Coated graphite tubeIt is a high-performance analytical tool coated with special materials on the surface of graphite tubes, widely used in fields such as atomic absorption spectroscopy (AAS) analysis, high-temperature mass transfer, and chemical research. Its core advantage lies in significantly improving the high temperature and corrosion resistance of graphite tubes through coating technology, while extending their service life and improving analysis accuracy. It is composed of a graphite substrate and a surface coating. The coating material is usually pyrolytic graphite, tungsten carbide, or refractory metal carbides (such as TaC, ZrC), which are formed into a dense protective layer by vacuum deposition or immersion method.
Coated graphite tubeMain functions:
1. Extend the lifespan of graphite tubes
Functional principle: Ordinary graphite tubes are easily oxidized at high temperatures (up to 3000 ° C) and are prone to react with certain samples (especially high salt, strong acid and alkali), causing corrosion, delamination, and cracking.
Coating function: Coatings (such as pyrolytic graphite, tantalum carbide TaC, zirconium carbide ZrC, etc.) form a dense and inert protective layer, effectively isolating high-temperature oxygen and corrosive samples from corroding the substrate graphite.
Effect: It can extend the service life of graphite tubes by several times or even more than ten times, reducing the cost of use.
2. Improve thermal stability and reduce memory effects
Functional principle: Coating materials have higher thermal stability and chemical inertness.
Reduce memory effect: After analyzing high concentration samples or elements that are prone to forming refractory compounds, some samples will remain on the inner wall of ordinary graphite tubes, resulting in a "carry over" effect during the next analysis, leading to higher results. The surface of the coated tube is smoother and more inert, reducing the adsorption and residue of the sample on the tube wall.
Effect: Improved the accuracy and precision of analysis, reduced cleaning procedures and blank values.
3. Improve atomization efficiency and sensitivity
Functional principle:
Pyrolytic Coating: It is the most common coating. It forms a highly ordered graphite layer on the inner wall of the graphite tube, with excellent longitudinal heating uniformity, making the sample heated more evenly inside the tube, reducing "hot spots" and "cold spots", thereby improving the atomization process, increasing sensitivity and peak symmetry.
Metal/carbide coatings (such as Ir, Ru, TaC): For certain elements that are prone to carbide formation (such as B, Si, V, Mo, W), ordinary graphite tubes will react with them to generate non-volatile carbides, resulting in incomplete atomization and low sensitivity. Coatings (especially precious metals) can suppress this reaction and promote the complete atomization of elements.
Effect: Obtain higher sensitivity, sharper symmetrical absorption peaks, and lower detection limits.
4. Reduce matrix interference
Functional principle: The chemical inertness of the coating can reduce the side reactions between the sample substrate (such as salts, organic compounds) and graphite tubes at high temperatures, thereby reducing the background absorption or molecular absorption interference caused by this.
Effect: Simplified the difficulty of background correction and improved the reliability of analysis results.
5. Suitable for a wider range of sample types
Functional principle: Due to its stronger corrosion resistance and anti-interference ability.
Effect: It can safely and reliably analyze complex samples with high salt content, high acidity, and high organic matter content (such as seawater, biological fluids, soil digestion solutions, petrochemical products, etc.), and ordinary graphite tubes are easily damaged under these conditions.