If you have been reading about quality control and want a single page that covers the useful parts, this is it: definitions, context, how it is studied, and the questions that come up repeatedly.
Last reviewed on 2025-09-21. Where a claim depends on a specific study, the study is described rather than over-claimed.
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.
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.
| 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 |
In quality control laboratories, HPLC testing supports batch release, raw material checks, stability studies, and impurity profiling. A validated method defines sample preparation, instrument settings, calibration, and acceptance criteria. Analysts compare results with specifications and investigate out-of-specification outcomes before a batch is approved. Documentation includes chromatograms, integration records, audit trails, and reagent details. Because results influence product decisions, laboratories follow formal quality systems and data integrity rules. The exact tests and limits depend on the material, its intended use, and the applicable regulatory framework.
Method validation examines whether an HPLC procedure is suitable for its intended purpose. Common parameters include accuracy, precision, specificity, linearity, range, detection limit, quantification limit, and robustness. Accuracy describes closeness to a true or accepted value, while precision describes agreement among repeated measurements. Specificity shows whether the method can measure the analyte without interference from related substances. Robustness tests small deliberate changes in flow, temperature, or solvent composition. Validation is not a one-time event; methods may need partial revalidation after changes to instruments, columns, sample handling, or specification limits. Regulatory guidance provides frameworks, but some details remain method-specific.
Regulatory and pharmacopeial texts shape how HPLC testing is performed and documented. The International Council for Harmonisation provides validation guidance, while pharmacopeias publish general chromatography chapters and monographs for specific materials. Accreditation standards such as ISO/IEC 17025 address laboratory competence and traceability. Inspectors may review instrument qualification, analyst training, reference material control, and electronic records. Open questions include how best to validate methods for new complex products and how to handle automated data processing. Laboratories generally resolve these issues through risk assessment, method lifecycle management, and documented scientific justification.
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.
Quality control for HPLC testing combines scheduled checks, documented procedures, and review of results. Before sample analysis, system suitability testing confirms that the instrument, column, and method meet predefined criteria. Common criteria include resolution between critical peaks, retention time precision, peak tailing, and theoretical plate count. Failure triggers investigation before results are reported. Records link raw data, calculations, instrument logs, and analyst identity to each batch, supporting audits and repeat analysis.
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.
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.
=== Organic carbon === The removal of organic carbon from water is one of the differentiators between deionized water and ultrapure water. Sources include bacteria, leaching from plastic piping, and dissolved atmospheric sources. Organic carbon can be removed using filtration by activated carbon and oxidation of organic carbon to carbon dioxide/bicarbonate.
== Effect of viruses == MHC class I molecules are loaded with peptides generated from the degradation of ubiquitinated cytosolic proteins in proteasomes. As viruses induce cellular expression of viral proteins, some of these products are tagged for degradation, with the resulting peptide fragments entering the endoplasmic reticulum and binding to MHC I molecules. It is in this way, the MHC class I-dependent pathway of antigen presentation, that the virus infected cells signal T-cells that abnormal proteins are being produced as a result of infection. The fate of the virus-infected cell is almost always induction of apoptosis through cell-mediated immunity, reducing the risk of infecting neighboring cells. As an evolutionary response to this method of immune surveillance, many viruses are able to down-regulate or otherwise prevent the presentation of MHC class I molecules on the cell surface. In contrast to cytotoxic T lymphocytes, natural killer (NK) cells are normally inactivated upon recognizing MHC I molecules on the surface of cells. Therefore, in the absence of MHC I molecules, NK cells are activated and recognize the cell as aberrant, suggesting that it may be infected by viruses attempting to evade immune destruction. Several human cancers also show down-regulation of MHC I, giving transformed cells the same survival advantage of being able to avoid normal immune surveillance designed to destroy any infected or transformed cells.
The nervous system is the part of an animal that coordinates its actions by transmitting signals to and from different parts of its body. In vertebrates it consists of two main parts, the central nervous system (CNS) and the peripheral nervous system (PNS). The CNS consists of the brain and spinal cord. The PNS consists mainly of nerves, which are enclosed bundles of the long fibers or axons, that connect the CNS to all remaining body parts. Nerves that exit from the cranium are called cranial nerves while those exiting from the spinal cord are called spinal nerves.
== History == Olaratumab was originally developed by ImClone Systems, which was acquired by Eli Lilly in 2008. A Phase I clinical trial was conducted in Japanese patients in September 2010, followed by a Phase II trial in 133 patients, starting in October 2010. In February 2015, the European Medicines Agency assigned olaratumab orphan drug status for the treatment of soft-tissue sarcoma. The European Commission granted a conditional marketing authorisation, based on the mentioned Phase II study, valid throughout the European Union on 9 November 2016. Previously considered a promising drug, the FDA granted olaratumab fast track designation, breakthrough therapy designation and priority review status. In October 2016, the US FDA issued an accelerated approval notice for use of olaratumab with doxorubicin to treat adults with certain types of soft-tissue sarcoma, based on the same study. A phase III trial completed in 2019, and unfortunately showed no benefit from the addition of olaratumab to doxorubicin. As noted above, these results led to withdrawal of approval in the United States and Europe.
Sources: en.wikipedia.org
== Contraindications == Plecanatide has not been shown to be safe or effective in persons 6 years to 18 years of age. Use of plecanatide by persons under the age of 6 poses a serious dehydration risk and studies have demonstrated plecanatide can cause death in juvenile mice due to this dehydrating effect. Use of plecanatide is also contraindicated in persons who are suspected of having a mechanical gastrointestinal obstruction.
== Medical significance == High levels of glucagon secretion has been implicated in both Type I and Type II diabetes. In fact, high levels of plasma glucagon is considered an early sign of the development of both Type I and Type II diabetes.
== Examples == The following is a list of human proteins containing the protein kinase domain: AAK1 ; AATK ; ABL1 ; ABL2 ; ACVR1 ; ACVR1B ; ACVR1C ; ACVR2A ; ACVR2B ; ACVRL1 ; AKT1 ; AKT2 ; AKT3 ; ALK ; AMHR2 ; ANKK1 ; ARAF ; AURKA ; AURKB ; AURKC ; AXL ; BLK ; BMP2K ; BMPR1A ; BMPR1B ; BMPR2 ; BMX ; BRAF ; BRSK1 ; BRSK2 ; BTK ; BUB1 ; BUB1B ; CAMK1 ; CAMK1D ; CAMK1G ; CAMK2A ; CAMK2B ; CAMK2D ; CAMK2G ; CAMK4 ; CAMKK1 ; CAMKK2 ; CAMKV ; CASK ; CDC42BPA ; CDC42BPB ; CDC42BPG ; CDC7 ; CDK1 ; CDK10 ; CDK11A ; CDK11B ; CDK12 ; CDK13 ; CDK14 ; CDK15 ; CDK16 ; CDK17 ; CDK18 ; CDK19 ; CDK2 ; CDK20 ; CDK3 ; CDK4 ; CDK5 ; CDK6 ; CDK7 ; CDK8 ; CDK9 ; CDKL1 ; CDKL2 ; CDKL3 ; CDKL4 ; CDKL5 ; CHEK1 ; CHEK2 ; CHUK ; CIT ; CLK1 ; CLK2 ; CLK3 ; CLK4 ; CSF1R ; CSK ; CSNK1A1 ; CSNK1A1L ; CSNK1D ; CSNK1E ; CSNK1G1 ; CSNK1G2 ; CSNK1G3 ; CSNK2A1 ; CSNK2A2 ; CSNK2A3 ; DAPK1 ; DAPK2 ; DAPK3 ; DCLK1 ; DCLK2 ; DCLK3 ; DDR1 ; DDR2 ; DMPK ; DSTYK ; DYRK1A ; DYRK1B ; DYRK2 ; DYRK3 ; DYRK4 ; EGFR ; EIF2AK1 ; EIF2AK2 ; EIF2AK3 ; EIF2AK4 ; EPHA1 ; EPHA10 ; EPHA2 ; EPHA3 ; EPHA4 ; EPHA5 ; EPHA6 ; EPHA7 ; EPHA8 ; EPHB1 ; EPHB2 ; EPHB3 ; EPHB4 ; EPHB6 ; ERBB2 ; ERBB3 ; ERBB4 ; ERN1 ; ERN2 ; FER ; FES ; FGFR1 ; FGFR2 ; FGFR3 ; FGFR4 ; FGR ; FLT1 ; FLT3 ; FLT4 ; FRK ; FYN ; GAK ; GRK1 ; GRK2 ; GRK3 ; GRK4 ; GRK5 ; GRK6 ; GRK7 ; GSG2 ; GSK3A ; GSK3B ; GUCY2C ; GUCY2D ; GUCY2F ; HCK ; HIPK1 ; HIPK2 ; HIPK3 ; HIPK4 ; HUNK ; ICK ; IGF1R ; IKBKB ; IKBKE ; ILK ; INSR ; INSRR ; IRAK1 ; IRAK2 ; IRAK3 ; IRAK4 ; ITK ; JAK1 ; JAK2 ; JAK3 ; KALRN ; KDR ; KIT ; KSR1 ; KSR2 ; LATS1 ; LATS2 ; LCK ; LIMK1 ; LIMK2 ; LMTK2 ; LMTK3 ; LRRK1 ; LRRK2 ; LTK ; LYN ; MAK ; MAP2K1 ; MAP2K2 ; MAP2K3 ; MAP2K4 ; MAP2K5 ; MAP2K6 ; MAP2K7 ; MAP3K1 ; MAP3K10 ; MAP3K11 ; MAP3K12 ; MAP3K13 ; MAP3K14 ; MAP3K15 ; MAP3K19 ; MAP3K2 ; MAP3K20 ; MAP3K21 ; MAP3K3 ; MAP3K4 ; MAP3K5 ; MAP3K6 ; MAP3K7 ; MAP3K8 ; MAP3K9 ; MAP4K1 ; MAP4K2 ; MAP4K3 ; MAP4K4 ; MAP4K5 ; MAPK1 ; MAPK10 ; MAPK11 ; MAPK12 ; MAPK13 ; MAPK14 ; MAPK15 ; MAPK3 ; MAPK4 ; MAPK6 ; MAPK7 ; MAPK8 ; MAPK9 ; MAPKAPK2 ; MAPKAPK3 ; MAPKAPK5 ; MARK1 ; MARK2 ; MARK3 ; MARK4 ; MAST1 ; MAST2 ; MAST3 ; MAST4 ; MASTL ; MATK ; MELK ; MERTK ; MET ; MINK1 ; MKNK1 ; MKNK2 ; MLKL ; MOK ; MOS ; MST1R ; MUSK ; MYLK ; MYLK2 ; MYLK3 ; MYLK4 ; MYO3A ; MYO3B ; NEK1 ; NEK10 ; NEK11 ; NEK2 ; NEK3 ; NEK4 ; NEK5 ; NEK6 ; NEK7 ; NEK8 ; NEK9 ; NIM1K ; NLK ; NPR1 ; NPR2 ; NRBP1 ; NRBP2 ; NRK ; NTRK1 ; NTRK2 ; NTRK3 ; NUAK1 ; NUAK2 ; OBSCN ; OXSR1 ; PAK1 ; PAK2 ; PAK3 ; PAK4 ; PAK5 ; PAK6 ; PAN3 ; PASK ; PBK ; PDGFRA ; PDGFRB ; PDIK1L ; PDPK1 ; PDPK2P ; PEAK1 ; PEAK3 ; PHKG1 ; PHKG2 ; PIK3R4 ; PIM1 ; PIM2 ; PIM3 ; PINK1 ; PKDCC ; PKMYT1 ; PKN1 ; PKN2 ; PKN3 ; PLK1 ; PLK2 ; PLK3 ; PLK4 ; PLK5 ; PNCK ; POMK ; PRKAA1 ; PRKAA2 ; PRKACA ; PRKACB ; PRKACG ; PRKCA ; PRKCB ; PRKCD ; PRKCE ; PRKCG ; PRKCH ; PRKCI ; PRKCQ ; PRKCZ ; PRKD1 ; PRKD2 ; PRKD3 ; PRKG1 ; PRKG2 ; PRKX ; PRKY ; PRPF4B ; PSKH1 ; PSKH2 ; PTK2 ; PTK2B ; PTK6 ; PTK7 ; PXK ; RAF1 ; RET ; RIOK1 ; RIOK2 ; RIOK3 ; RIPK1 ; RIPK2 ; RIPK3 ; RIPK4 ; RNASEL ; ROCK1 ; ROCK2 ; ROR1 ; ROR2 ; ROS1 ; RPS6KA1 ; RPS6KA2 ; RPS6KA3 ; RPS6KA4 ; RPS6KA5 ; RPS6KA6 ; RPS6KB1 ; RPS6KB2 ; RPS6KC1 ; RPS6KL1 ; RSKR ; RYK ; SBK1 ; SBK2 ; SBK3 ; SCYL1 ; SCYL2 ; SCYL3 ; SGK1 ; SGK2 ; SGK223 ; SGK3 ; SIK1 ; SIK1B ; SIK2 ; SIK3 ; SLK ; SNRK ; SPEG ; SRC ; SRMS ; SRPK1 ; SRPK2 ; SRPK3 ; STK10 ; STK11 ; STK16 ; STK17A ; STK17B ; STK24 ; STK25 ; STK26 ; STK3 ; STK31 ; STK32A ; STK32B ; STK32C ; STK33 ; STK35 ; STK36 ; STK38 ; STK38L ; STK39 ; STK4 ; STK40 ; STKLD1 ; STRADA ; STRADB ; STYK1 ; SYK ; TAOK1 ; TAOK2 ; TAOK3 ; TBCK ; TBK1 ; TEC ; TEK ; TESK1 ; TESK2 ; TEX14 ; TGFBR1 ; TGFBR2 ; TIE1 ; TLK1 ; TLK2 ; TNIK ; TNK1 ; TNK2 ; TNNI3K ; TP53RK ; TRIB1 ; TRIB2 ; TRIB3 ; TRIO ; TSSK1B ; TSSK2 ; TSSK3 ; TSSK4 ; TSSK6 ; TTBK1 ; TTBK2 ; TTK ; TTN ; TXK ; TYK2 ; TYRO3 ; UHMK1 ; ULK1 ; ULK2 ; ULK3 ; ULK4 ; VRK1 ; VRK2 ; VRK3 ; WEE1 ; WEE2 ; WNK1 ; WNK2 ; WNK3 ; WNK4 ; YES1 ; ZAP70
Sources: en.wikipedia.org
== Epidemiology == Weissenbacher-Zweymüller syndrome affects males and females in the same numbers. About 30 cases have been reported in medical literature. The disorder can be underdiagnosed causing no true frequency in the population.
Jan Jozef van Deemter (31 March 1918 – 10 October 2004) was a Dutch physicist and engineer known for the Van Deemter equation in chromatography. He obtained his doctorate in physics from the University of Amsterdam in June of 1950. Starting in 1947 he began work for Royal Dutch Shell as a researcher and it was there that he developed and published his article in 1956.
Hardtack is a mainstay in parts of Canada. Purity Factories is one maker of traditional hardtack. They specialize in a high density, high caloric product that is well suited for use by expeditions. Located in St. John's, Newfoundland and Labrador, they currently produce three varieties of hardtack:
The approximation formulae above relate to HOMA and are crude estimates of the model near normal levels of glucose and insulin in man. The actual calculated HOMA2 compartmental model is published and is available online.
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.
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.