Seven major faults and troubleshooting methods in atomic fluorescence spectrometer
01 Ignition problem
In the analysis work, it is often encountered that some of the instrument ignition coils are not lit and cannot be normally ignited. First of all, check whether the ignition wire is normal. If the wire is broken, the wire needs to be replaced. If the wire is bright but the flame is not burning, you need to check the gas or control valve to check whether the position of the wire and the core is appropriate. The instrument can be ignited normally.
02 No signal strength
In the process of instrument verification, there is often no response fluorescence intensity after the instrument measures the standard solution. In the case of such problems, first of all, you should check the static light source and check if the element light is on. If the instrument lamp energy is normal, indicating that the instrument circuit is normal, you need to further check the reaction system or atomization system. Check if the instrument pump tube is tight and the pipe is blocked or broken. If the above conditions occur, the reagent does not enter the system, and the instrument does not undergo redox reaction, no signal will be generated. Replacing the pipe and adjusting the tightness of the pump tubing can solve this problem.
The acidity or reducing agent concentration of the standard solution is not enough to generate the hydride of the measured element. Failure to atomize normally will also cause the instrument to have no response fluorescence intensity. This requires checking the acid and reducing agent concentrations used in the standard solution.
03 Instrument sensitivity is low
During the verification process, the linearity of the instrument's measurement linearity and detection limit is determined. The linearity of the mixed solution of 0.0 ng/mL, 1.0 ng/mL, 5.0 ng/mL, and 10.0 ng/mL arsenic and antimony is required. The measurement was repeated 3 times, the fluorescence intensity value was recorded, the slope b was calculated according to linear regression, and the fluorescence intensity measurement was performed 11 times for the blank solution continuously, and the standard deviation was calculated, and then the detection limit QL of the instrument was calculated. JJG939-2009 "Atomic Fluorescence Photometer Calibration Regulations" requires an instrument detection limit of 0.4 ng. In the verification, the sensitivity of the instrument is often low. After adjusting the lamp current and negative voltage of the instrument, the requirements of the verification procedure cannot be met. This requires troubleshooting to solve the problem of low sensitivity.
First check if the wire is aging, replace the wire if necessary, and then check if the position of the atomizer is offset to cause a change in the focal length and affect the sensitivity of the instrument. Poor dimming, focal length not in the center of the furnace will also cause low sensitivity of the instrument, which requires re-adjusting the core and optical path. Low carrier gas flow rate, too fast discharge, deformation or bending of the current-carrying tube or capillary, etc., will cause the standard solution to be unable to be atomized normally, resulting in reduced sensitivity of the instrument. This requires inspection of the sample injection system, if necessary Replace the instrument injection system tubing. During the verification process, the purity of the argon gas used in the instrument is often insufficient, which causes the sensitivity of the instrument to decrease. This problem can be solved by replacing high-purity argon gas. The intensity of the selected elemental lamp also affects the sensitivity of the instrument, requiring replacement of the elemental light when the instrument is less sensitive.
04 Instrument signal is unstable
It can reduce the lamp current of the instrument and the signal value after negative high voltage. If it is still unstable, it is necessary to check whether the environment where the instrument is located has strong light interference. If the instrument's detection window is illuminated by strong light, the fluorescence signal of the instrument will be unstable. This requires shading for verification. Then observe whether the flame of the instrument is beating. If there is obvious jump, check whether the pumping exhaust port has too much pumping force, and the airflow is affected, which causes the instrument flame to be unstable.
After the above problems are eliminated, the instrument signal is still unstable. It is necessary to check the water seal and waste liquid pipe of the instrument. The water seal and the waste liquid pipe may cause moisture to enter the atomizer, resulting in unstable instrument signal. This requires re-adjusting the water seal and waste tube position of the instrument. In the verification, the instrument carrier flow is too large and the instrument signal is unstable, and the carrier gas flow rate needs to be reduced. After the above troubleshooting process, the signal measured by the instrument can be basically guaranteed to be stable.
05 measurement blank height
For the phenomenon that the fluorimeter has a high blank during use, there may be problems of current carrying, blank solution, pipeline and pipeline pollution, etc. During the daily verification process, the measuring instrument is adjusted by adjusting the lamp current and the negative high voltage. The fluorescence intensity of the current-carrying current is maintained at around 200, and some of the instrument's current-carrying blank strength values ​​reach about 1000, which affects the linear measurement of the instrument. Most of these problems are due to reagent problems such as hydrochloric acid. Since the standard solution for verification needs to be configured on site, the glass measuring device such as the volumetric flask and pipette used for the solution should be cleaned to reduce the influence on the measurement results of the instrument. When the fluorescence value of the current carrying, standard and sample is zero or even negative, first confirm whether the light source and the peristaltic pump can work normally, and also confirm whether the pump tube is stuck to the proper position, current carrying and reducing agent passage. Is it smooth, etc., to confirm whether the gas-liquid separation device inside the instrument is blocked to the atomizer. For the difference between the standard fluorescence value and the previous measurement value, first confirm that the standard sample is prepared correctly, and then confirm whether the element lamp is installed to the normal position, and also check whether the reducing agent concentration is too low. In summer, it is recommended to reconfigure the reducing agent every half day. .
06 Baseline drift or noise
A stable baseline should be a straight line that keeps the baseline stable and is the most basic requirement for analysis. When doing a current-carrying blank, there is sometimes a drift, a drift, a pulse, or a gradient on the baseline, which affects the accurate determination of the spectral peak. The reason may be:
The fluorescence intensity of the instrument background is drifting, the light source is unstable, the power supply is unstable, the current carrying or reducing agent is not clean, and the pipeline or quartz tube is dirty. For the background fluorescence intensity drift, you can start the instrument without air injection, confirm which channel is unstable, or you can actually measure it. See if the fluorescence intensity of the instrument drifts. If there is, it may be by the pump tube. The drift caused by fatigue, but the confirmation of the fatigue of the pump tube can be determined after eliminating the light source and the background drift. For problems such as unsmooth carrier or reducing agent, dirty piping or quartz tube, thoroughly flush the instrument piping and flow path system. A regulated power supply should also be provided. For the phenomenon of noise, the instrument may not be stable, the gas path is unstable, the lamp preheating time is not enough, and the ambient temperature changes greatly. These problems should be noted in the experiment.
07 Fluorescence values ​​are generally low
When the fluorescence value is generally low, it should be confirmed whether the argon pressure meets the measurement requirements. Secondly, it is confirmed whether the quartz core in the atomizer is clean or clogging. In winter, the room temperature should be kept at about 25 °C, and the temperature will be too low. Generally low.
The treatment methods include: opening the main cover and adjusting the element lamp to the most suitable position. If it is mercury measurement, the capillary of the first-stage gas-liquid separator outlet to the secondary gas-liquid separator can be replaced (the humidity in the capillary is easy to shine) Mercury is adsorbed on the tube wall so that the fluorescence value is low) to improve the fluorescence intensity. The instrument injection line must have good sealing performance, otherwise the detection result will be low. The pump that excludes the waste liquid should be adjusted to an appropriate level. The pressure of the pump tube clamp is too tight, which may cause the pump tube to age prematurely. If it is too loose, the waste liquid will not be discharged in time. The excess waste liquid will be from the top of the gas-liquid separator. The air outlet is backflushed into the secondary gas-liquid separator, and the waste liquid will overflow into the furnace chamber. If it is not cleaned in time, it will corrode the furnace chamber. Excessive waste liquid may also be sprayed into the atomized gas to cause the quartz furnace core to burst. In addition, if the wind force of the air outlet is too large, it will cause the instrument to be unstable, which may result in low detection results. (When using this instrument, it is found that the quartz syringe is extremely vulnerable. To avoid damage to the syringe, remove the syringe into the flow bottle after the test is finished, and then remove the excess acid from the download tank. Clean the carrier and reinstall the syringe before the next start-up test.) In addition, each time the element lights are replaced, it must be refocused. All parts of the instrument should be removed every 2 months, thoroughly cleaned, and then re-installed after drying.
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