The analysis and detection method of gas chromatography is one of the most important means of modern detection technology. It offers the advantages of high separation efficiency, fast analysis speed, high sensitivity, high selectivity, lower sample consumption and multi-component measurement. Therefore, it is widely used in petroleum industry, chemical industry, agriculture, environmental protection, medicine and other industries.
With the continuous improvement of automation of gas chromatographic analyzers, although automation brings convenience and speed, unfavorable factors continue to appear.
Analysts know little about the instrument itself. However, during use, the contamination or damage of the instrument accessories, the specificity of the measured sample and the analyst's working methods can cause many problems analysis impossibleI.
Therefore, the most common problems and daily maintenance methods when using gas chromatographic analyzers are summarized.
Principle of gas chromatography
Gas chromatography is a novel analysis and separation method that utilizes the gas-solid phase of each component in the chromatographic column The partition coefficient of different phases and the adsorption capacity of each component in the solid phase are different;
Components are repeatedly distributed between the two phases and pass through the chromatographic column after passing a certain length, according to the boiling point of each component. High and low exit the chromatographic column alternately;
Enter the detector, the generated ion current signal is amplified and recorded by the recorder. and the analysis chromatogram is obtained.
Common problemswith chromatography columns
They can be divided into three aspects: column fouling, clogging and loss of stationary phase.
The cause of chromatography column contamination is generally the adsorption of high boiling point contaminants, which interfere with the normal adsorption of the analytical components and stationary phase, and result in increased baseline noise Leading peaks, tailing peaks and disordered peaks and unknown peaks, etc. A common way to resolve column contamination is to age the column. Generally, the column temperature is set 30℃ lower than the temperature limit, and the column aged more than 10 hours.
Small impurity particles enter the chromatography column and cause column clogging, resulting in increased baseline current, border peaks, bifurcated peaks, shoulder peaks and other abnormalitiespeak shapes or even no peaks. This can be solved by removing a few centimeters from the head of the chromatography column.
Note that the cutting tool (e.g. a special capillary cutter or a diamond glass knife) should be used must. and the incision should be in line with the inside wall of the column. 90°;
And make sure the column cut is clean and smooth, otherwise the turbulent vortex generated at the column cut will be destroyed and adversely affect the shape of the peak. The length of the detector is also required;
Typical insertion depths into the injector and detector are 2.5 cm and 8.5 cm, respectively.
Loss of stationary phase leads to a decrease in column efficiency and problems such as baseline drift, increase in baseline current, and erratic peak shape. The severity of the decrease in the column The efficiency you canrch lowering the column temperature to room temperature;
Observe if the baseline is okay. This can be judged by a zero adjustment. If zero adjustment is possible, try cutting the head of the chromatography column a certain distance to solve the problem. If zero adjustment is not possible, it means that the stationary phase is seriously lost. and a new chromatography column must be replaced.