When HPLC UV is used as a standard, why does the peak come out so early? It came out in less than 2

This should be an impurity in the sample or solvent. It is OK to compare with a standard with a known content. However, it can be adjusted to ignore these peaks on the spectrum and not detect these two components.

It can be determined with HPLC-ultraviolet detector UV, the literature you want belongs to the research results of individuals or tissues, HPLC-UV is the ultraviolet detection of liquid phase HPLC MS is liquid chromatography and mass spectrometry - liquid chromatography-mass spectrometry.

The determination of methanol is a constant analysis and there is no free of charge. Both have high-performance liquid chromatography systems, MS stands for mass spectrometry. Sugar has no ultraviolet absorption, but it has refraction, of course, and the principle is much the same.

Trimethoprim has ultraviolet absorption, and the peak is still out, 2. Other methods are much more complicated, so you can buy other people's instruments directly, 1. Set the integration parameters, high performance liquid chromatography hplc ultraviolet detector uv high performance liquid chromatography with ultraviolet detector. Methanol and organic residues are volatile substances that can be determined by gas chromatography, especially in experimental protocols. It is recommended that you go to the "World of Chromatography"** to take a look, which can be fixed wavelength, which can be measured with an HPLC parallax refractive IR detector, or it can be full wavelength (DAD).

This ** is very professional, set the minimum peak width and the like, and you can use the area external standard method. The integral parameters of the workstation can be set, including the inside. Re-integral.

Ultraviolet atoms fluoresce, but the detectors are different, so you're going to use liquid chromatography, and there are other ways that haven't happened to you. Metaphor: Adjust the minimum integral area to; Above the larger of the two peaks, DAD stands for full wavelength scanning ultraviolet detection.

Volume-fixing?. The latter is different: UV refers to ultraviolet detector, which will be of great help to you in chromatography learning.

To make a standard and prepare a chromatography, you should try the peak time first.

Take a blank stitch and take a look.

Isn't there any reservation?

OK! The premise is that you want to use UHPLC or use a short column!

The time to peak depends on the substance you are analyzing. and whether there is a national standard or corresponding standard for the analyzed substance.

Note: How to judge whether the peak time is appropriate.

1. Replace sample analysis with reference materials. Look at the retention time and theoretical plate under the same conditions.

2. The shorter the column, the higher the peak time.

3. Ultra-high pressure liquid phase analysis can also produce peaks within 2min.

The peak time within 2 minutes is too short, and about 10 minutes is better.

Different substances, different mobile phases, different flow rates, and peak times all have an impact. It is also possible to produce a peak within 2 minutes, and the peak shape is good and stable.

1.May be affected by solvent peaks.

2.Impurities may not be completely separated.

Change the mobile phase, which means that the mobile phase conditions are not good for the separation of these two substances, first change the mobile phase conditions, reduce the polarity of the mobile phase, and reduce the flow rate. There is also a change of mobile phase, with another mobile phase to try and finally it doesn't work, you can only change the column hee hee View the original post".

These two peaks are very close to each other, if the peaks are slightly larger, they will overlap, if you want to better separate these two peaks, it is best to know the characteristics of these two peaks, such as boiling point temperature, polarity, etc., now the lack of this condition can only be explained by Pang Tong:

1. If there is a certain distance between the boiling point temperature, you can consider using the program to increase the temperature, which can increase the separation effect;

2. If the polarity is different, you can consider replacing the polar column, which can also increase the sharing effect;

3. Appropriately reducing the column temperature can increase the retention time and increase the separation effect;

4. Lengthen the capillary chromatographic column, or increase the film thickness, increase the retention time of the components as much as possible, and increase the separation effect;

5. If the sample peak is large, the injection amount can be reduced, or the split ratio can be increased, and the separation effect can also be increased;

The way I can think of to increase the degree of separation is basically the above method, for reference, other people have a way, please give advice!

The possible reasons for the non-peak of VB1 are as follows:

1. The relevant parameters of your data processing software are not set, and the peak from VB1 is outside the integration range;

2. The content in the sample is very small, and there is some loss in the pretreatment process;

3. The wavelength you set is not the maximum absorption wavelength of VB1, you can perform 3D acquisition to find out its maximum absorption wavelength.

The core reason for the constant variation of retention time is that there is no guarantee that the chromatographic detection conditions will be exactly the same for each test. The chromatographic conditions are as follows: room temperature, change in mobile phase composition, column temperature, sensitivity of the detector, etc.

You can rule them out one by one, and then you'll find out why.

If the standard is also at the position of the sample peak, it means that it is caused by matrix effect, and the standard addition method is needed for quantification; If the standard is still at the position of the original standard and separated from the sample peak, it means that the sample and the standard are not the same thing, and the sample peak needs to be recharacterized. If the sample is acidic and alkaline, and the pH of the mobile phase is similar to the sample PKA, it should be noted that the pH is in the range of plus or minus 1 of the PKA, and the retention time varies greatly

Difference: The standard is the reference standard for the determination of content by microbiological methods.

The reference substance is a standard for the determination of content by instrumental analysis or other analytical methods, both of which are provided by the China Biological Products Certification, a state-designated department.

A reference strain is a reference material used for identification, inspection, content determination and calibration of the performance of an instrument.

A standard is a reference material used for bioassays, antibiotics or biopharmaceutical medium or potency determination, expressed in potency units (u).

At present, there are 15 kinds of standards stipulated by the state, which are macroviewase, gentamicin, tyransin, kanamycin, erythromycin, chorionic gonadotropin, guitarase, bacitracin zinc, halose, synthetic oxytocin, lincozysin, streptomycin, amplase, dupilin G, and neomycin.

The use of chemical methods to determine is called the reference substance, that is, the instrument is generally called the reference substance, there are 107 kinds of national regulations, too many are not easy to play, such as morphine, amoxicillin, dexamethasone, diazepam, oxytetracycline, too much to fight, in short, according to the above principles: the biochemical method is called the standard, the chemical method is called the reference substance!

Reference and standard are two different concepts, which have been clearly defined in the Chinese Pharmacopoeia: reference refers to the reference material used for identification, inspection, content determination and calibration of the performance of the verification instrument, while the standard refers to the reference material used for biological testing, antibiotic or biopharmaceutical content or potency determination, expressed in potency unit (u). In the literature, the two concepts are often confused, and it is believed that the reference substance is the standard substance, which is just one substance and two formulations, and the reason for the error may be that some drugs have both reference and standard substances.

For example, when determining cefaclacro titer by microbiological method, cefaclor standard is used, and when determined by HPLC or UV method, a control substance is used; When phenacetin is used as a melting point calibration substance, a melting point standard is used, and when the content is determined, a control substance is used. Even standards and reference substances for the same substance may have different specifications, calibration methods, and uses. (Beijing Reference Materials Network).

Then consider the internal standard method, and find an internal standard to do the same.

Find out if there is any homemade.