A practical reference on Calibration curve: what it is, how it behaves, what the literature reports, and where the honest uncertainties sit.
This page was last updated on 2025-10-10 and is reviewed periodically as new material appears.
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.
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.
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.
| Property | Value | Notes |
|---|---|---|
| Accuracy | Closeness to true value | Often assessed by recovery of spiked samples |
| Precision | Agreement among repeated measurements | Often reported as relative standard deviation |
| Specificity | Ability to measure analyte without interference | Must separate analyte from impurities and matrix |
| Linearity | Proportional detector response | Evaluated across a defined concentration range |
| Robustness | Resistance to small method changes | Tests flow rate, pH, temperature, and mobile phase composition |
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.
System suitability testing is performed before and during analytical runs to confirm that the instrument and method are working as expected. Typical checks include retention time, peak area precision, resolution between critical pairs, tailing factor, and theoretical plate count. Acceptance criteria are set in the method or pharmacopeial monograph. If a suitability check fails, the run may be rejected and the instrument or sample preparation may need investigation. This practice helps prevent release of data from a system that has drifted out of control.
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.
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.
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.
Method validation evaluates accuracy, precision, specificity, linearity, range, detection limit, quantitation limit, and robustness. Regulatory guidance for pharmaceuticals, foods, and environmental testing defines expected documentation and acceptance criteria. Verification confirms that a validated method works in a specific laboratory with its own instruments and reagents. Calibration curves use reference standards with known purity and traceability, while measurement uncertainty is estimated from validation data, control charts, and collaborative studies. The scope of validation depends on the method's intended use.
However, the topical application of 1–3% solutions of the drug to the nasal mucosa of patients with sinusitis did produce a beneficial constriction without local irritation. Administration of synephrine by continuous intravenous infusion, at the rate of 4 mg/minute, significantly increased mean arterial and systolic pressure, but diastolic pressure and heart rate were unaltered.; further details of this investigation are summarized in a review by Fugh-Berman and Myers. There are a number of studies, references to many of which may be found in the review by Stohs and co-workers dealing with the effects produced by dietary supplements and herbal medications that contain synephrine as only one of many different chemical ingredients. These are outside the scope of the present article (see also the "Safety/Efficacy/Controversy" sub-section).
Glutamic acid (symbol Glu or E; known as glutamate in its anionic form), molecular formula C5H9NO4, is an α-amino acid that is used by almost all organisms for the biosynthesis of proteins. It is a conditionally essential amino acid, meaning that the body can generally synthesize it intrinsically, but under certain circumstances needs to procure it through food. It is also the most abundant excitatory neurotransmitter in the vertebrate nervous system. It serves as the precursor for the synthesis of the inhibitory gamma-aminobutyric acid (GABA) in GABAergic neurons. Glutamic acid exists in two optically isomeric forms; the dextrorotary L-form is usually obtained by hydrolysis of gluten, from the waste waters of beet-sugar manufacturing, or by fermentation. Its molecular structure could be idealized as HOOC−CH(NH2)−(CH2)2−COOH, with two carboxyl groups −COOH and one amino group −NH2. However, in the solid state and mildly acidic water solutions, the molecule assumes an electrically neutral zwitterion structure −OOC−CH(NH+3)−(CH2)2−COOH. It is encoded by the codons GAA or GAG. The acid can lose one proton from its second carboxyl group to form the conjugate base, the singly-negative anion glutamate −OOC−CH(NH+3)−(CH2)2−COO−. This form of the compound is prevalent in neutral solutions. The glutamate neurotransmitter plays the principal role in neural activation. This anion creates the savory umami flavor of foods and is found in glutamate flavorings such as monosodium glutamate (MSG).
If there is an increase in length of the material line, the normal strain is called tensile strain; otherwise, if there is reduction or compression in the length of the material line, it is called compressive strain.
Sources: en.wikipedia.org
=== Loans === In 2014, the museum conducted its first major loan of artifacts to another institution. Approximately 2,000 objects from its collection went on display at the John Heinz History Center in Pittsburgh, Pennsylvania, on May 31, 2014. Because the Arabia was built in Pittsburgh and Brownsville, Pennsylvania, in 1853, the temporary exhibition was called "Pittsburgh's Lost Steamboat: Treasures of the Arabia". In addition to the artifacts, Heinz curators displayed information about the preservation process and a replica of the mule that represents the only fatality of the sinking. This exhibition ran through January 4, 2015.
=== ColdFusion and Java === The standard ColdFusion installation allows the deployment of ColdFusion as a WAR file or EAR file for deployment to standalone application servers, such as Macromedia JRun, and IBM WebSphere. ColdFusion can also be deployed to servlet containers such as Apache Tomcat and Mortbay Jetty, but because these platforms do not officially support ColdFusion, they leave many of its features inaccessible. As of ColdFusion 10 Macromedia JRun was replaced by Apache Tomcat. Because ColdFusion is a Java EE application, ColdFusion code can be mixed with Java classes to create a variety of applications and use existing Java libraries. ColdFusion has access to all underlying Java classes, supports JSP custom tag libraries, and can access JSP functions after retrieving the JSP page context (GetPageContext()). Prior to ColdFusion 7.0.1, ColdFusion components could only be used by Java or .NET by declaring them as web services. However, beginning in ColdFusion MX 7.0.1, ColdFusion components can now be used directly within Java classes using the CFCProxy class. Recently, there has been much interest in Java development using alternate languages such as Jython, Groovy and JRuby. ColdFusion was one of the first scripting platforms to allow this style of Java development.
== Career == Platt makes his decisions about accepting acting roles based on the role being "different from what I just did...I do have to be interested in the role". After Married to the Mob, he appeared in Working Girl (1988), Flatliners (1990), Beethoven (1992), The Three Musketeers (1993), A Time to Kill (1996), Executive Decision (1996), and Bulworth (1998). In 1998 Platt and Stanley Tucci played two deadbeat actors who improvise with unsuspecting strangers in The Impostors. Tucci and Platt developed the characters while working on a play at Yale University in 1988, with Tucci later completing the screenplay and directing the film. In 1999, Platt played the wealthy and eccentric crocodile enthusiast Hector in David E. Kelley's Lake Placid, alongside Bill Pullman and Bridget Fonda. Platt described Hector as "pretty abrasive and obnoxious at times, but, I hope, he has a way of growing on you. I think David originally thought of him as a great white hunter sort of guy, but when I signed on for the role he sort of wrote him in a different direction." The short-lived drama Deadline provided Platt's first lead role on television. Created by Dick Wolf, who also created Law & Order, Deadline focused on the lives of newspaper journalists in New York City. Platt starred as Pulitzer Prize-winning columnist Wallace Benton, an "unlikely hero". The strong cast, which also included Bebe Neuwirth and Hope Davis, could not compensate for substandard writing and the series was soon canceled.
Sources: en.wikipedia.org
==== Synroc ==== The Australian Synroc (synthetic rock) is a more sophisticated way to immobilize such waste, and this process may eventually come into commercial use for civil wastes (it is currently being developed for U.S. military wastes). Synroc was invented by Ted Ringwood, a geochemist at the Australian National University. The Synroc contains pyrochlore and cryptomelane type minerals. The original form of Synroc (Synroc C) was designed for the liquid high-level waste (PUREX raffinate) from a light-water reactor. The main minerals in this Synroc are hollandite (BaAl2Ti6O16), zirconolite (CaZrTi2O7) and perovskite (CaTiO3). The zirconolite and perovskite are hosts for the actinides. The strontium and barium will be fixed in the perovskite. The caesium will be fixed in the hollandite. A Synroc waste treatment facility began construction in 2018 at ANSTO.
In Swansea's maritime quarter are the Dylan Thomas Theatre, home of the Swansea Little Theatre of which Thomas was once a member, and the former Guildhall, built in 1825 and now occupied by the Dylan Thomas Centre, a literature centre, where exhibitions and lectures are held and setting for the annual Dylan Thomas Festival.
=== Clostridioides difficile infection === S. boulardii has been associated with a reduction in recurrence rates among patients with recurrent Clostridioides difficile infection and may be effective as a secondary preventive intervention. Evidence does not support its use as a primary treatment for acute infection.
The reason for using one or more housekeeping genes is to correct non-specific variation, such as the differences in the quantity and quality of RNA used, which can affect the efficiency of reverse transcription and therefore that of the whole PCR process. However, the most crucial aspect of the process is that the reference gene must be stable. The selection of these reference genes was traditionally carried out in molecular biology using qualitative or semi-quantitative studies such as the visual examination of RNA gels, northern blot densitometry or semi-quantitative PCR (PCR mimics). Now, in the genome era, it is possible to carry out a more detailed estimate for many organisms using transcriptomic technologies. However, research has shown that amplification of the majority of reference genes used in quantifying the expression of mRNA varies according to experimental conditions. It is therefore necessary to carry out an initial statistically sound methodological study in order to select the most suitable reference gene. A number of statistical algorithms have been developed that can detect which gene or genes are most suitable for use under given conditions. Those like geNORM or BestKeeper can compare pairs or geometric means for a matrix of different reference genes and tissues. The entire qPCR analysis workflow with proper error propagations is implemented in GenEx.
Sources: en.wikipedia.org
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.
Validation demonstrates that a method produces reliable results for a defined purpose. It documents performance limits and acceptance criteria. Regulated industries require validation before routine testing of products or samples.
Retention time shifts can arise from changes in mobile phase composition, pH, temperature, column age, or flow rate. Contamination or worn seals may also alter pressure and delivery. Systematic checks of these factors help identify the cause.
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.