Key Points for the Daily Maintenance of Solid-Phase Extraction Instruments: Essential Measures to Extend Instrument Lifespan and Ensure Data Reliability

 **Author:Orginal from Internet

Solid-phase extraction instruments are central to the sample preparation process and are widely used in various physical and chemical testing applications, including environmental monitoring, food testing, pharmaceutical analysis and water quality testing. These instruments primarily utilise negative pressure adsorption and liquid elution to separate impurities from samples and enrich target compounds; their operational stability directly determines the recovery rate and reproducibility of sample preparation, ultimately affecting the accuracy of the entire set of test data.

In day-to-day laboratory work, whilst most laboratory staff focus on optimising analytical methods, they often overlook routine instrument maintenance. This can lead to issues such as unstable vacuum pressure, residual liquid, tubing leaks and uneven flow rates at the ports, which not only shorten the instrument’s service life but also cause deviations in experimental data and excessive variations in parallel sample results, thereby increasing the cost of reworking experiments. Carrying out standardised routine maintenance is fundamental to ensuring both the long-term operation of the instrument and the reliability of analytical data. Taking into account actual laboratory usage scenarios, the key maintenance points for the entire process are summarised as follows.

I. Pre-use inspection: Avoiding operational risks at source

Basic checks prior to switching on the instrument are a low-cost, highly efficient maintenance procedure that enables the early detection of potential faults, thereby preventing interruptions during experiments that could affect sample analysis. First, carry out a visual inspection of the exterior and the chamber to check whether any eluent, sample residues or solid impurities from the previous experiment remain inside the instrument chamber. If any liquid residue is present on the inner walls of the chamber, it must be thoroughly wiped clean using lint-free absorbent paper to prevent cross-contamination between different batches of samples and to eliminate data errors caused by matrix interference at source. Secondly, inspect the sealing components. Sealing pads and O-rings are core components for maintaining a negative pressure environment; prolonged use can lead to ageing, deformation and the accumulation of particulate matter. Before switching on the instrument, check that the surface of the sealing pads is flat and remove any fine solid-phase extraction packing material or impurity powders lodged in the gaps to ensure that each port is tightly sealed.

At the same time, carry out an inspection of the tubing and connection points to check whether the external negative pressure tubing shows any signs of kinking, crushing or cracking, and whether the tubing connections are loose or detached. Deformation of the negative pressure tubing will directly result in insufficient negative pressure within the chamber, causing uncontrolled flow rates during the elution, activation and washing steps, and leading to incomplete enrichment of the target compounds. Finally, carry out a no-load negative pressure test: without placing an extraction column in the chamber, activate the instrument’s negative pressure system to observe how the chamber pressure is maintained. If the pressure drops rapidly, this indicates a leak; in this case, inspect all sealing points and tubing connections one by one, and only proceed with the formal experiment once repairs have been made.

II. Standard Operating Procedures During Operation: Minimising Irreversible Wear and Tear on the Instrument

Improper operation of the instrument is the primary cause of damage to the equipment and a significant factor in data fluctuations; therefore, operational procedures must be strictly adhered to during experiments to minimise wear and tear on the equipment. During the sample injection stage, control the droplet placement to prevent sample solutions and eluents containing strong acids or alkalis from splashing directly onto the side walls of the chamber, the sealing gasket or the vacuum port. Prolonged contact with corrosive solvents will corrode the chamber material, accelerate the ageing of the seals and cause localised contamination, thereby affecting the results of all subsequent sample analyses.

Strictly control the rate at which negative pressure is adjusted; under no circumstances should maximum negative pressure be applied immediately upon switching on the equipment. A sudden rise in negative pressure may cause the packing material in the extraction columns to become dislodged, which not only affects the efficiency of sample extraction but may also result in fine particles being drawn into the negative pressure piping, causing blockages.

During the experiment, observe the rate at which the liquid falls from each well at regular intervals. Should an abnormal flow rate be detected in any single well, pause the experiment immediately to investigate the issue, thereby preventing the liquid from being sucked back into the main vacuum control system. Furthermore, under no circumstances should the chamber lid be forced open or closed during the experiment, as this may damage the hinges and sealing mechanisms through impact, compromising the chamber’s integrity and seal.

III. Thorough cleaning after the experiment: removing residual contamination and preventing blockages in the pipework

Immediate cleaning following the completion of an experiment is a key part of routine maintenance and comprises three parts: chamber cleaning, pipework cleaning and cleaning of the waste liquid collection system. Firstly, empty the waste liquid collection container; if waste liquid is left to accumulate for long periods, it will produce volatile gases that corrode the instrument’s internal vacuum components, whilst the aerosols formed by the evaporation of the waste liquid will adhere to the inner walls of the chamber, forming stubborn contaminants. After emptying the waste liquid, wipe the interior of the chamber with a neutral, phosphate-free cleaning agent. For chambers that have come into contact with organic solvents or strong acids and alkalis, wipe them first with pure water and then with anhydrous ethanol to remove any residual moisture, ensuring the chamber is completely dry.

Secondly, it is essential to clear the negative pressure pipework. Traces of sample residue and packing powder drawn in during experiments can easily accumulate on the inner walls of the pipework; over time, this leads to narrowing of the pipework and impaired negative pressure transmission. After each experiment, the internal pipework can be flushed by drawing anhydrous ethanol under negative pressure without a load, thereby dissolving any residual organic contaminants and maintaining the patency of the pipework. Finally, maintain the sealing components. Remove the detachable gaskets, wipe them clean and lay them flat to air-dry naturally, avoiding folding or compression that could cause permanent deformation. Never use high-temperature drying methods on rubber sealing components, as this may cause the rubber to age and crack.

IV. Long-term Storage and Periodic Maintenance: Ensuring the Long-term Stability of the Instrument

Differentiated maintenance plans should be drawn up for the two scenarios of short-term disuse and long-term inactivity. Following routine daily use of the instrument, it is sufficient to carry out basic cleaning, switch off the power supply and cover the unit with a dust cover to prevent laboratory dust from entering the chamber and tubing. If the instrument is not to be used for more than a week, comprehensive moisture-proof maintenance is required: thoroughly empty all waste liquids, flush and dry the entire negative-pressure pipework, wipe down the exterior of the entire unit, and leave the chamber cover slightly ajar to prevent the accumulation of moisture in a sealed environment, which could lead to mould growth and corrosion of internal metal components and electrical connections.

At the same time, maintain a regular maintenance log; carry out a comprehensive leak detection check and inspection of seals once a month, and perform a thorough decontamination of the instrument’s internal exhaust channels and negative pressure buffer zones every three months. Even if the instrument shows no obvious faults, it is necessary to carry out regular maintenance on wear-and-tear parts and replace slightly aged seals in good time; do not wait until faults such as leaks or insufficient negative pressure occur before carrying out repairs, so as to avoid sudden breakdowns disrupting the progress of experiments.

V. The Significance of Maintenance: Balancing Equipment Lifespan and Data Accuracy

Many laboratories equate instrument maintenance with superficial cleaning, overlooking the direct link between maintenance and test data. Inadequate sealing can lead to unstable negative pressure, resulting in sample elution recovery rates and parallel deviations exceeding acceptable limits; blocked tubing can cause inconsistent flow rates, making it impossible to standardise sample preparation conditions across a single batch; and residual contaminants can cause cross-contamination, leading to false-positive test results.

Standardising routine maintenance not only reduces the frequency of instrument breakdowns and repairs, thereby lowering the costs of replacing parts and carrying out major repairs whilst extending the instrument’s service life, but also ensures that the negative pressure environment and flow rate conditions remain consistent for every experiment. This makes the entire sample preparation process controllable, eliminates systematic errors at the equipment level, and lays a solid foundation for the reliability of test data.

Conclusion

The maintenance of solid-phase extraction instruments does not involve complex procedures; the key lies in regularity and standardisation. From pre-start-up checks and standard operating procedures during experiments to thorough cleaning after experiments and periodic maintenance during periods of inactivity, implementing maintenance details throughout the entire process not only reduces instrument failures and extends the service life of the equipment, but also helps to avoid experimental data errors caused by equipment-related factors. For laboratory sample preparation work, standardised daily maintenance is not an additional task, but an essential step in ensuring the accuracy of test results and the efficient operation of experimental procedures.