Everything below concerns quality control. We keep the language plain, cite what the science says, and separate well-supported claims from open questions.
Updated 2025-08-11. Numbers and descriptions here follow the published literature rather than marketing material.
Method validation establishes that an HPLC procedure is suitable for its intended purpose. Typical parameters include accuracy, precision, specificity, linearity, range, limit of detection, limit of quantitation, robustness, and solution stability. Accuracy reflects closeness to a reference value, while precision reflects agreement among repeated measurements. Specificity shows whether the method can measure the analyte without interference from matrix components. Validation is documented through protocols and reports, and the required extent depends on the method's use and regulatory context.
Routine quality control uses system suitability, blank injections, check standards, and control samples to detect drift or contamination. System suitability criteria may specify minimum resolution, maximum tailing factor, and a permitted range for repeated injections. Blank injections reveal carryover or solvent contamination, while check standards confirm calibration accuracy over a batch. Control samples with known analyte levels can show whether results remain within statistical limits. When a control result falls outside limits, the analyst investigates the cause and may invalidate affected results before repeating the batch.
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.
| Property | Value | Notes |
|---|---|---|
| Accuracy | Recovery near 100% | Depends on acceptance criteria and matrix |
| Precision | Relative standard deviation | Often at or below 2% for replicate injections |
| Limit of detection | Signal-to-noise ratio 3:1 | Approximate and method-specific |
| Limit of quantitation | Signal-to-noise ratio 10:1 | Confirmed by precision and accuracy |
| Resolution | 1.5 or greater | Typical system suitability target |
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.
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.
In 2012, newly elected President Enrique Peña Nieto, from the PRI, emphasized that he did not support the involvement of armed American agents in Mexico and was only interested in training Mexican forces in counter-insurgency tactics. At the start of his term, Peña Nieto promised to de-escalate the conflict, focusing on lowering criminal violence rates, as opposed to the previous policy of attacking drug-trafficking organizations by arresting or killing the cartel leaders and intercepting their shipments. His administration's security policy was shaped by Miguel Ángel Osorio Chong (Secretary of the Interior), Jesús Murillo Karam (Attorney General), and Salvador Cienfuegos (National Defense). In the first 14 months of his administration, between December 2012 and January 2014, 23,640 people died in the conflict. During 2012 and 2013, Mexico saw the rise of grupos de autodefensa comunitaria, vigilante self-defense groups in rural communities that took up arms against criminal groups that wanted to impose dominance in their towns, entering a new phase in the Mexican drug war. This strategy, encouraged by Óscar Naranjo, one of Peña Nieto's security advisors, crumbled when autodefensas began having internal struggles and disagreements with the government, as well as infiltration and co-optation by organized crime, causing Peña Nieto's administration to distance from them.
=== Strontium === Strontium is naturally deposited in hydroxyapatite, the mineral component of bones and teeth, following its consumption in food and water. Each locale has a unique Sr isotope ratio and, therefore, the ratio found in a bone or enamel sample can be cross referenced against a record of environmental Sr ratios and assigned to a region. Dental enamel forms in childhood, therefore, Sr extracted from dental enamel reflects the environment in which an individual lived during infancy and childhood. Bone, however, is constantly being renewed and can therefore be used to infer the adult diet and location of the individual. As such, if the Sr ratios are the analogous in the bones and teeth, it can be inferred that an individual remained in the same general region throughout their life. If the ratios differ, the individual's birthplace and death place can be mapped, allowing inference of their movements. This has been applied to determine the functionality and significance of Stonehenge, finding that both the visitors and cattle used in feasting travelled great distances, with Sr ratios attributed to both Scotland and Wales.
Sorafenib's inhibition of UGT1A9 and UGT1A1 may increase plasma concentration of other drugs. The same goes for the CYP2B6 and CYP2C8 pathways, they are inhibited by sorafenib. Giving sorafenib in combination with rifampicin or inducers of CYP3A4 can decrease plasma concentration of sorafenib. CYP3A4 inhibitors are unlikely to affect sorafenib. Sorafenib is a competitive inhibitor of CYP2C19, CYP2D6 and CYP3A4. It inhibits P-glycoprotein, therefore it can increase the plasma concentration of drugs which are P-glycoprotein substrates. Pazopanib is metabolized in the liver by CYP3A4 enzyme. Strong CYP3A4 inhibitors, other than pazopanib, can increase the plasma concentration of pazopanib, and CYP3A4 inducers will do the opposite. Grapefruit juice is a CYP3A4 inhibitor and should be avoided when taking pazopanib. It is also a weak inhibitor of other liver enzymes, CYP2C8 and CYP2D6. Axitinib is metabolized by CYP3A4 and UGT1A1. Strong inhibitors of CYP3A4 will increase the plasma concentration of axitinib, while weak inhibitors have less effect on the plasma concentration. Strong inducers of CYP3A4 will decrease the plasma concentration of axitinib and should be avoided.
Sources: en.wikipedia.org
== Research == AAS, alone and in combination with progestogens, have been studied as potential male hormonal contraceptives. Dual AAS and progestins such as trestolone and dimethandrolone undecanoate have also been studied as male contraceptives, with the latter under active investigation as of 2018. Topical androgens have been used and studied in the treatment of cellulite in women. Topical androstanolone on the abdomen has been found to significantly decrease subcutaneous abdominal fat in women, and hence may be useful for improving body silhouette. However, men and hyperandrogenic women have higher amounts of abdominal fat than healthy women, and androgens have been found to increase abdominal fat in postmenopausal women and transgender men as well.
== Selected publications == Robinson, Arthur B.; McKerrow, James H.; Cary, Paul (1970). "Controlled Deamidation of Peptides and Proteins: An Experimental Hazard and a Possible Biological Timer". PNAS. 66 (3): 753–757. Bibcode:1970PNAS...66..753R. doi:10.1073/pnas.66.3.753. PMC 283114. PMID 5269237. Pauling, Linus; Robinson, Arthur B.; Teranishi, Roy; Cary, Paul (1971). "Quantitative Analysis of Urine Vapor and Breath by Gas-Liquid Partition Chromatography". PNAS. 68 (10): 2374–2376. Bibcode:1971PNAS...68.2374P. doi:10.1073/pnas.68.10.2374. PMC 426616. PMID 5289873. Robinson, Arthur B.; Robinson, Laurelee R. (1991). "Distribution of glutamine and asparagine residues and their near neighbors in peptides and proteins". PNAS. 88 (20): 8880–8884. Bibcode:1991PNAS...88.8880R. doi:10.1073/pnas.88.20.8880. PMC 52614. PMID 1924347. Soon, Willie H.; Baliunas, Sallie L.; Robinson, Arthur B.; Robinson, Zachary W. (1999). "Environmental effects of increased atmospheric carbon dioxide". Climate Research. 13 (2): 149–164. Bibcode:1999ClRes..13..149S. doi:10.3354/cr013149. Robinson, Noah E.; Robinson, Arthur B. (2001). "Molecular clocks". PNAS. 98 (3): 944–949. Bibcode:2001PNAS...98..944R. doi:10.1073/pnas.98.3.944. PMC 14689. PMID 11158575. Robinson, Arthur B.; Robinson, Noah E. (2008). "Use of Merrifield solid phase peptide synthesis in investigations of biological deamidation of peptides and proteins". Peptide Science. 90 (3): 297–306. doi:10.1002/bip.20852. PMID 17896348. S2CID 35618789.
=== Mood and stress === The involvement of KOR in stress, as well as in consequences of chronic stress such as depression, anxiety, anhedonia, and modulating drug-seeking behavior, has been widely investigated. KOR is postulated to play an important and varied role in regulating various affective state and stress responses in humans through multiple complex processes. There have been numerous studies implicating KOR in pathology of various psychiatric disorders. One of the main premises for this investigation comes from the receptor activation causing cellular hyperpolarization and, in neurons, decreased neurotransmitter release through a reduction in calcium and increase in potassium conductance. Through these mechanisms, KORs are thought to regulate the release of many signaling molecules including: γ-aminobutyric acid (GABA), glutamate, serotonin, dopamine, norepinephrine. Results on exact influence on neuronal activity and neurotransmitter release vary in vivo. KOR activation elicits immediate hyperpolarization of dopamine neurons (in 1–2 min), followed by decreased dopamine release (5–10 min) and secondary effects on serotonin and glutamate (10–30 min).
=== Emerging orthopoxvirus infections === With the eradication of smallpox, the remaining Orthopoxvirus infection of great human consequence is Mpox, a disease endemic to West and Central Africa. A number of regional Mpox outbreaks lead to the renewal of a speculation that a poxvirus closely related to smallpox such as Mpox or cowpox could become adapted to humans over time and take up the ecological niche vacated by the extinction of smallpox. Among the requried adaptations for this niche is human-to-human transmission: this is known to occur in these small Mpox outbreaks, albeit inefficient enough for these outbreaks to stay local. The 2022–2023 mpox outbreak was unusual in that it featured higher rates of human-to-human transmission than previous regional outbreaks, allowing it to spread throughout the world to affect 121 countries and territories. The WHO declared a public health emergency of international concern (PHEIC) for this clade IIb outbreak on 23 July 2022 and smallpox vaccines were used off label (or given emergency approval) for Mpox prevention. A new 2023–2026 mpox epidemic by a novel clade Ib caused an (ongoing) epidemic in Central Africa, especially DR Congo, with limited local transmission in a few countries outside of Africa. At the same time, cases caused by descendants of the 2022 outbreak continues occurring at a low rate outside of Africa.
Sources: en.wikipedia.org
Validation establishes suitability for a new method, while verification confirms that a method works in a specific laboratory. Verification is often used when a validated method is adopted with existing equipment and staff. Both rely on documented acceptance criteria.
Quantification usually compares detector response to a standard curve made from reference standards. The curve may be external, internal, or based on standard addition depending on matrix effects. Results are reported with units and, when required, uncertainty.
Carryover occurs when analyte from a previous injection remains in the system and appears in a later chromatogram. It can come from the injector, column, or tubing. Blank injections and needle washes help detect and reduce it.
It measures the amounts and identities of compounds in liquid samples by separation and detection. Depending on the detector and reference standards, results can be qualitative or quantitative. The technique is used in fields such as pharmaceutical analysis, food safety, and environmental monitoring.