GC3900 Gas Chromatograph- Issue Description: The Solid Phase Microextraction (SPME) device is very compact, resembling a manual chromatography injector, typically consisting of a handle and extraction...
The head or fiber head is composed of two parts, the extraction head being a 1cm-long fused quartz fiber head coated with different stationary phases, encased in a thin stainless steel tube. The fiber head is not specified.
The stainless steel tube is freely retractable for extracting and adsorbing samples, with the handle designed for installation or securing the extraction head, ensuring long-lasting use.
Answer:
Factors Affecting Extraction Efficiency
The choice of the extraction head is the core of the solid-phase microextraction device, with the properties of its coating becoming the key to the success of the solid-phase microextraction method.
The choice should be determined by the nature of the substance to be tested, generally based on the principle of "like dissolves like." For highly polar substances to be tested, a strongly polar coating should be selected.
The small test substance is selected with a weakly polar coating.
② Sample Quantity, Container Volume Since solid-phase microextraction is a fixed extraction process, in order to ensure the effectiveness of the extraction, the sample quantity and the volume of the sample container must be carefully controlled.
Volume selection is crucial. The sample quantity and the volume of the sample container are greatly related to the results, and there exists a matching relationship between the sample quantity and the volume of the sample container.
Under larger conditions, reproducibility has significantly improved, and detection quantities have increased.
③ Extraction Time is the duration from the contact between the quartz fiber and the sample to the adsorption equilibrium. Many factors can affect the extraction time, such as partition coefficient, sample concentration, and temperature.
The rate of diffusion, sample quantity, container volume, the matrix of the sample itself, temperature, etc.
④ Inorganic Salt Usage: Adding a small amount of inorganic salts such as sodium chloride and sodium sulfate to the liquid sample can enhance ionic strength and reduce the solubility of polar organic substances in water.
The salt precipitation effect is achieved, allowing the fixed phase of the quartz fiber to absorb more analytes. Generally, this can effectively improve the extraction efficiency, but it may not be applicable to all cases.
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⑤ Altering pH Values - Just like the use of inorganic salts, altering the pH value can change the distribution coefficient between the analytical components and the sample medium, as well as between phases, which is beneficial for improving the distribution of analytical components in the sample.
The adsorption is beneficial. Due to the non-ionic polymer of the stationary phase, it is more effective for the adsorption of analytes in neutral form. Adjusting the pH value of the liquid sample prevents the separation
Polarity ionization enhances the adsorption capacity of the stationary phase.
⑥ Derivatization reactions can be used to reduce the polarity of phenolic, fatty acid, and other polar compounds, enhance volatility, and increase the ability to be adsorbed by the stationary phase. In solid-phase micro-...
During extraction, or directly add derivatization reagents to the sample, or first coat the derivatization reagents onto the quartz fiber stationary phase, under certain conditions, derivation occurs.
Biochemical reactions produce the analyte to be tested.
2. Factors Affecting Extraction Speed
① Heating Heating the sample accelerates the movement of the sample molecules, particularly enabling the analytical components of solid samples to be released from the sample more quickly, increasing the vapor pressure, and enhancing the analysis speed.
High sensitivity is particularly important for headspace analysis. However, excessively high temperatures can reduce the adsorption ability of the fixed phase in quartz fibers. Therefore, selecting an appropriate temperature is crucial.
It is very important.
② Magnetic rotor stirring, high-speed homogenization, ultrasonic Magnetic rotor stirring facilitates sample homogenization and achieves equilibrium, with the speed of rotation being higher, the speed of achieving equilibrium also increases.
The rationale for utilizing high-speed homogenizationMagnetic rotor stirring is consistent.However, the high-speed homogenization speed is far greater than that of magnetic rotor stirring, yielding better efficiency, and the extraction time is significantly reduced compared to magnetic stirring.
One-third of the sample is stirred by a force rotor. Ultrasonic treatment of the sample is more conducive to analyzing the adsorption of components, with the best effect among the three methods.
③ Treatment of the Fixed Phase The key component in solid-phase microextraction is the quartz fiber fixed phase, which is responsible for adsorption and desorption of the analyte components. If the fixed phase has been used before,
If the components above are not desorbed, they may interfere with future analytical results.
3. Solid-phase microextraction can be coupled with gas chromatography instruments (GC) and others.
Solid-phase microextraction (SPME) is a sample pretreatment technique that emerged in the 1990s. Compared to traditional liquid-liquid extraction and liquid-solid extraction, SPME is more suitable for...
Extract and concentrate volatile and semi-volatile substances in liquid or gaseous form; SPMES technology can complete sampling, extraction, concentration, and sample introduction in a single step.
Especially with the continuous improvement of techniques like automated SPME and GC-MS, the advantages of SPME technology are being fully realized.
