Chromatography detector explained

A chromatography detector is a device that detects and quantifies separated compounds as they elute from the chromatographic column. These detectors are integral to various chromatographic techniques, such as gas chromatography,^[1] liquid chromatography, and high-performance liquid chromatography,^[2] and supercritical fluid chromatography^[3] among others. The main function of a chromatography detector is to translate the physical or chemical properties of the analyte molecules into measurable signal, typically electrical signal, that can be displayed as a function of time in a graphical presentation, called a chromatograms. Chromatograms can provide valuable information about the composition and concentration of the components in the sample.

Detectors operate based on specific principles, including optical, electrochemical, thermal conductivity, fluorescence, mass spectrometry, and more. Each type of detector has its unique capabilities and is suitable for specific applications, depending on the nature of the analytes and the sensitivity and selectivity required for the analysis.

There are two general types of detectors: destructive and non-destructive. The destructive detectors perform continuous transformation of the column effluent (burning, evaporation or mixing with reagents) with subsequent measurement of some physical property of the resulting material (plasma, aerosol or reaction mixture). The non-destructive detectors are directly measuring some property of the column eluent (for example, ultraviolet absorption) and thus affords greater analyte recovery.

Destructive detectors

In liquid chromatography:

• Charged aerosol detector electrically charged aerosol is used for the detection of non-UV-absorbing chargeable molecules, especially saccharides and lipids^{[4] [5] [6]}
• Evaporative light scattering detector evaporating non volatile solutes inside a volatile mobile phase for universal detection. used for saccharides and lipids and other non-UV-absorbing molecules^[7]

In gas chromatography:^[8]

• Flame ionization detector which uses ionizing flame to detect most hydrocarbon molecules^{[9] [10]}
• Flame photometric detector which uses atomizing flame to get light emitted from specific elements to detect and quantify them^{[11] [12]}
• Nitrogen Phosphorus Detector a thermionic detector with photometeric detection, sensitive specifically to nitrogen and phosphorus hydrocarbons^[13]
• Atomic-emission detector is a hyphenation between gas chromatography and atomic emission spectrophotometer for detection of elements.^{[14] [15]}

In all types of chromatography:

• Mass spectrometer is in fact hyphenation between the separative instrument and a mass spectrometry instrument to get information on the molecular weight or atomic weight of the solute. In the advanced mass spectrometry technologies there is information on solutes structure and even chemical properties. The hyphenation between ultra high performance chromatography^[16] with high resolution mass spectrometers^[17] revolutionalized entire new scientific fields of research and application, such as toxicology, proteomics, lipidomics, genomics, metabolomics and metabonomics.^[18]

Non-destructive detectors

Non-destructive detectors in liquid chromatography:

• Ultraviolet light detectors, fixed or variable wavelength, which includes diode array detectors. The ultraviolet light absorption of the effluent is continuously measured at single or multiple wavelengths. These are by far most popular detectors for liquid chromatography.^{[19] [20]}
• Fluorescence detector. Irradiates the effluent with a light of set wavelength and measure the fluorescence of the effluent at a single or multiple wavelength.^[21]
• Refractive index detector.^[22] Continuously measures the refractive index of the effluent. The lowest sensitivity of all detectors. Often used in size exclusion chromatography for polymer analysis.^[23]
• Radio flow detector. Measures radioactivity of the effluent. This detector can be destructive if a scintillation cocktail is continuously added to the effluent.
• Chiral detector continuously measures the optical angle of rotation of the effluent. It is used only when chiral compounds are being analyzed.^[24]
• Conductivity monitor.^[25] Continuously measures the conductivity of the effluent. Used only when conductive eluents (water or alcohols) are used.

Non-destructive detectors in gas chromatography:^[26]

• Thermal conductivity detector:^[27] measures the thermal conductivity of the eluent.
• Electron capture detector:^[28] the most sensitive detector known. Allows for the detection of organic molecules containing halogen, nitro groups etc.
• Photoionization detector^[29] measures the increase in conductivity achieved by ionizing the effluent gas with ultraviolet light radiation.
• Olfactometric detector:^[30] assesses the odor activity of the eluent using human assessors.
• Electronic nose detector^[31] which mimics human nose is emerging as a modern and advanced version of the olfactory detection is the electronic nose detector.^[32]

Notes and References

1. Adlard . E.R. . Juvet . R.S. . January 1975 . A Review of Detectors for Gas Chromatography Part I: Universal Detectors . C R C Critical Reviews in Analytical Chemistry . en . 5 . 1 . 03–13 . 10.1080/10408347508542678 . 0007-8980.
2. Swartz . Michael . 2010-07-13 . HPLC Detectors: A Brief Review . Journal of Liquid Chromatography & Related Technologies . en . 33 . 9–12 . 1130–1150 . 10.1080/10826076.2010.484356 . 39911656 . 1082-6076.
3. West . Caroline . 2018-10-01 . Current trends in supercritical fluid chromatography . Analytical and Bioanalytical Chemistry . en . 410 . 25 . 6441–6457 . 10.1007/s00216-018-1267-4 . 30051210 . 51725022 . 1618-2650.
4. Vehovec . Tanja . Obreza . Aleš . 2010-03-05 . Review of operating principle and applications of the charged aerosol detector . Journal of Chromatography A . 1217 . 10 . 1549–1556 . 10.1016/j.chroma.2010.01.007 . 20083252 . 0021-9673.
5. Schilling . Klaus . Holzgrabe . Ulrike . 2020-05-24 . Recent applications of the Charged Aerosol Detector for liquid chromatography in drug quality control . Journal of Chromatography A . 1619 . 460911 . 10.1016/j.chroma.2020.460911 . 32007219 . 211015385 . 0021-9673.
6. Ghosh . Rajarshi . Kline . Paul . 2019-05-14 . HPLC with charged aerosol detector (CAD) as a quality control platform for analysis of carbohydrate polymers . BMC Research Notes . 12 . 1 . 268 . 10.1186/s13104-019-4296-y . 1756-0500 . 6518655 . 31088532 . free .
7. Nayak . V. S. . Tan . Z. . Ihnat . P. M. . Russell . R. J. . Grace . M. J. . 2012-01-01 . Evaporative Light Scattering Detection Based HPLC Method for the Determination of Polysorbate 80 in Therapeutic Protein Formulations . Journal of Chromatographic Science . en . 50 . 1 . 21–25 . 10.1093/chromsci/bmr015 . 0021-9665 . 3252124 . 22291052.
8. Book: Scott, Raymond P. W. . Chromatographic detectors: design, function, and operation . 1996 . Dekker . 978-0-8247-9779-9 . Chromatographic science series . New York, NY.
9. Web site: Gas Chromatography (GC) with Flame-Ionization Detection .
10. Zhou . Jia . Lu . Xiaoqing . Tian . Baoxia . Wang . Chonglong . Shi . Hao . Luo . Chuping . Li . Xiangqian . 2020 . A gas chromatography-flame ionization detection method for direct and rapid determination of small molecule volatile organic compounds in aqueous phase . 3 Biotech . en . 10 . 12 . 520 . 10.1007/s13205-020-02523-8 . 2190-572X . 7655889 . 33194524.
11. Ferguson . D. A. . Luke . L. A. . 1979-04-01 . Critical appraisal of the flame photometric detector in petroleum analysis . Chromatographia . en . 12 . 4 . 197–203 . 10.1007/BF02411361 . 97533335 . 1612-1112.
12. Cheskis . Sergey. . Atar . Eitan. . Amirav . Aviv. . 1993-03-01 . Pulsed-flame photometer: a novel gas chromatography detector . Analytical Chemistry . en . 65 . 5 . 539–555 . 10.1021/ac00053a010 . 0003-2700.
13. Burgett . Charles A. . Smith . Douglas H. . Bente . H. Bryan . 1977-04-01 . The nitrogen-phosphorus detector and its applications in gas chromatography . Journal of Chromatography A . 134 . 1 . 57–64 . 10.1016/S0021-9673(00)82569-8 . 0021-9673.
14. Wylie . P. L. . Quimby . B. D. . 1989 . Applications of gas chromatography with an atomic emission detector . Journal of High Resolution Chromatography . en . 12 . 12 . 813–818 . 10.1002/jhrc.1240121210 . 0935-6304.
15. van Stee . Leo L. P. . Brinkman . Udo A. Th. . Bagheri . Habib . 2002-09-10 . Gas chromatography with atomic emission detection: a powerful technique . TrAC Trends in Analytical Chemistry . 21 . 9 . 618–626 . 10.1016/S0165-9936(02)00810-5 . 0165-9936.
16. Cielecka-Piontek . Judyta . Zalewski . Przemysław . Jelińska . Anna . Garbacki . Piotr . 2013 . UHPLC: The Greening Face of Liquid Chromatography . Chromatographia . en . 76 . 21–22 . 1429–1437 . 10.1007/s10337-013-2434-6 . 0009-5893 . 3825615 . 24273332.
17. Maurer . Hans H. . 2013-05-31 . What is the future of (ultra) high performance liquid chromatography coupled to low and high resolution mass spectrometry for toxicological drug screening? . Journal of Chromatography A . State-of-the art of (UHP)LC--MS(--MS) techniques and their practical application . 1292 . 19–24 . 10.1016/j.chroma.2012.08.069 . 22964051 . 0021-9673.
18. Zaikin . V. G. . Borisov . R. S. . 2021-12-01 . Mass Spectrometry as a Crucial Analytical Basis for Omics Sciences . Journal of Analytical Chemistry . en . 76 . 14 . 1567–1587 . 10.1134/S1061934821140094 . 1608-3199 . 8693159.
19. Logan . Barry K. . 1994-03-30 . Liquid chromatography with photodiode array spectrophotometric detection in the forensic sciences . Analytica Chimica Acta . 288 . 1 . 111–122 . 10.1016/0003-2670(94)85120-4 . 0003-2670.
20. Book: W. John Lough. Irving W. Wainer. High Performance Liquid Chromatography: Fundamental Principles and Practice. 2 September 2013. 1995. Blackie Academic & Professional. 978-0-7514-0076-2. 120–.
21. Lingeman . H. . Underberg . W. J. M. . Takadate . A. . Hulshoff . A. . 1985 . Fluorescence Detection in High Performance Liquid Chromatography . Journal of Liquid Chromatography . en . 8 . 5 . 789–874 . 10.1080/01483918508067120 . 0148-3919.
22. Al-Sanea . Mohammad M. . Gamal . Mohammed . 2022-07-01 . Critical analytical review: Rare and recent applications of refractive index detector in HPLC chromatographic drug analysis . Microchemical Journal . 178 . 107339 . 10.1016/j.microc.2022.107339 . 247277480 . 0026-265X.
23. Hong . Mei . Liu . Wei . Liu . Yonggang . Dai . Xuemin . Kang . Yu . Li . Rui . Bao . Feng . Qiu . Xuepeng . Pan . Yanxiong . Ji . Xiangling . 2022-11-08 . Improved characterization on molecular weight of polyamic acids using gel permeation chromatography coupled with differential refractive index and multi-angle laser light scattering detectors . Polymer . 260 . 125370 . 10.1016/j.polymer.2022.125370 . 252578680 . 0032-3861.
24. Bobbitt . Donald R. . Linder . Sean W. . 2001-03-01 . Recent advances in chiral detection for high performance liquid chromatography . TrAC Trends in Analytical Chemistry . 20 . 3 . 111–123 . 10.1016/S0165-9936(00)00083-2 . 0165-9936.
25. Book: R.P.W. Scott. Liquid Chromatography Detectors. 2 September 2013. 1 February 1986. Elsevier. 978-0-08-085836-4. 2–.
26. Book: McNair . Harold Monroe . Basic gas chromatography . Miller . James M. . Snow . Nicholas H. . 2019 . John Wiley & Sons, Inc . 978-1-119-45073-3 . 3rd . Hoboken, NJ.
27. Rastrello . Fabio . Placidi . Pisana . Scorzoni . Andrea . Cozzani . Enrico . Messina . Marco . Elmi . Ivan . Zampolli . Stefano . Cardinali . Gian Carlo . May 2013 . Thermal Conductivity Detector for Gas Chromatography: Very Wide Gain Range Acquisition System and Experimental Measurements . IEEE Transactions on Instrumentation and Measurement . 62 . 5 . 974–981 . 10.1109/TIM.2012.2236723 . 2013ITIM...62..974R . 33546808 . 0018-9456.
28. Book: Zlatkis . A. . Electron Capture: Theory and Practice in Chromatography . Poole . C.F. . Elsevier . 1981 . 428.
29. Driscoll . J. N. . 1985-11-01 . Review of Photoionization Detection in Gas Chromatography: The First Decade . Journal of Chromatographic Science . 23 . 11 . 488–492 . 10.1093/chromsci/23.11.488 . 0021-9665.
30. Brattoli . Magda . Cisternino . Ezia . Dambruoso . Paolo Rosario . De Gennaro . Gianluigi . Giungato . Pasquale . Mazzone . Antonio . Palmisani . Jolanda . Tutino . Maria . 2013 . Gas Chromatography Analysis with Olfactometric Detection (GC-O) as a Useful Methodology for Chemical Characterization of Odorous Compounds . Sensors . en . 13 . 12 . 16759–16800 . 10.3390/s131216759 . 1424-8220 . 3892869 . 24316571 . 2013Senso..1316759B . free .
31. Kim . Chuntae . Lee . Kyung Kwan . Kang . Moon Sung . Shin . Dong-Myeong . Oh . Jin-Woo . Lee . Chang-Soo . Han . Dong-Wook . 2022-08-19 . Artificial olfactory sensor technology that mimics the olfactory mechanism: a comprehensive review . Biomaterials Research . 26 . 1 . 40 . 10.1186/s40824-022-00287-1 . 2055-7124 . 9392354 . 35986395 . free .
32. Song . Jianxin . Chen . Qinqin . Bi . Jinfeng . Meng . Xianjun . Wu . Xinye . Qiao . Yening . Lyu . Ying . 2020-11-30 . GC/MS coupled with MOS e-nose and flash GC e-nose for volatile characterization of Chinese jujubes as affected by different drying methods . Food Chemistry . 331 . 127201 . 10.1016/j.foodchem.2020.127201 . 32562976 . 219959356 . 0308-8146.