The sample shall be dissolved as much as possible in solvents that are mutually soluble with the mobile phase. Except for special designation, the resolution of the sample HPLC column may be reduced if it is dissolved using a strong solvent. Besides, the sample solution shall be pre-filtered using a needle filter before injection. Frequent changes in the composition of the mobile phase will accelerate the reduction of column efficiency.
HPLC column is filled with high-pressure slurry and can withstand high pressure. In order to obtain the best separation effect, please do not exceed 200kgf when using, and avoid the sudden rise or change of pressure, otherwise, it will cause the destruction of silica gel filler and reduce the service life of the chromatographic column. The maximum operating temperature shall not exceed 60°C except for special requirements.
Reason ① Column temperature fluctuates. (Even small changes in temperature can cause baseline fluctuations. They usually affect differential detectors, conductivity detectors, lower-sensitivity UV detectors, or other photoelectric detectors.) ② The mobile phase is not uniform. (Baseline drift caused by changes in mobile phase conditions is greater than temperature-induced drift.) ③ The flow cell is polluted or has gas. ④ Detector outlet is blocked. (The high pressure caused the flow cell window to rupture, resulting in a noise baseline.) ⑤ Improper mobile phase ratio or flow rate change ⑥ The column equilibrium is slow, especially when the mobile phase changes.
⑦ Mobile phase contamination, deterioration or mixing with low-quality solvents ⑧ The highly retained material (high K ‘value) in the gadolinium sample was eluted as a gimmick peak, showing a gradual rising baseline. ⑨ The use of recycled solvents is not recommended. The detector is not adjusted. ⑩ The radon detector is not set at a large absorption wavelength.
Solution ① Control the temperature of the column and mobile phase, and use a heat ex-changer before the detector. ② Use HPLC-grade solvents, high-purity salts, and additives. The mobile phase is degassed before use, and in-line degassing or helium degassing is used during use. ③ Rinse the flow cell with methanol or other strong polar solvents. If necessary, 1N nitric acid can be used. (Do not use hydrochloric acid) ④ Remove the obstruction or replace the tube. Refer to the detector manual to replace the flow cell window. ⑤ Change the ratio or flow rate. To avoid this problem, check the mobile phase composition and flow rate regularly. ⑥ Rinse with a medium-strength solvent. When changing the mobile phase, wash the column with 10-20 times the volume of the new mobile phase before analysis. When using ion-pairing reagents and buffer salts, pay more attention to the equilibrium column. ⑦ Check the composition of the mobile phase. Use high-quality chemicals and HPLC-grade solvents. ⑧ Change the analysis conditions. Use a guard column and, if necessary, periodically flush the column with a strong solvent between injections or during analysis. ⑨ Reset the baseline. Use a new mobile phase. ⑩ Adjust the wavelength to a large absorption wavelength. Re-select the detection wavelength.