A practical reference on quality control: what it is, how it behaves, what the literature reports, and where the honest uncertainties sit.
Reviewed 2025-05-03. Anything still debated is marked as such rather than presented as settled.
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.
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.
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.
| 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. |
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.
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.
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.
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.
Vaginal films are soluble, thin sheets of medication that are inserted into the vagina where they dissolve and release the substances. Typical uses include delivery of contraceptive substances or antibiotics for infections. These films are inserted by simply pushing them into the vagina with one’s fingers. There they dissolve quickly upon interaction with natural vaginal fluids. Bioadhesives are substances that naturally stick to live tissue. Currently, studies are being done on bioadhesives adhering to cervical mucous membranes to allow for an extended release period. The drug would be released with mucus to create a localized treatment with high effectiveness. This is anticipated to be highly useful for treatment of cervical cancer. Bioadhesives can come in multiple forms, such as films, tablets, or gels. The appeal of bioadhesives is that they take advantage of the mucous environment surrounding the cervix and utilize it to benefit the drug delivery mechanism.
5-Oxo-ETE contracts smooth muscle and organ-cultured bronchi isolated from guinea pigs but relaxes bronchi isolated from human lung; the relaxation of human bronchi caused by 5-oxo-ETE may not involve its OXER1. These results suggest that 5-oxo-ETE is not directly involved in the bronchoconstriction) that occurs in eosinophil-based allergic asthma reactions in humans. 5-Oxo-ETE (or other 5-HETE family member) stimulates the growth and/or survival of human cell lines derived from cancers of the prostate, breast, lung, ovary, colon and pancreas These preclinical studies suggest that 5-oxo-ETE (or other 5-HETE family member) may contribute to the cited cancers progression in humans. 5-oxo-ETE stimulates human H295R adrenocortical cells to increase transcription of steroidogenic acute regulatory protein messenger RNA and produce aldosterone and progesterone by an apparent OXER1-dependent pathway. 5-Oxo-ETE induces an isotonic volume reduction in guinea pig intestinal crypt epithelial cells.
Outbreaks of disease Food-born illness Bioterrorism Natural disasters APHL plays a critical role in crisis response to these public health emergencies through the Laboratory Response Network (LRN). The LRN was formed in 1999 in a cooperative effort between APHL, the CDC and FBI to rapidly detect, and respond to public health emergencies. The Department of Defense has joined in the effort to support biological response activities. In addition to their leadership during times of crisis, APHL has a strong focus on preparing public health laboratories on how to respond to emergencies when they happen through training and capacity-building, as well as creating model frameworks that labs around the country can use in order to have procedures in place to handle a crisis when it happens.
Greater emphasis on risk management Introduces “Special Requirements” Introduces “Critical Items” Measure: Requirements conformance Measure: Delivery performance Adopt proven product development processes Eliminate “recurring corrective actions” AS9100 Revision C was released in January, 2009, with considerable delay in application of the new version in audits, largely due to the delay in the release of AS9101 Revision D and auditor training to the increased auditing rigor of that update. AS9100 Revision D (2016), Quality Management System – Requirements for Aviation, Space and Defense Organizations The update of AS9100 from revision C to D includes the full text of ISO 9001:2015. In addition to aligning the structure of the aviation, space and defense requirements to the new structure of ISO 9001:2015, the following key changes were implemented:
Sources: en.wikipedia.org
Cell membranes contain a variety of biological molecules, notably lipids and proteins. Composition is not set, but constantly changing for fluidity and changes in the environment, even fluctuating during different stages of cell development. Specifically, the amount of cholesterol in human primary neuron cell membrane changes, and this change in composition affects fluidity throughout development stages. Material is incorporated into the membrane, or deleted from it, by a variety of mechanisms:
There are many applications for AMS throughout a variety of disciplines. AMS is most often employed to determine the concentration of 14C, e.g. by archaeologists for radiocarbon dating. Compared to other radiocarbon dating methods, AMS requires smaller sample sizes (about 50 mg), while yielding extensive chronologies. MS technology has expanded the scope of radiocarbon dating. Samples ranging from 50,000 years old to 100 years old can be successfully dated using AMS, as other forms of mass spectrometry provide insufficient suppression of molecular isobars to resolve 13CH and 12CH2 from 14C atoms. Because of the long half-life of 14C, decay counting requires significantly larger samples. 10Be, 26Al, and 36Cl are used for surface exposure dating in geology. 3H, 14C, 36Cl, and 129I are used as hydrological tracers. Accelerator mass spectrometry is widely used in biomedical research. In particular, 41Ca has been used to measure bone resorption in postmenopausal women. List of accelerator mass spectrometry facilities Arizona Accelerator Mass Spectrometry Laboratory
Nanoghosts are nanosized vesicles containing a chosen drug delivery payload manufactured from extracted leukocyte membranes with the cell cytoplasm content removed. The use of biological membranes serves to mask the particles from the immune system to reduce the likelihood of an immunogenic response, as well as to extend circulation of the particles in the blood. They are produced by homogenizing the cells to remove the cytosol, and then sonicating the empty cell membranes to create nanoghosts between 100 and 200 nm in diameter. Membranes used to make nanoghosts harvested form red blood cells have been shown to circulate for about 120 days and avoid phagocytotic cells. Neutrophil based nanoghosts retain the chemotaxis capacity of neutrophils to sites of inflammation, which encourages tumor targeting. NK based nanoghosts exhibit metastatic cancer targeting behavior. Monocyte based nanoghosts are effective at infiltrating the tumor microenvironment. Mesenchymal stem cell derived nanoghosts exhibit cancer targeting properties.
Cardona completed his PhD at the University of Barcelona (2000–2005), where he studied developmental biology. He then undertook postdoctoral research on Drosophila neuroanatomy at UCLA (2005–2008). Between 2008 and 2011, Cardona was a Group Leader at the Institute of Neuroinformatics, jointly run by the University of Zurich and ETH Zurich. During this period, he developed computational and image-processing methods for neural circuit reconstruction and co-founded two influential open-source platforms that have become widely adopted in the neuroscience community. Cardona joined the Howard Hughes Medical Institute (HHMI) Janelia Research Campus in 2012, serving as Group Leader until 2019. In 2019, he was appointed Programme Leader at the MRC Laboratory of Molecular Biology and Professor at the University of Cambridge, where he leads research on whole-brain connectomics, circuit development, and structure–function relationships in neural systems.
Amino acids are the building blocks of protein and together they form the protein requirements in formula needed for growth and development. The amino acids are in the simplest form, making it easy for the body to process and digest. Amino acid-based formula may be considered hypoallergenic since it does not contain peptides that may trigger an immune response. Because infants and children have different nutritional needs, amino acid-based formulas are typically formulated either for infants 0–1 years of age or for children 1–10 years of age. Amino acid-based formulas may be used for those with cow's milk or soy protein allergy. However, most infants who suffer from food allergy respond well to extensively hydrolysed formulas, and only few of those with the most severe form of the illness require the use of amino acid-based formulas. It may also be used for other medical conditions requiring an amino acid-based diet, such as short bowel syndrome, and for transition from parenteral to enteral nutrition. Milk allergy Food allergy
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.
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.