Chromatogram 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.
Last reviewed on 2026-05-11. Where a claim depends on a specific study, the study is described rather than over-claimed.
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.
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.
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.
Routine quality control monitors retention time shifts, baseline noise, system pressure, and peak shape. Trends can reveal column aging, mobile phase preparation errors, detector drift, or sample degradation. Corrective actions may include replacing the column, preparing fresh mobile phase, or recalibrating the detector. Stability testing often uses HPLC to measure parent compound loss and degradation product formation. Open questions remain about how accelerated stability results extrapolate to long-term storage under varied conditions.
| Property | Value | Notes |
|---|---|---|
| Common abbreviation | HPLC | High-performance liquid chromatography |
| Separation basis | Differential partitioning | Between liquid mobile phase and solid stationary phase |
| Common mode | Reverse phase | Nonpolar column, polar mobile phase |
| Typical detector | UV-Vis absorbance | Widely used for compounds with chromophores |
| Typical column particle size | 2–5 µm | Smaller particles can improve resolution |
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.
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.
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.
In Ethiopia, the Civil Aviation Accident Prevention and Investigation Bureau of the Ethiopian Civil Aviation Authority (ECAA), which is an agency of the Ministry of Transport and Communications, conducts aircraft accident investigations in Ethiopia or involving Ethiopian aircraft. In France, the agency responsible for investigation of civilian air crashes is the Bureau d'Enquêtes et d'Analyses pour la Sécurité de l'Aviation Civile (BEA). Its purpose is to establish the circumstances and causes of the accident and to make recommendations for their future avoidance. In Germany, the agency for investigating air crashes is the Federal Bureau of Aircraft Accidents Investigation (BFU). It is an agency of the Federal Ministry of Transport and Digital Infrastructure. The focus of the BFU is to improve safety by determining the causes of accidents and serious incidents and making safety recommendations to prevent recurrence.
Liquid metal molybdenum-containing targets have been proposed that would aid in streamlined processing, ensuring better production yields. A particular problem associated with the continued reuse of recycled, enriched 100Mo targets is unavoidable transmutation of the target as other Mo isotopes are generated during irradiation and cannot be easily removed post-processing.
Proprotein convertases (PPCs) are a family of proteins that activate other proteins. Many proteins are inactive when they are first synthesized, because they contain chains of amino acids that block their activity. Proprotein convertases remove those chains and activate the protein. The prototypical proprotein convertase is furin. Proprotein convertases have medical significance, because they are involved in many important biological processes, such as cholesterol synthesis. Compounds called proprotein convertase inhibitors can block their action, and block the target proteins from becoming active. Many proprotein convertases, especially furin and PACE4, are involved in pathological processes such as viral infection, inflammation, hypercholesterolemia, and cancer, and have been postulated as therapeutic targets for some of these diseases.
And here is The Mystery of the Yellow Room. That - ah, that is really a classic! I approve of it from start to finish. Such a logical approach! There were criticisms of it, I remember, which said it was unfair. But it is not unfair, my dear Colin. No, no. Very nearly so, perhaps, but no not quite. There is the hair's breadth of difference. No. All through there is truth, concealed with a careful and cunning use of words. Everything should be clear at that supreme moment when the men meet at the angle of the three corridors." He laid it down reverently. "Definitely a masterpiece, and, I gather, almost forgotten nowadays. In a 1981 poll by Edward D. Hoch of 17 mystery writers and reviewers, this novel was voted the third-best locked-room mystery of all time, behind Hake Talbot's Rim of the Pit (1944) and John Dickson Carr's The Hollow Man (1935). The popular 1946 Japanese detective novel The Honjin Murders (本陣殺人事件, Honjin satsujin jiken) by Seishi Yokomizo refers to The Mystery of the Yellow Room numerous times, the narrator quipping that Leroux's novel "bears the closest resemblance" to the story recounted in the novel. The final episode of the 2025 Netflix miniseries The Residence is titled The Mystery of the Yellow Room and concludes the series with a locked-room murder deduction.
Sources: en.wikipedia.org
Raleigh's industrial base includes financial services, electrical, medical, electronic and telecommunications equipment, clothing and apparel, food processing, paper products, and pharmaceuticals. Raleigh is part of North Carolina's Research Triangle, one of the country's largest and most successful research parks, and a major center in the United States for high-tech and biotech research, as well as advanced textile development. The city is a major retail shipping point for eastern North Carolina and a wholesale distributing point for the grocery industry. The healthcare and pharmaceutical industry has experienced major growth in recent years with many companies based in Raleigh including PRA Health Sciences, Chiesi USA (subsidiary of Chiesi Farmaceutici), formerly Mallinckrodt prior to tax inversion to Ireland, MAKO Surgical Corp., Metabolon, Inc., TearScience, and American Board of Anesthesiology. Companies based in Raleigh include Advance Auto Parts, Bandwidth, Building Materials Holding Corporation, Capitol Broadcasting Company, First Citizens BancShares, Golden Corral, Japan Tobacco International, Martin Marietta Materials, PRA Health Sciences, Red Hat, Vontier, Waste Industries, and Lulu. Social Blade, a website that tracks social media statistics and analytics, and Temple Run developer Imangi Studios are based in Raleigh. The North Carolina Air National Guard, a unit of the Air National Guard, is also headquartered in Raleigh. In April 2014 Steven P. Rosenthal of Northland Investment Corp. referred to Raleigh as "a real concentration of brain power.
=== HIV transmission and treatment === In 1981, while working at UCSF in a lab that could perform the immunologic tests needed to detect immunodeficiency in AIDS patients, Ammann observed immunodeficiency disorders in children that mirrored those of gay men who had contracted the Human Immunodeficiency Virus. Ammann's investigations into the cause of the symptoms led him to identify two new means of transmission, in utero mother to infant and blood transfusions. With the medical community wanting not to believe that AIDS could affect infants, Ammann's initial publication blood transfusion infection was rejected by prominent medical journals. This discovery changed the perception of HIV/AIDS as an epidemic solely within the gay community. In 1985, Ammann left his position at UCSF in order to work with the biotechnology firm, Genentech. There he developed clinical products focused on HIV/AIDS, and although while with Genentech a successful vaccine was not developed, the discoveries made by Ammann's research team were used by other researchers in a partially successful study performed in Thailand in 2009. In 1994, Ammann was selected to become a member of the Presidential National AIDS Task Force on Drug and Vaccine Development. Three years later, in 1996, he was recognized by POZ magazine as one of the fifty most influential AIDS researchers.
Uniformity and precision in dosage for each dosage form. Results of therapeutic effects during the course of the treatment. Physical stability and appeal of the drug. Labeling of storage conditions and expiration dates.
The METLIN Metabolite and Chemical Entity Database is the largest repository of experimental tandem mass spectrometry and neutral loss data acquired from standards. The tandem mass spectrometry data on over 960,000 molecular standards (as of October, 2025) is provided to facilitate the identification of chemical entities from tandem mass spectrometry experiments. In addition to the identification of known molecules, it is also useful for identifying unknowns using its similarity searching technology. All tandem mass spectrometry data comes from the experimental analysis of standards at multiple collision energies and in both positive and negative ionization modes. METLIN serves as a data management system to assist in metabolite and chemical entity identification by providing public access to its repository of comprehensive MS/MS and neutral loss data. METLIN's annotated list of molecular standards include metabolites and other chemical entities, searching METLIN can be done based on a molecule's tandem mass spectrometry data, neutral loss masses, precursor mass, chemical formula, and structure within the METLIN website. Each molecule is linked to outside resources such as the Kyoto Encyclopedia of Genes and Genomes (KEGG) for further reference and inquiry. The METLIN database was developed and is maintained solely by the Siuzdak laboratory at The Scripps Research Institute.
The Soviet Union had built up a military that consumed as much as 25 percent of its gross national product at the expense of consumer goods and investment in civilian sectors. Soviet spending on the arms race and other Cold War commitments both caused and exacerbated deep-seated structural problems in the Soviet system, which experienced at least a decade of economic stagnation during the late Brezhnev years. Soviet investment in the defense sector was not driven by military necessity but in large part by the interests of the nomenklatura, which was dependent on the sector for their own power and privileges. The Soviet Armed Forces became the largest in the world in terms of the numbers and types of weapons they possessed, in the number of troops in their ranks, and in the sheer size of their military–industrial base. However, the quantitative advantages held by the Soviet military often concealed areas where the Eastern Bloc dramatically lagged behind the West. For example, the Persian Gulf War demonstrated how the armor, fire control systems, and firing range of the Soviet Union's most common main battle tank, the T-72, were drastically inferior to the American M1 Abrams, yet the USSR fielded almost three times as many T-72s as the US deployed M1s.
Sources: en.wikipedia.org
HPLC testing measures the presence and amount of one or more compounds in a liquid sample. It separates mixture components and records detector responses as peaks, which are compared with reference standards. Results are usually reported as concentrations or relative percentages.
Retention time is the interval between sample injection and the detector response for a given compound. It depends on the compound's interactions with the stationary and mobile phases under set conditions. Matching a retention time to a standard supports tentative identification but is not always unique.
HPLC alone can separate unknown compounds and provide retention times, but it often cannot identify them with certainty. Coupling HPLC to mass spectrometry gives mass information that improves identification. Confirmation usually requires comparison with reference standards or complementary techniques.
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.