Ion chromatography detectors

A conductivity detector in ion chromatography measures changes in electrical conductivity to detect and quantify ions. Here is how it works:

1. The eluent, which is the liquid carrying the sample and ions, flows through a separation column in the ion chromatography system.
2. In the separation column, the analytes are separated (anion or cation exchange) and enter time-resolved the conductivity cell. The conductivity cell contains two electrodes with a small voltage applied across the electrodes.
3. The presence of ions in the eluent affects the conductivity of the cell. Ions enhance the electrical conductivity of the eluent, causing changes in the electrical current flowing through the cell.
4. The changes in electrical conductivity are converted into electrical signals. These signals are typically amplified and sent to a data acquisition system for further processing and analysis.
5. The detector response is calibrated using known standards to establish a relationship between the signal generated and the concentration of the analyte ions. This calibration allows for the quantification of the analyte ions in the sample.

A UV/VIS detector in ion chromatography measures the absorption of light by compounds in a sample and provides information about their presence and concentration in the sample. Here is how it works:

1. The UV/VIS detector consists of a light source that emits a broad spectrum of light, including ultraviolet (UV) and visible (VIS) wavelengths.
2. The sample, dissolved in an appropriate solvent, is continuously injected into the chromatography system and carried through a flow cell.
3. As the sample flows through the flow cell, it interacts with the light beam emitted by the light source. Some of the wavelengths of light are absorbed by the compounds present in the sample.
4. The UV/VIS detector measures the amount of light that passes through the sample (transmittance) rather than being absorbed. It does this by comparing the intensity of the light beam before and after it passes through the sample.
5. The detector generates an electrical signal proportional to the amount of light transmitted through the sample. This signal is typically converted into a numerical value or a chromatogram peak, indicating the absorbance of the sample at specific wavelengths.
6. The detector response is calibrated using known standards with known concentrations of compounds. This calibration curve establishes a relationship between the absorbance and the concentration of the analyte of interest. By comparing the absorbance of the sample with the calibration curve, the concentration of the analyte in the sample can be determined.

An amperometric detector is a type of electrochemical detector commonly used in chromatography to detect and quantify analyte compounds. Here is how it works:

1. The amperometric detector consists of an electrochemical cell containing two electrodes: a working electrode (WE) and a reference electrode (RE).
2. As the analyte compounds elute from the chromatography column, they reach the electrochemical cell. Depending on their nature, they undergo oxidation or reduction reactions at the surface of the working electrode.
3. During the oxidation or reduction reaction, electrons are either gained or lost by the analyte compounds. This electron transfer generates an electrical current proportional to the concentration of the analyte.
4. The electrical current produced by the oxidation or reduction reaction is measured by the amperometric detector. The current is typically amplified and converted into a detectable signal.
5. To determine the concentration of the analyte compounds, the amperometric detector response is calibrated using known standards with known concentrations. This calibration allows for the quantification of the analyte compounds in the sample.