Plastic formaldehyde determination method (headspace gas chromatography method)

This law applies to polyethylene terephthalate used in pharmaceutical packaging（PET）Determination of Acetaldehyde in Products.

This law uses qi-Based on solid equilibrium, the sample is placed in a sealed container. At a certain temperature, acetaldehyde diffuses into space and reaches equilibrium. Then, a quantitative headspace gas is injected into the gas chromatograph for determination, with retention time as the qualitative measure and peak area as the quantitative measure.

According to the gas chromatography method (general rules)0521）Measurement.

System Applicability Test

The separation degree between the acetaldehyde chromatographic peak and its adjacent peaks should meet the requirements.

Preparation of test samples

Take the flat part of the sample and cut it into long strips（0.5cm×3cmIf the length of the sample is insufficient3cmCut according to the maximum length of the sample. take5.0gAccurately weighed and placed20mlCover the headspace bottle quickly and seal it tightly. Parallel sampling shall not be less than2Share.

Preparation of reference solution

The first method (external standard method)20mlHeadspace bottle, accurately measure a few microliters of acetaldehyde solution reference substance (equivalent to1Mg）Inject into the headspace bottle and quickly seal it with a lid.

The second method (standard curve method) takes20mlSeveral headspace bottles were used to accurately measure a few microliters of acetaldehyde solution reference substance, which were quickly injected into the headspace bottles, sealed with caps, and prepared to contain acetaldehyde0.2～3.0MgThe series reference solution should not be less than5At each concentration point, the linear range can be adjusted according to the actual situation of the test sample if necessary.

Gas chromatography determination method

Chromatographic conditionsFixed phase is（6%）Cyanopropyl phenyl-（94%）Dimethylsiloxane or a capillary column with similar polarity, with a column temperature of40℃Maintain it10minute; The temperature at the injection port is220℃The temperature of the flame ionization detector is250℃The flow rate of the carrier gas is1.5ml/min(Recommended, can be adjusted according to the selected chromatographic column).

The First Law external standard method

Take the solution of the test sample and the control sample, and place them separately40℃±2℃Under the condition of balance1Hour. Inject samples separately (continuous injection of reference solution)3The peak area of acetaldehyde obtained from the second and third measurementsRSDShould not exceed10%）Calculate the amount of acetaldehyde in the test sample based on peak area using the external standard method.

The Second Law Standard curve method

Take the solution of the test sample and the control sample, and place them separately40℃±2℃Under the condition of balance1Hour. Inject samples separately (select a reference solution of intermediate concentration for continuous injection)3Next, the peak area obtainedRSDShould not exceed10%）Measure the peak area of acetaldehyde. Draw a standard curve of the concentration and peak area of the reference solution, and determine its correlation coefficientrShould not be less than0.995Calculate the amount of acetaldehyde in the test sample based on the standard curve.

[Note]（1）The chromatographic conditions used should separate impurities and acetaldehyde in the sample, such as acetaldehyde and ethylene oxide.

（2）After the preparation of the test sample, it should be injected immediately for measurement.