robustness raises a handful of sensible questions. This page answers them in order, starting with the fundamentals and moving to applications.
This page was last updated on 2025-07-27 and is reviewed periodically as new material appears.
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.
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.
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.
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.
| 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 |
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.
Otherwise: Roast the potatoes like chestnuts in the ashes, peel and cut into slices. Sprinkle with chopped mint, pour boiled raisins, vinegar and sprinkle with pepper. (French: Autrement. Mettez roſtir la tartoufle dedans le cendres chaudes comme on cuit les caſtaignes, puis la faut peler & coupper par trãches, mettez ſus mente haſchee, des carentines boullies par deſſus, & vinaigre, vn peu de poiure, & ſeruez ainſi.)
This method was not limited to Douglas; the Irish doctor Francis Hare, who worked in a sanatorium outside London from 1905 onward, also used low-dose apomorphine as a treatment, describing it as "the most useful single drug in the therapeutics of inebriety". He wrote:In (the) sanatorium it is used in three different sets of circumstances: (1) in maniacal or hysterical drunkenness: (2) during the paroxysm of dipsomania, in order to still the craving for alcohol; and (3) in essential insomnia of a special variety... [after giving apomorphine] the patient's mental condition is entirely altered. He may be sober: he is free from the time being from any craving from alcohol. The craving may return, however, and then it is necessary to repeat the injection, it may be several times at intervals of a few hours. These succeeding injections should be quite small, 3 to 6 min. being sufficient. Doses of this size are rarely emetic. There is little facial pallor, a sensation as of the commencement of sea-sickness, perhaps a slight malaise with a sudden subsidence of the craving for alcohol, followed by a light and short doze.He also noted there appeared to be a significant prejudice against the use of apomorphine, both from the associations of its name and doctors being reluctant to give hypodermic injections to alcoholics. In the US, the Harrison Narcotics Tax Act made working with any morphine derivatives extremely hard, despite apomorphine itself not being an opiate.
Cannabis had been decriminalised by the Prayut government in 2022, with the move being most supported by the Bhumjaithai Party (BJT) as one of its flagship policies. The Pheu Thai party had run in 2023 on an anti-drug policy and opposed the use of cannabis except for medical use and, under Srettha, had proposed legislation aimed at restricting the use of cannabis. The party's stance on cannabis thus led to tension with the BJT – creating a rift between the two parties which remained in a coalition when Paetongtarn became prime minister. The Thai government had hoped that decriminalising cannabis would turn it into a cash crop. A lack of laws governing cannabis were blamed for the rise in illegal distribution and the creation of a saturated market. Shortly after becoming prime minister, the Ministry of Public Health proposed a new bill on 12 September 2024 restricting cannabis to medical and research reasons. It also proposed the establishment of a Cannabis Control Board (CCB) to regulate the industry. The bill did not pass and Paetongtarn pledged that the government would not reverse its policy on cannabis again. However, by 2025, tourists smuggling cannabis out from Thailand was on the rise. Somsak Thepsuthin, the Minister of Public Health, listed in May that Hong Kong, India, Pakistan and the United Kingdom were the main destinations. On 22 May, the Paetongtarn government announced it planned to introduce new restrictions limiting cannabis usage to individuals (including foreigners) with medical prescriptions from doctors.
Sources: en.wikipedia.org
=== Signaling === D-Serine, synthesized in neurons by serine racemase from L-serine (its enantiomer), serves as a neuromodulator by coactivating NMDA receptors, making them able to open if they then also bind glutamate. D-serine is a potent agonist at the glycine site (NR1) of canonical diheteromeric NMDA receptors. For the receptor to open, glutamate and either glycine or D-serine must bind to it; in addition a pore blocker must not be bound (e.g. Mg2+ or Zn2+). Some research has shown that D-serine is a more potent agonist at the NMDAR glycine site than glycine itself. However, D-serine has been shown to work as an antagonist/inverse co-agonist of t-NMDA receptors through the glycine binding site on the GluN3 subunit.
Besides public research, it was eventually learned that the United States government had also conducted research into psychedelics, as possible mind-control and truth-serum drugs, in the 1940s through the 1970s, for instance Project MKUltra by the Central Intelligence Agency (CIA) and the Edgewood Arsenal research by the U.S. Army.
The oil-drug emulsion must have low solubility with the polymer membrane to ensure that the drug will be carried throughout the system properly and be released at the proper time and location. When the proper emulsion is obtained, the drug should be uniformly dispersed throughout the entire internal cavity of the polymeric membrane.
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.
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.