This is a working overview of Chromatogram, written for readers who want more than a one-paragraph summary but less than a textbook.
This page was last updated on 2026-01-07 and is reviewed periodically as new material appears.
Routine quality control uses system suitability, blank injections, check standards, and control samples to detect drift or contamination. System suitability criteria may specify minimum resolution, maximum tailing factor, and a permitted range for repeated injections. Blank injections reveal carryover or solvent contamination, while check standards confirm calibration accuracy over a batch. Control samples with known analyte levels can show whether results remain within statistical limits. When a control result falls outside limits, the analyst investigates the cause and may invalidate affected results before repeating the batch.
Documentation and traceability are central to regulated HPLC testing. Records typically include instrument logs, column history, mobile-phase preparation, sample preparation, injection sequences, raw chromatograms, and audit trails. Electronic systems may require user access controls, time-stamped changes, and backup procedures. Training records show that analysts are qualified for assigned methods. Audits and inspections check whether written procedures match actual practice and whether deviations are documented. These controls support reproducibility and allow results to be reconstructed if questions arise later.
Method validation establishes that an HPLC procedure is suitable for its intended purpose. Typical parameters include accuracy, precision, specificity, linearity, range, limit of detection, limit of quantitation, robustness, and solution stability. Accuracy reflects closeness to a reference value, while precision reflects agreement among repeated measurements. Specificity shows whether the method can measure the analyte without interference from matrix components. Validation is documented through protocols and reports, and the required extent depends on the method's use and regulatory context.
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.
| Property | Value | Notes |
|---|---|---|
| Accuracy | Recovery near 100% | Depends on acceptance criteria and matrix |
| Precision | Relative standard deviation | Often at or below 2% for replicate injections |
| Limit of detection | Signal-to-noise ratio 3:1 | Approximate and method-specific |
| Limit of quantitation | Signal-to-noise ratio 10:1 | Confirmed by precision and accuracy |
| Resolution | 1.5 or greater | Typical system suitability target |
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.
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.
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.
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.
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.
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.
On 23 January, Iraq dumped 400 million US gallons (1,500,000 m3) of crude oil into the Persian Gulf, causing the largest offshore oil spill in history at that time. It was reported as a deliberate natural resources attack to keep US Marines from coming ashore (Missouri and Wisconsin had shelled Failaka Island during the war to reinforce the idea that there would be an amphibious assault attempt). About 30–40% of this came from allied raids on Iraqi coastal targets.
==== Larva ==== Cabbage looper larvae are a type of cabbage worm, green in colour with a white stripe on the side. After hatching, they are green and slightly hairy, but eventually turn green and lose the hair, leaving only a few bristles. They are identified by their looping behaviour, in which they arch their body in a loop when they crawl. Larvae are generally 3–4 cm long, and can have four to seven instars within 9–14 days. Larvae initially do not consume much food but increase their consumption during their lifetime until they are consuming three times their weight daily.
== The Monolith Summer School == Since 2004, BIA Separations has organized and hosted the Monolith Summer School and Symposium (MSS) which takes place every 2 years. MSS was established as there were no dedicated conferences to this technology and to bring together the top international scientists and researchers in the area of monolith chromatography to share their experiences and innovative applications.
Sources: en.wikipedia.org
"wildly violating the sovereignty of Venezuela" by calling it a "high-handedness act", stating "The incident is another example that clearly confirms once again the rogue and brutal nature of the U.S., which the international community has so frequently witnessed for a long time". It added that North Korea "strongly denounces the U.S. hegemony-seeking act committed in Venezuela as the most serious form of encroachment of sovereignty and as a wanton violation of the U.N. Charter and international laws". It also called on the international community to recognize the "catastrophic" situation in Venezuela and denounce the U.S.'s "habituated violation of sovereignty of other countries". South Korea: On 3 January, President Lee Jae Myung instructed officials to ensure the protection of South Korean nationals in Venezuela and to prepare evacuation plans in case the situation worsens. The Ministry of Foreign Affairs set up a task force to protect its nationals. On 4 January, The Ministry of Foreign Affairs spokesperson urged "all parties to make every effort to ease tensions in the region" and hoped "that democracy will be restored with the will of the Venezuelan people respected and that the situation in Venezuela will be stabilised at an early date through dialogue". Malaysia: The Ministry of Foreign Affairs reaffirmed its position of "opposing all forms of foreign intervention in the internal affairs of sovereign states, as well as the threat or use of force".
Under Maher's supervision, the 4th Armoured Division expanded captagon production and trafficking from Syria into a "business model controlled by the regime". In 2022, 90% of all Captagon pills manufactured in Syria exported by drug cartels affiliated with Assad regime arrived at its customer destinations across the world. Although hundreds of millions of pills were intercepted and seized by police forces, these accounted only for 10% of the total Captagon exports of the drug cartels linked to the Assad regime. In 2020, Italian police seized 84 million captagon pills originating from Syrian ports while intercepting a single shipment. In June 2023, US State Department's Bureau of Near Eastern Affairs published a detailed report to the US Congress, elucidating a strategy to eliminate the narcotics production, drug trafficking and drug cartel networks affiliated with the Assad regime and Hezbollah. A joint investigation conducted by Organized Crime and Corruption Reporting Project (OCCRP) and BBC News Arabic published a documentary in June 2023, revealing further details about the activities of regime officials, Ba'athist military commanders and Assad family members in their involvement in Syria's drug cartel. The investigation found that Lebanese criminal and drug kingpin Hassan Daqou collaborated with Syria's Fourth Armoured Division on trafficiking billions of dollars of drugs, under the command of General Ghassan Bilal, the right-hand man of Maher al-Assad. The report also unearthed Hezbollah's close participation in the drug production and smuggling networks.
Symmetric spin and symmetric under parity. In this case, the exchange of the two nucleons will multiply the deuterium wavefunction by (−1) from isospin exchange, (+1) from spin exchange and (+1) from parity (location exchange), for a total of (−1) as needed for antisymmetry. Antisymmetric spin and antisymmetric under parity. In this case, the exchange of the two nucleons will multiply the deuterium wavefunction by (−1) from isospin exchange, (−1) from spin exchange and (−1) from parity (location exchange), again for a total of (−1) as needed for antisymmetry. In the first case the deuteron is a spin triplet, so that its total spin s is 1. It also has an even parity and therefore even orbital angular momentum l. The lower its orbital angular momentum, the lower its energy. Therefore, the lowest possible energy state has s = 1, l = 0. In the second case the deuteron is a spin singlet, so that its total spin s is 0. It also has an odd parity and therefore odd orbital angular momentum l. Therefore, the lowest possible energy state has s = 0, l = 1. Since s = 1 gives a stronger nuclear attraction, the deuterium ground state is in the s = 1, l = 0 state. The same considerations lead to the possible states of an isospin triplet having s = 0, l = even or s = 1, l = odd. Thus, the state of lowest energy has s = 1, l = 1, higher than that of the isospin singlet.
Sources: en.wikipedia.org
Validation establishes suitability for a new method, while verification confirms that a method works in a specific laboratory. Verification is often used when a validated method is adopted with existing equipment and staff. Both rely on documented acceptance criteria.
Quantification usually compares detector response to a standard curve made from reference standards. The curve may be external, internal, or based on standard addition depending on matrix effects. Results are reported with units and, when required, uncertainty.
Carryover occurs when analyte from a previous injection remains in the system and appears in a later chromatogram. It can come from the injector, column, or tubing. Blank injections and needle washes help detect and reduce it.
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.