Gas Chromatography Instrument System - Detector Operation Points NPD Usage Notes: Antimicrobial Central Venous Catheter Central Venous Catheter,CVC,central venous catheter set,central venous catheter double lumen,central venous catheter kit Anesthesia Medical Co., Ltd. , https://www.jssinoanesthesias.com
1. NPD is developed on the basis of FID. It differs from FID in that it adds a thermal ion source (consisting of strontium salt beads) using a micro-hydrogen flame. Under the condition that the thermionic source is heated by electricity, the ionization efficiency of the nitrogen-containing and phosphorus-containing compounds is greatly improved, so that the two types of compounds can be selectively detected. Due to the use of hydrogen, the safety of NPD is the same as for FID.
2. The temperature change of the thermionic source has a great influence on the sensitivity of the detector. The temperature is high and the sensitivity is high, but the life of the salt bead is shortened. Increasing the voltage of the thermionic source and increasing the hydrogen flow rate can increase the sensitivity. However, it must be noted that the air flow rate is too low and the balance time of the detector is too long; the hydrogen flow rate is too high, and a flame like FID is formed, which greatly reduces the service life of the beryllium salt beads and destroys the nitrogen and phosphorus. The choice of a trusted response. The gas flow rate is generally set to 3~4ml/min for hydrogen and 100~120ml/min for air. The packed column and large-diameter column are used. The carrier gas flow rate is about 20ml/min, without tail gas, when using conventional capillary column, tail. The blowing is set to about 30 ml/min.
3. When adjusting and setting the voltage of the thermionic source, remember to turn off the detector power to avoid accidentally burning the salt beads.
4. The active element (onium salt) of the hot ion source is easily contaminated and shortens its service life. Pay attention to the extension of its service life;
First, to avoid SiO2 entering the detector, the column should be well aging, especially for silicone-based fixatives, which have a thin film. Also avoid SiO2 residues in the sample after derivatization into the column.
Second, before turning off the carrier gas (such as changing the cylinder or changing the column), the voltage of the thermionic source should be adjusted to 0. Otherwise, no carrier gas will pass through, and the salt beads will burn out within a few minutes.
Third, use a low thermal ion source voltage as much as possible while meeting the sensitivity requirements.
Fourth, the instrument should be stored to avoid moisture. When the instrument is not in use, it is best to keep the detector temperature above 100 (thermionic source voltage should be turned off).
Fifth, if you do not inject the analysis for a period of time (such as overnight), you should lower the thermionic source voltage, but do not turn it off. Because the salt beads are still hot after the voltage is reduced, the voltage is quickly stabilized when the sample is injected again. If the voltage is turned off after the shutdown, the detector requires a few hours of equilibration time.