Discussion on application of free-empty column changing device in solvent residue of cigarette packets

Implementation of the new version of "Safety and Hygienic Requirements for Cigarette Strips and Box Packaging Paper" The testing capabilities of printing companies have put forward higher requirements. Among them, phthalate esters, photoinitiators, solvent residues and other indicators involve gas chromatography-mass spectrometry, which is carried out with only one GC/MS. During the inspection of the project, it is inevitable that the operation of venting, shutting down, restarting, and evacuating frequently occurs due to the replacement of the column. In order to effectively solve this problem, our company tried to install the vent-free column replacement device on the Agilent 7890A+5977A GC/MS. Now we will briefly analyze the test situation before and after the installation of the vent-free column changing device for reference by the industry colleagues. .

Structure and working principle of the vent-free column changing device

Structure

The vent-free column changing device is mainly used to replace the column without shutting down the mass spectrometry detection system. It includes 3 interfaces, respectively connected to 3 gas channels (as shown in Figure 1), and A channel is connected to the column outlet; Use an empty column (about 50 cm in length, no packing) to connect to the mass spectrometer inlet; C to connect to the electronic gas path control system.

2. Working principle

When the column is replaced, the flow rate of the A channel is closed. At this time, the B channel is in the constant pressure mode (10 psi), and then the A channel is disassembled. In order to maintain the preset pressure of the B channel, the electronic gas path control system compensates the C channel flow. When the carrier gas flows from the C road to the A road and the B road, the outside air is prevented from entering the mass spectrum from the A road, thereby realizing the replacement of the chromatography column when the mass spectrometry detection system is turned on.

Influence on determination of solvent residue index of cigarette packets

The Agilent 7890A+5977A GC/MS test was carried out on the same batch of standard solution (Grade 1 to 5) prepared by China Tobacco Standardization Research Center in two states without the installation and installation of the vent-free column replacement device. .

The test found that after the gas-mass spectrometer was installed with the vent-free column changing device, although the column can be avoided frequently, the determination of the residual index of the tobacco packet solvent also brought some influence, mainly in the following three points.

(1) After installing the vent-free column changing device, in order to ensure that the components separated from the column smoothly pass through the three-way interface of the vent-free column changing device to enter the mass spectrometer end, the B channel flow must be set slightly larger than the A channel flow (increase About 0.2 mL/min).

However, during the data acquisition process, the column (A) flow rate could not reach the standard set flow rate 4 minutes before the start, resulting in an increase in the retention time of each component. The retention time and response values ​​of the components before and after the installation of the vent-free column changing device are shown in Tables 1 and 2.

(2) After adding the vent-free column changing device, 2-ethoxyethyl acetate peaks before o-xylene, and the two are difficult to separate, especially at higher concentrations, the two are more difficult to separate. .