You must know these about the determination of solvent residues in cigarette paper.
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YC/T 207-2014 "Determination of Solvent Residues in Tobacco Papers by Headspace-Gas Chromatography/Mass Spectrometry" (hereinafter referred to as "New Standard") was released on December 24, 2014 and officially implemented on January 15, 2015. The 8-year old standard YC/T 207-2006 "Determination of Volatile Organic Compounds in Cigarette Strips and Box Packaging Paper" (headspace-gas chromatography) (hereinafter referred to as "the old standard") was simultaneously invalidated.
Solvent residue is a testing program commonly carried out by various cigarette printing companies and material manufacturers. Some enterprises have used headspace-gas chromatography mass spectrometry before the release of the new standard, and have been using headspace-gas chromatography. The testing companies are under pressure to upgrade their instruments.
According to our company's testing experience in the past two years, we believe that the new standard is a major change to the old standard. The most important change is that the detection method is upgraded from headspace-gas chromatography to headspace-gas chromatography/mass spectrometry. While improving the detection limit and sensitivity of the test method, it also puts forward higher professional requirements for the testers. In order to help the industry to further understand the changes in the new standards, as well as the testing work that needs to be focused on, this article will explain and analyze the following.
Change Description
1. Adjust the test name
The new version of the standard adjusts the name of the test to "headspace-gas chromatography/mass spectrometry for the determination of solvent residues in cigarette paper."
2. Adjust the scope of application
The new version of the standard has been adapted to the scope of application, adding paper for cigarettes such as tipping paper and liner paper.
3. Modify the test indicators
(1) The new standard is in the old standard benzene, toluene, ethylbenzene, (o-, m-, p-) xylene, ethanol, isopropanol, n-butanol, acetone, 4-methyl-2-pentanone, butanone, Based on 16 indicators of cyclohexanone, ethyl acetate, n-propyl acetate, n-butyl acetate, isopropyl acetate and propylene glycol methyl ether, styrene, methanol, n-propanol and 1-ethoxyl groups were added. 9-propanol, 2-ethoxyethyl acetate, 2-ethoxyethanol, dimethyl succinate, dimethyl glutarate and dimethyl adipate The name of the methyl ether was modified to 1-methoxy-2-propanol, a total of 25 typical detection indicators.
(2) Based on the above 25 typical test indicators (3.2.1), 3.2.2 proposes the concept of “other solvent residue standards”, which is determined by the qualitative analysis results of cigarette paper (6.1.2).
Therefore, the new version of the standard has increased the detection index compared with the old version of the standard, and changed the detection index to open type, which is divided into typical solvent residues (25 items) and other solvent residues (not fixed).
4. Modify the instrument detection method
The instrument detection method change is the core change of the new standard. The detection method is upgraded from headspace-gas chromatography (GC-FID) to headspace-gas chromatography/mass spectrometry (GC-MS).
GC-FID and GC-MS are two common detection methods, each with advantages and disadvantages. The following is a brief description.
(1) Qualitative analysis. GC-FID uses the retention time to characterize the compound to be tested, while GC-MS is characterized by the retention time of the target compound and the abundance ratio of the target compound. The qualitative reliability is greatly improved compared with GC-FID. Basically, it can effectively avoid the false positive problem that GC-FID is prone to occur.
(2) Detection limit and limit of quantitation. Compared to GC-FID, GC-MS can achieve lower detection and quantitation limits.
(3) Linear range. The linear range of GC-FID is about 106, while the linear range of GC-MS is only 103, that is, the range of accurate quantitation of GC-MS is much smaller than that of GC-FID.
(4) Instrument operation. The hardware and software operations of GC-MS are more complicated than GC-FID, and the requirements for inspectors are also higher.
(5) Instrument status. GC-FID is basically static, and GC-MS is dynamic, which means that its instrument state is always changing dynamically, and monitoring needs to be strengthened.
5. Adjust the standard solution concentration
The standard solution concentration of the new standard is adjusted according to the actual residue of the test compound, and the highest concentration and the lowest concentration are reduced from 625 times to 100 times, which is more favorable for obtaining better linearity on the basis of strengthening the detection specificity.
6. Increase quality control
(1) Blank test (6.2.2). The blank test is one of the conventional quality control methods in the field of chemical detection. The blank test can effectively eliminate the abnormality of the test data caused by blank pollution.
(2) Quality control samples (6.2.1). A standard working solution of medium concentration should be determined after 20 sample tests. If the measured value differs from the original value by more than 5%, the standard working curve should be re-made.
Through the quality control sample, the system deviation can be effectively identified, and if necessary, the standard working curve can be re-created to ensure the accuracy of the test data.
Key Analysis
1. Standard curve linear
Since the linear range of GC-MS is much smaller than GC-FID, when using GC-MS, the linearity of some of the compounds to be tested is more difficult to meet the standard requirement of R2 ≥ 0.995.
In this regard, on the one hand, it is necessary to strengthen the skill training of the inspectors, on the other hand, it is necessary to set the instrument parameters reasonably according to the characteristics and actual state of the respective instruments (the new standard is based on the headspace parameters established by the Agilent G1888, and the current Agilent 7697A and The headspace parameter settings of other brands are different. In addition, the GC-MS of different brands and models have different sensitivity, so the instrument parameters need to be set reasonably, and the experiment is repeated until the standard requirements are fully met.
2. Quality control
Since the GC-MS has been in a dynamic state of change, the requirement that the measured value of the quality control sample after 20 samples is different from the original value should be ≤ 5% is difficult to achieve.
In this regard, as a professional testing organization or a cigarette paper printing company, the final determination of an abnormal product should be carried out in strict accordance with the terms. However, the company should firmly grasp the principle of testing in the daily monitoring work to ensure the principle of qualified products leaving the factory. The conditions can be relaxed according to the actual situation. For example, if the product is far below the warning value exceeding the standard, even if the quality control sample exceeds the detection value. Standard requirements may also not re-create standard working curves, thereby reducing the economic and time cost increases caused by repeated production of standard operating curves. The specific limits require enterprises to explore the characteristics of their own products to achieve a reasonable balance of costs and risks to ensure the quality of the factory.
3. Limited requirements
YQ 57-2015 "Safety and Hygienic Requirements for Tobacco Pickup Paper", YQ 58-2015 "Safety and Hygienic Requirements for Cigarette Lining Paper" and YQ 69-2015 "Safety and Hygienic Requirements for Cigarette Strips and Box Packaging Paper" Requirements for Solvent Residue Limits See Table 1.
As shown in Table 1, the total amount of residual solvent refers to the sum of the residual amount of solvent permitted to be used in addition to ethanol and the residual amount of solvent impurities. Among them, the solvent used is YQ 15 specified ethanol, n-propanol, isopropanol, ethyl acetate, n-propyl acetate, isopropyl acetate, propylene glycol methyl ether, propylene glycol ether, dimethyl succinate, glutaric acid Dimethyl acrylate, dimethyl adipate and 2-butanone; solvent impurities are unlicensed volatile substances of YQ 15 , wherein the benzene series are toluene, ethylbenzene and xylene.
The solvent residual amount, benzene series and benzene content other than ethanol can be directly detected and added by typical solvent residues. The total amount of solvent impurities and total solvent residues are within the range of typical solvent residues (6.2.1, 25 kinds). ) is also easy to obtain. However, as can be seen from the above description, the solvent impurity refers to a volatile substance which is not permitted to be used by YQ 15, that is, it includes not only a substance which is deducted from the permitted use portion of the typical solvent residue, but also other solvent residues (6.1.2).
Typical solvent residue detection is generally carried out by SIM method, while other solvent residue detection requires SCAN scanning for each sample. If an unknown compound is found, a spectral search is required. After preliminary characterization, the standard is used for qualitative and quantitative confirmation analysis. The workload is large, it takes a long time, and the requirements for testing personnel are high. It is very difficult to carry out, and whether the testing of other solvent residues is required must be carried out according to the specific requirements of each Chinese cigarette company.
At present, Agilent equipment software can set up SIM and SCAN data at the same time, and judge the existence of other solvent residues through SCAN spectrum, but there are large peaks. For qualitative analysis, it is best to perform standard spectrum tuning and use SCAN mode. After the collection, the library is searched for preliminary confirmation. If qualitative and quantitative are required, the corresponding standard products need to be purchased before analysis.
At present, some printing companies carry out fuzzy quantitative methods by comparing the peak height or peak area with typical solvent residues. This is a positive exploration, but it is scientifically lacking because of the peak height and response of different substances at the same concentration. The values are likely to be different (as can be seen from the typical concentrations of typical solvents remaining in the same concentration).
In this regard, if the printing company is only for the purpose of controlling and avoiding risks, it does not need to invest too much manpower and material resources to carry out exact qualitative and quantitative determination. When other solvent residual peaks appear, it can be based on the printing company only for printing materials. Reorganize without adding any substances. All the components of the product are derived from the characteristics of the printed materials. By comparing the spectrum of the raw materials of the products, the source is determined, and the relevant raw material suppliers are required to carry out rectification.