The short version of Stationary phase fits in a sentence. The long version — which is the one that helps — is below.
This page was last updated on 2025-08-12 and is reviewed periodically as new material appears.
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.
Detection in HPLC testing commonly relies on ultraviolet-visible absorbance, fluorescence, refractive index, or mass spectrometry. A diode array detector records full spectra across a wavelength range, which helps identify co-eluting peaks. Mass spectrometry provides mass-to-charge ratios and can confirm molecular identity at low concentrations. The choice of detector depends on analyte structure, required sensitivity, and whether quantitation or identification is the goal. No single detector works for every compound, and method development often compares responses before selecting one.
High-performance liquid chromatography is an analytical technique that separates components of a liquid sample by passing it 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 interaction with the stationary phase cause analytes to migrate at different rates. Detectors record elution as peaks, and a data system converts signals into a chromatogram. The method is suited to compounds that dissolve in a liquid and are not volatile enough for gas chromatography.
| Property | Value | Notes |
|---|---|---|
| Abbreviation | HPLC | Also called high-performance liquid chromatography |
| Separation mechanism | Differential partitioning | Compounds distribute between mobile and stationary phases |
| Typical column chemistry | C18 (octadecylsilane) | Used in reversed-phase separations |
| Typical detector | UV-Vis or photodiode array | Mass spectrometry is common for trace and confirmatory work |
| Typical particle size | 1.8–5 µm | Smaller particles require higher pressure and can improve speed |
Quality control samples are inserted at intervals to monitor accuracy and precision throughout a batch. Blank samples detect contamination, while spiked samples assess recovery from the sample matrix. Calibration standards establish the relationship between detector response and concentration, and control samples are prepared independently from them whenever possible. Laboratories also participate in proficiency testing and maintain audit trails, instrument logs, and reagent records. Ongoing review of control charts can reveal trends before they cause out-of-specification results.
Method validation demonstrates that an HPLC procedure is suitable for its intended purpose. Common validation parameters include accuracy, precision, specificity, linearity, range, limit of detection, limit of quantification, and robustness. Accuracy reflects agreement with a reference value, while precision describes repeatability under defined conditions. Specificity shows whether the method can measure the analyte in the presence of impurities or matrix components. Validation documents are reviewed before a method is used for routine testing or regulatory submissions.
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.
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.
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.
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.
Thirlby's Anderson was also highlighted, such as by Berkshire for carrying the film's emotional story and said, "one of the film's true thrills comes in watching Thirlby effortlessly balance the conflict between a Judge's merciless duties and a psychic's compassionate understanding." The New Statesman's Laura Sneddon noted that Dredd passed the Bechdel test, lacking in sexism or misogyny and positively portraying female characters who are no weaker, more sexualised or shown less than their male counterparts. Sneddon described Anderson as repeatedly shown to have power over men who underestimate her, while Ma-Ma displays more intelligence and sadism than any of her male gang members, and neither woman interacts with the other on the basis of their gender. Many US newspaper critics were less taken with the film. Mark Olsen of the Los Angeles Times called it "a clunk-headed action picture" that "simply becomes a monotonous series of bad-guy confrontations". Frank Lovece of Newsday described it as a "soullessly gritty" film, which apart from one believable scene involving Thirlby, is "all tough-guy talk and humorless cynicism". Stephen Whitty of The Star-Ledger called it a "gray and ugly film", said that there was little to draw viewers in, and wrote that apart from the drug-induced slow-motion sequences, the film offers nothing new.
In fact, it is possible to ionize most elements with a single laser set-up, thus enabling rapid switching from one element to another. In the early days, optical schemes from RIMS have been used to study over 70 elements and over 39 elements can be ionized with a single laser combination using a rapid computer-modulated framework that switches elements within seconds.
==== Calorimetry errors ==== The calculation of excess heat in electrochemical cells involves certain assumptions. Errors in these assumptions have been offered as non-nuclear explanations for excess heat. One assumption made by Fleischmann and Pons is that the efficiency of electrolysis is nearly 100%, meaning nearly all the electricity applied to the cell resulted in electrolysis of water, with negligible resistive heating and substantially all the electrolysis product leaving the cell unchanged. This assumption gives the amount of energy expended converting liquid D2O into gaseous D2 and O2. The efficiency of electrolysis is less than one if hydrogen and oxygen recombine to a significant extent within the calorimeter. Several researchers have described potential mechanisms by which this process could occur and thereby account for excess heat in electrolysis experiments. Another assumption is that heat loss from the calorimeter maintains the same relationship with measured temperature as found when calibrating the calorimeter. This assumption ceases to be accurate if the temperature distribution within the cell becomes significantly altered from the condition under which calibration measurements were made. This can happen, for example, if fluid circulation within the cell becomes significantly altered. Recombination of hydrogen and oxygen within the calorimeter would also alter the heat distribution and invalidate the calibration.
=== Grain-free and low-carbohydrate === Some dog food products differentiate themselves as grain- or carbohydrate-free to offer the consumer an alternative, claiming carbohydrates in pet foods to be fillers with little or no nutritional value. A study published in Nature suggests that domestic dogs' ability to easily metabolize carbohydrates may be a key difference between wolves and dogs. Some consumers and manufacturers say dogs perform better on grain-free diets, while some veterinarians doubt this for a lack of scientific evidence. In 2019, a study comparing dry dog food that was manufactured in the United States found that 75% of food containing feed grade grains also contained measurable levels of various mycotoxins (discussed below), while none of the grain-free dry diets tested had any detectable levels of mycotoxins. Feed grade (lower quality grade) grains that are allowed to spoil and become moldy are the suspected source of the mycotoxins. This is the first published study to show a potential health benefit to feeding grain-free commercial dry pet foods. In 2019, the U.S. Food and Drug Administration identified 16 dog food brands linked to canine heart disease. The FDA has investigated more than 500 cases of dilated cardiomyopathy (DCM) in dogs eating food marketed as grain-free. The 16 brands are: Acana, Zignature, Taste of the Wild, 4Health, Earthborn Holistic, Blue Buffalo, Nature's Domain, Fromm, Merrick, California Natural, Natural Balance, Orijen, Nature's Variety, NutriSource, Nutro, and Rachael Ray Nutrish.
The East Prussian plebiscite (German: Volksabstimmung in Ostpreußen), also known as the Allenstein and Marienwerder plebiscite or Warmia, Masuria and Powiśle plebiscite (Polish: Plebiscyt na Warmii, Mazurach i Powiślu), was a plebiscite for the self-determination of the regions of southern Warmia (Ermland), Masuria (Mazury, Masuren) and Powiśle, which had been in parts of the East Prussian Government Region of Allenstein and of the West Prussian Government Region of Marienwerder in accordance with Articles 94 to 97 of the Treaty of Versailles. Prepared in early 1920, the plebiscite took place on 11 July 1920 and was conducted by German authorities under Inter-Allied control. The plebiscite reported that most voters had selected East Prussia over Poland (over 97% in the Allenstein Plebiscite Area and 92% in the Marienwerder Plebiscite Area). As a result, most of the territories in question remained in the Free State of Prussia and therefore in Germany.
Sources: en.wikipedia.org
== See also == First 100 days of the second Trump presidency – Period from January to April 2025 List of executive actions by Donald Trump Lists of presidential trips made by Donald Trump (international trips) Second presidential transition of Donald Trump – Transfer of presidential power from Joe Biden to Donald Trump Timeline of the 2024 United States presidential election
== Instrumentation and Performance == Initially the digital ion trap was constructed in form of a 3D ion trap, where the drive signal was fed to the ring electrode of the trap. Instead of scanning up the RF voltage, in the DIT, the frequency of the rectangular waveform signal is scanned down during a forward mass scan. This avoided the high voltage breakdown which set the upper limitation of a mass scan. Mass range of DIT up to 18,000 Th was demonstrated by use of an atmospheric MALDI ion source and was later expanded to cover m/z of a singly charged antibody at about 900,000 Th by Koichi Tanaka etc. The MOSFET switch circuit is responsible to provide the rectangular wave drive signal. The drive circuit of DIT is much compact compared to the RF generator with LC resonator circuit used for conventional sinusoidal wave ion trap. It also provides the capability of fast start up and fast termination of the waveform, which enables injection and ejection of ion with high efficiency. A field adjusting electrode placed adjacent to the entrance end-cap and biased with certain dc voltages helped to achieve good mass resolution for both forward and reverse mass scans, as well as for precursor isolation. With trapping voltage of +/- 1kV, a zoom scan resolving power of 19,000 was demonstrated.
Bucillamine is an antirheumatic agent developed from tiopronin. Activity is mediated by the two thiol groups that the molecule contains. Research done in USA showed positive transplant preservation properties. Bucillamine is currently being investigated for COVID-19 drug repurposing. Bucillamine has a well-known safety profile and is prescribed in the treatment of rheumatoid arthritis in Japan and South Korea for over 30 years. It is a cysteine derivative with 2 thiol groups that is 16-fold more potent than acetylcysteine (NAC) as a thiol donor in vivo, giving it vastly superior function in restoring glutathione and therefore greater potential to prevent acute lung injury during influenza infection. Bucillamine has also been shown to prevent oxidative and reperfusion injury in heart and liver tissues. Bucillamine has both proven safety and proven mechanism of action similar to that of NAC, but with much higher potency, mitigating the previous obstacles to using thiols therapeutically. It is hypothesized that similar processes related to reactive oxygen species (ROS) are involved in acute lung injury during nCov-19 infection, possibly justifying the investigation of bucillamine as an intervention for COVID-19. On July 31, 2020, the U.S. Food & Drug Administration (FDA) has approved Revive Therapeutics Ltd. to proceed with a randomized, double-blind, placebo-controlled confirmatory Phase 3 clinical trial protocol to evaluate the safety and efficacy of Bucillamine in patients with mild-moderate COVID-19.
In biology, radionuclides (most often of carbon) can serve as radioactive tracers because they are chemically very similar to the nonradioactive nuclides, so most chemical, biological, and ecological processes treat them in a nearly identical way. One can then examine the result with a radiation detector, such as a Geiger counter, to determine where the provided atoms were incorporated. For example, one might culture plants in an environment in which the carbon dioxide contained radioactive carbon; then the parts of the plant that incorporate atmospheric carbon would be radioactive. Radionuclides can be used to monitor processes such as DNA replication or amino acid transport. In physics and biology radionuclide X-ray fluorescence (conventional X-ray sources may also be used) is used to determine chemical composition of the compound. Radiation from a radionuclide source hits the sample and excites characteristic X-rays in the sample. This radiation is registered and the chemical composition of the sample can be determined from the analysis of the measured spectrum. By measuring the energy of the characteristic radiation lines, it is possible to determine the proton number of the chemical element that emits the radiation, and by measuring the number of emitted photons, it is possible to determine the concentration of individual chemical elements. In nuclear medicine, radioisotopes are used for diagnosis, treatment, and research.
== External links == Overview of all the structural information available in the PDB for UniProt: P09958 (Human Furin) at the PDBe-KB. Overview of all the structural information available in the PDB for UniProt: P23188 (Mouse Furin) at the PDBe-KB.
Sources: en.wikipedia.org
It measures the presence and amount of one or more compounds in a liquid sample. Separation occurs in a column, and detection produces a signal proportional to concentration. Identification usually requires comparison with a known reference standard under the same conditions.
In most cases the sample is consumed or altered during analysis, though some detectors are non-destructive. Fractions can be collected after separation for further study. Repeated testing therefore requires additional sample.
Run times range from under a minute for fast methods to over an hour for complex separations. Sample preparation, equilibration, and data review add time. Throughput depends on instrument configuration and method requirements.
HPLC testing separates and quantifies components in a liquid sample. It is used to check identity, purity, concentration, or stability. The technique works best for compounds that dissolve and are not easily vaporized.