia.org
=== Army service === In the U.S. Army, Jones took part in World War I in an all-Black unit until his mechanical skills were spotted, and he was promoted to sergeant working as an electrician and even teaching other soldiers. Jones performed the wiring necessary to equip his camp with electricity, telegraph, and telephone services.
In 1997, Freeman narrated the Academy Award-winning documentary The Long Way Home, about Jewish refugees' liberation after World War II and the establishment of Israel. He also appeared in Steven Spielberg's historical epic Amistad alongside Djimon Hounsou, Anthony Hopkins, and Matthew McConaughey. Based on the events in 1839 aboard the slave ship La Amistad, the film was mostly well-received and earned four nominations at the Academy Awards. The critic from Salon magazine, however, thought the film lacked inspiration and Freeman's role was "utterly cryptic". In that same year, he was cast as psychologist Alex Cross in Kiss the Girls, a thriller based on James Patterson's 1995 novel of the same name. In a mixed review, Peter Stack of San Francisco Chronicle thought Freeman and co-star Ashley Judd gave strong performances despite the lengthy plot. Freeman went on to star in Deep Impact (1998), a science-fiction disaster film in which he played President Tim Beck. The story depicts humanity's attempt to destroy a 7-mile (11 km) wide comet set to collide with Earth and cause a mass extinction. The film was a box-office hit, despite competition from Armageddon, another summer blockbuster of the year. Continuing with the disaster genre, he then starred opposite Christian Slater in 1998's Hard Rain, centering on a heist and man-made treachery amidst a natural disaster in a small Indiana town. The film was unpopular with critics; Lawrence Van Gelder of The New York Times called the characters "one-dimensional" and the film "routine".
== Treatment == During the early 1940s, rabbit models in combination with the drug penicillin allowed for a long-term drug treatment. These experiments established the groundwork that modern scientists use for syphilis therapy. Penicillin can inhibit T. pallidum in 6–8 hours, though the cells still remain in lymph nodes and regenerate. Penicillin is not the only drug that can be used to inhibit T. pallidum; any β-lactam antibiotics or macrolides can be used. The T. pallidum strain 14 has built-in resistance to some macrolides, including erythromycin and azithromycin. Resistance to macrolides in T. pallidum strain 14 is believed to derive from a single-point mutation that increased the organism's livability. Many of the syphilis treatment therapies only lead to bacteriostatic results, unless larger concentrations of penicillin are used for bactericidal effects. Penicillin overall is the most recommended antibiotic by the Centers for Disease Control, as it shows the best results with prolonged use. It can inhibit and may even kill T. pallidum at low to high doses, with each increase in concentration being more effective. The Guideline Development Group has recommended the development of a new treatment, a short course treatment that is administered orally and can cross the placental barriers in pregnant women.
Sources: en.wikipedia.org
At least one study indicates that individuals with a DSD condition may be more prone to psychological difficulties, due at least in part to parental attitudes and behaviors, and concludes that preventative long-term psychological counseling for parents as well as for affected individuals should be initiated at the time of diagnosis. A retrospective study shows that the prevalence of anxiety and depressive disorders among CAIS individuals is approximately twice as high as in male referents without DSD, but no evident corresponding difference has been found compared to female referents. Lifespan is not thought to be affected by AIS. Despite the well-developed breasts in CAIS women, and for reasons that are not well-understood, breast cancer has never been reported in CAIS women and does not seem to occur or occurs only rarely. Only one case report of juvenile fibroadenoma exists. A few cases of breast cancer have been reported in individuals with partial androgen insensitivity syndrome. In contrast to bone health, both transdermal estradiol treatment and testosterone treatment in women with CAIS results in worsening in lipid profiles. A case report in 2009 also shows that CAIS individuals with intact testes (with endogenous hormone) are more likely to be obese. A study which includes five CAIS and two PAIS adolescents with ages ranging from 15 to 24 shows elevated homeostatic model assessment for insulin resistance (HOMA-IR) scores for all subjects.
The simulated moving bed (SMB) technique is a variant of high performance liquid chromatography; it is used to separate particles and/or chemical compounds that would be difficult or impossible to resolve otherwise. This increased separation is brought about by a valve-and-column arrangement that is used to lengthen the stationary phase indefinitely. In the moving bed technique of preparative chromatography the feed entry and the analyte recovery are simultaneous and continuous, but because of practical difficulties with a continuously moving bed, simulated moving bed technique was proposed. In the simulated moving bed technique instead of moving the bed, the sample inlet and the analyte exit positions are moved continuously, giving the impression of a moving bed. True moving bed chromatography (TMBC) is only a theoretical concept. Its simulation, SMBC is achieved by the use of a multiplicity of columns in series and a complex valve arrangement. This valve arrangement provides for sample and solvent feed and analyte and waste takeoff at appropriate locations of any column, whereby it allows switching at regular intervals the sample entry in one direction, the solvent entry in the opposite direction, whilst changing the analyte and waste takeoff positions appropriately as well.
A capsule is a gelatinous envelope enclosing the active substance. Capsules can be designed to remain intact for some hours after ingestion in order to delay absorption. They may also contain a mixture of slow and fast release particles to produce rapid and sustained absorption in the same dose.
Tanaka Team have developed a diagnostic technology that enables early detection of diseases from a small amount of blood. By artificially modifying antibodies with polyethylene glycol at their base, the arms can move like springs, allowing simultaneous binding to antigens. In experiments with protein fragments related to Alzheimer's disease, the modified antibodies captured antigens more than 100 times more strongly than conventional antibodies. Later improvements enabled glycan analysis from trace mixed samples without peptide selection, leading to the detection of Alzheimer’s-related proteins from 1 mL of blood and the identification of eight previously unknown related substances. This technology is expected to contribute to the early detection of various diseases, including Alzheimer’s disease and prostate cancer. The research originated from work awarded the Nobel Prize in 2002, though the initial methods lacked sufficient sensitivity for medical applications. In 2009, it was selected for the FIRST Program, Development of Next-Generation Mass Spectrometry Systems and Contributions to Drug Discovery and Diagnosis, which provided about 4 billion yen over five years. With a team of around 60 researchers, a breakthrough analytical method was developed within a year, achieving up to a 10,000-fold increase in sensitivity. In November 2011, the team described the results as a technology applicable to early diagnosis and antibody-based drug development, publishing findings in the electronic edition of an English journal issued by the Japan Academy.
Sources: en.wikipedia.org
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.
Pressure drives the liquid mobile phase through a column packed with small particles. Without pressure, flow would be very slow or stop because the packed bed resists liquid movement. Modern pumps maintain a steady flow despite the resistance.
A chromatogram is a plot of detector signal against time after sample injection. Each peak represents a compound or group of compounds eluting from the column. Retention time and peak area are the main measurements read from the plot.
It is a set of checks performed before or during an HPLC run to confirm the system works as expected. Parameters may include resolution, tailing factor, theoretical plates, and retention time precision. Failure can trigger maintenance, method adjustment, or repeat analysis.