quality control 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 2025-09-06. Where a claim depends on a specific study, the study is described rather than over-claimed.
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.
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.
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.
| Property | Value | Notes |
|---|---|---|
| Validation parameter | Accuracy | Measured value compared with true or accepted value |
| Precision type | Repeatability | Same analyst, instrument, and short time interval |
| Linearity range | 50–150% of target concentration | Common for assay methods; method-dependent |
| Limit of quantitation | Signal-to-noise ratio of 10:1 | Lowest concentration with acceptable precision |
| Common synonyms | Method validation, analytical validation | Documented confirmation that a method is suitable |
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.
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.
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.
Validation demonstrates that a method is suitable for its intended use. Typical performance characteristics include accuracy, precision, specificity, linearity, range, limit of detection, limit of quantitation, and robustness. Regulators and standards organizations provide frameworks, but specific requirements depend on the application and jurisdiction. System suitability tests are run before sample analysis to confirm resolution, peak symmetry, retention time repeatability, and sensitivity. A validated method is not permanently fixed; changes may require partial or full revalidation.
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.
Laboratories apply HPLC testing across pharmaceutical, food, environmental, and industrial chemistry. The method can measure active ingredients, impurities, additives, preservatives, and degradation products. Sample preparation often includes dilution, filtration, and sometimes extraction or derivatization. The choice of column, mobile phase, pH, temperature, and detector depends on the analytes and matrix. Results are compared with reference standards to assign identity and concentration. Method suitability is judged by resolution, precision, and accuracy.
HPLC testing is not a single fixed procedure; it is a family of separation modes. Reversed-phase, normal-phase, ion-exchange, size-exclusion, and affinity chromatography each suit different analyte properties. Reversed-phase methods dominate because they handle many neutral and moderately polar compounds. Detection can be optical, electrochemical, or mass spectrometric, and the detector dictates what information is available. Coupling with mass spectrometry increases selectivity and enables identification when standards are unavailable. The technique cannot separate every mixture without adjustment.
HPLC testing is an analytical technique used to separate, identify, and quantify components in a liquid sample. It relies on a pressurized mobile phase that carries the sample through a column packed with stationary phase. Different compounds travel at different rates because of interactions with the stationary and mobile phases. The resulting signal versus time is a chromatogram. Peak position indicates identity under specified conditions, while peak area or height relates to amount.
Agrobacterium tumefaciens, a soil rhizosphere bacterium, can attach to plant cells and infect them with a callus-inducing Ti plasmid by horizontal gene transfer, causing a callus infection called crown gall disease. Schell and Van Montagu (1977) hypothesised that the Ti plasmid could be a natural vector for introducing the Nif gene responsible for nitrogen fixation in the root nodules of legumes and other plant species. Today, genetic modification of the Ti plasmid is one of the main techniques for introduction of transgenes to plants and the creation of genetically modified crops.
==== Australian Aboriginals (Northern Territory) ==== Northern Territory Australian Aboriginals have unique traditions associated with a loved one's death. The death of a loved one sparks a series of events such as smoking out the spirit, a feast, and leaving the body out to decompose. Immediately after death, a smoking ceremony is held in the deceased's home. The smoking ceremonies purpose is to expel the spirit of the deceased from their living quarters. A feast is held where mourners are covered in ochre, an earthy pigment associated with clay, while they eat and dance. The traditional corpse disposal of the Aboriginals includes covering the corpse in leaves on a platform. The corpse is then left to decompose.
The concept was successful enough to become a permanent fixture of the chain, and Little Caesars' business model has shifted to focus more on carryout. In 1998, Little Caesars filled what was then the largest pizza order, filling an order of 13,386 pizzas from the VF Corporation of Greensboro, North Carolina. Little Caesars was among the first to use a new kind of speed-cooking conveyor oven, the "Rotary Air Impingement Oven". On December 10, 2014, Little Caesars announced plans for a new eight-story, 205,000-square-foot Global Resource Center to be built at Woodward Avenue and Columbia Street in downtown Detroit. Intended to double the size of Little Caesars World Headquarters Campus, the new building's location was chosen near the Fox Office Center building, which houses both the Fox Theatre, and 186,000 square feet of office space for Little Caesars, and other Ilitch-affiliated ventures. An overhead pedestrian bridge over Columbia Street was planned to connect the Fox with the new Little Caesars Global Resource Center and workspace for an additional 600 jobs to be brought to Detroit over time. On January 31, 2016, it was announced that the proposed new Little Caesars Pizza Global Resource Center had grown by one floor to be a nine-story building at Woodward and Columbia Street. The building was scheduled to be completed in 2018, but in October of that year, was pushed back due to construction delays.
Sources: en.wikipedia.org
=== OS Fund === In October 2014, Johnson announced the launch of the OS Fund, which invests in early-stage science and technology companies and which he backed with $100 million of his personal capital.
Some scientists prefer to end the actinides with nobelium and consider lawrencium to be the first transition metal of the seventh period. Lawrencium is expected to be a trivalent, silvery metal, easily oxidized by air, steam, and acids, and having an atomic volume similar to that of lutetium and a trivalent metallic radius of 171 pm. It is expected to be a rather heavy metal with a density of around 14.4 g/cm3. It is also predicted to have a melting point of around 1900 K (1600 °C), not far from the value for lutetium (1925 K).
=== Bladder cancer === On 9 June 2011, the French Agency for the Safety of Health Products decided to withdraw pioglitazone due to high risk of bladder cancer. This suspension was based on the results of an epidemiological study conducted by the French National Health Insurance. According to the results of the epidemiological study, the French agency found that patients, who were taking Actos for a long time to aid in type 2 diabetes mellitus, had a significantly increased risk of bladder cancer compared with patients who were taking other diabetes medications. On 10 June 2011, Germany's Federal Institute for Drugs and Medical Devices also advised doctors not to prescribe the medication until further investigation of the cancer risk had been conducted. On 15 June 2011, the U.S. FDA announced that pioglitazone use for more than one year may be associated with an increased risk of bladder cancer, and two months later the label was updated with an additional warning about this risk. A 2017 meta-analysis found no difference in the rates of bladder cancer attributed to pioglitazone.
Sources: en.wikipedia.org
System suitability is a set of checks that confirm the instrument and method perform within limits before sample analysis. It typically includes resolution, tailing factor, retention time, and peak area reproducibility. If a check fails, the run is invalidated until the cause is resolved.
QC samples are usually injected at the beginning, at intervals during the run, and at the end. The exact frequency depends on the method, sample count, and regulatory requirements. Results outside acceptance limits can require rejection of the affected samples and investigation.
Method validation demonstrates that an HPLC procedure produces reliable results for its intended purpose. It provides documented evidence for accuracy, precision, specificity, and other performance characteristics. Regulators and quality systems require validation before a method is used for release or stability testing.
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.