Simple and practical manual of the hottest atomic

Simple and practical manual of atomic fluorescence

part I some key points that atomic fluorescence must understand

1 Advantages of atomic fluorescence: ① simple spectral line; ② High sensitivity and low detection limit; ③ It is suitable for multi-element analysis

2. Relationship between fluorescence intensity and the concentration of the measured object: for low concentration atomic fluorescence analysis, the fluorescence intensity and the concentration of the measured object show a simple linear relationship, and the concentration increases. Due to the spectral line broadening effect, self absorption, scattering and other effects, the working curve appears curved

3. Atomic fluorescence intensity and excitation light source intensity are only applicable within a certain range of excitation light source intensity. It is impossible to improve the detection limit by increasing the radiation intensity of the light source without limitation

4. The ways to overcome the interference of liquid phase and gas phase: ① increase the pH and the solubility of metal particles; ② Reduce the concentration of potassium borohydride; ③ Add anti-interference reagent

5. Atomic fluorescence photometer consists of hydride generator, excitation light source, optical system, atomization system and photometric system

6. Correction of light source drift and fluctuation: determine the blank again after a certain number of samples to fit the standard curve

7. Several concepts

afs: abbreviation of atomic fluorescence spectrometry. Atomic vapor is excited by absorbing the energy of light radiation of a specific wavelength. The excited atom emits light radiation of a certain wavelength in the process of de excitation, which is called atomic fluorescence. The analytical method of detecting atomic fluorescence to obtain analytical data is called atomic fluorescence spectrometry

current carrying: its main function is to react with reducing agent to generate primary hydrogen (H)

reductant: the main source of primary hydrogen (H)

atomizer: the location of hydride atomization, with the structure of quartz furnace and electric furnace wire. The hydride produced by the hydride generator is pushed to the quartz furnace core by the carrier gas, and then ignited to form an argon hydrogen flame, which makes the hydride entered the former Jinan LANBO Experimental Equipment Co., Ltd. a subsidiary of a high-tech enterprise integrating R & D, production, sales, service and technical consultation

peristaltic pump: an injection device that achieves the purpose of injection by peristaltic extrusion of silicone tube

hydride generator: hydride generation (Hg), a device that provides current carrying and sample and reductant response conditions. It is composed of a sample injection system, a gas-liquid separation system and a gas path. Hydride generation atomic fluorescence is usually referred to as HG-AFS for short

carrier gas: the gas that pushes the hydride to move in the pipeline

shielding gas: as the protective gas around the argon hydrogen flame, it prevents the atomic vapor from being oxidized by the surrounding air, and plays a role in protecting the stability of the flame shape

atomizer height: the vertical distance from the top of atomizer to the horizontal line of lens center

atomizer temperature: refers to the temperature in the quartz furnace core, that is, the pre heating temperature, which is basically 200 ℃

atomization temperature: refers to the temperature of argon hydrogen flame, about 780 ℃

detector: a device for spectroscopic detection of fluorescence, commonly used as a photomultiplier tube

light drift: the drift of the detection value caused by the light source factor

temperature drift: the drift of detection value caused by ambient temperature is particularly obvious for Hg lamp

lamp current: the working current of the cathode lamp, within a certain range, increases with the increase of lamp current, and the fluorescence intensity increases. If it is too large, it will produce self absorption phenomenon, and the noise will increase significantly and the service life will be shortened

element lamp: a specific cathode lamp is used to detect specific elements, with the exception of mercury lamp, which is an anode lamp

negative high voltage: the voltage at both ends of the photomultiplier tube. When the negative high voltage of the photomultiplier tube is between 200V and 500V, the signal (s) to noise (n) ratio of the photomultiplier tube is constant

8. The whole process of atomic fluorescence detection: peristaltic pump sample, reductant injection carrier flow injection to the primary gas-liquid separator to generate hydride carrier gas push to the secondary gas-liquid separator push to the atomizer atomization excitation fluorescence detector detection computer data processing

Part II fault and self inspection

instrument fault self inspection procedure:

1 Check the power supply

2. Check the carrier gas

3. Check elements, etc

4. Check the peristaltic pump

5. Check the pipeline

6. Check atomizer

7. Check the software system

system fault problem

mostly refers to computer hardware system fault

1 Fault performance: communication failure, the single chip microcomputer cannot be connected with the computer and cannot enter the operating software after starting up

fault cause: communication failure between the instrument and the computer, wrong setting of the computer serial port, or incompatibility between the instrument software and the computer operating system, or circuit hardware failure, or mechanical failure

solution: check whether the communication line is correctly set with the port, or check whether the instrument software is compatible with the computer operating system, Or check the main board of the machine circuit (professional technicians of the manufacturer are required)

2 Fault performance: the instrument cannot automatically recognize the element lamp

fault cause: the lamp interface is not connected well, or the lamp is broken

solution: check or replace the element lamp, and check the machine circuit motherboard

3 Fault performance: the instrument stops running during the measurement process and prompts an error

cause of fault: the sample will be displayed at the npe2015 exhibition held in Orlando, Florida, USA in combination with the overall deployment of scientific and technological system reform. The concentration of this technology (Booth No. s28196) is too high, or the instrument software is incompatible with the computer operating system, or the hardware is bad, or the element light is bad

solution: dilute the sample, or replace the operating system, Or replace the maintenance hardware

element lamp problem

1 Fault performance: the lamp doesn't light up

solution: most of them are mercury lamps, which won't light up automatically after starting up. It needs to light up with a discharge device for lighting gas or wipe the surface of the lamp with a sponge

2. Fault performance: light spot deflection

solution: the element lamp is fixed with four screws, place the dimmer in the atomizer, and adjust the screws so that the light spot is concentrated in the center of the dimmer

peristaltic pump problem

1 Fault performance: no drainage

solution: adjust the pressure of the peristaltic pump on the silicone tube. The pressure should be moderate. The silicone tube must have a clip, otherwise it will often cause no drainage because the pump squeezes the silicone tube

2. Fault performance: the peristaltic pump rotates constantly

solution: it is a system fault, shut down the machine and restart it

problems of gas-liquid separator

1 Fault performance: too much foam

solution: incomplete digestion, caused by too much organic matter, can be used to continue digestion, at the same time, appropriately reduce the concentration of reducing agent potassium borohydride, or appropriately add polyols to defoaming

2. Fault performance: air leakage of the secondary gas-liquid separator

solution: check whether the pipeline is connected reversely. At the same time, pay attention to the speed of adding water to seal, and the amount of water to be added should be slightly larger. Block the vent hole at one time, and slowly add it, it will be blown out by the carrier gas, resulting in air leakage when the water seal is not added

detection value problem

1 Fault performance: the detected value is very low and relatively constant, and the measured values at each point of the curve are similar

solution: A. check whether there are some users who often neglect that this point is lit. If the lamp is not lit, the value will be very low and constant; B check whether there is ignition, and a similar situation will occur without ignition; C. Check whether the position of the light spot is in the center of the atomizer. If it deviates a lot, a similar situation will occur; D. Check whether the pipeline injects samples, especially for machines that inject samples with peristaltic pumps, the probability of non injection is relatively high; E. Check whether the water seal of the secondary gas-liquid separator is added. If there is air leakage, the detection value will be very low and cannot be detected

2. Fault performance: the detection value is very low and relatively constant, so a curve can be made

solution: A. check whether the position of the light spot is in the center of the atomizer. If there is a deviation, a similar situation will occur. If a small amount of fluorescence is detected by the detector, a curve can be made, that is, the value is very low; B. Check the ambient temperature. It is normal that the detection value below 5 ℃ is low. Just increase the ambient temperature; C. The warm-up time, just start-up and detection, not only the value is unstable, but also the value will be low

3. Fault performance: high blank value

solution: A. check whether the pipeline is polluted. Generally speaking, mercury above 40ug/l and arsenic above 100ug/l will cause pipeline pollution; B. Reagent pollution can be solved by self inspection

4. Fault performance: blank drift

solution: A. extend the preheating time of element lamp, especially when the ambient temperature is low; B. Curve retest