Ordinary graphite tube can be used to determine various elements, especially those with low atomization temperature. These elements are Cd, Pb, Na, K, Zn and Mg. It is also suitable for low-sensitivity or high-concentration samples. For example, when measuring Al, Fe and Cu, 1 ppb can be measured with a pyrolytic graphite tube and 100 ppb with an ordinary graphite tube. Figure 2 shows the working curve of copper (Cu) measured with a conventional graphite tube and a pyrolytic graphite tube with 20, 40 and 60 ppb for the normal graphite tubes and 2, 4 and 6 for the pyrolytic graphite tubes ppb, shows similar absorption.
The role of graphite tube
Atomic absorption spectroscopy is based on the state of the ground state of the measured element in the gaseous state of the element of atomic resonance radiation has a strong absorption effect was established. The method has the advantages of high detection limit, high accuracy, good selectivity and fast analysis.
When the experimental conditions such as temperature absorption optical path and sampling mode are fixed, the ground state atoms of the element to be detected produced by the sample absorb the monochromatic light radiated by the hollow cathode lamp of the element which is the sharp line light source, and the absorbance (A) Is proportional to the elemental concentration (C) in the sample. That A = KC where K is a constant. Accordingly, by measuring the absorbance of standard solution and unknown solution, but also known the concentration of standard solution can be used as a standard curve to determine the concentration of unknown elements in the test element.
The method is mainly applied to trace and trace components in the sample analysis.
Graphite furnace method according to the elements to be tested and sample selection of suitable graphite tube, graphite tubes are now commonly used in three, ordinary graphite tube, pyrolytic graphite tube and platform graphite tube. Ordinary graphite tube made of ordinary graphite, the most widely used. Due to the porous nature of graphite, the liquid sample will have some penetration in the graphite wall. Pyrolytic graphite tubes are pyrolyzed by the CVD method on the surface of ordinary graphite tubes, with a metallic, shiny surface, with less sample penetration on the tube wall. The platform graphite tube is equipped with a flat plate (platform)
The production of graphite tube
The invention discloses a graphite tube with heat exchange function. The graphite tube with heat exchange function comprises the outermost high temperature refractory material, the middle layer of phenolic resin and the innermost layer of graphite are combined The high-temperature refractory material includes molybdenum disulfide, nano-alumina, composite dispersant, nano calcium carbonate and carbon black powder, and the high-temperature refractory material accounts for 21% of the total weight of the graphite pipe with heat exchange function. 25% of the phenolic resin accounts for 25% ~ 26% of the total weight of the graphite tube having the heat exchange function, and the graphite accounts for 48% ~ 56% of the total weight of the graphite tube having the heat exchange function. The present invention provides a graphite tube with heat exchange function, which has the advantages of low preparation cost, good use effect and improved heat exchange efficiency.
Graphite tube classification
1, according to the heating method points: Longitudinal heating graphite tube, transverse heating graphite tube
2, by performance points: ordinary graphite tube (non-pyrolysis) for low temperature (≤ 2000 ℃) atomic elements such as silver, cadmium, lead; pyrolytic graphite tube for low, medium and high temperature (> 2500 ℃) atomization Element; platform graphite tube for medium and low temperature (≤ 2400 ° C) atomic elements.
Graphite tube brand
Imported graphite tube brand thermoelectric, Varian, Hitachi, Shimadzu and other foreign brands, including the United States and Canada’s graphite tube database contains the number of these graphite tube, to facilitate the inquiry!