Gas chromatography is a chromatographic method that uses a gas as a mobile phase (carrier gas) to flow through a chromatographic column equipped with a filler for separation and measurement. The instrument used for gas chromatography is a meteorological chromatograph. The gas chromatograph consists of carrier gas source, Jinyang part, chromatographic column, column thermostat, detector and data processing system. In the injection part, the temperature of the column and detector are under control. Meteorological chromatograph is mainly used to analyze various weather and volatile organic substances, but under certain conditions, it can also analyze high-boiling substances and solid samples. At present, gas chromatograph has been widely used in petroleum industry, environmental protection, clinical chemistry, pharmacology, food industry. The gas chromatograph has also been successfully applied in the drug quality monitoring of Harbin Pharmaceutical Group's general pharmaceutical factory. For example, a gas chromatograph is used to determine the residual amount of amoxicillin acetone, dichloromethane organic solvent and residual solvent chloroform in etopril.
Advantages and disadvantages of gas chromatograph
Advantages of gas chromatograph: high separation efficiency and fast analysis speed. For example, more than 200 chromatographic peaks can be separated in a gasoline sample within two hours, and general sample analysis can be completed within 20 minutes. 2.2.2 Low sample consumption and high detection sensitivity. For example, the amount of gas sample is 1 ml, the total amount of liquid sample is 0.1 microliter, and the amount of solid sample is a few micrograms. Impurities with a content between ten parts per million and a few parts per billion can be detected with an appropriate detector. 2.2.3 Good selectivity, separation, analysis of azeotropic mixtures, substances with similar boiling points, certain isotopes, cis and trans isomers, ortho, meta, para isomers, optical isomers, etc. Wide range of applications. Disadvantages of gas chromatograph: mainly when the qualitative analysis of the components is performed directly, it must be compared with the corresponding chromatographic peak with known substances or known data, or combined with other methods (such as mass spectrometry, spectroscopy) to obtain Directly positive results. In quantitative analysis, it is often necessary to use a pure sample of a known substance to correct the output signal after detection.
Matters needing attention in the application of gas chromatograph
The general requirement is that the instrument must work under the specified conditions, and the operation should be carried out according to the rules, otherwise the results are inaccurate and meaningless. 3.1 Precautions for gas circuit system.
The most common problem with gas systems is leakage. Therefore, leak detection must be carried out frequently. The method is to use a brush or brush dipped in soapy water to detect, and the EPC system can automatically detect leaks to a certain extent.
Put the handle on the regulator valve and the needle valve to prevent fatigue failure of the ripple tube; on the contrary, the needle valve should be in the "open" state to prevent the valve sealing ring from being damaged on the valve. 3.1.3 When the pressure of the carrier gas cylinder is lower than 1.5xl06pa, because it is easy to make the pressure of the flow path unstable and the purity of the mobile phase decreases, a new gas cylinder should be replaced. 3.2 Precautions for sampling system. 3.2.1 Jinyang is faster. 3.2.2 The sampling volume should be accurate.
To avoid mutual interference between the test articles, wash the needle with the test article solvent at least three times before sampling, and then wash the needle with the test article to be analyzed at least three times. 3.2.4 Select the appropriate syringe.
After use, the microsyringe must be cleaned with methanol and other organic solvents. 3.3 Notes on the column system.
New chromatographic columns are generally tested for column performance before analysis. 3.3.2 If the chromatographic column is not used in a short period of time, it should be removed from the instrument, and the two ends of the column are plugged with a piece of silicone rubber, and placed in the corresponding column packing box to avoid contamination of the column head.
Before each shutdown, the column temperature box should be lowered below 50 degrees, and then turn off the power and carrier gas.
Each time a new column is installed, the oven protection temperature must be reset before use to ensure that the temperature does not exceed the maximum use temperature of the column.
When the column is used for a period of time, the baseline will fluctuate or ghost peaks will appear due to the high boiling point components retained in the column. At this time, the column should be aged.
When aging the chromatographic column, the pipeline behind the column should be disconnected from the detector to avoid contamination of the instrument pipeline and detector. 3.4 Notes on the detector
The carrier gas must be vented before starting the instrument. TCD must use a high-purity gas source, operate under the optimal N2 :: H2 ratio and optimal air flow rate, and the chromatographic column must undergo strict aging treatment.
Precautions for connecting the instrument. The host and recorder should be grounded, and all grounding points of the instrument should be connected together to make them equipotential to prevent mutual interference signals.
Abnormal situation and maintenance of gas chromatograph in application
The maintenance of chromatographic peaks does not occur after injection. When the chromatographic peak is not encountered, it should be checked in the order from sample injection needle, sample inlet to detector. First check whether the syringe is clogged, if there is no problem, then check whether the inlet and detector are leak-free, then check the column for breakage and leakage, and finally observe whether the detector outlet is smooth.
Resolution of the baseline problem. Chromatographic baseline fluctuations and drifts are all baseline issues. When encountering baseline problems, you should check whether the instrument conditions have changed, whether the sampling pad is aging, whether quartz wool should be replaced, and whether the liner is clean.
Chromatographic peaks are lost, and false peaks are resolved. If peak loss occurs, it can be solved by multiple dry runs and cleaning the gas circuit. If false peaks occur, the solution is also to check for leaks and remove pollution.
Here are the maintenance methods of three common problems in the work. The gas chromatograph has more failure points and longer recovery time. Therefore, the key to equipment maintenance is correct analysis of the cause.
Conclusion
There are still many problems that need to be solved in the gas chromatograph in drug inspection. The operator needs to have a deeper understanding of the working principle of the chromatograph and have a certain knowledge and experience in chromatography to implement preventive daily maintenance. Only in this way can the meteorological chromatograph play a more active role in drug inspection.
drinking bottle
Baby Drinking Bottle is made of food grade PP material, BPA Free, safe for baby. With scales on bottle, parents can control baby`s water intake, avoid excessive drinking. Made from durable polypropylene plastic, each bottle is individually shrink-wrapped to deliver the highest level of cleanliness
Products pass EN14350 test, OEM is possible, customized colors are also available, Let we know your demand, suitable recommendation would be provided within 2 days. Quality is our culture, service is also what we emphasis. Choose us, you just give order, we will do the following all things, keep you posted on order details periodically, and delivery on time.
Drinking Bottle
Drinking Bottle,Baby Sippy Cup,Baby Water Bottle,Water Drinking Bottle
​Taizhou Howawa Baby Products Co., Ltd. , https://www.howawa.com