Method for eliminating pseudo chromatographic peak in chromatographic analysis
In chromatographic analysis, many chromatographers often encounter false peaks. This phenomenon brings great interference and influence to normal chromatographic analysis. To solve this problem, we must first understand the cause of the false peak.
The simplest case is that the mobile phase used absorbs at the detection wavelength, and if the solvent is not absorbed at this wavelength, a "cavity" will appear in the mobile phase, and the inverted peak will appear after passing through the column.
As for the cause of false peaks, it can be explained as follows:
Usually there may be two effects between the sample (X) and the mobile phase (M) —synergistic sorption and competitive sorption.
Assuming that the sample molecule X is not detectable (no UV absorption), the mobile phase component M is detectable. M is often an impurity in the mobile phase, and X may be an impurity or component that dissolves in the sample solvent, or it may be a real sample component. Under the effect of co-adsorption, if tM is less than tX, the mobile phase component first leaves the column, then M leaves the column first with an inverted peak, and then X produces a positive peak; if the retention times of M and X are opposite, that is, tM is greater than tX, then X First leave the column to produce the inverted peak, and then the outflowing M produces the positive peak.
In ion-pair chromatography, the mode of cooperative adsorption is used. In reversed-phase or normal-phase chromatography, there is competition rather than synergy, which results in different forms of pseudo-peaks: the first-out pseudo-peak is a positive peak, and the later-out pseudo-peak is an inverted peak.
Once the false peak appears, you can consider using the following ideas to correct it:
(1) Use pure reagent as mobile phase. The mobile phase is prepared with high-quality ion-pair reagents and buffer substances, and the sum of all kinds of reagents should produce the smallest false peak effect.
(2) Dissolve the sample in the mobile phase. Dissolving the sample with other solvents may produce false peaks or cause false peaks. Dissolving the sample with mobile phase can reduce the chance of false peaks.
(3) Enter the smallest volume of sample solution. Pseudo-peaks are often proportional to the sample volume, and the injection volume of ion-pair chromatography is less than 50 microliters.
(4) Pre-process the sample. Impurities in the sample will contribute to the appearance of spurious peaks.
If the above method can not remove the false peak, it can be treated as a special interference peak, that is, as a special component. Change the chromatographic conditions to change the position of the false peak and avoid the disturbed peak.
The dining table and chair combination in a restaurant refers to the combination of tables and chairs used for dining. According to different needs and styles, restaurant dining table and chair combinations can be classified into various categories. The following will classify and introduce common dining table and chair combinations in restaurants.
1. Classified by purpose
1) Dinner table and chair combination: mainly used in formal dining venues, such as high-end restaurants, banquet halls, etc. The combination of dining tables and chairs usually uses high-end materials such as solid wood, marble, etc. The chairs are generally equipped with soft cushions to provide a comfortable dining experience.
2) Fast food table and chair combination: mainly used in fast food restaurants, coffee shops, and other fast-food restaurants. The combination of fast food tables and chairs usually adopts a simple and practical design. The tables are generally small, and the chairs are generally made of plastic or metal materials, which are easy to clean and move.
3) Outdoor table and chair combination: mainly used in outdoor dining venues, such as outdoor restaurants, balconies, etc. Outdoor table and chair combinations usually use materials with special treatments such as waterproof and anti-corrosion, such as aluminum alloy, plastic, etc., which have the characteristics of durability and easy cleaning.
2. Classify by Style
1) Modern style table and chair combinations: Modern style table and chair combinations usually adopt a simple and streamlined design, emphasizing practicality and comfort. The combination of modern style tables and chairs is suitable for modern restaurants, cafes, and other places.
2) European style table and chair combinations: European style table and chair combinations usually adopt gorgeous carved and curved designs, emphasizing details and decoration. The European style table and chair combination is suitable for high-end restaurants, banquet halls, and other places.
In summary, restaurant table and chair combinations are classified based on factors such as purpose and style. Different classifications are suitable for different types and needs of restaurants, and choosing the appropriate combination of dining tables and chairs can provide a better dining experience and comfort for the restaurant.
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