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INTERNATIONAL RESEARCH JOURNAL OF PHARMACY ISSN 2230 – 8407 Available online http://www.irjponline.com Review Article

HIGH PERFORMANCE LIQUID CHROMATOGRAPHY DETECTORS – A REVIEW Kaushal Ramni, Kaur Navneet, Upadhyay Ashutosh, Suri O. P, Thakkar Arti *

I. S. F. College of Pharmacy, Ferozepur Road, Ghal Kalan, Moga, Punjab, India

Article Received on: 15/03/2011 Revised on: 17/04/2011 Approved for publication: 05/05/2011 *I. S. F. College of Pharmacy, Ferozepur Road, Ghal Kalan, Moga 142 001, Punjab, India Email: artirthakkar@gmail.com ABSTRACT HPLC is the most versatile and widely used elution chromatography. The technique is used to resolve and determine species in a variety of organic, inorganic, biological, ionic and polymeric materials. Detector is the heart of an instrument and efficiency of system is dependent upon detecting techniques. Many types of HPLC detectors exist, each of which has some valuable performance feature such as refractive index detector, ultraviolet detector, fluorescent detector, electrochemical detector, electric conductivity detector, liquid light scattering detector, evaporative light scattering detector. Due to strong requirement for improvements in sensitivity, selectivity and other performance characteristics of the detector recent developments in conventional techniques and some other new technologies have been adopted such as laser light scattering detector, charged aerosol detector, nano quantity aerosol detector, chiral detector and pulsed amperometric detector. These detectors provide accurate concentration analysis, excellent sensitivity, wide dynamic range, consistent response and broad applicability of the drug components. Working of these detectors involve different principles such as optical techniques, aerosol based techniques, refractive methods, light scattering principle, amperometric and fluorescence. The present review enlightens both conventional and advanced techniques and compares their capabilities of analyzing drug components and need for new techniques for better and wide range of applicability. KEYWORDS: Refractive index detector, Charged aerosol detector, Nano quantity aerosol detector, Chiral detector, Pulsed amperometric detector. INTRODUCTION HPLC (High Performance Liquid Chromatography) is the most versatile and widely used elution chromatography. The technique is used to separate and determine species in a variety of organic, inorganic, biological, ionic and polymeric materials1. A standard instrument of HPLC incorporates following components: Solvent reservoir, Mobile phase, Pump, Loop injector, Guard column or an in-line filter, Analytical Column, Temperature control, Detector, HPLC Data Acquisition. Column is connected to the injector and detector with tubing of narrow internal diameter (0.2 mm) 2, 3. DETECTORS Detector in HPLC is placed at the end of analytical column. Function of detector is to examine the solution which is eluting from the column. An electronic signal (output from detector) is proportional to the concentration of individual components of analyte. Detectors are classified as bulk property detectors and solute property detectors. Bulk property detectors measure the changes in the property of combined eluting mobile phase and eluting solute. Solute property detectors detect the changes in physical and chemical property of eluting component of the mobile phase.

HPLC detector should have particular characteristics such as excellent linear response as a function of concentration of the solute, wide linear dynamic range, high signal to noise ratio. A robust detector with good sensitivity works approximately in range of 0.01-100 μg of compound in elutes4. Various types of HPLC detectors are mentioned in Tab. 1. REFRACTIVE INDEX DETECTORS Refractive index is a bulk property of column eluent. In this detector, detection depends on solute modifying overall refractive index of the mobile phase. Bulk property detectors have an inherently limited sensitivity. These were one of the first on-line detectors to be developed by Tiselius and Claesson5 in 1942. This detector can be very useful for detection of non-ionic compounds that neither absorb in UV region nor fluoresce. Methods employed for detection using refractive index detector are such as angle of deviation method and Fresnel method. Various types of RI detectors are mentioned here. Christiansen effect detector This detector was developed by Christiansen on crystal filters6,7. Liquid and particulate matter have indices of refraction those are substantially equal to one another at

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a specific wavelength. Variations of transmitted light can determine changes of refractive index of liquid. Differences in the intensity of light transmitted through sample cell and reference device can be determined. Interferometer detector Detector response depends on change in effective path length of light beam passing through cell. Detector consists of carrier such as metal chain, wire or disc that passes continually through column, extracting a sample of mobile phase containing solute. Mobile phase is eliminated by evaporation leaving solute as a coating on carrier wire. Scanning is done with specific sensing technique8. Thermal lens detector (TL) TL effect is induced when a laser beam passes through a material and the absorbed energy is converted into heat. Change in the optical path length induced by a temperature rise produce a lens like optical element at sample. This affects the propagation of a probe beam through TL. Measurement of the beam centre describes thermo-optical properties of sample9,10. Dielectric constant detector Refractive index of substance is complementary property to dielectric constant and in some circumstances; it is direct function of dielectric constant. Relationship between dielectric constant (e) and refractive index (n) for non polar substances is given by equation11 (i)

e = n2 (i) Dielectric constant detector provides an electrical signal that is proportional to concentration of a component being passed through the detector. ULTRAVIOLET DETECTORS As most organic compounds absorb light in the UV region (190–400 nm) and visible region (400–750 nm), UV–VIS spectophotometric detectors are most commonly used detectors in HPLC. Fixed wavelength, variable wavelength and diode array detectors are available for detection in these regions. All the UV-VIS detectors are based on Beer-Lambert law of ability of solute to absorb light at defined wavelengths based on chemical structure and functional groups present in the solute molecule. Sensitivity of the detector depends on A (1%, 1 cm) value of analyte. Source of UV light is a deuterium or high pressure xenon lamp while for visible range tungsten lamp is preferable. A beam of light is allowed to pass through a flow cell mounted at the end of column. Schematic diagram of UV detector is described in Fig. 112. Fixed wavelength UV detector Fixed wavelength detectors operate at a single wavelength either at 254 or 280 nm in the UV region. Most popular lamp is low pressure mercury vapour lamp

which generates light at wavelength of 254 nm. Variable wavelength UV detector These detectors can be adjusted to operate at any wavelength over full UV-Visible range. The wavelengths can be selected with difference of 3 nm or less in this detector. Multi wavelength UV detector This detector selects a single or narrow range of wavelengths. There are two types of multi wavelength detector, dispersion detector that monitors eluent at one wavelength, used for separation of some carboxylic acids, a series of common fatty acids13 and the diode array detector (DAD) that monitors solute absorption simultaneously over a range of wavelengths. DAD is used for detection and identification of poison in traditional medicines14,15. The ideal multi wavelength detector is combination of dispersive system and diode array detector. FLUORESCENCE DETECTOR Fluorescence detectors are most sensitive, specific and selective among existing modern HPLC detectors. It is possible to detect presence of a single analyte molecule in the flow cell. Fluorescence sensitivity is 10-1000 times higher than UV detector for strong UV absorbing materials16. Schematic diagram of simple form of fluorescence detector17 is shown in Fig. 2. Single wavelength excitation fluorescence detector The excitation light is normally provided by a low pressure mercury lamp. Fixed wavelength fluorescence detector have sensitivity of about 1 x 10-9 g/ml and linear dynamic range of about 500 with a response index of 0.96 < r <1.0418. Multi wavelength fluorescence detector It contains two monochromators, one to select the excitation wavelength and second to select the fluorescence wavelength. Laser induced fluorescence detector (LIFD) It is optical emission from molecules that have been excited to higher energy levels by absorption of electromagnetic radiations. LIFD is most sensitive optical detection technique. LIFD is usually used with capillary electrophoresis technique19. LIFD is applied as separating tool for analysis of polymerase chain reaction products, determination of solutes like proteins, nucleic acids, polycyclic aromatic hydrocarbons, toxic elements like cyanide20. TRANSPORT DETECTORS A transport detector consists of a carrier such as metal chain, wire or disc that passes continually through column eluent extracting sample of mobile phase containing solute as a thin film adhering to its surface. Mobile phase is eliminated by evaporation leaving solute

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as a coating on carrier. Carrier is then scanned by an appropriate sensing technique to monitor the residual solute. Moving wire, chain and disc detector are type of transport detectors available for HPLC system (schematic diagram in Fig. 3). Moving wire detector In 1960 decade Karmen21; Scott and Lawrence developed a modified form of original moving wire detector. Carrier wire from a spool passes through an oven and any residual lubricants remaining on wire after drawing are burnt off. Wire was passed through an evaporator at about 105 ˚C. In evaporation chamber a nitrogen stream is allowed to flow counter-current to wire movement to improve rate of solvent evaporation. The wire carrying solvent-free solute enters (via a restriction) a pyrolysis tube that is maintained at about 500 ˚C. Chain detector Haahti and Nikkari22 described a device that employed chain loops in place of wires as carrier (Fig. 3 B). Carrier, a gold chain driven by a synchronous motor, passes through a coating block where it is wetted with column eluent. Chain enters an evaporator tunnel, is heated, and solvent volatilized leaving solute deposited on chain. Chain exits tunnel into actual flame of a flame ionization detector. ELECTROCHEMICAL DETECTOR Electrochemical detector responds to those substances that are oxidizable or reducible. A reaction takes place at the surface of electrode, due to which generation of electron leads to production of electrical signals23. Suitability of electrochemical detector depends upon voltammetric characteristics of solute molecules in aqueous or aqueous-organic mobile phase. Electrochemical detector requires three electrodes, working electrode (oxidation or reduction takes place), auxiliary electrode and reference electrode (which compensate any changes in background conductivity of mobile phase). This detector can be grouped into two types, the dynamic detector which involves electron transfer and the equilibrium detector which do not promote oxidation or reduction of analyte24. Dynamic detector Dynamic or amperometric detection relies on oxidation or reduction of analyte at a potential corresponding to energy required to free or add electron from molecule. Dynamic type of detection system is involved in multi electrode array detector which allows detection of several analyte at a time by operating each electrode in array at different potential25. Neuro-active substances are identified and separated using this detector. Equilibrium detector This detector measures conductance of flowing solvent

stream. Changes in conductance induced by solute are recorded by the detector. ELECTRICAL CONDUCTIVITY DETECTOR Electrical conductivity detector provides universal, reproducible, high-sensitivity detection of all charged species such as anions, cations, metals, organic acids, and surfactants. These detectors measure conductivity of the total mobile phase hence categorized in bulk density detectors. Sensors of electrical conductivity detector consist of a flow-through cell which has few μl of volume containing two electrodes. Electrodes are usually made up of platinum, stainless steel or some other noble metal. It is used for determination of alkali and alkaline earth cations26. LIQUID LIGHT SCATTERING DETECTOR These detectors are based on measurement of scattered light. When light is scattered by a polymer or large molecular weight substance present in the column eluent, it is examined by passing through an appropriate sensor cell. High intensity beam of light is used for illuminating the scattered light which is achieved by the use of a laser. There are two types of detectors based on laser principle such as low angle laser light scattering (LALLS) detector and multiple angle laser light scattering (MALLS) detector. Low angle laser light scattering detector It is also known as low angle light scattering (LALLS), Fraunhofer diffraction or Mie Scattering detector. It applies to those particles which are larger than wavelength (1µ) of light. Angle of scattering is dependent on size of the particles and thus for large particles, light scatters from edge of particle. Thus intensity of light scattered at different angles can help to determine relative amount of different size particles. In LALLS detector scattered light is measured at very small angle to incident light (virtually 0°). This detector provides sensitive, simple and accurate molecular weight measurement for large molecules. Schematic diagram of LALLS detector is shown in Fig. 4 (A)27. Multiple angle laser light scattering (malls) detector In MALLS detector scattering measurements are made at a number of different angles, none of which are close to incident light. Variation of scattered intensity depends upon size, shape, material, orientation, and internal structure of the particle. Schematic diagram of detector is shown in Fig. 4 (B)28. AEROSOL BASED DETECTORS These are generally classified into evaporative light scattering detector (ELSD), charged aerosol detector (CAD) and nano quantity aerosol detector (NQAD). ELSD is based on light scattering principle while CAD detects charged aerosols and NQAD count particles

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through optical detection. The working of general aerosol detector can be explained by Fig. 5 (A)29. Evaporative light scattering detector (ELSD) This detector is based on three steps such as nebulisation, evaporation and detection. Eluent from HPLC column is transformed into a fine mist of droplets, using nebulizer. Small droplets are selected in order to minimize background noise. These droplets are allowed to evaporate using a hot evaporation (drift) tube at a different temperature. Solutes molecules left as fine particulate matter are passed through an optical head designed to measure light scattering30. It provides universal measurement under isocratic and gradient conditions. In advance systems such as low temperature ELSD, evaporation is done at very low temperature. This unique feature minimizes the thermal decomposition of analyte. This technology is highly sensitive, efficient and reproducible and enables detection of semi-volatile and thermo-sensitive compounds due to detection through low temperature evaporation and gas supported focusing within the optical head. Compounds such as caffeine, Carbohydrates, lipids or triglycerides, surfactants and polymer blends or copolymers can be analyzed. Charged aerosol detector (CAD) Charged aerosol detection is a unique HPLC detection technology that delivers advanced and better capabilities of analysis than other detection technologies such as refractive index, UV, ELS (Evaporative Light Scattering). It can deliver excellent sensitivity, wide dynamic range, superior reproducibility, consistent response and broad applicability31. In CAD technology, eluent is nebulised with nitrogen gas and dried to produce a stream of analyte particles which are collided with a stream of positive ions produced by corona discharge. This impact produces charged analyte particles which are detected by an electrometer. Detection is based on the particle size and mobility of analyte. A secondary stream of nitrogen becomes positively charged as it passes a high-voltage corona wire32. Schematic diagram of detector is shown in Fig. 5 (B).It is applicable for virtually any non-volatile or semi-volatile compounds including pharmaceuticals, lipids, proteins, steroids, surfactants, carbohydrates, polymers, oligosaccharides and in chemical as well as food industries. Drugs like ibuprofen, dextrin, amitriptyline, estradiol, propranol and salicylic acid are analysed by CAD33. Nano quantity aerosol detector (NQAD) A new aerosol-based HPLC detector using condensation nucleation has been developed to provide high sensitivity and a wider linear range than existing aerosol-based HPLC detectors. The NQAD utilizes a water

condensation particle counter (WCPC) that selectively grows particles by condensation of water vapour. The droplets evaporate leaving particles in the form of non-volatile residue. As level of non-volatile residue increases the size of particles increases enough to be detected optically. NQAD converts particle count rate into a chromatogram output signal34. This detector offers a wide dynamic range with superior linearity when compared to other aerosol-based detectors. The detector is ideal for searching drug impurities, degradation products and excipients. NQAD is applicable in analysis of nonvolatile and semi-volatile compounds such as amino acids, carbohydrates, steroids, caffeine, cations, cholesterol, amine, artemisinin and dihydroartemisinin, sulfonic acid and sulfanilamide, saccharin, theophylline and sucrose35. CHIRAL DETECTOR Chiral detector is used for detection of optically active compounds such as amino acids, sugars, terpenes, and other compounds containing an asymmetric carbon. Chiral compounds have strong chirality in the near UV-UV region than in the visible to near IR region. There are two chiral detection techniques, polarimetry or optical rotary dispersion (ORD) and circular dichroism (CD). ORD detectors are based on differences in refractive index and CD detectors differentiate enantiomers by measuring differences between the absorption of right and left-handed circularly polarized light. Polarimetric detectors Polarimetric detector is a useful instrument for detecting and measuring chiral molecules in HPLC. Solutions of such molecules have property of rotating plane-polarized light in preferred direction and to a specific degree. This specific property for each chiral molecule is measured by detector. Amount of optical rotation, α, depends on the number of optically active species through which light passes, and thus depends on both sample path length and analyte concentration. Specific rotation, [α], provides a normalized quantity to correct for this dependence, and is defined as:

(ii) Where α is measured optical rotation in degrees, l is sample path length in decimeters (dm), and d is density if the sample is pure liquid, or concentration (g/100ml) if sample is a solution. Polarimetric detectors are useful in isolating and identifying compounds crystallized from various solvents or separated by HPLC. Compounds such as amino acids, antibiotics, analgesics, diuretics, vitamins etc and flavours like camphor, orange oil and lemon oil are examined by this detector36. Circular dichroism detector Circular dichroism based detectors differentiate

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enantiomers by measuring differences between the absorption of right and left-handed circularly polarized light due to the existence of a chiral chromophore. These detectors provide sensitive and selective detection of chiral compounds that have a UV absorption in the 220-420 nm range. CD detector also provides a UV signal in addition to CD signal which allows optical purity determinations without chiral separation37. Detection is unaffected by gradient elution or other changes in non-chiral components during elution. Polarimetric or optical rotation based detectors remain as an alternative for compounds that do not contain chromophore by allowing universal detection with reduced sensitivities. Compounds such as flavanone, sugar, triadimefon, trans-stilbene oxide, naproanilide , pindolol, indapamide, ibuprofen and flubiprofen can be examined using this technique. PULSED AMPEROMETRIC DETECTOR (PAD) This technique was developed to remove the poisons from electrode surface during detection. A three step waveform system called as pulsed amperometric detection is applied to electrode approximately once every second. Waveform system consists of measurement and recording of current at electrode followed by surface oxidation to remove foreign particles and then oxidation stripping. Amperometric detection utilizes a flowing current to initiate a chemical conversion of electro-active analyte. PAD is an important method for separation and detection of polar aliphatic compounds which have poor detection properties and require derivatization for optical measurements. PAD combines Amperometric detection at a noble metal electrode with positive and negative potential excursions for on-line cleaning and reactivation of the electrode. The result is direct detection of compounds containing amine, alcohol, or sulphur moieties and carbohydrates38. CONCLUSION Thus new technologies like LLSD, CAD, NQAD, PAD, and chiral detector have been proved to be powerful new detection methods for HPLC that perhaps comes closest to achieving true "universality" in a single platform detection technology. These systems deliver superior performance than conventional detectors which include their broad applicability which enables easy detection of large number and variety of molecules, consistent response and high sensitivity (nanogram level). REFERENCES 1. Willard H, Merritt L, Dean A. Instrumental methods of analysis.

Delhi: CBS publishers and distributors; 1986. p. 580-581. 2. WatsonG. Pharmaceutical analysis: A text book for pharmacy

students and pharmaceutical chemists.Churchill: Livingstone; 1999. p 240-241.

3. Skoog A, Donald M. Fundamentals of analytical chemistry. Thomson brooks/cole; 2004. p 974-975.

4. Swarbrick J. Encyclopaedia pharmaceutical technology. New York: Informa healthcare. 1993; 1: 533.

5. Raymond S. Chromatographic detectors design: Function and operation. Chromatographic Science Series. 1995; 73: 201-204.

6. Christiansen C. Handbook of Chemical Microscopy. New York: John Wiley and Sons. 1958.

7. Thomas. Liquid Chromatography Detectors. 4th ed. New York: Marcel Dekker Inc; 1983. p. s165-172,179.

8. Kenmore CK, Ersline SR. Refractive Index Detection by Interferometric Backscatter in Packed-Capillary High Performance Liquid Chromatography. J Chr 1997; 219-225.

9. Steinle E, Faubel W, Ache HJ. Near Field Thermal Lens Detector for Gradient Elution Liquid Chromatography. Anal. Chimica. Acta. 1997; 207-213. doi:10.1016/S0003-2670(97)87779-3.

10. Hui Yiu H. Handbook of Food Science: Technology and Engineering. vol. 1. Washington, DC: Taylor and Francis; 5-6.

11. Cepria G, Castillo JR. Surface Plasmon Resonance-based Detection An alternative to Refractive Index Detection in High-Performance Liquid Chromatography. J Chromatogr A. 1997; 759: 27-35. doi:10.1016/S0021-9673(96)00752-2.

12. Katz ED. HPLC: Principles and Methods in Biotechnology. Marcel Dekker; 1998. 70.

13. Gorden JP, Leite RCC, Moore RS, Posto SPS, Whinnery JR. Am. Phys. Soc. 1964; 501.

14. Foukaridis GN, Muntingh GL, Osuch E. Application of Diode Array Detection for the Identification of Poisoning by Traditional Medicines. J Ethnopharmacology 1994; 43: 135-146. doi:10.1016/0378-8741(94)90029-9.

15. Engelhardt H, Konig T. Application of Diode Array Detectors for Solute Identification in Toxicological Analysis. vol. 28. J. Chromatographia. 1989; 341-353.

16. Raymond S. Chromatographic Detectors Design: Function and Operation. vol. 73. Chromatographic Science Series. 1995; 201-204.

17. Millner P. High Resolution Chromatography: A practical approach. vol. 64. Oxford University Press; 1999. p. 204.

18. Jack C, Marcel D. Encyclopedia of Chromatography; 2001. p. 352.

19. Landers JP. The Handbook of Capillary and Microchip Electrophoresis. CRC/ Taylor and Francis; 2007. p. 144.

20. Marti V, Aguilar M. Indirect Fluorescence Detection of Free Cyanide and Related Compounds by CE. J Chromatography 1995; 2: 367-374. doi:10.1016/0021-9673(95)00446-T.

21. Raymond S. Chromatographic Detectors Design: Function and Operation. vol. 73. Chromatographic Science Series; 1995. p. 289.

22. Maggs RJ. A Commercial Detector for Monitoring the Eluent from Liquid Chromatography Detectors. vol. 1. Viewag Verlag, Springerlink; 1968. p. 43-48.

23. Ismail H, Kassandra K, Dernick G. Electrochemical Imaging of Fusion Pore Openings by Electrochemical Detector Arrays.vol. 102. Center for Scientific Studies; 2005. 13879-13884.

24. Richard FV. Principles and Practice of Bioanalysis. vol. 1. Taylor and Francis; 2000. p. 108, 120-122.

25. Lijiang W, Qingjun L, Zhaoying H, Yuanfan Z, Chunsheng W, Yang M. A Novel Electrochemical Biosensor based on Dynamic Polymerase-Extending Hybridization for E. coli O157:H7 DNA Detection. J Talanta 2008; 647-652.doi:10.1016/j.talanta. 2008.12.001.

Thakkar Arti et al. IRJP 2 (5) 2011 1-7

IRJP 2 (5) May 2011 Page 1-7

26. Bruce KG, Karin D, Bruno A. Electrical Conductivity Particle Detector for Use in Biological and Chemical Micro-analysis Systems, Departments of Bioengineering, Electrical Engineering and Chemistry, University of Utah, Salt Lake City.

27. Howard GB, Jimmy WM. Modern Methods of Polymer Characterization. vol. 113. Wiley Interscience; 1991. p. 331.

28. Brown W. Light Scattering: Principles and Development. vol. 53. Oxford University Press; 1996. p. 507.

29. Flanagan RJ, Taylor AA, Watson ID, Whelpton R. Fundamentals of Analytical Toxicology. John Wiley and Sons; 2007. p. 193.

30. Monsuur F, Denoulet B, Dobark A, Vandezande P. Evaporative Light Scattering Detector: Toward a General Molecular Weight Cutoff Characterization of Nanofiltration Membranes. J NCBI 2009.

31. Yan B, Zhang B, Xiaofeng L. Advances in HPLC Detectors towards Universal Detection. Anal Bioanal Chem 2008; 390: 299-301.

32. Gamche PH, Mccarthy RS, Freeto SM, Asa DJ, Woodcock MJ. HPLC Analysis of Nonvolatile Analytes Using Charged Aerosol Detection. LCGC North America, 2005.

33. Asa D. Development of a New Universal HPLC Detector: The Corona CAD. Marketing Manager, ESA Inc.

34. Chiu-sen W, Friedlander SK, Madler L. Nanoparticle Aerosol Science and Technology: An Overview. J China Particuology 2005; 3:243-254. doi:10.1016/S1672-2515(07)60196-1.

35. Allen L, Koropchak JA. Condensation Nucleation Light Scattering: A New Approach to Development of High Sensitivity, Universal Detectors for Separations. Analytical Chemistry 1993; 65:841-844.

36. Bernard A, Bryan C, Castle, Myers DP. Advances in HPLC Technology for the Determination of Drug Impurities. Tr Ana Chem 2006; 25:796-805.

37. Tran CD, Victor IG. Chiral Detection in High-Performance Liquid Chromatography by Vibrational Circular Dichroism. Anal Chem 1994; 66:2630–2635. doi: 10.1021/ac00089a007.

38. El Rassi Z. Carbohydrate Analysis: High Performance Liquid Chromatography and Capillary Electrophoresis. Elsevier, Amsterdam; 1994. p. 391-429.

Table 1. TYPE OF HPLC DETECTORS

# Types of Detectors Sub type of Detectors

1 Refractive index Detector a) Christiansen effect Detector

b) Interferometer Detector

c)Thermal lens Detector

2 Ultraviolet Detector a)Variable wavelength UV absorption Detector

b)Fixed wavelength UV Detector

c)Multi wavelength

dispersive UV Detector

3 Fluorescent Detector a)Single wavelength excitation fluorescence

Detector

b)Multi wavelength fluorescence Detector

c)Laser induced fluorescence

Detector 4 Transport Detector a) Moving wire Detector b) Chain Detector c) Disc Detector

5 Electrochemical detector a) Dynamic Detector or Multi electrode array

Detector

b) Equilibrium Detector

6 Electric conductivity Detector

7 Liquid light scattering Detector

a) Low angle laser light scattering Detector

b) Multiple angle laser light scattering Detector

8 Advanced Detectors

9 Aerosol based Detectors a) Evaporative light scattering Detector

b) Charged aerosol Detector c) Nano quantity aerosol

Detector 10 Chiral Detector a) Polari metric Detector b) Circular dichroism

Detector

11 Pulsed Amperometric Detector

Figure 1: Typical UV detector Figure 2: Simple fluorescence detector

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Figure 3: Transport detectors (A) Moving wire detector (B) Chain detector

Figure 4: Liquid light scattering detector (A) Low angle light scattering detector (B) multiple angle laser light scattering detector.

Figure 5: (A) Aerosol based detector, (B) Corona charged aerosol detector

(A) (B)

(A) (B)