Atomic fluorescence spectrometer uses the inert gas argon as the carrier gas. After mixing the gaseous hydride and excess hydrogen with the carrier gas, it is introduced into the heated atomization device, and the hydrogen and argon are heated by combustion in a specially designed flame device.
Atomic fluorescence spectroscopy is a method for qualitative and quantitative analysis of substances using the wavelength and intensity of atomic fluorescence spectral lines. After the atomic vapor absorbs radiation at characteristic wavelengths, the atoms are excited to higher energy levels, and the excited atoms then de-activate by radiation, and the light emitted during the jump from higher to lower energy levels is called
atomic fluorescence. The process of fluorescence emission stops when the excitation source stops irradiating.
Atomic fluorescence can be divided into 3 categories, namely resonant fluorescence, non-resonant fluorescence and sensitized fluorescence, among which resonant atomic fluorescence is the strongest and most widely used in the analysis. The fluorescence emitted by resonance fluorescence and the radiation absorbed is at the same wavelength. Resonant fluorescence can be generated only when the ground state is a single state and there is no intermediate energy level. Non-resonant fluorescence is where the wavelength of fluorescence emitted by the excited atoms and the wavelength of radiation absorbed is not the same. Non-resonant fluorescence can be divided into direct line fluorescence, step line fluorescence and anti-Stokes fluorescence. Direct line fluorescence is the fluorescence produced by excited atoms jumping from a higher energy level to a sub-stable energy level above the ground state. Step-line fluorescence is the fluorescence emitted by an excited atom that first loses some of its energy by non-radiative de-activation, returns to a lower excited state, and then leaps to the ground state by radiative de-activation. Both direct and step-line fluorescence is longer than the wavelength of the absorbed radiation. Anti-Stokes fluorescence is characterized by a fluorescence wavelength that is shorter than the wavelength of the absorbed light radiation. Sensitized atom fluorescence is fluorescence emitted by an excited atom transferring excitation energy to another atom by collision, which in turn de-activates by radiation.
Qualitative analysis can be performed based on the wavelength of fluorescence spectral lines. Under certain experimental conditions, the fluorescence intensity is proportional to the concentration of the element under test. Accordingly, quantitative analysis can be performed.
Atomic fluorescence spectrometers are divided into two categories: dispersive and non-dispersive. The structure of the two types of instruments is similar, the difference is that non-dispersive instruments do not use monochromators. Dispersive instruments consist of a radiation source, a monochromator, an atomizer, a detector, a display and a recording device. The radiation source is used to excite the atoms to produce atomic fluorescence. A continuous light source or a sharp line light source is available. The commonly used continuous light source is a xenon arc lamp, and the available sharp line light sources are high-intensity hollow cathode lamps, induction discharge lamps, and controlled temperature gradient atomic spectroscopy lamps and lasers. The monochromator is used to select the required fluorescence spectral lines and exclude the interference of other spectral lines. Atomizers are used to convert the measured element into atomic vapor, and there are flame, electrothermal, or inductively coupled plasma flame atomizers. Detectors are used to detect light signals and convert them into electrical signals, of which the most commonly used detectors are photomultiplier tubes. Display and recording devices are used to display and record the measurement results, available electric meters, digital meters, recorders, etc.
Atomic fluorescence spectrometry has the advantages of simple equipment, high sensitivity, low spectral interference, a wide linear range of working curves, and can be used for multi-element determination. It has gained wide application in various fields such as geology, metallurgy, petroleum, biomedicine, geochemistry, materials and environmental science.
Atomic fluorescence spectrometry is a method to determine the content of an element to be measured by measuring the intensity of fluorescence emission from the atomic vapor of the element to be measured when excited by radiation energy. After the gaseous free atom absorbs the characteristic wavelength radiation, the outer electrons of the atom leap from the ground state or low energy level to the high energy level after about 10-8s, and then leap back to the ground state or low energy level, while emitting the same or different radiation from the original excitation wavelength, called
atomic fluorescence. In atomic fluorescence emission, the fluorescence intensity decreases or even disappears because some of the energy is converted to heat or other forms of energy, this phenomenon is called fluorescence burst.
The
atomic fluorescence spectrometer reduces the element to be analyzed in the sample solution to a volatile covalent gaseous hydride (or atomic vapor), which is then introduced into the atomizer with a carrier gas and atomized in an argon-hydrogen flame to form a ground state atom. The atoms in the ground state absorb the energy from the light source and become excited. The excited atoms release the absorbed energy in the form of fluorescence during the de-activation process, and the intensity of this fluorescence signal is linearly related to the content of the element to be measured in the sample. Atomic fluorescence spectrometer using hydride generation - atomic fluorescence spectrometry (HG-AFS) to determine As, Sb, Bi, Hg, Ge, Pb, Sn, Se, Te, Zn, Cd and Cu 12 elements. The detection limit can be up to the ppb level. In terms of practical application, the current national standard method is mostly used to detect arsenic, mercury, selenium and other elements.
a. When measuring the mercury content, turn on the instrument host power and sequential syringe power. If the mercury lamp is not lit, the operator can use ignition to stimulate it. No ignition is required when measuring mercury content.
b. Check whether the element light spot is right, and adjust it with a dimmer.
c. Clean after the test is completed. Click the cleaning program and put the carrier and reductant capillary into clean water to clean. Cleaning can be done without ignition.
d. Close the software again after cleaning. Turn off the power of the main unit and the power of the sequential syringe, loosen the pump tube pressure block, turn off the computer, and turn off the argon gas.
e. Sample tubes, volumetric flasks, and all used vessels, where it is necessary to use again, should be cleaned with 10% nitric acid soak before use.
f. The instrument has a high sensitivity of determination and requires special attention to all aspects of contamination.
g. If the sample matrix is complex, eliminate the interference first if possible.
h. When installing the element lamp, the lamp plug convex must coincide with the concave of the socket, and do not plug and unplug with electricity, otherwise it will damage the instrument.
i. Open the gas cylinder first during the test to prevent liquid from backing up and corroding the gas circuit system.
j. The pump tube should be properly maintained. Pay attention to the proper level of tube pressure and head tightness and do not let the pump tube run empty.
k. If you encounter a sudden power failure, turn off the power switch, close the valve of the argon gas cylinder, and wait for the restoration of power before restarting the test.
