HPLC Electro Chemical Detector ( ECD )

There are several different types of ECs. The detection is based on amperometry, polarography, coulometry, and conductrometry. They offer high sensitivity, simplicity, convenience, and wide-spread applicability. It is especially suitable for the use with semi-micro or capillary type system.

Introduction Of Electro Chemical Detector ( ECD )

Electrochemical detection (ECD) for HPLC or UHPLC is an extremely selective and sensitive detection technique that is applied in a number of analyses such as the neurotransmitters dopamine, serotonin and noradrenalin. In combination with the proper electronics, ECD has an enormous linear dynamic range of more then 6 orders of magnitude. This means that concentrations can be measured as low as 50 pmole/L and as high as 100 µmol/L or more.

principle of EC detection

Fig. 1. HPLC with amperometric electrochemical detection.

Detection principle Of Electro Chemical Detector ( ECD )

In amperometric electrochemical detection the electrical current is measured resulting from oxidation or reduction reactions (Fig. 1). A sample is introduced in HPLC and separated on the chromatographic column. The column is connected to an ECD cell, an electrochemical sensor where a reaction takes place at an electrode. Electrochemically active substances that elute from the column undergo an electrochemical reaction, electrons are transferred resulting in an electrical current. The electrodes are connected to an electronic circuitry with a powerful -low noise- amplifier that converts a pico- or nanoampere current in a signal in the range of ± 1 Volt which is commonly used in data acquisition.

Chromatogram

The detector is connected to a computer where the data is collected and stored in data acquisition software. The resulting chromatogram (fig. 2) shows the detector response and is used for identification and quantification, the ultimate goal of analysis. Using calibration standards, the signal height (current, in nA) is related to concentration and the retention time identifies a substance.

chromatogram neurotransmitters

Fig. 2. A chromatogram with calibration standards of several neurotransmitters.

Powerpoint about Electro Chemical Detector ( ECD )

For more information, see our powerpoint presentation on HPLC/ECD.

HPLC Optical Rotation Detector (ORD)

Specific for the optical isomer measurement. The column can separate R- and L- type optical isomers, but the general detectors (e.g., UV) cannot distinguish which is R nor L. OR detector provides this information.

In chiral chromatography, the technology of detecting chiral molecules using optical devices has lagged behind until now. The stability and sensitivity of this type of instrument is an important issue in chiral chromatography. However, with the availability of the single wavelength LED, increased sensitivity and increased economics with simplified instrument design was possible. In addition, a newly designed glass coated steel flow cell has produced a superior, third generation optical rotation detector. Aided with the Faraday compensation technique, this instrument gives high optical rotation power with excellent signal to noise ratio. This instrument is an excellent supplemental detector to standard UV detection. For chiral separations, it permits the identification of elutionorder which is important when quantifying to establish minimum levels of detection. It allows for the identification of enantiomeric pairs when dealing with multiple chiral centers. During the method development process, this detector detects marginal selectivity when UV detection fails. The important features of this instrument will be described. Also, examples of absolute sensitivity, identification of enantiomer pairs and reversed elution order will be included.

  • Identifies the chirality of a molecule with a positive or negative sign of rotation.
  • Detects only optically active compounds.
  • Can detect optically active compounds with no or low UV absorbance.
  • Works with gradients.
  • Simple determination of enantiomeric excess (ee) and optical purity.

for more information about HPLC  Optical Rotation Detector download this PDF.

 

HPLC Chemiluminescent Nitrogen Detector (CLND)

Similar to FL, but instead of using a light source to excite the analyte atoms, the excitation is initiated by chemical reaction. Since it is not relied on the external excitation source, the noise is small, results in high signal to noise ratio, i.e. it provides even higher sensitivity than FL.

The Chemiluminescent Nitrogen Detector (CLND) for use with high-performance liquid chromatography (HPLC) allows for the low-level detection of nitrogen-containing compounds with simple quantitation. The nitrogen selective detector’s equimolar response (i.e., equal response for nitrogen independent of its chemical environment) allows for any nitrogen-containing compound to be quantitated as long as the number of nitrogens are known. The HPLCCLND provides a new detection method for analytes that are not available in large quantities or have unknown chemical or physical characteristics such as oxidation products, metabolites, or impurities. Ethoxyquin is a primary antioxidant that is used to preserve many food products and animal feeds. HPLCCLND is used in the study of the oxidation products of ethoxyquin because limited quantities of these compounds are available and subsequent calibration curves are difficult to maintain. HPLCCLND as a new method of detection has been evaluated for its equimolarity of response, linear range, limit of detection, and limit of quantitation.

For more information about HPLC Chemiluminescent Nitrogen Detector (CLND) download this PDF.

 

HPLC Fluorescence Detector (FLD)

The advantage of fluorescence method is its high sensitivity for selective groups of compounds at ~fg level. By using a specific wavelength, analyte atoms are excited and then emit light signal (fluorescence). The intensity of this emitted light is monitored to quantify the analyte concentration. Most pharmaceuticals, natural products, clinical samples, and petroleum products have fluorescent absorbance. For some compounds which do not have fluorescence absorbance or low absorbance, they can be treated with fluorescence derivatives such as dansylchloride. The system is easy to operate and relatively stable.

Principles Of HPLC  Fluorescence Detector (FLD)

Fluorescence detectors are probably the most sensitive among the existing modern HPLC detectors. It is possible to detect even a presence of a single analyte molecule in the flow cell.  Typically, fluorescence sensitivity is 10 -1000 times higher than that of the UV detector for strong UV absorbing materials. Fluorescence detectors are very specific and selective among the others optical detectors. This is normally used as an advantage in the measurement of specific fluorescent species in samples.

When compounds having specific functional groups are excited by shorter wavelength energy and emit higher wavelength radiation which called fluorescence. Usually, the emission is measured at right angles to the excitation.

Roughly about 15% of all compounds have a natural fluorescence. The presence of conjugated pi-electrons especially in the aromatic components gives the most intense fluorescent activity. Also, aliphatic and alicyclic compounds with carbonyl groups and compounds with highly conjugated double bonds fluoresce, but usually to a lesser degree. Most unsubstituted aromatic hydrocarbons fluoresce with quantum yeld increasing with the number of rings, their degree of condensation and their structural rigidity.

Fluorescence intensity depends on both the excitation and emission wavelength, allowing selectively detect some components while suppressing the emission of others.

The detection of any component significantly depends on the chosen wavelength and if one component could be detected at 280 ex and 340 em., another could be missed. Most of the modern detectors allow fast switch of the excitation and emission wavelength, which offer the possibility to detect all component in the mixture.. For example, in the very important polynuclear aromatic chromatogram the excitation and emission wavelengths were 280 and 340 nm, respectively, for the first 6 components, and then changed to the respective values of 305 and 430 nm; the latter values represent the best compromise to allow sensitive detection of compounds.

Figure below shows the optical schematic of a typical fluorescence detector for liquid chromatography. The detectors available on the market differ in the method in which the wavelengths are controlled. Less expensive instruments utilize filters; medium priced units offer monochromator control of at least emission wavelength, and full capability research-grade instruments provide monochromator control of both excitation and emission wavelengths.

Optical schematic of a typical fluorescence detector for liquid chromatography.

HPLC Conductivity Detector (CDD)

Solutions containing ionic components will conduct electricity. Conductivity detector measures electronic resistance and measured value is directly proportional to the concentration of ions present in the solution. Thus it is generally used for ion chromatography.

 

HPLC Mass Spectrometer Detector

The analytes are detected based on their MW. The obtained information is especially useful for compound structure identification. However, its use is not limited to structure identification and can be used to quantify very low detection limit of elemental and molecular components.

Mass spectrometry (MS) is an analytical technique that ionizes chemical species and sorts the ions based on their mass to charge ratio. In simpler terms, a mass spectrum measures the masses within a sample. Mass spectrometry is used in many different fields and is applied to pure samples as well as complex mixtures.

A mass spectrum is a plot of the ion signal as a function of the mass-to-charge ratio. These spectra are used to determine the elemental or isotopic signature of a sample, the masses of particles and of molecules, and to elucidate the chemical structures of molecules, such as peptides and other chemical compounds.

In a typical MS procedure, a sample, which may be solid, liquid, or gas, is ionized, for example by bombarding it with electrons. This may cause some of the sample's molecules to break into charged fragments. These ions are then separated according to their mass-to-charge ratio, typically by accelerating them and subjecting them to an electric or magnetic field: ions of the same mass-to-charge ratio will undergo the same amount of deflection. The ions are detected by a mechanism capable of detecting charged particles, such as an electron multiplier. Results are displayed as spectra of the relative abundance of detected ions as a function of the mass-to-charge ratio. The atoms or molecules in the sample can be identified by correlating known masses to the identified masses or through a characteristic fragmentation pattern.

 

HPLC Multi-Angle Light Scattering Detector (MALS)

For the SEC analysis, MW of analyte is estimated from the calibration curve drown using a set of known standards. However, by using a MALS, MW can be determined directly without the need of calibration curve. Also MALS can provide an absolute MW of the analyte with very low detection limit.

HPLC Refractive-Index (RI) Detector

RI detector measures change in reflex index. A glass cell is divided into two chambers (cells). The effluent from LC column flow through the "sample cell", while other cell called "reference cell" is filled with only mobile phase. When the effluent going through the sample cell does not contain any analyte, the solvent inside both cells are the same (Figure 1A). When a beam is irradiate on the cells, the observed beam will be straight in this case. However, in a case the effluent contains any components other than mobile phase; bending of the incident beam occurs due to the reflex index difference between the two solvents (Figure 1B). By measuring this change, the presence of components can be observed.

RI detector has lower sensitivity compared to UV detector, and that's the main reason why RI is not as commonly used as UV. However there are some advantages over UV detector.

  • It is suitable for detecting all components. For an example, samples which do not have UV absorption, such as sugar, alcohol, or inorganic ions obviously cannot be measured by a UV detector. In contrast, change in reflective index occurs for all analyte, thus a RI detector can be used to measure all analyte.
  • It is applicable for the use with solvent that has UV absorbance. A UV detector cannot be used with solvent which has UV absorbance. Sometimes the organic solvent used for GPC analysis absorbs UV, and thus UV detector cannot be used.
  • It provides a direct relationship between the intensity and analyte concentration. The amount of UV absorbed depends on each analyte, thus the intensity of UV detector peak does not provide information on the analyte concentration. While intensity observed by a RI detector is comparable to the concentration of analyte. Because of those advantages, RI is often used for the detection of sugars and for SEC analysis.

HPLC UV, VIS, and PDA Detectors

The UV, VIS, and PDA detectors are categorized as absorbance detectors. They provide good sensitivity for light-absorbing compounds at ~pg level. They are easy to operate and provide good stability. UV detector is a very commonly used detector for HPLC analysis. During the analysis, sample goes through a clear color-less glass cell, called flow cell. When UV light is irradiated on the flow cell, sample absorbs a part of UV light. Thus, the intensity of UV light observed for the mobile phase (without sample) and the eluent containing sample will differ. By measuring this difference, the amount of sample can be determined. Since the UV absorbance also differs depend on what wavelength is used, it is important to choose an appropriate wavelength based on the type of analyte. A standard UV detector allows user to choose wavelength between 195 to 370 nm. Most commonly used is 254 nm. Compared to a UV detector, a VIS detector uses longer wavelength (400 to 700 nm). There are detectors that provide wider wavelength selection, covering both UV and VIS ranges (195 to 700 nm) called . PDA detects an entire spectrum simultaneously. UV and VIS detectors visualize the obtained result in two dimensions (light intensity and time), but PDA adds the third dimension (wavelength). This is convenient to determine the most suitable wavelength without repeating analyses.

High Performance Liquid Chromatography Detectors ( HPLC Detectors)

1. HPLC UV, VIS, and PDA Detectors 2. HPLC Refractive-Index Detector 3. HPLC Evaporative Light Scattering Detector 4. HPLC Multi-Angle Light Scattering Detector 5. HPLC Mass Spectrometer 6. HPLC Conductivity Detector 7. HPLC Fluorescence Detector 8. HPLC Chemiluminescence Detector 9. HPLC Optical Rotation Detector 10.HPLC Electro Chemical Detector

The actual separation of each component in the sample is carried inside a column; however this separation needs to be "collected" for us to be able to see it. The detectors are used for this purpose. The separated coponents are monitored and expressed electronically. There is no universal detector that can monitor all compounds and there are many detectors used for LC analysis. Some are listed below.

Type Common Abbreviation
Ultra Violet UV
Visible VIS
Photo Diode Array PDA
Refractive Index RI
Evaporative Light Scattering ELS
Multi Angle Laser Light Scattering MALS
Mass Spectrometer MS
Conductivity CD
Fluorescence FL
Chemiluminescence CL
Optical Rotation OR
Electro Chemical EC
1. HPLC UV, VIS, and PDA Detectors

The UV, VIS, and PDA detectors are categorized as absorbance detectors. They provide good sensitivity for light-absorbing compounds at ~pg level. They are easy to operate and provide good stability. UV detector is a very commonly used detector for HPLC analysis. During the analysis, sample goes through a clear color-less glass cell, called flow cell. When UV light is irradiated on the flow cell, sample absorbs a part of UV light. Thus, the intensity of UV light observed for the mobile phase (without sample) and the eluent containing sample will differ. By measuring this difference, the amount of sample can be determined. Since the UV absorbance also differs depend on what wavelength is used, it is important to choose an appropriate wavelength based on the type of analyte. A standard UV detector allows user to choose wavelength between 195 to 370 nm. Most commonly used is 254 nm. Compared to a UV detector, a VIS detector uses longer wavelength (400 to 700 nm). There are detectors that provide wider wavelength selection, covering both UV and VIS ranges (195 to 700 nm) called . PDA detects an entire spectrum simultaneously. UV and VIS detectors visualize the obtained result in two dimensions (light intensity and time), but PDA adds the third dimension (wavelength). This is convenient to determine the most suitable wavelength without repeating analyses.

2. HPLC Refractive-Index Detector

RI detector measures change in reflex index. A glass cell is divided into two chambers (cells). The effluent from LC column flow through the "sample cell", while other cell called "reference cell" is filled with only mobile phase. When the effluent going through the sample cell does not contain any analyte, the solvent inside both cells are the same (Figure 1A). When a beam is irradiate on the cells, the observed beam will be straight in this case. However, in a case the effluent contains any components other than mobile phase; bending of the incident beam occurs due to the reflex index difference between the two solvents (Figure 1B). By measuring this change, the presence of components can be observed.

RI detector has lower sensitivity compared to UV detector, and that's the main reason why RIis not as commonly used as UV. However there are some advantages over UV detector.

  • It is suitable for detecting all components. For an example, samples which do not have UV absorption, such as sugar, alcohol, or inorganic ions obviously cannot be measured by a UV detector. In contrast, change in reflective index occurs for all analyte, thus a RI detector can be used to measure all analyte.
  • It is applicable for the use with solvent that has UV absorbance. A UV detector cannot be used with solvent which has UV absorbance. Sometimes the organic solvent used for GPC analysis absorbs UV, and thus UV detector cannot be used.
  • It provides a direct relationship between the intensity and analyte concentration. The amount of UV absorbed depends on each analyte, thus the intensity of UV detector peak does not provide information on the analyte concentration. While intensity observed by a RI detector is comparable to the concentration of analyte. Because of those advantages, RI is often used for the detection of sugars and for SEC analysis.

3. HPLC Evaporative Light Scattering Detector

An evaporative light scattering detector (ELSD) is a detector used in conjunction with high-performance liquid chromatography (HPLC). It is commonly used for analysis of compounds that do not absorb UV radiation and therefore cannot be detected by UV detectors, such as sugars, antivirals, antibiotics, lipids, phospholipids, terpenoids, and alcohols.ELSDs fall under the category of general-purpose detectors, similar to refractive index detectors (RI).

4. HPLC Multi-Angle Light Scattering Detector

For the SEC analysis, MW of analyte is estimated from the calibration curve drown using a set of known standards. However, by using a MALS, MW can be determined directly without the need of calibration curve. Also MALS can provide an absolute MW of the analyte with very low detection limit.

5. HPLC Mass Spectrometer

Mass spectrometry (MS) is an analytical technique that ionizes chemical species and sorts the ions based on their mass to charge ratio. In simpler terms, a mass spectrum measures the masses within a sample. Mass spectrometry is used in many different fields and is applied to pure samples as well as complex mixtures.

6. HPLC Conductivity Detector

Solutions containing ionic components will conduct electricity. Conductivity detector measures electronic resistance and measured value is directly proportional to the concentration of ions present in the solution. Thus it is generally used for ion chromatography.

7. HPLC Fluorescence Detector

The advantage of fluorescence method is its high sensitivity for selective groups of compounds at ~fg level. By using a specific wavelength, analyte atoms are excited and then emit light signal (fluorescence). The intensity of this emitted light is monitored to quantify the analyte concentration. Most pharmaceuticals, natural products, clinical samples, and petroleum products have fluorescent absorbance. For some compounds which do not have fluorescence absorbance or low absorbance, they can be treated with fluorescence derivatives such as dansylchloride. The system is easy to operate and relatively stable.

8. Chemiluminescence Detector

The HPLC Chemiluminescent Nitrogen Detector (CLND) for use with high-performance liquid chromatography (HPLC) allows for the low-level detection of nitrogen-containing compounds with simple quantitation.

9. HPLC Optical Rotation Detector

Specific for the optical isomer measurement. The column can separate R- and L- type optical isomers, but the general detectors (e.g., UV) cannot distinguish which is R nor L. OR detector provides this information.

10. HPLC Electro Chemical Detector

Electrochemical detection (ECD) for HPLC or UHPLC is an extremely selective and sensitive detection technique that is applied in a number of analyses such as the neurotransmitters dopamine, serotonin and noradrenalin. In combination with the proper electronics, ECD has an enormous linear dynamic range of more then 6 orders of magnitude. This means that concentrations can be measured as low as 50 pmole/L and as high as 100 µmol/L or more.

References Analytical Chemistry 7th (Seventh) Edition by Skoog 1999 Ekikurono Kotsu Detector (in Japanese) by Hiroshi Nakamura 2006  

Shimadzu RF-20A/RF-20Axs Fluorescence LC Detector

Shimadzu RF-20A/RF-20Axs Fluorescence LC Detector

The RF-20A/20AXS fluorescence detectors offer world-leading sensitivity and ease-of-maintenance. The RF-20AXS is a high-sensitivity model that incorporates a temperature-controlled cell with a cooling function as standard.

  • RF-20A / Standard model:

The RF-20A, which offers best-in-class sensitivity, features a water Raman S/N ratio of at least 1200, as well as excellent ease-of-use with such features as maintenance from the front panel and adoption of a long-life lamp.

  • RF-20AXS / Achieves World-Leading Sensitivity :

Offering world-class levels of sensitivity and easy maintenance, the RF-20AXS features a water Raman S/N ratio of at least 2000 and a temperature-controlled cell with a cooling function. This maintains a constant detector cell temperature, even if the room temperature fluctuates significantly, to ensure superb reproducibility with no drop in sensitivity. In addition, the RF-20AXS incorporates an automatic wavelength accuracy check function using an internal low-pressure mercury lamp to provide simple confirmation of the wavelength accuracy for validation.

Achieves World-Leading Sensitivity:

A powerful tool for the detection of ultra-trace components, the RF-20Axs achieved a 21.5 S/N ratio for an injection of 10.48 fg anthracene. This is equivalent to an approx. 1.5 fg detection limit (S/N ratio = 3) and indicates superb sensitivity.

Cell Temperature Control Further Enhances Reproducibility (RF-20AXS) :

The fluorescence intensity drops as the temperature rises. A fluctuation of about 1°C near room temperature may result in approximately 5% intensity fluctuations for some compounds. To prevent this, the RF-20AXS features a temperature-controlled cell with a cooling function. It maintains a constant detector cell temperature, even if the room temperature fluctuates significantly, to ensure superb reproducibility with no drop in sensitivity.

Achieves World-Leading Sensitivity :

A powerful tool for the detection of ultra-trace components, the  RF-20Axs achieved a 21.5 S/N ratio for an injection of 10.48 fg anthracene. This is equivalent to an approx. 1.5 fg detection limit (S/N ratio = 3) and indicates superb sensitivity.

Cell Temperature Control Further Enhances Reproducibility (RF-20AXS) :

The fluorescence intensity drops as the temperature rises. A fluctuation of about 1°C near room temperature may result in approximately 5% intensity fluctuations for some compounds. To prevent this, the RF-20AXS features a temperature-controlled cell with a cooling function. It maintains a constant detector cell temperature, even if the room temperature fluctuates significantly, to ensure superb reproducibility with no drop in sensitivity.

Easy Maintenance :

The Xenon lamp and flow cell can be replaced at the front panel. No positional adjustment is required when replacing the Xenon lamp, and no tools are required to replace the flow cell. The standard flow cell or semimicro flow cell can be rapidly switched. In addition, the Xenon lamp life has been extended to 2000 hours, four times longer than previous Shimadzu lamps.

Support for Ultra Fast Analysis :

  • Switch from Conventional LC to Ultra Fast LC

Fast response is required to follow the sharp peaks obtained in ultra fast LC analysis. The 10 ms response of the RF-20A/20AXS permits ultra fast LC analysis with no loss of separation. In this analysis example, the analysis time was reduced by a factor of more than three, while maintaining the separation.

  • Multi-Component, High-Sensitivity UFLC Analysis

The highly sensitive simultaneous analysis of multiple components requires detection at the optimal wavelengths. The RF-20A/20AXS permit ultra fast, high-sensitivity multi-component analysis using wavelength switching by time program.

Support for Improved Quantitative Analysis Accuracy :

  • Utility of Four-Wavelength Measurement Function

Using detection at a single wavelength when performing multicomponent simultaneous analysis of components with different optimal detection wavelengths necessitates sacrificing sensitivity for certain components. The RF-20A/20AXS detectors eliminate this issue by incorporating a four-wavelength measurement function that permits detection of each component at the optimal wavelength. Detection using wavelength switching in the left-hand diagram exhibits incomplete separation in area (1) and one peak of reduced size in area (2). In such a case, setting up to four optimal wavelengths enhances the quantitative analysis accuracy by reducing the effects of adjacent peaks and improving sensitivity.

Shimadzu CDD-10AVP Conductivity LC Detector

Shimadzu CDD-10AVP Conductivity LC Detector

Handles a Wide Variety of Analysis Options

The CDD-10AVP conductivity detector achieves an even higher level of sensitivity and makes it possible to perform a wide variety of analysis scenarios with a single unit. An option card enables the simultaneous 2-channel measurement of anions and cations, and a suppressor option allows expansion to a suppressor system for ultra-high sensitivity work. Organic acids can be analyzed using Shimadzu's unique post-column pH-buffered electroconductivity method.

Low noise, low drift and wide dynamic range assure proven performance of the Shimadzu VP series HPLC. Data acquired by the CDD-10AVP is transferred to the SCL system controller via an optical fiber interface and are digitally processed by workstation. By adding the optional cell (dual kit NS), a low-cost and compact non-suppressor type dual ion chromatograph, which detects anions and cations simultaneously, can be made.

Perform Analysis with Highest Sensitivity:

The sensitivity of detectors that monitor weak electrical signals from analytes is affected by the inherent electrical noise of the detector itself. With the CDD-10AVP, electronic parts with low electrical noise are used, and the layout of the electronic components has been optimized in order to reduce noise levels, thereby attaining an extremely high level of sensitivity. Combining the CDD-10AVP with a suppressor unit makes it possible to perform ultra-high sensitivity ion analysis Reproducibility in Anion Analysis on the order of 0.25 μg/ L (detection limit: S/N=3) for Cl-.

Applicable to Both Suppressor and Non-Suppressor Systems (available in limited regions) :

When used with a CTO-20AC, expansion to a full suppressor system can be realized by adding the suppressor option. Suppressor functions can be disabled when necessary, making it possible to switch between anion analysis using a suppressor system and cation analysis using a non-suppressed system. In addition to a single flow-line system, expansion to a dual flow-line system is also possible, allowing the creation of a variety of system configurations. For example, simultaneous analysis of anions and cations using a combination of suppressed and non-suppressed detection is possible.

High-Sensitivity Analysis of Organic Acids :

Shimadzu's post-column pH-buffered electroconductivity method (Patent No. 2017498) enables selective, high-sensitivity analysis of organic acids. Even samples that traditionally require time-consuming pretreatment to handle unwanted constituents can be analyzed after simple pretreatment procedures such as dilution and filtration. The level of reliability attained in quantitative analysis is much higher than that attained conventionally with a low-wavelength UV method or a simple conductivity method. Superior linearity enables batch analysis in cases where constituent concentrations differ greatly and, consequently, helps reduce analysis time.

Shimadzu UV-VIS SPD-20A/20AV LC Detectors

Shimadzu UV-VIS SPD-20A/20AV LC Detectors

Offering dual-wavelength mode

The SPD-20A/20AV is a UV-VIS detector that takes sensitivity to the limit (Noise level 0.5 x 10(-5) AU), and offers wide linearity (2.5AU). SPD-20A: Wavelength range: 190 to 700nm The SPD-20AV has a mode that allows the deuterium lamp and tungsten lamp to be lit simultaneously, enabling high-sensitivity wavelength-programming detection fro ultraviolet light and the entire visible-light range. Wavelength range 190 to 900nm.

Shimadzu Photodiode Array SPD-M20A LC Detector

Shimadzu Photodiode Array SPD-M20A LC Detector

General-purpose model

The SPD-M20A is a general-purpose model incorporating a deuterium lamp. The light-source compensation function achieves a noise level of 0.6×10-5AU. Cell temperature control ensures baseline stability.

Key Benefits:

  • Noise level of 0.6×10-5 AU
  • Superior Linearity - 2.0AU
  • Ethernet interface & web control functions
  • Can be incorporated into non-Shimadzu HPLC systems
  • Light source: Deuterium (D2) lamp, tungsten (W) lamp
  • Wavelength range: 190 to 800 nm
  • Wavelength accuracy: 1 nm max.
  • Wavelength precision: 0.1 nm max
  • Cell temperature control range: 5°C above room temperatre to 50°C
  • Operating temperature 4°C to 35°C
  • Power requirements: 100 VAC, 150 VA, 50/60 Hz

The SPD-M20A PDA is the third member of the UV-Vis absorbance detectors. The M20A, like the others, offers the world’s best noise and linearity specifi cation in its class. It also includes a temperature-controlled fl ow cell and the ability to have both lamps lit simultaneously. The Prominence PDA offers you more power to get more done by offering two slit widths: 1.2 nm for high resolution work and 8 nm for quantitative runs. Shimadzu software is used to perform spectral library searches for compound identification and peak purity determinations. Four analog output channels provide multi-wavelength detector functionality and are available for triggering fraction collection or other devices, or collecting chromatographic data into any other software package. Self-diagnostic features such as wavelength accuracy and wavelength calibration ensure compliance with regulatory requirements. The Prominence PDA offers a user-friendly design that includes front-panel access to detector lamps and fl ow cell,easy connection through a standard ethernet terminal, and front-panel illumination of the detector’s status. The Shimadzu SPD-M20A truly establishes a new standard for today’s PDA detectors.

Shimadzu Photodiode Array SPD-M30A LC Detector

Shimadzu Photodiode Array SPD-M30A LC Detector

Supports diverse applications from HPLC to UHPLC

The SPD-M30A detector achieves a 0.4×10-5 AU noise level. The SR-Cell (Sensitivity and Resolution Cell) significantly cuts peak dispersion. This model supports analysis from conventional LC to ultra-fast and UHPLC analysis. The optional high-sensitivity cell has an 85 mm optical path length and is able to detect trace components that were conventionally difficult to detect. The TC-Optics function further improves baseline stability.

Shimadzu Refractive Index LC Detector 20A (RID-20A)

Shimadzu Refractive Index LC Detector 20A (RID-20A)
Inheriting the stability and extensibility that are the strengths of the Prominence series, the new Shimadzu Refractive Index LC Detector 20A (RID-20A) model of differential refractive index detector is designed with a new reference-cell auto-purge feature and validation support function.

Specifications :

RID-20A specification  
  • Pressure Relief Valve :

The RID-20A incorporates various safety features. Its maximum pressure is five times that of former Shimadzu products and, as a standard feature, it incorporates a sensor that detects leakage from the cell unit. For extra safety, a pressure relief valve that prevents problems related to back-pressure irregularities is also available as an option.

Shimadzu Evaporative Light Scattering LC Detector LTII (ELSD-LTII)

Shimadzu Evaporative Light Scattering LC Detector LTII (ELSD-LTII)

In the history of high-performance liquid chromatographs, which dates to the early 1960s, refractive index detectors (RI detectors) have often been used as general-purpose detectors. RI detectors enable the detection of components that do not possess UV absorbance and give a proportional relationship between the heights of detected peaks and the quantities of detected components. So, in comparison with absorbance detectors (UV detectors), they offer advantages such as the ability to ascertain unknown component quantities and obtain molecular weight distributions for macromolecules. On the other hand, they also have various disadvantages. For example, they cannot be used for gradient analysis, the baselines they produce are susceptible to the influence of fluctuations in the ambient temperature, their sensitivity is low compared to that of UV detectors, and they are prone to giving negative peaks, which make quantitative analysis difficult. Furthermore, with both UV and RI detectors, in cases where the solvent peaks of the analyzed samples appear at the start of the chromatogram, it is sometimes not possible to detect target substances with short elution times. Therefore, RI detectors cannot truly be described as general-purpose detectors. The principle of evaporative light scattering detectors (ELSD), which solve these problems, is extremely simple. The target components are converted to a fine spray by a nebulizer and heated so that only the mobile phase is evaporated. Light is directed at the remaining target substances and the scattered light is detected. ELSDs can detect almost all components that are less volatile than the mobile phase. These detectors first appeared in 1966, but were subsequently overshadowed by high-performance liquid chromatographs, which advanced significantly at that time. They were first commercialized in the early 1980s, and the basic technology of modern-day ELSDs was  established in the mid-1980s. In addition to describing the operating principles and practical benefits of ELSDs, this article uses the ELSD-LT 2, a product that achieves greater sensitivity, speed, and convenience than conventional products by incorporating the latest technology, to present application examples that utilize ELSD characteristics.

What Is an Evaporative Light Scattering Detector (ELSD)?

The target substances separated in a column are, together with the mobile phase, converted to a fine spray by a nebulizer, and this spray is carried to a drift tube. In the drift  tube, heat is applied so that only the mobile phase is evaporated. The remaining target substances that were in the mobile phase are converted to minute solid particles and are carried to the detection unit. In the detection unit, the target substance particles cause the light emitted from a light source to be scattered. This scattered light is measured by a photo multiplier and the target substances are thereby detected. The intensity of the signal detected in the ELSD can  be represented by the following equation:

(Signal intensity) = a x (Quantity of target substance)b

Here, "a" and "b" are constants that are determined by a variety of factors, such as the size of the particles, the concentration and type of the target substances, the gas flow rate, the mobile phase flow rate, and the temperature of the drift tube. In principle, ELSDs are capable of analyzing all substances that have an evaporation temperature lower than that of the mobile phase, and can attain roughly the same level of detection sensitivity for any compound. For this reason, they are well-suited to the detection of components such as sugars, fats, surfactants, synthetic macromolecules, and steroids, as these components have low light absorbance, making them difficult to detect with UV detectors. If the target substances are nonvolatile, detection is possible down to the nanogram level in nearly all cases.

ELSDs and RI Detectors:

Like RI detectors, ELSDs are classified as general-purpose detectors but they differ from RI detectors in the following ways:

  1.  They are 5 to 10 times more sensitive than RI detectors.
  2.  They support the use of the gradient elution method.
  3. They are not easily affected by changes in the ambient temperature.
  4.  They are not affected by interference due to solvent peaks.
  5.  Time is not required to allow for the instrument and the baseline to stabilize.

Although the gradient elution method is effective for the batch analysis of, for example, multiple components in natural products, RI detectors cannot be used for this because of fluctuations in the baseline caused by changes in the refractive index of the mobile phase.

With ELSDs, baseline fluctuations do not occur in gradient elution, meaning this method can be used to perform the efficient, high-sensitivity analysis of multiple components.

This feature of ELSDs is useful for the following types of analysis:

  1. The analysis of compounds that cannot be detected with UV detectors: Carbohydrates (sugars), sugar alcohols, alcohols, terpenoids, surfactants, natural macromolecules, and synthetic macromolecules
  2.  The batch analysis of compounds for which the gradient elution method is difficult to use ecause absorbance occurs only in the short wavelength region:

          Fats, phospholipids, glycerides, fatty acids, natural macromolecules, and synthetic macromolecules Also, because ELSDs can be applied to all                 aspects of the methods used for LC/MS, including the mobile phases, they can be used as substitute detectors in place of expensive LC/MS            instruments in the screening of compounds.

Features of ELSD-LT2:

  • High-Sensitivity Detection of Semi-Volatile Substances Achieved with Low-Temperature Evaporation of Mobile Phase:

With an ELSD, the larger the nebulized droplets, the higher the evaporation temperature must be set in order to evaporate them. If analysis is performed at a low temperature, the larger droplets that are not evaporated create scattered light that gives rise to a high level of noise. The ELSD-LT2 solves this problem by incorporating a glass cell with a unique structure. Minute droplets that leave the ELSD-LT2 nebulizer are carried by the nebulizer gas stream through the glass cell and into the drift tube. Larger droplets, however, are not carried by the nebulizer gas stream and adhere to the inside surface of the glass tube, where they change to liquid form. This liquid accumulates in a siphon tube and is subsequently discharged. There is always waste liquid in the siphon section, so all of the nebulizer gas flows into the drift tube (siphon split method). In this way, the larger droplets that cause noise are separated selectively, and the smaller droplets are efficiently carried into the drift tube. This technology makes it possible for the ELSDLT2 to suppress noise, even at low evaporation temperatures. Because mobile phases can be evaporated at low drift tube set temperatures in the range of 35°C (organic solvent mobile phases) to 40°C (aqueous mobile phases), efficient, high sensitivity analysis is possible for nearly all compounds. Also, with the ELSD-LT2, assisting gas is  projected in a cylindrical shape centering on the drift tube outlet. This increases the concentration of the target substances that reach the detection unit from the drift tube and, consequently, increases sensitivity. In this way, with both a reduction in noise achieved through low-temperature evaporation technology and an increase in peak intensity achieved through superior detection technology, the ELSD-LT2 realizes high-sensitivity detection.

  • More User Friendly :

Setting the drift tube temperature and gain is the only preparation required to perform analysis with the ELDS-LT2. It is also possible to turn off the lamp and stop the nebulizer after the completion of analysis using the auto power-down function. The use of a long-life LED lamp and the auto power-down function enable reductions in the frequency of lamp replacement and the consumption of nebulizer gas, and thereby making it possible to reduce running costs. Furthermore, an automatic cleaning function for the drift tube helps make maintenance easier.

Agilent 1290 Infinity II Refractive Index LC Detector

Agilent 1290 Infinity II Refractive Index LC Detector

The 1290 Infinity II Refractive Index Detector is equipped with an ultralow dispersion microflow cell, which significantly reduces run times for higher sample throughput and improved resolution. Lower solvent consumption means much lower cost of analysis. A high-performance detector of choice for accurate, reproducible, routine analysis of polymers and other compounds that aren’t detectable by UV.

Features Of Agilent 1290 Infinity II Refractive Index LC Detector:

  • Shorter run times – for considerably higher sample throughput.
  • Ultralow dispersion – for improved sample definition and resolution.
  • Reduced solvent consumption – for significant savings in analysis cost.
  • Ideal tool for polymer analysis – consistent molecular weights, micro or analytical scale.
  • Excellent sensitivity – achieve low limits of detection.
  • 148 Hz data rate – even the narrowest distribution peaks can be detected and accurately quantified.
  • Minimized band broadening – high-definition sample profiling.
  • Fast startup – advanced low thermal mass design means that initial setup is typically less than two hours.
  • Further time and solvent saving – a recycle valve enables sample to be recirculated when the sample is not passing through the flow cell.
  • Automatic purging of reference flow cell – using programmable purge and wait times.
  • Easy maintenance – convenient front access for maintaining instrument uptime.
  • Early maintenance feedback (EMF) – indicates that preventative maintenance is due.
  • Extensive diagnostics – includes error detection and display with Instant Pilot controller and Lab Advisor software.
  • RoHS compliant – aligned with European Union directives regarding specific hazardous materials.
  • Software and Informatics

Agilent 1260 Infinity II Variable Wavelength LC Detector

Sensitive, fast and even more analyte information with dual wavelength capabilities

The Agilent 1260 Infinity II Variable Wavelength Detector offers lowest baseline noise and drift, resulting in lowest detection limits for robust quantification of trace level components. Even more sample information can be acquired in dual-wavelength mode. Time-programmable wavelength switching provides optimum sensitivity and selectivity for your applications.Highest productivity can be achieved with fast analysis at up to 120 Hz data rates.

Features :

  • Robust quantification of trace level components -lowest baseline noise and drift results in lowest detection limits.
  • More analyte information per run- withdual-wavelength capabilities.
  • High-resolution gainin fast LC -at up to 120 Hz data acquisition rate.
  • Reliable, simultaneous quantification- Wide linear range (>2.5 AU upper limit) for reliable, simultaneous quantification of primary compounds, by-products and impurities.
  • Efficient temperature control - next generationelectronic temperature control (ETC) provides maximum baseline stability and practical sensitivity under fluctuating ambient temperature and humidity conditions.
  • Automatic wavelength verification - provided using built-in holmium oxide filter.
  • Fast wavelength optimization- withstop-flow wavelength scanning.
  • New levels of data traceability - withradio frequency identification (RFID) technology for flow cells and lamps.
  • Maximum flexibility, compatibility and investment protection – with a range of 7 analytical and preparative flow cells provide.
  • Continuous tracking of instrument usage-early maintenance feedback (EMF), continuously tracks lamp burn time, with user-defined limits and message types.
  • Extensive analytics, error detection and displays-using Agilent Lab Advisor software.
  • Software & Informatics

Agilent 1260 Infinity II Variable Wavelength LC Detector

Agilent 1260 Infinity II Variable Wavelength Detector

Sensitive, fast and even more analyte information with dual wavelength capabilities

The Agilent 1260 Infinity II Variable Wavelength Detector offers lowest baseline noise and drift, resulting in lowest detection limits for robust quantification of trace level components. Even more sample information can be acquired in dual-wavelength mode. Time-programmable wavelength switching provides optimum sensitivity and selectivity for your applications.Highest productivity can be achieved with fast analysis at up to 120 Hz data rates.

Features Of Agilent 1260 Infinity II Variable Wavelength Detector:

  • Robust quantification of trace level components -lowest baseline noise and drift results in lowest detection limits.
  • More analyte information per run- withdual-wavelength capabilities.
  • High-resolution gainin fast LC -at up to 120 Hz data acquisition rate.
  • Reliable, simultaneous quantification- Wide linear range (>2.5 AU upper limit) for reliable, simultaneous quantification of primary compounds, by-products and impurities.
  • Efficient temperature control - next generationelectronic temperature control (ETC) provides maximum baseline stability and practical sensitivity under fluctuating ambient temperature and humidity conditions.
  • Automatic wavelength verification - provided using built-in holmium oxide filter.
  • Fast wavelength optimization- withstop-flow wavelength scanning.
  • New levels of data traceability - withradio frequency identification (RFID) technology for flow cells and lamps.
  • Maximum flexibility, compatibility and investment protection – with a range of 7 analytical and preparative flow cells provide.
  • Continuous tracking of instrument usage-early maintenance feedback (EMF), continuously tracks lamp burn time, with user-defined limits and message types.
  • Extensive analytics, error detection and displays-using Agilent Lab Advisor software.
  • Software & Informatics

Agilent 1260 Infinity II Multiple Wavelength LC Detector

Agilent 1260 Infinity II Multiple Wavelength LC Detector

Reliable, simultaneous quantification of primary compounds, by products and impurities

The diode array design of the Agilent 1260 Infinity II Multiple Wavelength Detector offers very low detector noise (less than ± 7 μAU) for precise quantification of trace levels, regardless of the number of signals recorded. Over a wavelength range from 190 to 950 nm, simultaneous detection of up to eight compound-specific wavelengths for optimum selectivity is provided. High-speed UV detection with up to 120 Hz data rates keeps pace with the analysis speed of fast LC.

Features:

  • Increased sensitivity and selectivity - with simultaneous acquisition of up to eight compound-specific wavelengths.
  • Low detection limits - low noise front-end electronics and special flow cell design deliver lowest detection limits thanks to minimization of short-term noise (less than ± 7 µAU ASTM).
  • Up to 100% resolution gain in fast LC - by 120 Hz data acquisition rate.
  • Electronic temperature control (ETC) - maximum baseline stability and practical sensitivity under fluctuating ambient temperature and humidity conditions.
  • Wide linear range - for reliable, simultaneous quantification of primary compounds, by-products and impurities.
  • Rapid optimization of sensitivity and linearity - programmable slit (1 to 16 nm).
  • New levels of data security and traceability – provided by radio frequency identification (RFID) technology.
  • Automatic wavelength verification - by built-in holmium oxide filter.
  • Maximum flexibility, compatibility and investment protection – with a range of 12 analytical, preparative and SFC flow cells.
  • Extensive analytics , error detection and display - with Agilent 1200 Series Instant Pilot controller and Agilent Lab Advisor software.
  • Software & Informatics
  • Wavelength(s): 190-950 nm
  • Linearity: > 2.0 AU (5 %) at 265 nm
  • Detection: 1024-element diode array
  • Light Source: Deuterium lamp / Tungsten lamp

Two Types Of UV Detectors Are Commonly Used Today

Two types of UV detectors are commonly used today:

  • Variable-wavelength (sometimes called "spectrophotometric" detectors )
  • Photodiode Array (sometimes simply called "diode array" detectors.)

Variable-wavelength detectors are less expensive; they are the standard detector type for quantitative analysis and routine assays. Photodiode array detectors are more versatile, because they allow simultaneous acquisition of both chromatographic and spectral information; they are frequently used in method development.

The detector wavelength is an important characteristic of an HPLC separation. As a general rule, the wavelength is set to the absorbance maximum of the analyte. Using the wrong wavelength may result in decreased peak sizes, or even no peaks at all!

Because different compounds can have different absorbance spectra, a direct quantitative comparison of different peaks in the same chromatogram can be misleading. A small quantity of a compound which absorbs strongly at the detector wavelength can give a bigger peak than a large quantity of a weak absorber. For reliable quantitation, a calibration must be carried out with a known quantity of the exact compound to be analyzed.

The Variable Wavelength UV Detector uses a monochromator (slits and a grating) to select one wavelength of light to pass through the sample cell.

The Photodiode Array Detector passes all wavelengths of light through the sample cell, then focuses each wavelength on a single sensor element.

source:lcresources.com