Preservation and Regeneration of the HPLC Column

1.The preservation of the HPLC column

(1) Maintenance of the reversed-phase column after the daily experiment:
The buffer or saline mobile phase was used and rinsed with 10% methanol/water for 30 minutes after the experiment was completed. The salt in the column was washed off and rinsed with methanol for 30 minutes.

(2) long-term preservation of the HPLC column:
If the column is to be stored for a long time, it must be stored in a suitable solvent. For the reverse phase column, it can be stored in pure methanol or acetonitrile. The normal phase column can be stored in pure n-hexane after dehydration. The ion exchange column can be stored in water (containing preservative sodium azide or thimerosal). Plug the plug that came with the purchase of the new column. The stored temperature is preferably room temperature.

2. Regeneration of the HPLC column

Because the HPLC column is a consumable, as the time of use or the number of injections increases, the peak height decreases, the peak width increases, or the shoulder peak appears. Generally, the efficiency may be reduced.

(1) Regeneration of the reversed-phase HPLC column: sequentially using 20-30 times the column volume of methanol: water = 10:90 (V/V), acetonitrile, isopropanol as the mobile phase to wash the column, and then Rinse the column in the reverse order. Such as

(2) Regeneration of normal phase HPLC column: The column is washed with n-hexane, isopropanol, dichloromethane, and methanol as the mobile phase in the order of 20-30 times column, and then the column is washed in the reverse order. It is to be noted that the above solvents must be strictly dehydrated.

Preservation and Regeneration of the HPLC Column

Pipetting Method of Pipette

Pipetting methods for pipettes are divided into two types, namely, forward pipetting and reverse pipetting.

1. Forward pipetting

This technology uses a blow-out function to ensure complete transfer of liquid. Press the pipette button to stop. Put the suction nozzle into the liquid surface 2-3mm, gently release the button to return to the origin. Carefully lift the applicator and dock on the container wall to remove excess liquid.

Press the button to the stop point and the liquid is discharged. Hold the button for a while and continue to press the button to the second stop point (ie, blow out). This step will empty the nozzle to ensure accurate liquid transfer. Release the button and return to the origin. If you need to change the nozzle, continue to pipette.

2. Reverse pipetting

Using this technique, more than the set range of liquid will be inhaled, and the pipetting does not require a blowout function so that excess liquid remains in the pipette.

This technique is recommended when transferring highly viscous liquids, bioactive liquids, easily foaming liquids or very small amounts of liquid. Press the pipette button to the second stop point, immerse the nozzle at 2-3mm below the liquid level, and gently release the button to return to the origin.

Carefully lift the applicator and dock on the container wall to remove excess liquid. Tap the button to the stop point, exit the set range, and continue to hold down the button, the liquid will remain in the pipette without being transferred. The excess liquid is discarded with the suction nozzle or returned to the original container.

Pipetting Method of Pipette

Features of Vacuum Pumps

What is a vacuum pump? The vacuum pumps are a rotary variable displacement vacuum pump that must be used with a foreline pump. It has a large pumping speed over a wide pressure range and is insensitive to dust and water vapor in the extracted gas. It is widely used. Metallurgy, chemical, food, electronic coating, and other industries.

Vacuum pump features

(1) Large pumping speed over a wide range of pressures;
(2) The compression is relatively low, and the effect on hydrogen gas pumping is poor;
(3) There is no compression in the pump chamber, no exhaust valve.
(4) There is a gap between the rotor and between the rotor and the casing, no lubrication, and the friction loss is small, which can greatly reduce the driving power, thereby achieving a higher rotation speed;

At present, vacuum pumps have been widely used in metallurgy, chemical, food, electronic coating, and other industries. Therefore, the quality of the vacuum pump determines the development of our metallurgical, chemical and other industries, then we need to pay attention to some related matters when using the vacuum pump, and protect it to the maximum extent.

If the volatile organic solvent is distilled, the organic solvent is absorbed by the oil, which increases the vapor pressure, thereby reducing the evacuation efficiency. If it is water vapor, the oil becomes an emulsion and the vacuum pump is pumped.

Features of Vacuum Pumps

QuEChERS Method to Overcome Matrix Interference

Extraction is often susceptible to matrix interference. One analytical method is fine in this matrix but can become problematic in another matrix. If we encounter such a situation, how can we improve the QuEChERS method to overcome it?

For pesticide residues, most of the food samples do not exhibit matrix interference except for some dry and greased samples. However, for some complex samples such as tea, traditional Chinese medicine, spices, liver and citrus oil, regardless of the QuEChERS method we apply, there is always the adsorption of the substrate on the pesticide residue. This is related to the method itself.

When the matrix contains impurities similar in structure to the analyte, it is difficult to purify it by the sample pretreatment process. Of course, some means such as adjusting the extractant, adjusting the pH, adding salt, changing the volume ratio, adding water, adding adsorbent can be of some help.

For example, acidic herbicides like phenoxyalkanoic acids tend to form covalently bonded residues. Such legally used pesticides are quite typical and therefore must be released prior to liquid-liquid extraction. Usually, we can firstly perform alkaline hydrolysis for 30 minutes by adjusting the pH to 12, and then have it return to neutral for QuEChERS extraction.

QuEChERS Method to Overcome Matrix Interference

A Brief Introduction of QuEChERS

As an acronym for Quick, Easy, Cheap, Effective, Rugged and Safe, the method of QuEChERS achieves as a variety of sample preparation and clean-up techniques for the analysis of multiple pesticide residues in the field of agriculture.

Originally designed for the analysis of fruits and vegetables, QuEChERS extends its range to more agricultural products nowadays. After published at USDA in 2003, QuEChERS has gained significant achievement, combining few easy preparation steps and extending the range of analytes replace the old and interminable extraction methods.

The rapid growth of QuEChERS is driven by the emerging need to determine trace amounts of analytes. And the expansion of the QuEhERS shows that it is not only a method of sample extracting and cleaning-up in the lab, but also the solution of detecting lots of pesticides, herbicides, fungicides, antibiotics, and other compounds throughout the entire food industry.

QuEChERS is now a generic technique with many modifications. And all modifications have the same mission: quick and easy sample extraction and clean-up.

A Brief Introduction of QuEChERS

Some Tips In QuEChERS D-SPE?

Why choose anhydrous magnesium sulfate as a water remover?

In the d-SPE purification process, the moisture content plays a crucial role in the purification effect of PSA. The lower the moisture content, the better the purification effect of PSA. Experiments show that the water removal effect of MgSO4 is much better than that of NaSO4.

Why introduce GCB (graphitized carbon black) in d-SPE?

The experimental results show that when a large amount of pigment is present in the sample, as the number of injections increases, the pigment will seriously contaminate the liner and the column, which will result in distortion of the later results and increase the frequency of maintenance of the instrument.

GCB is produced by heating carbon black to an inert atmosphere at 2700 °C to 3000 °C. The graphitized carbon black surface is a planar hexagon composed of six carbon atoms. It is mostly used for the removal of pigments in pesticide samples. At the very beginning, activated carbon was widely used for the removal of pigments, but the adsorption of activated carbon was too strong (irreversible adsorption), resulting in a low recovery rate of many pesticides. Thus it has been slowly replaced by graphitized carbon black in recent years.

Some Tips In QuEChERS D-SPE?

Benefits of Bottle-Top Dispenser

Generally speaking, bottle-top dispenser which is a scientific device could improve the wide application, safety performance, speed and reliability. In addition, it could save your time and work, even protect you and your samples. To be more specific, the advantages of the bottle-top dispenser are as follows:

 

1. It’s convenient to use bottle-top dispenser, which ensures the lab security. It’s time-saving and labor-saving for the reason that every bottle could have its own dispenser. In addition, the enclosed environment of solvent could eliminate the risk of accidental splashing. The smoke is under control so that there is no potential danger for human bodies.

2. The accuracy of the bottle-top dispenser is about 0.5%-0.6%. Apart from that, the narrow tube makes it more easy to dispenser in small containers whose volume is 1-5ml.

3. It could not only help daily and complicated lab working but also accelerate working space and improve total productivity. For example, if a mass of samples (50-150) need to be produced without mistake, it could easily speed up working procedure to minimize the risk of contamination.

Benefits of Bottle-Top Dispenser