How to maintain the liquid chromatograph?

1. HPLC water source. Specialized pure water or ultrapure water machine; Re-distilled with deionized water; Re-distilled water twice or three times; Water purifier similar to home use; Pure water or distilled water bottled on the market; The above water is divided by the first item. Water can be used for gradient elution, and the rest of the water is difficult to use for gradient elution. Regardless of the route used, the application of fresh water to the mobile phase preparation means that the higher the water quality, the shorter the settling time. The ideal HPLC water should be 18.2 MΩ of ultrapure water and pass 0.22 μm filter to remove heat, organics, inorganic ions, and air.

2. Several basic rules should be followed when maintaining the instrument.

A, a rule. When the system fails, you can tentatively change certain states and change one parameter at a time. For example, to limit the problem of de-dimensionalization of chromatographic peaks, it is possible to change the mobile phase, change the protection column, change the analytical column, etc. in order. Doing some simple change steps may solve the problem.

B. Secondary comparison rules Before the hands-on inspection, the fault has been identified, or the solution to the failure has been determined. In other words, the solution has already been found. For example, during the injection process, the peak value of the internal standard was found to be low, and the repeatability could be repeated. If it happened to be low, it was a bubble in the quantitation tube. This rule can be used to examine the situation after the system has changed. Change flow backwards Two standards can be entered before the formal injection to check the stability of the retention time and the stability of the chromatographic peaks. If there are extra peaks in the gradient elution, you can elute it once with a gradient of no load (Is it really a problem?). Use this rule to avoid unnecessary changes and to determine the corrective action as soon as possible.

C. Substitution Rules Substituting suspect parts with good parts is the best way to find faults. If you suspect that the detector caused noise, replace it with a good detector. If the fault is eliminated, there is a problem with the replaced detector. The size of the application of this rule is very large and small, from the replacement of the entire component to the replacement of printed circuit board integrated block.

D. Replacement Rule This rule is used together with the substitution rule. After a good part replaces a suspicious part, the situation is not improved and the original part should be replaced. This minimizes maintenance costs and also prevents overstocking of parts. This rule applies only to a single failure. The replacement principle does not apply to the following situations: New parts are damaged (such as pump gaskets) when removed; parts are low in price (such as column lining filters); risk of damage if the original part is reinstalled; regular replacement part.

E,. The reference condition rule usually has two reference conditions: 1 standard reference condition; 2 test reference condition. Standard reference conditions, also called standard test conditions, are conditions that can be easily verified from one system to another and from one laboratory to another. The data measured with this condition helps to identify actual test and system problems. If the system pressure rises under certain test conditions, the pressure is normal under standard conditions. This shows that system abnormalities are caused by changes in the laboratory.

The test reference conditions are used to check the daily working conditions of the normal system. To choose the most convenient method to verify this condition. Two calibration chromatograms can be printed daily for comparison, checking for changes in retention time, peak width, and system pressure. The slope of the peak, the number of columns in the column, and other parameters were found to have changed compared to the original chromatogram, indicating that problems may have occurred during the operation of the system. Of course, the problem does not come into consideration with the actual analysis procedure. It is not immediately clear by looking up the standard reference chromatogram.

F. Record Rules This rule is often overlooked. It should be recorded after every maintenance and troubleshooting. For example, it is impossible and time-consuming to systematically analyze problems for a particular fault in a system because it is not recorded. From a long-term point of view, the specific faults that occur in the system are also extremely important for future operations. Each instrument should be provided with a maintenance log book, including the date, the location of the fault, the phenomenon, the cause of the problem, the solution to the problem, and the results. Another point to note is that the parts that are tried or replaced must be labeled.

G. Predicting rules Persons with maintenance practices and maintenance habits should be able to predict system failures, and usually spend more time on maintenance. The system will use the reduction of failures as a reward, and it also eliminates chain-linked damage. For example, if you do not pay attention to maintenance at all times, the pump's sealing gasket will be broken, causing leakage of the mobile phase and corrosion of the pump and other components. Being good at maintenance can save time and money, rather than the instrument controlling the operator. For example, when you start work or finish work every day, you find that the life of the lamp causes baseline drift and the lamp is replaced. If you wait until the lights are completely broken, you need to stop and the damage may be higher than the cost of a light.

H. Buffer Rules This rule reminds you to wash the system's buffers when shutting down. Residual buffers in the system can cause wear, corrosion, and blockage. In addition, physiological buffers are highly susceptible to bacteria and mold. The ideal rinse is a mobile phase of the same composition without a buffer. Do not store pure water in the system to prevent the growth of bacteria. In water, 10% organic solvent or 0.02-0.05% sodium azide can be added. In the laboratory should be flushed according to the following procedures: rinse with pure water for 30 ~ 60min (1mL/min) and then rinsed with methanol for 30min after shutdown. Do not flush organic solvents as soon as you turn on the machine, otherwise the inorganic salts will precipitate in the system and cause adverse consequences.