This is a working overview of retention time, written for readers who want more than a one-paragraph summary but less than a textbook.
This page was last updated on 2026-05-03 and is reviewed periodically as new material appears.
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.
Validation establishes that a method is suitable for its intended purpose. Typical parameters include accuracy, precision, specificity, linearity, range, limit of detection, limit of quantification, robustness, and stability of standards and samples. Acceptance criteria are defined in advance, and results are documented in a validation report. Regulatory guidance for pharmaceuticals, foods, and environmental testing differs, so the applicable framework must be identified. Ongoing verification uses control samples and trend charts after validation. Method transfer to another laboratory may require partial revalidation.
Routine quality control includes blanks, duplicates, spiked samples, and certified reference materials. Calibration curves are prepared with standards at several concentrations, and the detector response is checked for linearity. Carryover, column aging, mobile phase evaporation, and temperature drift can shift retention times or peak areas. Maintenance such as replacing seals, filters, and columns helps prevent failures. Records of injections, integration, and deviations support traceability. Audits may request raw data and instrument logs for each batch.
Developing an HPLC test begins with defining the analytes, matrix, and required reporting limits. Chemists select a separation mode, column chemistry, mobile phase composition, flow rate, and detection wavelength or mass transition. Experiments then adjust these variables to achieve adequate retention, resolution, and peak shape. System suitability tests confirm that the instrument and method perform consistently before sample analysis. Without suitable resolution, quantitative results may be unreliable. Preliminary runs often use scouting gradients to locate retention windows.
| Property | Value | Notes |
|---|---|---|
| Retention time RSD | ≤1% for five replicate injections | Typical criterion; method-specific limits apply. |
| Resolution | ≥1.5 between critical pair | Baseline separation is generally desired. |
| Tailing factor | ≤2.0 | Measures peak symmetry. |
| Theoretical plates | ≥2000 per column | Method-dependent; higher values indicate greater efficiency. |
| Peak area RSD | ≤2% for replicate injections | Reflects autosampler and detector precision. |
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.
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.
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.
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.
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.
=== Dihydrolipoyl dehydrogenase Binding protein (E3BP) === An auxiliary protein unique to most eukaryotes is the E3 binding protein (E3BP), which serves to bind the E3 subunit to the PDC complex. In the case of human E3BP, hydrophobic proline and leucine residues in the BP interact with the surface recognition site formed by the binding of two identical E3 monomers.
=== Growth-related === TCTP has properties of a tubulin binding protein that associates with microtubules in a cell cycle-dependent manner. The transient overexpression of TCTP in HeLa cells prevented them from undergoing etoposide-induced apoptosis. Expressing TCTP in U2OS (human bone osteosarcoma epithelial cells) protected them from cell death induced by etoposide over various concentrations and durations of exposure. TCTP overexpression inhibited caspase-3-like activity as assessed by the cleavage of fluorogenic substrate. Expression levels of TCTP were down-regulated at the mRNA and protein levels during tumor suppression and by the activation of p53 and Siah-1 very well known anti-tumor genes. Down-regulation of TCTP can induce tumor reversion, and in combination with some drugs that decrease the level of TCTP and will lead to kill tumor cells. TCTP knockdown in primary mammary tumor cells, results in increased p53 expression and a decreased number of stem-like cancer cells. Reducing TCTP (dTCTP) levels in Drosophila reduces cell size, cell number and organ size, which mimics Drosophila Rheb (dRheb) mutant phenotypes; human TCTP (hTCTP) shows similar biochemical properties compared to dTCTP.
== Pathology == Aflatoxin B1 can permeate through the skin. Dermal exposure to this aflatoxin in particular environmental conditions can lead to major health risks. The liver is the most susceptible organ to aflatoxin B1 toxicity. In animal studies, pathological lesions associated with aflatoxin B1 intoxication include reduction in weight of liver, vacuolation of hepatocytes, and hepatic carcinoma. Other liver lesions include enlargement of hepatic cells, fatty infiltration, necrosis, hemorrhage, fibrosis, regeneration of nodules, and bile duct proliferation/hyperplasia.
These data show that the perchlorate and chlorate are stronger oxidizers in acidic conditions than in basic conditions. Gas phase measurements of heats of reaction (which allow computation of ΔfH°) of various chlorine oxides do follow the expected trend wherein Cl2O7 exhibits the largest endothermic value of ΔfH° (238.1 kJ/mol) while Cl2O exhibits the lowest endothermic value of ΔfH° (80.3 kJ/mol).
Sources: en.wikipedia.org
=== Diagnosis === ESR can sometimes be useful in diagnosing diseases, such as multiple myeloma, temporal arteritis, polymyalgia rheumatica, various autoimmune diseases, systemic lupus erythematosus, rheumatoid arthritis, inflammatory bowel disease and chronic kidney diseases. In many of these cases, the ESR may exceed 100 mm/hour. It is commonly used for a differential diagnosis for Kawasaki's disease (from Takayasu's arteritis; which would have a markedly elevated ESR) and it may be increased in some chronic infective conditions like tuberculosis and infective endocarditis. It is also elevated in subacute thyroiditis also known as DeQuervain's. In markedly increased ESR of over 100 mm/h, infection is the most common cause (33% of cases in an American study), followed by cancer (17%), kidney disease (17%) and noninfectious inflammatory disorders (14%). Yet, in pneumonia the ESR stays under 100. The usefulness of the ESR in current practice has been questioned by some, as it is a relatively imprecise and non-specific test compared to other available diagnostic tests. Current literature suggests that an ESR should be "obtained on all patients over the age of 50" who have an intense headache.
== External links == David S, Lancaster T, Stead LF. Opioid antagonists for smoking cessation (Cochrane Review), The Cochrane Library, Issue 2, 2005. Chichester, UK: John Wiley & Sons, Ltd. Opioid+Antagonists at the U.S. National Library of Medicine Medical Subject Headings (MeSH)
The way a drug product is designed and manufactured Its physical and chemical properties Other ingredients it contains The physiologic characteristics of the person taking the drug How the drug is stored
Sources: en.wikipedia.org
System suitability is typically performed before each batch or according to the validated method and laboratory procedure. Some long runs include periodic checks during analysis. The required frequency depends on regulatory expectations and method performance.
Retention time drift can result from changes in mobile phase composition, column temperature, pump flow, or column age. A gradual shift often points to column degradation. A sudden shift may indicate a leak, mixing error, or incorrect mobile phase.
Retention time alone cannot confirm identity because different compounds may elute at similar times. Coupling HPLC with mass spectrometry or comparing against authenticated standards increases confidence. Confirmation usually requires orthogonal data.
System suitability is a set of checks performed before and during a run to confirm that the instrument, column, and method work as expected. Common checks include resolution, tailing factor, theoretical plates, and relative standard deviation of replicate injections. Failure triggers troubleshooting or method adjustment.