What are the petroleum additive detectors available

A petroleum additive detector is a device that detects changes in the quality concentration of substances flowing out of a chromatographic column. In gas chromatography analysis, using the characteristics of each component of the separated sample, the physical quantities determined by the detector based on the physical chemical properties of each component are converted into corresponding electrical signals determined through electronic instruments. At present, there are more than 20 types of detectors that can be used in gas chromatographs, including commonly used thermal conductivity detectors (TCD), hydrogen flame ionization detectors (FID), nitrogen phosphorus detectors (NPD), electron capture detectors (ECD), flame photometric detectors (FPD), photo ionization detectors (PID), etc

Main working principles of the detector

thermal conductivity detector（Thermal Conductivity Detector，TCD）

In gas chromatography analysis, how should we choose the appropriate detector according to the characteristics of the analysis sample? The thermal conductivity detector is a universal non-destructive concentration type detector that can theoretically be applied to the detection of any component. However, due to its low sensitivity, it is generally used for constant analysis. The structural schematic diagram of TCD is shown in Figure 1, its main principle is to work based on the principle that different components carrier gases have different thermal conductivity. The thermal sensitive element of the thermal conductivity detector is a hot wire, such as gold-plated tungsten wire, platinum wire, etc. When the tested component the carrier gas enter the thermal conductivity cell together, due to the difference in thermal conductivity between the mixed gas the pure carrier gas (usually lower than the thermal conductivity of the carrier gas), the heat transmitted by the hot wire to the cell wall also changes, resulting in a change in the temperature of the hot wire its resistance. This causes an unbalanced potential to be generated at the output end of the bridge as a signal output, which is recorded to obtain the chromatographic peak.

flame photometric detector（Flame-PhotometricDetector，FPD）

FPD is a quality selective detector mainly used for the determination of sulfur phosphorus compounds. The amount of hydrogen introduced during use must be greater than the usual amount of hydrogen required for combustion, that is, to burn to obtain a flame in hydrogen rich conditions. It is widely used in the analysis of trace sulfur compounds in petroleum products Organophosphorus chemistry in pesticides. The structural diagram of FPD is shown in Figure 3. Its main principle is that when components burn in a hydrogen rich flame, they become fragments molecules to varying degrees, their outer electrons are excited due to collision with each other. When the electrons return the Excited state to the low-energy state ground state, they emit a spectrum of characteristic wavelengths. This characteristic spectrum is measured by selecting a filter. Sulfur generates a spectrum of 350-430nm in flames, while phosphorus generates a spectrum of 480-600nm, with 394nm 526nm being the characteristic wavelengths of sulfur containing phosphorus containing compounds, respectively.

Fid（FlameIonization Detector，FID）

FID is a versatile destructive quality universal detector with high sensitivity wide linear range, widely used for constant trace detection of organic compounds. The main principle is that hydrogen air burn to generate a flame. When organic compounds enter the flame, they undergo ionization reactions to generate ions several orders of magnitude higher than the base current. Under the action of an electric field, these positively charged ions electrons move towards the negative positive electrodes respectively, forming an ion flow. After being amplified by an amplifier, these ions can be detected