GC-7890 supplied by Shanghai gas chromatograph manufacturer

GC-7890 supplied by Shanghai gas chromatograph manufacturerThe instrument adopts a fully microcomputer control system, and the bus control platform of * can modularize and expand the chromatographic system; Large screen LCD display in Chinese/English, displaying rich and intuitive content; New digital design, highly integrated electronic circuit, excellent reliability and anti-interference ability, Chinese keyboard style operation, convenient parameter setting and operation. This instrument can be widely used for routine analysis of control and detection in power, environment, medicine, pesticides, petroleum, coal, commercial inspection, epidemic prevention, universities, scientific research, and chemical industry. It can also be modified into a chromatograph according to different user needs.

Main technical indicators:

A 320 × 240 graphic large screen is used to display both Chinese and English, with simple and intuitive parameter settings;

● Comprehensive self diagnostic function, which enables users to conveniently check the location and type of faults;

A reliable anti-interference system ensures that power fluctuations or momentary power outages will not affect the normal operation of the instrument;

Complete temperature overheating protection and platinum resistance open circuit and short circuit alarm functions to ensure that the temperature does not lose control;

● Carrier gas pressure monitoring system to achieve the function of protecting chromatographic columns, TCD, and ECD;

Adopting advanced FLASH memory system, data protection is no longer trapped by battery failure;

The highly stable and sensitive microcurrent amplification technology significantly improves the detection limit of FID;

The new thermal conductivity detector has higher sensitivity;

The instrument can be equipped with a built-in AD conversion circuit for direct digital output of chromatographic signals;

The instrument can be optionally equipped with XS-H2000 workstation, capable of completing all control and analysis tasks on a PC;

The instrument pneumatic system can be equipped with electronic flow display;

New pneumatic control valves ensure the repeatability of analysis parameters;

Capillary systems have split and split/non split injection modes;

● Rear door opening technology enables near room temperature operation and 9-stage programmed heating;

The instrument can be equipped with manual/automatic FID and FPD ignition devices;

instrumentoperate：

In practical work, we measure the carrier gas flow rate, injection technique, gasification chamber temperature, and chromatographic columnThe selection of column temperature, detector temperature, and other six aspects effectively improves column efficiency, resulting in normal peak shapes of the analyzed chromatographic peaks without any adverse phenomena such as peak expansion, tailing, or missed detection. The separation degree is high, thereby improving the accuracy of the analysis results. The column effect refers to achieving satisfactory analysis results in a shorter period of time using a shorter column. In order to improve the column efficiency of the chromatographic column, reduce the phenomena of chromatographic peak expansion, tailing, and peak leakage, we have explored the selection of column operating conditions from the following six aspects in practical work.

1Selection of carrier gas flow rate

The most commonly used carrier gases for gas chromatographs are hydrogen, nitrogen, argon, and helium. For a general chromatograph, the carrier gas flow rate is 20-100ml/min. At present, we use thermal conductivity detectors for liquefied gas analysis and hydrogen gas as the carrier gas, with a flow control of 30 ml/min. The hydrogen flame ionization detector is used to analyze the pentane foaming agent, and nitrogen, combustion gas hydrogen, and oxygen are used as carrier gases. The volume ratio of these three gases is 1:1:10 for nitrogen: hydrogen: oxygen, and the analysis effect is good.

2Selection of Injection Techniques

In gas chromatography analysis, a syringe or a six way valve is generally used for injection. Injection volume: The instantaneous injection volume of the packed column flushing method is generally 0.01-10 μ l for liquid or solid sample solutions, and 0.11-10ml for gas samples,

3Selection of gasification chamber temperature

The temperature of the gasification chamber depends on the chemical and thermal stability of the sample, the boiling range, and the type of injection port. The appropriate gasification chamber temperature can maintain the instantaneous gasification of the sample without causing sample decomposition. The temperature is too low and the gasification rate is relatively slow, resulting in irregular peak shapes such as flat head peaks or tongue sticking peaks; Excessive temperature can cause changes in the number of peaks, leading to delayed peaks and even sample decomposition. To select the appropriate gasification chamber temperature, we found in multiple injections that a gasification chamber temperature 50-100 ℃ higher than the column temperature or 50-70 ℃ higher than the highest boiling point of the sample components is more suitable. Both high and low temperatures can affect column efficiency

4chromatographic column

Chromatography is a separation and analysis method, and separation is the core. Therefore, the chromatographic column responsible for separation is the heart of the chromatographic system. The requirements for chromatographic columns are high column efficiency, good selectivity, and fast analysis speed.

5Column temperature

Column temperature is an important operating parameter, and the impact of changes in column temperature on different components is not equivalent. If two types of compounds cannot be separated at a certain column temperature, it is possible to separate them when the column temperature changes by 20 ℃. The column temperature mainly affects the distribution coefficient, distribution ratio, diffusion coefficient of components in the mobile phase, and diffusion coefficient in the stationary phase, thereby affecting the separation degree and analysis time by affecting the column selectivity and efficiency.

The selection of column temperature should first consider that each fixed liquid has a certain operating temperature. The column temperature should not be higher than the operating temperature of the fixed liquid, otherwise the fixed liquid will evaporate and lose.

6detector

Classification of gas chromatography detectors: hydrogen flame ionization detector, thermal conductivity detector, nitrogen phosphorus detector, electron capture detector, flame photometric detector. These 5 detectors