Tetworth is a leading supplier of chromatography instruments, and its products and technical solutions are widely used in the fields of chemistry, environmental protection, food, medicine and life sciences.

1. The basic principle of gas chromatography instrument application

Separation principle of gas chromatography analysis:

If you compare a column to a fractionation column, the column is made up of many plates. Some of the space is occupied by the liquid phase coated on the support, and the other part is filled with the carrier gas (gas phase). The different materials have different partition coefficients between the two phases. When the two phases are in relative motion, the components in the sample The distribution is repeated a plurality of times in between the two phases, so that the components having a small difference in the original distribution coefficient produce a large separation effect, so that the components are separated from each other.

2. Basic composition of gas chromatography

At present, there are many manufacturers of gas chromatography on the market, and the models are different, but the basic components are similar. Basically, it consists of a pneumatic system, a detection system, a data analysis and processing system, a sample introduction system, and a column system. They have their own roles and work together, and Zui finally detects the results.

3. Pre-treatment of wine sample

For liquor samples, it is not necessary to carry out sample pretreatment, and it can be directly injected. However, it is necessary to carry out simple treatment for the preparation of wine, wine and fruit wine. For example, it is possible to perform simple distillation on the sample to remove impurities in the sample. The substance that affects the instrument can be.

4. Precautions in the wine sample

1. The injection volume should be less:

Analysis of alcohol samples by gas chromatography requires less injection. In the case of a small injection volume, the chance of contamination of the instrument is relatively reduced, and the sensitivity is also improved. Most of the current injections are automatic injections, and the injection speed can be set by the instrument.

2. The temperature should be as low as possible:

1 For the sake of the wine sample, the function of the vaporization chamber is to vaporize the wine sample into the instrument and enter the column. If the temperature is too high, it may cause sample cleavage to affect sample analysis.

2 The wine is generally separated by a capillary column. The trace sample present in the carrier gas can also be moved as a vapor at a temperature lower than the boiling point. Therefore, the temperature should not be too high.

3 Most of the detectors currently used for making wine samples are FID detectors, which are used at temperatures where the components flowing out of the column do not condense, so as to reduce pollution.

3. To make alcohol samples, the general carrier gas is nitrogen, and the purity requirement is five or more, that is, 99.999%. The purity of hydrogen is also the same requirement. The higher the purity of the gas, the better it is to protect the column and detector. Gases with low purity enter the column and detector, which can cause damage. In terms of economic efficiency, the capillary column and the detector are much more expensive than the gas, so it is necessary to pay attention to the purity requirement of the gas.

4. Always use a regulated power supply when using the instrument to make the current stable. Also, all the wires used in the lab need to be grounded. This will allow the instrument to operate normally with a stable voltage and current. Otherwise it will affect the noise of the baseline and increase the sensitivity of the instrument.

5. Be sure to pay attention to safety during the operation. Do not smoke in the instrument room. Because the instrument room has flammable gas. If you encounter an open flame, it may cause fire. Therefore, you must pay special attention when using the gas cylinder. slow. After use, except for nitrogen, other gases are turned off in time. The temperature of the instrument such as nitrogen is lowered and then turned off to protect the column.

V. Analysis of results

1. trailing peak

Analyze the reasons:

It is possible that the temperature of the vaporization chamber is low; the vaporization chamber is contaminated; the injection operation is improper; the column is not suitable; the column temperature is low.

2. The peak of the chromatographic peak appears

Analyze the reasons:

It is possible that the injection volume is too much for the column overload;

The sample agglomerates inside the system.

3. Peak tail deviation is negative

Analyze the reasons:

May be detector contamination.

4. The baseline will also rise when warming up

Analyze the reasons:

The carrier gas flow rate is not adjusted well; the column is contaminated;

5. Irregular changes in the baseline during warming up

Analyze the reasons:

The column is not aged well; the carrier gas flow rate is not adjusted well; the column is contaminated.

6. The baseline cannot be returned to zero, and the peak is flat.

Analyze the reasons:

There may be a bad grounding of the device.

7. The noise floor is large

Analyze the reasons:

There may be column contamination; there may be carrier gas contamination; vaporization chamber contamination; connection conduit contamination of the column and detector; detector contamination; air or hydrogen contamination.

summary:

Whether it is the process of wine sample or the process of analysis of results, you need to pay attention to the details, sloppy, otherwise, it will be a big mistake!