The solvent management system of the liquid chromatography system is responsible for providing a suitable mobile phase, which is often composed of a mixture of multiple solvents such as methanol, acetonitrile, water, etc. Different samples and separation requirements require different compositions and mobile phases. For example, in reverse phase liquid chromatography, the mobile phase can affect the elution sequence of components, and the weaker the elution ability of components. Pumps play a crucial role in solvent management systems, as they can continuously and stably transport the mobile phase, ensuring the smooth progress of the chromatographic process. Common pumps include binary pumps and quaternary pumps. Quaternary pumps can mix and transport four solvents, allowing for more flexible adjustment of the composition of the mobile phase.

The injection system is responsible for introducing the sample to be analyzed into the chromatographic column. It requires accurate control of the injection volume to ensure the accuracy and repeatability of the analysis results. Modern liquid chromatography systems generally use automatic injectors, which can accurately extract and inject samples according to preset programs, improving analysis efficiency.

The core of the separation system is the chromatographic column, which is filled with a specific stationary phase. There are various types of stationary phases, such as silica gel and bonding, and different types of stationary phases are suitable for analyzing samples with different properties. In the chromatographic process, the sample is continuously distributed between the stationary phase and the mobile phase, and each component gradually separates due to different forces with the two phases.

The detection system is used to monitor and determine the separated components. Common detectors include ultraviolet detectors, fluorescence detectors, etc. UV detectors are widely used for quantitative analysis of components by measuring the absorption of specific wavelengths of ultraviolet light by the sample; The fluorescence detector detects based on the fluorescence characteristics of the sample and has high sensitivity.

The data processing system is responsible for collecting, processing, and analyzing the signals output by the detector. It can record the retention time, peak height, peak area and other information of chromatographic peaks, and determine the content and purity of each component in the sample by comparing with standard samples or calculating using relevant software.

Calibration method for liquid chromatography system:

1. Appearance and integrity inspection:

-Check whether all components are complete, including infusion pump, sampler, chromatographic column, detector, etc., and whether there is any damage, deformation, corrosion, etc. on the appearance.

-Check if all connecting pipelines are intact, without any damage, aging, leakage, or other issues, to ensure that the pipeline connections are tight.

2. Function check:

-Infusion pump: Turn on the infusion pump and check if it can operate normally and if there are any abnormal noises or vibrations. Check whether the pressure display of the pump is normal and whether it can work stably within the set pressure range. At the same time, check the flow rate adjustment function of the pump to see if it can accurately set and stably output different flow rates.

-Injector: For manual injectors, check whether their operation is smooth, whether the injection needle is blocked or damaged, and whether the injection accuracy meets the requirements. For an automatic sampler, in addition to checking the status of the injection needle, it is also necessary to check whether its functions such as injection sequence, injection volume accuracy, and repeatability are normal.

-Detector: Different types of detectors have different calibration methods. Like a UV detector, check whether its light source emits light normally and whether the wavelength adjustment is accurate; The fluorescence detector needs to check whether the excitation wavelength and emission wavelength settings are accurate, and whether the sensitivity is normal. At the same time, check whether the baseline of the detector is stable and whether there is any abnormal noise or drift.

-Chromatographic column: Check whether the appearance of the chromatographic column is damaged and whether the column joints are intact. Check if the identification of the chromatographic column is clear, including column length, inner diameter, packing type, and other information.

3. System adaptability test:

-Theoretical tray number determination: Select appropriate standard substances, such as naphthalene, prepare a solution of a certain concentration, and inject it for analysis under specified chromatographic conditions. Calculate the theoretical plate number based on the retention time and half width of the chromatographic peak to evaluate the separation efficiency of the chromatographic column.

-Separation determination: Use a mixed standard solution containing multiple components to perform separation analysis under selected chromatographic conditions. By measuring the retention time, peak width, and other parameters of adjacent components, the separation degree is calculated to check whether the system's separation ability for different components meets the requirements.

-Repeatability test: Inject the same concentration of standard solution multiple times in a row, observe the consistency of retention time, peak area, or peak height parameters of each injection to evaluate the repeatability of the system.