This is a working overview of quality control, written for readers who want more than a one-paragraph summary but less than a textbook.
This page was last updated on 2025-09-15 and is reviewed periodically as new material appears.
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.
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.
Detection in HPLC testing commonly relies on ultraviolet-visible absorbance, fluorescence, refractive index, or mass spectrometry. UV detection is widely used because many organic compounds absorb light, but it requires a chromophore. Mass spectrometry provides mass-based identification and high sensitivity for trace analytes. Each detector has trade-offs in selectivity, cost, and compatibility with mobile phases. Quantification typically uses calibration curves prepared from reference standards. Results are reported as concentration, purity, or presence above a limit.
HPLC testing separates dissolved compounds by passing a liquid sample through a column packed with stationary phase. A pump delivers mobile phase at controlled flow, and the sample components interact differently with stationary and mobile phases. Compounds that spend more time in mobile phase elute earlier; those retained by stationary phase elute later. Detectors record elution as peaks, and peak area or height relates to amount. This mechanism underpins quantitative analysis of mixtures.
Most routine HPLC testing uses reversed-phase columns, where the stationary phase is nonpolar and the mobile phase is a polar mixture such as water with an organic solvent. Analytes partition between the two phases according to polarity, size, and charge. Gradients that change solvent composition over time can separate compounds with broad retention ranges. Isocratic conditions keep solvent composition constant and suit simpler mixtures. The choice of column chemistry, pH, and temperature affects selectivity and peak shape.
| Property | Value | Notes |
|---|---|---|
| Separation mode | Reversed-phase | Most common for neutral and moderately polar analytes |
| Column particle size | 3–5 µm | Smaller particles improve resolution but raise backpressure |
| Mobile phase pH range | 2–8 | Silica-based columns may degrade outside this range |
| Typical flow rate | 1.0–2.0 mL/min | For analytical columns with 4.6 mm internal diameter |
| Common synonyms | HPLC, LC, high-pressure liquid chromatography | High-performance liquid chromatography is the standard expansion |
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.
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.
Key performance measures include retention time, peak area, peak height, resolution, tailing factor, and plate count. Retention time helps identify a peak under fixed conditions, but confirmation often requires a second method or detector. Peak area and height relate to concentration through calibration curves, which may be linear or nonlinear depending on the detector response. Resolution describes separation between adjacent peaks, while tailing factor and plate count describe peak shape and column efficiency. Performance checks verify these values before and during a run to confirm that the instrument is performing within limits.
High-performance liquid chromatography testing separates components of a liquid sample by forcing a mobile phase through a packed column. The stationary phase inside the column interacts with analytes to different degrees, so each compound exits at a characteristic retention time. A pump delivers solvent at controlled flow and pressure, while an injector introduces a precise sample volume. Detectors such as ultraviolet-visible, fluorescence, refractive index, or mass spectrometric instruments record the separated bands. The resulting chromatogram provides qualitative and quantitative information about the mixture.
Separation modes differ by the chemistry of the stationary phase and the composition of the mobile phase. Reversed-phase testing uses a nonpolar column and polar solvents, making it common for pharmaceutical, environmental, and food analytes. Normal-phase testing uses a polar column and nonpolar solvents for compounds that are poorly retained in reversed-phase systems. Ion-exchange and ion-pair methods separate charged species, while size-exclusion methods sort molecules by hydrodynamic volume. Gradient elution changes solvent strength over time to resolve complex mixtures, and isocratic elution holds solvent composition constant for simpler assays.
System suitability testing is performed before and during analytical runs to confirm that the instrument and method are working as expected. Common checks include retention time, peak area, resolution between critical pairs, tailing factor, and theoretical plate count. Results are compared with predefined limits, and a failed check requires investigation before sample results are reported. Quality control samples at low, middle, and high concentrations are injected at intervals to monitor accuracy and precision. Blank injections detect carryover and contamination, while control charts track performance over time.
Data handling and documentation are central to HPLC quality control. Electronic systems should have audit trails that record changes to methods, sequences, and results. Integration parameters, such as peak baseline and threshold, can affect reported areas and must be defined in advance. Out-of-specification results trigger a structured investigation that may include reanalysis, instrument checks, and review of sample preparation. Regulatory inspections often examine raw data, audit trails, and training records to verify that reported results are traceable and reliable.
Method validation establishes that an HPLC procedure is suitable for its intended use. Key parameters include accuracy, precision, specificity, linearity, range, limit of detection, limit of quantitation, and robustness. Accuracy measures agreement with a true or accepted value, while precision describes repeatability and intermediate precision. Specificity confirms that the method measures the analyte without interference from impurities, degradants, or excipients. Validation is documented in a protocol and report, and acceptance criteria are set before experiments begin. Regulatory guidance varies by region, but the general principles are widely harmonized.
The source of ADP-ribose for most enzymes that perform this modification is the redox cofactor NAD+. In this transfer reaction, the N-glycosidic bond of NAD+ that bridges the ADP-ribose molecule and the nicotinamide group is cleaved, followed by nucleophilic attack by the target amino acid side chain. (ADP-ribosyl)transferases can perform two types of modifications: mono(ADP-ribosyl)ation and poly(ADP-ribosyl)ation.
"Chelating agents are organic compounds which are capable of linking to metal ions". They are usually useful for removing toxic heavy metal ions from body. Dimercaprol is a common chelating agent to treat toxic exposure to arsenic, mercury, gold, and lead. It is in the chelating class of drugs. From Figure 3, the SH-ligands of dimercaprol can compete with -SH groups in natural enzymes for heavy metal, forming a stable metal complex to be excreted through urine. The action antagonises the toxic metal ions and helps remove them from body circulation. However, dimercaprol has a narrow TI and is later replaced by its derivative, 2,3-dimercaptosuccinic acid (DMSA). Neutralising antibodies block pathogen entry into cells to prevent further infection and replication. Infliximab is a monoclonal antibody binding with tumour necrosis factor-alpha (TNF-alpha), inhibiting its pro-inflammatory action. Its efficacious anti-inflammatory action is clinically used in Crohn's Disease, active rheumatoid arthritis, psoriatic arthritis, and active ankylosing spondylitis.
== Further reading == Fetter, Steve; Cheng, E. T.; Mann, F. M. (1990). "Long-term radioactive waste from fusion reactors: Part II". Fusion Engineering and Design. 13 (2): 239–246. CiteSeerX 10.1.1.465.5945. doi:10.1016/0920-3796(90)90104-E. ISSN 0920-3796. {{cite journal}}: Cite uses deprecated parameter |citeseerx= (help) Holland, Jason P.; Sheh, Yiauchung; Lewis, Jason S. (2009). "Standardized methods for the production of high specific-activity zirconium-89". Nuclear Medicine and Biology. 36 (7): 729–739. doi:10.1016/j.nucmedbio.2009.05.007. ISSN 0969-8051. PMC 2827875. PMID 19720285. McCarthy, Deborah W.; Shefer, Ruth E.; Klinkowstein, Robert E.; Bass, Laura A.; Margeneau, William H.; Cutler, Cathy S.; Anderson, Carolyn J.; Welch, Michael J. (1997). "Efficient production of high specific activity 64Cu using a biomedical cyclotron". Nuclear Medicine and Biology. 24 (1): 35–43. doi:10.1016/S0969-8051(96)00157-6. ISSN 0969-8051. PMID 9080473.
== Mechanism of action == Lixisenatide is a member of the class of glucagon-like peptide-1 receptor agonist drugs, each of which activates the GLP-1 receptor. GLP-1 is a hormone that helps pancreatic beta cells to secrete insulin in response to high blood sugar. Because it works like the normal hormone, insulin is only secreted when blood sugar is high. Like GLP-1, it also slows gastric emptying.
Latynina noted that while Kokoity and Russia had been preparing to defend from the Georgian attack for 4 years, there was no bomb shelter in the headquarters of Russian peacekeepers. Latynina finally concluded that by the time when Russia formally declared that it had entered the war against Georgia, the Russian 58th army (not the peacekeepers), had already been engaged in military clashes: "It is obvious that [on August 8] at 3 pm Russia decided not to start the war but to acknowledge it." In December 2008, Pavel Baev named Sergei Makarov, Commander of the North Caucasus Military District, and Anatoly Khrulyov, Commander of the 58th Army, as persons to have possibly given orders for deployment in August 2008. In 2009, Andrey Illarionov in the book 'The Guns of August 2008' authored the chapter The Russian Leadership's Preparation for War, 1999-2008. He wrote that the decisions were made by the Russian authorities between September 1999 and June 2003 that caused the Russo-Georgian war. When Vladimir Putin became Prime Minister of Russia in August 1999, the Russian government changed its policy regarding Georgia, even before Saakashvili came to power in Georgia in November 2003 and could play a part in the deterioration of the relations between two countries.
Sources: en.wikipedia.org
== See also == Best practice Clinical Laboratory Improvement Amendments (CLIA) Corrective and preventive action (CAPA) EudraLex Food safety Good automated manufacturing practice (GAMP) in the pharmaceutical industry Site Master File Washdown
== Medical uses == Nalbuphine is indicated for the relief of moderate to severe pain. It can also be used as a supplement to balanced anesthesia, for preoperative and postoperative analgesia, and for obstetrical analgesia during labor and delivery. However, a 2014 Cochrane Systematic Review concluded that from the included studies, there was limited evidence to demonstrate that "0.1 to 0.3 mg/kg nalbuphine compared to placebo might be an effective postoperative analgesic" for pain treatment in children. Further research is therefore needed to compare nalbuphine with other postoperative opioids. In addition to relieving pain, nalbuphine has been shown to reduce morphine-induced pruritus (itching). Pruritus is a common side effect of morphine and other pure μ-opioid receptor (MOR) agonists. A systematic review of clinical trials concluded that nalbuphine is effective in counteracting morphine-induced pruritus, likely through central nervous system mechanisms. Evidence suggests that κ-opioid receptor (KOR) activation can counteract MOR-mediated effects in the brain. This interaction may have broader implications for central nervous system disorders, including potential applications in treating Parkinson's disease, where KOR agonism and MOR antagonism have been shown to reduce levodopa-induced dyskinesia and normalize striatal function. Morphine-induced pruritus may also result from histamine release by mast cells in the skin. Both MORs and KORs are expressed in skin nerves and keratinocytes, indicating potential peripheral mechanisms for opioid-induced pruritus.
=== Express, freight and cold chain === SF Holding focuses on the mid- to high-end express delivery market. The company entered the express freight market in 2013. On June 13, 2017, SF Cold Chain Logistics Co., Ltd. was officially established, becoming the first express logistics company in China to establish a nationwide cold chain logistics network.
The inner workings of The Culture are not especially described in detail though it is shown that the society is populated by an empowered, educated and augmented citizenry in a direct democracy or highly democratic and transparent system of self-governance. In comparisons to the real world, intended or not, the Culture could resemble various posited egalitarian societies including in the writings of Karl Marx, the end condition of communism after a withering away of the state, the anarchism of Bakunin and Fourier et al., libertarian socialism, council communism and anarcho-communism. Other characteristics of The Culture that are recognisable in real world politics include pacifism, post-capitalism, and transhumanism. Banks deliberately portrayed an imperfect utopia whose imperfection or weakness is related to its interaction with the 'other', that is, exterior civilisations and species that are sometimes variously warred with or mishandled through the Culture's Contact section which cannot always control its intrigues and the individuals it either 'employs' or interacts with. This 'dark side' of The Culture also alludes to or echoes mistakes and tragedies in 20th century Marxist–Leninist countries, although the Culture is generally portrayed as far more 'humane' and just.
Juven is a medical food that is manufactured by Abbott Laboratories and used to provide nutritional support under the care of a physician in individuals with muscle wasting due to AIDS or cancer, to promote wound healing following surgery or injury, or when otherwise recommended by a medical professional. It is a powdered nutritional supplement that contains 3 grams of calcium β-hydroxy β-methylbutyrate, 14 grams of L-arginine, and 14 grams of L-glutamine per two daily servings. Juven has been shown to increase lean body mass during clinical trials in individuals with AIDS and cancer, but not rheumatoid cachexia. Clinical trials with Juven for AIDS have also demonstrated improvements in immune status, as measured by a reduced HIV viral load relative to controls and higher CD3+ and CD8+ cell counts. The efficacy of Juven for the treatment of cancer cachexia was also examined in a phase 3 clinical trial which found a strong trend (i.e., p=.08) for an improvement in lean body mass relative to controls; however, according to the authors of the trial itself and a systematic review that included it, the trial did not adequately test the ability of Juven to prevent or reverse the loss of lean body mass in individuals with cancer cachexia since the majority of participants did not complete the study. Further research involving the treatment of cancer cachexia with Juven over a period of several months is required to adequately determine treatment efficacy.
Sources: en.wikipedia.org
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.
The pump maintains a steady flow rate and pressure, which keeps retention times reproducible. Pulsation or flow errors can shift peaks and distort quantitation. Modern pumps use feedback control to reduce these variations.
HPLC alone usually separates compounds but does not always identify them. Retention time matching with a known standard provides tentative identification. Coupling HPLC to mass spectrometry adds mass information that supports structural identification.
It separates components in a liquid sample and measures their amounts using a detector. Results can indicate concentration, purity, or identity based on retention time and detector response. The technique works for mixtures that can be dissolved and filtered.