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1. liquid chromatograph

Liquid chromatography is divided into liquid-liquid chromatography (LLC) and liquid-solid chromatography (LSC) according to whether the stationary phase is liquid or solid. Modern liquid chromatograph consists of high-pressure infusion pump, injection system, temperature control system, chromatographic column, detector, signal recording system and so on. Compared with the classical liquid column chromatography device, it has the characteristics of high xiao, fast and sensitive.

Characteristics of 2. liquid chromatograph

1High pressure: liquid chromatography with liquid as the mobile phase (called carrier liquid), the liquid flows through the chromatographic column, subject to greater resistance, in order to quickly through the chromatographic column, the carrier liquid to apply high pressure. Generally up to 150~350 × 105Pa.

2High speed: the flow rate of the mobile phase in the column is much faster than that of the classical chromatography, generally up to 1~10 ml/min. The analysis time required by liquid chromatography is much less than that of classical liquid chromatography, generally less than 1h.

3High sensitivity: high sensitivity detectors have been widely used in liquid chromatography to further improve the sensitivity of analysis. Such as fluorescence detector sensitivity up to 10-11g. In addition, the sample size is small, usually a few microliters.

4Wide range of application: comparison of gas chromatography and liquid chromatography: gas chromatography has the advantages of good separation ability, high sensitivity, fast analysis speed, convenient operation, etc., but limited by technical conditions, substances with too high boiling point or substances with poor thermal stability are difficult to analyze by gas chromatography. The liquid chromatography method only requires that the sample can be made into a solution, and does not need to be gasified, so it is not limited by the volatility of the sample.

3. liquid chromatograph operation five steps

1Preparation

① Prepare the required mobile phase, filter with a suitable 0.45 filter membrane, and degas with ultrasound for 20min.

② Replace the appropriate column (pay attention to the direction) and quantitative loop according to the needs of the sample to be tested.

③ Prepare the standard solution of the sample and filter it with a suitable 0.45um filter membrane.

Check whether the components of the instrument are connected normally, including the power line, data line, ground line and infusion pipe.

2Start-up

① Turn on the power supply, turn on the detector and infusion pump once, and turn on the computer, printer and computer monitor when the self-test of the detector is finished and the measurement status is displayed.

② Replace the mobile phase with side by side bubbles.

③ Put the stainless steel filter head of the pipeline into the prepared mobile phase reservoir bottle

④ Turn the exhaust valve of the pump counterclockwise, about half a turn, and then loosen the exhaust valve.

⑤ Press the pump (purge) key, start flushing at a flow rate of 5.0 ml/min for about 2 minutes when the green light is on, press the (stop) key when there is no bubble in the pipeline, and reset the flow rate value.

3Design parameters

① Flow rate setting

② Wavelength setting

③ Set to complete press the run (run) button

④ Operation of chromatographic workstation: Execute → Open "Online Workstation" → "Channel 1" → "OK" → "Data Acquisition" in turn, perform zero correction, view the baseline, and close the baseline after confirming that the baseline is stable. Sample injection can be performed.

4Injection

① Before injection, set the (A/Z) detector key to zero to check whether the base number is 0mv. If there is any deviation, the (zero point correction) key is used for debugging.

② Clean the syringe with the sample, eliminate bubbles, and adjust the manual injection valve rod to the (Load) position after extracting the appropriate amount. After the sample is injected into the injection valve, adjust it to the (Inject) position, and then complete the injection operation steps and enter the online workstation to automatically collect data flow.

5System cleaning

Since the mobile phase system contains buffer salts when analyzing samples, 10% methanol aqueous solution needs to be used. After washing for 40 minutes at 1.0 ml/min, methanol reagent needs to be replaced. After washing for 40 minutes at the same 1.0 ml/min, the (stop) key stops the pump and shuts down.

Working principle of 4. liquid chromatograph

First, the mobile phase is pumped into the system by a high-pressure pump, and the sample solution enters the mobile phase through the sample injector and is loaded into the chromatographic column (stationary phase) by the mobile phase. Since each component in the sample solution has different distribution coefficients in the two phases, when the two phases move relative to each other, after repeated adsorption-desorption distribution processes, each component has a large difference in moving speed, is separated into individual components and flows out of the column in turn. When passing through the detector, the sample concentration is converted into electrical signals and transmitted to the recorder, and the data is printed in the form of maps. The high-xiao liquid chromatograph mainly has injection system, infusion system, separation system, detection system and data processing system. Liquid chromatographs are often distinguished by adsorption column chromatography, distribution column chromatography, ion exchange column chromatography, gel column chromatography, and four types of chromatography named according to their working principles.