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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.
Instrumentation includes a solvent delivery system, an autosampler, a column oven, and one or more detectors. Reversed-phase columns with chemically modified silica are widely used, but normal-phase, ion-exchange, size-exclusion, and affinity modes exist for specific separations. Detectors may rely on ultraviolet absorbance, fluorescence, refractive index, or mass spectrometry. Column temperature, mobile phase composition, and flow rate are adjusted to improve resolution. System pressure is monitored because rising pressure can indicate column blockage or deteriorating packing.
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.
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.
Key performance measures include retention time, peak area, peak height, resolution, tailing factor, and plate count. Retention time helps identify a peak under fixed conditions, but confirmation often requires a second method or detector. Peak area and height relate to concentration through calibration curves, which may be linear or nonlinear depending on the detector response. Resolution describes separation between adjacent peaks, while tailing factor and plate count describe peak shape and column efficiency. Performance checks verify these values before and during a run to confirm that the instrument is performing within limits.
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.
| 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. |
Data handling and documentation are central to HPLC quality control. Electronic systems should have audit trails that record changes to methods, sequences, and results. Integration parameters, such as peak baseline and threshold, can affect reported areas and must be defined in advance. Out-of-specification results trigger a structured investigation that may include reanalysis, instrument checks, and review of sample preparation. Regulatory inspections often examine raw data, audit trails, and training records to verify that reported results are traceable and reliable.
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.
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.
== Eigenschaften == Etliche Tetrapeptide sind pharmakologisch aktiv. In der Natur findet man neben linearen Tetrapeptiden (enthalten drei Peptidbindungen) auch cyclische Tetrapeptide, deren Cyclisierung auf einer vierten Peptidbindung oder einer anderen kovalenten Bindung beruht. Beispiele:
Tuftsin (L-Threonyl-L-Lysyl-L-Prolyl-L-Arginin) wird aus einer γ-Globulin-Fraktion enzymatisch freigesetzt und stimuliert die Phagozytose. Rigin (Glycyl-L-Glutaminyl-L-Prolyl-L-Arginin) ist ein Tetrapeptid, das eine ähnliche Funktion wie Tuftsin erfüllt. Postin (Lys-Pro-Pro-Arg) ist ein N-terminales Tetrapeptid von Cystatin C und ein Antagonist von Tuftsin. Morphiceptin (Tyr-Pro-Phe-Pro) ist Peptid, das aus β-Casein gewonnen werden kann. Tubulysine sind synthetische Peptide zur experimentellen Behandlung von Tumoren.
Ötzi, auch Mann vom Tisenjoch, Mann vom Hauslabjoch, Der Mann aus dem Eis, Mumie vom Similaun u. ä. genannt, ist eine Gletschermumie aus der späten Jungsteinzeit bzw. Kupfersteinzeit, die 1991 im Südtiroler Anteil der Ötztaler Alpen gefunden wurde. Untersuchungen zu Ötzis Todeszeitpunkt haben ergeben, dass er zwischen 3368 und 3108 v. Chr. gestorben ist. Ötzi ist damit die älteste bekannte natürliche menschliche Mumie Europas, und eine der ältesten der Welt. Ihrer Untersuchung sind eine Vielzahl an Erkenntnissen über das Leben der Steinzeitmenschen in Europa zu verdanken. Sie wird heute im Südtiroler Archäologiemuseum in Bozen aufbewahrt.
Die Mumie wurde am 19. September 1991 beim 3188 m s.l.m. hohen Tisenjoch in den Ötztaler Alpen oberhalb des Niederjochferners gefunden (rund 70 Meter südwestlich vom Fundort wurde an folgender Position ein Obelisk errichtet: ). Das Tisenjoch, eine Senke des Schnalskamms zwischen der Fineilspitze und dem Similaun, verbindet das Tisental mit dem Niedertal bzw. großräumiger das Schnalstal mit dem Ötztal (der niedrigste Sattel zwischen Fineilspitze und Similaun ist allerdings das vielbegangene, in 3017 m s.l.m. Höhe befindliche Niederjoch). Der mit dem Gesicht nach unten liegende Mann vom Tisenjoch, von dem das schmelzende Eis den Hinterkopf und den Rücken freigegeben hatte, wurde von den beiden deutschen Bergwanderern Erika und Helmut Simon aus Nürnberg beim Abstieg von der Fineilspitze zum Niederjoch entdeckt und ist die einzige erhaltene, durch natürliche Gefriertrocknung konservierte Leiche aus der Kupfersteinzeit (auch als Spät- bzw. Endneolithikum bezeichnet) in Mitteleuropa.
Sources: de.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.
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.