Analysis of Common Problems in Detection of VOC, Formaldehyde and O-Benzene Substances in Tobacco Packets


For the quality and safety control of cigarette packets, in addition to real-time monitoring of the quality and safety of cigarette packets throughout the production process, it is also important to do the testing of raw and auxiliary materials for cigarette packets and cigarette packets. In general, the indicators associated with cigarette packs include three, namely the detection of VOC, formaldehyde and ortho-benzene. In response to the common problems in these three tests, the author summarized the following solutions and shared them with you.

VOC detection frequently asked questions

Our company uses Agilent 7890A+7694E headspace-gas chromatograph when testing VOC. The common problem of this instrument is that the headspace pipeline is easy to be polluted, that is, there is residue in the headspace pipeline. The VOC detection residue is generally ethanol and different. Propanol, ethyl acetate, n-propyl ester. When the amount of residue in the headspace pipeline is large, the quantitative accuracy of the working curve will be affected, resulting in a large detection data.

Problem analysis
First, the gas phase of the instrument is run dry. If the baseline is stable and there is no material peak, it can be judged that the gas phase pipeline is free from pollution. Due to the high daily operating temperature of the gas phase, the inlet is 150 ° C, the column temperature is up to 180 ° C, and the FID detector temperature is 250 ° C. The organic compounds do not substantially remain at this series of temperatures. The temperature in the headspace is generally 80 to 120 ° C, and usually a part of organic compounds remain therein. Therefore, in the case of determining that the gas phase is not polluted, the headspace bottle cover (to ensure that the empty bottle storage environment is pure, the air inside is not polluted) is placed in the sample tray, and the empty bottle sample is run according to the normal detection method of VOC, such as detection. When there is a material peak in the empty bottle, it can be judged that the headspace pipeline is contaminated.

2. Solution
The solution for headspace contamination is to clean the headspace. The specific steps are as follows:
(1) Prepare 12 sample vials (repeatable), 10 packs of approximately 1/6 bottles of distilled or ultrapure water, and 2 empty bottles.
(2) Disconnect the transfer line from the GC inlet and set a suitable headspace carrier gas flow (carrier gas <100ml/min).
(3) If the transfer line is not disconnected from the GC inlet, the GC oven temperature is set to 200 ° C for 5 min, and the split ratio is 40:1 or 50:1.
(4) Headspace setting. Area temperature: sample balance 125 ° C, sample ring 140 ° C, transfer line 150 ° C; time event: sample equilibration time 2.5 min, sample bottle press time 1 min, inflation time 1 min, sample loop equilibration time 1 min, injection time 1 min.
(5) 10 water bottles and 2 empty bottles are sequentially loaded into the sample tray and run in the headspace.
(6) Check the residual condition of the headspace. If the cleaning is not satisfactory, repeat the above steps.
It should be noted that this solution may not completely remove the residue of the headspace pipeline, but can greatly reduce the residual amount and improve the detection accuracy.

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