Method for detecting volatile organic compounds in offset printing ink

Abstract

The invention relates to a method for detecting volatile organic compounds in offset printing ink, and belongs to the technical field of chemical or physical analysis. According to the method for detecting the volatile organic compounds in the offset printing ink, the content of the volatile organic compounds in the offset printing ink is measured by adopting a gas chromatography-flame ionization method, the method comprises GC-FID detection, and GC conditions in the GC-FID detection at least meet the following conditions: a heating program is that the initial temperature is kept for 1-3 minutes at the initial temperature of 35-45 DEG C, then the temperature is increased to 175-185 DEG C at the rate of 4-20 DEG C / min and kept for 14-16 minutes, and then the initial temperature is kept for 2-3 minutes at the rate of 4-20 DEG C / min; and then maintaining the temperature of 255-260 DEG C for 10-20 minutes after the program operation is completed. When the detection method is used for continuously detecting the VOCs in the offset printing ink, the detection efficiency is high, and the detection repeatability is good.

Description

Technical Field

[0001] The invention relates to the technical field of chemical or physical analysis, and in particular to a method for detecting volatile organic compounds in offset printing ink. Background Art

[0002] Volatile organic compounds (VOCs) are a class of organic compounds that can exist in the air in the form of vapor at room temperature. They include some alkanes, aromatic hydrocarbons, alkenes, chlorinated hydrocarbons, esters, alcohols, ethers, aldehydes and ketones with boiling points between 50°C and 250°C. Studies have shown that VOCs are easily accumulated in organisms and have acute or chronic toxicity, which can cause symptoms such as headaches, nausea, vomiting, and weakness in the limbs. In severe cases, they may even cause convulsions, coma or memory loss, and are seriously harmful to the liver, kidneys or nervous system functions. Industrial sources are the main source of man-made VOCs emissions, and the industries involved include key industries such as petrochemicals, chemicals, industrial coatings, packaging and printing, oil storage, transportation and marketing, as well as hundreds of sub-industries.

[0003] Regarding offset inks, the current main method used is to detect VOCs in offset inks by using the "Instructions for testing volatile organic compounds in offset inks by gas chromatography" in Appendix B of "HJ 2542-2016 Technical Requirements for Environmental Labeling Products - Offset Inks". This test method refers to the standard "GB / T 23986-2009 Paints and varnishes - Determination of volatile organic compound (VOC) content - Gas chromatography", which is mainly aimed at paint and varnish products; and offset ink is a viscous colloidal fluid composed of a binder (resin), pigments, fillers, additives and solvents. In order to better respond to the implementation of the test standard "GB / T38608-2020 Determination of the content of volatile organic compounds (VOCs) in inks" specifically for ink VOCs in 2020, and to solve the problems of low efficiency and poor repeatability in continuous and large-scale detection of offset ink VOCs in actual testing, it is urgent to develop a test method for VOCs in offset inks. Summary of the invention

[0004] The purpose of the present invention is to overcome the shortcomings of the prior art and provide a method for detecting volatile organic compounds in offset printing ink.

[0005] To achieve the above object, the technical solution adopted by the present invention is:

[0006] The invention provides a method for detecting volatile organic matter in offset printing ink. The method adopts a gas chromatography-flame ionization method to determine the content of volatile organic matter in the offset printing ink, wherein the method comprises GC-FID detection, wherein the GC condition in the GC-FID detection at least satisfies the following conditions: a temperature rising program is firstly maintained at an initial temperature of 35-45°C for 1-3 minutes, then heated to 175-185°C at a rate of 4-20°C / min and maintained for 14-16 minutes, and then maintained at 255-260°C for 10-20 minutes after the program is run.

[0007] The present invention reduces the influence of residual VOCs of the previous sample on the detection results in continuous detection by regulating the temperature rising program in GC-FID detection and continuing to maintain the temperature at a specific time after the temperature rising operation is completed, thereby significantly improving the accuracy of the detection results and the detection efficiency, and significantly improving the detection repeatability.

[0008] Optionally, the initial temperature may be 36°C, 38°C, 40°C, 42°C or 44°C, and the holding time at the initial temperature may be 1.5 min, 2 min or 2.5 min, preferably 2 min at the initial temperature of 40°C. In addition, the temperature may be raised to 176°C, 178°C, 180°C, 182°C or 184°C, and the temperature may be maintained for 14.5 min, 15 min or 15.5 min, preferably 180°C and maintained for 15 min.

[0009] As a preferred embodiment of the method for detecting volatile organic compounds in offset ink of the present invention, the GC conditions also include an injection mode, and the injection mode is split injection, and the column flow rate is 3 mL / min.

[0010] As a preferred embodiment of the method for detecting volatile organic compounds in offset ink of the present invention, the split flow rate of the split injection is 27 to 33 mL / min, preferably 30 mL / min.

[0011] As a preferred embodiment of the method for detecting volatile organic compounds in offset ink of the present invention, the split ratio of the split injection is (9-11):1, preferably 10:1.

[0012] As a preferred embodiment of the method for detecting volatile organic compounds in offset ink of the present invention, the GC conditions also include a carrier gas, the carrier gas is high-purity nitrogen (purity is at least 99.999% (volume fraction)), and the flow rate of the carrier gas is 2.5-3 mL / min.

[0013] As a preferred embodiment of the method for detecting volatile organic compounds in offset ink of the present invention, the model of the chromatographic column in the GC-FID detection is DB-624.

[0014] As a preferred embodiment of the method for detecting volatile organic compounds in offset ink of the present invention, the FID conditions in the GC-FID detection meet at least one of (a) to (d): (a) the heater temperature is 245 to 255°C, preferably 250°C; (b) the air flow rate is 395 to 405 mL / min, preferably 400 mL / min; (c) the hydrogen fuel gas flow rate is 25 to 35 mL / min, preferably 30 mL / min; (d) the tail gas is high-purity nitrogen (purity is at least 99.999% (volume fraction)), and the tail gas flow rate is 20 to 30 mL / min, preferably 25 mL / min.

[0015] As a preferred embodiment of the method for detecting volatile organic compounds in offset ink of the present invention, the sample solution to be tested for GC-FID detection is prepared by the following preparation method: 0.3-0.5 g of offset ink is mixed with an n-heptane internal standard solution and ethanol, and after ultrasonic extraction for 10-20 minutes, the upper clear liquid is taken and filtered to obtain the sample solution to be tested; the n-heptane internal standard solution is a mixture of n-heptane and chromatographic grade ethanol.

[0016] As a preferred embodiment of the method for detecting volatile organic compounds in offset ink of the present invention, the concentration of the n-heptane internal standard solution is 15000 mg / L, and the amount added is 200 μL; the amount added of the ethanol is 9.8 mL.

[0017] As a preferred embodiment of the method for detecting volatile organic compounds in offset ink of the present invention, n-tetradecane is used as a time marker for volatile organic compounds; the concentration of the n-tetradecane solution is 50 mg / L, and the solution matrix is ​​chromatographic grade ethanol.

[0018] As a preferred embodiment of the method for detecting volatile organic compounds in offset ink of the present invention, the offset ink includes at least one of heatset rotary offset ink, sheet-fed offset ink, coldset rotary offset ink, and energy-curable offset ink.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] The present invention reduces the influence of residual VOCs of the previous sample on the detection results in continuous detection by regulating the temperature rising program in GC-FID detection and continuing to maintain the temperature at a specific time after the temperature rising operation is completed, thereby significantly improving the accuracy of the detection results and the detection efficiency, and significantly improving the detection repeatability. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 The gas chromatogram of Example 5 (overlay of spectra of 5 parallel samples injected continuously);

[0022] Figure 2 The gas chromatogram of Example 10 (overlay of spectra of 5 parallel samples injected continuously);

[0023] Figure 3 The gas chromatogram of Example 15 (overlay of spectra of 5 parallel samples injected continuously);

[0024] Figure 4 The gas chromatogram of Example 20 (overlay of spectra of 5 parallel samples injected continuously);

[0025] Figure 5 The gas chromatogram of Comparative Example 2 (overlay of spectra of 5 parallel samples injected continuously);

[0026] Figure 6 The gas chromatogram of Comparative Example 5 (overlay of spectra of 5 parallel samples injected continuously);

[0027] Figure 7 The gas chromatogram of Comparative Example 8 (overlay of spectra of 5 parallel samples injected continuously);

[0028] Figure 8 It is the gas chromatogram of Comparative Example 11 (the spectra of 5 parallel samples injected continuously are superimposed). DETAILED DESCRIPTION

[0029] In order to better illustrate the purpose, technical solutions and advantages of the present invention, the present invention will be further described below in conjunction with specific embodiments.

[0030] Other materials and reagents used in the examples, unless otherwise specified, can be obtained from commercial sources. Among them, chromatographically pure ethanol reagent, n-heptane standard, and n-tetradecane standard are all from Shanghai Anpu Experimental Technology Co., Ltd.; the ultrasonic generator uses the KQ-300DE ultrasonic generator supplied by Kunshan Ultrasonic Instrument Co., Ltd.; the gas chromatograph-mass spectrometer uses the 8860GC gas chromatograph supplied by Agilent, and the chromatographic column is the Agilent J&W gas chromatograph DB-624 (length 60m, inner diameter 0.25mm, film thickness 1.4μm).

[0031] Examples 1 to 20

[0032] An embodiment of a method for detecting volatile organic compounds in offset printing ink of the present invention comprises the following steps:

[0033] S1. Sample preparation: Take offset ink as the target sample, stir and mix it evenly with a glass rod to obtain a paste sample to be tested, and divide the sample to be tested into 5 parallel samples;

[0034] S2. Preparation of internal standard solution: prepare the n-heptane standard substance into a n-heptane internal standard solution with a concentration of 15000 mg / L (the solvent is chromatographic grade ethanol);

[0035] S3, extraction: the sample to be tested (0.3 g) described in S1 is placed in an extraction bottle, and then the n-heptane internal standard solution (200 μL) and ethanol (9.8 mL) described in S2 are added, and then the extraction bottle is placed in an ultrasonic generator for ultrasonic extraction at room temperature (the extraction time is shown in Table 1), and the supernatant is taken and filtered to obtain the sample solution to be tested;

[0036] S4, GC-FID detection: The sample solution to be tested described in S3 is subjected to GC-FID detection, and the model of the chromatographic column is DB-624;

[0037] GC conditions: the degree of heating and post-operation are shown in Table 1; the sample injection volume is 1 μL; the injection method is split injection, the split ratio is 10:1, and the split flow rate is 30 mL / min; the carrier gas is high-purity nitrogen, and the flow rate is 3 mL / min;

[0038] FID conditions: heater temperature is 250°C; air flow rate is 400 mL / min; hydrogen gas flow rate is 30 mL / min; tail gas is high-purity nitrogen, and the tail gas flow rate is 25 mL / min;

[0039] Run sequence: continuous sample injection;

[0040] S5. Determination of VOCs integration time: prepare a 50 mg / L n-tetradecane time marker standard solution (the solvent is chromatographic grade ethanol), and test according to the GC conditions and FID conditions in step S4;

[0041] S6. Acquisition of quantitative results: within the integration time obtained in S5, the peak area of ​​each substance in the chromatogram of the test sample obtained in S4 is integrated to obtain an integral result, and the integral result is compared with the peak area integral result of the internal standard to calculate the VOCs content in the test sample.

[0042] Table 1 Extraction time, GC conditions and VOCs content in the sample to be tested in Examples 1 to 20

[0043]

[0044]

[0045]

[0046]

[0047] According to the data in Table 1, the detection repeatability RSD of Examples 1 to 20 all meet the requirements for detection repeatability in the GB / T 38608-2020 standard (the relative standard deviation of five repeated measurement values ​​is not more than 5%) or the HJ 2542-2016 standard (the relative standard deviation of five repeated measurement values ​​is between 1% and 8%), indicating that the detection method of volatile organic compounds in offset ink of the present invention has good repeatability. For thermosetting web offset ink, it can be seen from Examples 1 and 2 that after the heating program is completed, the temperature is extended to 260°C for 10 min and 20 min, respectively, and the corresponding RSDs are 2.42% and 1.55%, respectively, indicating that the detection repeatability can be significantly improved by keeping it at 260°C for 10 min; it can be seen from Examples 1, 3 and 4 that the average values ​​of VOCs contents corresponding to ultrasonic extraction times of 10 min, 20 min and 30 min are 2.73%, 2.91% and 2.93%, respectively, indicating that increasing the ultrasonic extraction time is conducive to fully extracting VOCs in offset ink, and the extraction efficiency is higher when the extraction time is about 20 min, and the VOCs content does not change significantly after the extraction time is further increased; it can be found from Examples 3 and 5 that when the heating rate increases from 4°C / min to 20°C / min, the detection repeatability corresponding to the two is close and meets the requirements of the relevant test standards, and the detection time is shortened from 62 min to 34 min, that is, the detection efficiency is greatly improved while ensuring the accuracy of the results. At the same time, according to Examples 6 to 20, it can be found that, in addition to heat-set web offset printing inks, the detection method of volatile organic compounds in offset printing inks of the present invention also has good detection repeatability for sheet-fed offset printing inks, cold-set web offset printing inks or energy-curable offset printing inks. Figure 1 to Figure 4 The VOCs gas chromatography of different offset inks further proves that the detection method of volatile organic compounds in offset inks of the present invention can be applied to different inks and has good repeatability.

[0048] Embodiment 21

[0049] The method detection limit for determining the volatile organic compounds in the offset printing ink of the present invention comprises the following steps:

[0050] S1. Preparation of internal standard solution: Prepare the n-heptane standard substance into a n-heptane internal standard solution with a concentration of 300 mg / L (the solvent is chromatographic grade ethanol);

[0051] S2, extraction: add the n-heptane internal standard solution (200 μL) and ethanol (9.8 mL) described in S1 into the extraction bottle, then place the extraction bottle in an ultrasonic generator for ultrasonic mixing at room temperature (mixing time is shown in Table 2), and obtain a sample solution to be tested (the volatile organic compound content of the sample solution to be tested is about 0.02%, calculated based on the sample weight of 0.3 g);

[0052] S3, GC-FID detection: The sample solution to be tested described in S2 is subjected to GC-FID detection, and the model of the chromatographic column is DB-624;

[0053] GC conditions: the degree of heating and post-operation are shown in Table 2; the sample injection volume is 1 μL; the injection method is split injection, the split ratio is 10:1, and the split flow rate is 30 mL / min; the carrier gas is high-purity nitrogen, and the flow rate is 3 mL / min;

[0054] FID conditions: heater temperature is 250°C; air flow rate is 400 mL / min; hydrogen gas flow rate is 30 mL / min; tail gas is high-purity nitrogen, and the tail gas flow rate is 25 mL / min;

[0055] Run sequence: continuous sample injection;

[0056] S4, determination of VOCs integration time: prepare a 50 mg / L n-tetradecane time marker standard solution (the solvent is chromatographic grade ethanol), and test according to the GC conditions and FID conditions in step S3;

[0057] S5. Acquisition of quantitative results: within the integration time obtained in S4, the peak area of ​​each substance in the chromatogram of the test sample obtained in S3 is integrated to obtain the integral result, and the integral result is compared with the peak area integral result of the internal standard to calculate the VOCs content in the test sample.

[0058] The test results are specifically shown in Table 2. According to the data in Table 2, the detection limit of the method for detecting volatile organic compounds in offset ink of the present invention is as low as 0.02% (calculated based on 0.3g sample weight), which indicates that the method for detecting volatile organic compounds in offset ink of the present invention has high sensitivity.

[0059] Table 2 Mixing time, GC conditions and test results in Example 21

[0060]

[0061] Comparative Examples 1 to 12

[0062] A comparative example of a method for detecting volatile organic compounds in offset printing ink of the present invention, the detection method comprises the following steps:

[0063] S1. Sample preparation: Take offset ink as the target sample, stir and mix it evenly with a glass rod to obtain a paste sample to be tested, and divide the sample to be tested into 5 parallel samples;

[0064] S2. Preparation of internal standard solution: prepare the n-heptane standard substance into a n-heptane internal standard standard solution with a concentration of 15000 mg / L (the solvent is chromatographic grade ethanol);

[0065] S3, extraction: the sample to be tested (0.3 g) described in S1 is placed in an extraction bottle, and then the n-heptane internal standard solution (200 μL) and ethanol (9.8 mL) described in S2 are added, and then the extraction bottle is placed in an ultrasonic generator for ultrasonic extraction at room temperature (the extraction time is shown in Table 3), and the supernatant is taken and filtered to obtain the sample solution to be tested;

[0066] S4, GC-FID detection: The sample solution to be tested described in S3 is subjected to GC-FID detection, and the model of the chromatographic column is DB-624;

[0067] GC conditions: the degree of heating and post-operation are shown in Table 3; the sample injection volume is 1 μL; the injection method is split injection, the split ratio is 10:1, and the split flow rate is 30 mL / min; the carrier gas is high-purity nitrogen, and the flow rate is 3 mL / min;

[0068] FID conditions: heater temperature is 250°C; air flow rate is 400 mL / min; hydrogen gas flow rate is 30 mL / min; tail gas is high-purity nitrogen, and the tail gas flow rate is 25 mL / min;

[0069] Run sequence: The injection method is shown in Table 3;

[0070] S5. Determination of VOCs integration time: prepare a 50 mg / L n-tetradecane time marker standard solution (the solvent is chromatographic grade ethanol), and test according to the GC conditions and FID conditions in step S4;

[0071] S6. Acquisition of quantitative results: within the integration time obtained in S5, the peak area of ​​each substance in the chromatogram of the test sample obtained in S4 is integrated to obtain an integral result, and the integral result is compared with the peak area integral result of the internal standard to calculate the VOCs content in the test sample.

[0072] Table 3 Extraction time, GC conditions, injection method and VOCs content in the liquid samples in comparative examples 1 to 12

[0073]

[0074]

[0075]

[0076] According to the data in Table 3 and Figures 5 to 8It can be seen that whether it is heatset rotary offset ink or sheet-fed offset ink, or coldset rotary offset ink or energy-curing offset ink, if the GC conditions are directly tested after the heating program is completed (that is, omitting keeping it at 260°C for a certain time), the test repeatability will be significantly deteriorated and will not meet the requirements for test repeatability in GB / T 38608-2020 or HJ 2542-2016.

[0077] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the essence and scope of the technical solution of the present invention.

Claims

1. A method for detecting volatile organic compounds in offset printing ink, characterized in that: The content of volatile organic matter in offset ink is determined by gas chromatography-flame ionization method, which includes GC-FID detection. The GC conditions in the GC-FID detection at least meet the following requirements: the temperature rise program is to first maintain the initial temperature at 35-45°C for 1-3 minutes, then increase the temperature to 175-185°C at a rate of 4-20°C / min and maintain for 14-16 minutes, and then maintain at 255-260°C for 10-20 minutes after the program is completed.

2. The detection method according to claim 1, characterized in that The GC conditions also include an injection method, and the injection method is split injection.

3. The detection method according to claim 2, characterized in that The split flow rate of the split injection is 27-33 mL / min.

4. The detection method according to claim 3, characterized in that The split ratio of the split injection is (9-11):

1.

5. The detection method according to claim 1, characterized in that The GC conditions also include a carrier gas, which is high-purity nitrogen, and a flow rate of the carrier gas is 2.5 to 3 mL / min.

6. The detection method according to claim 1, characterized in that The model of the chromatographic column used in the GC-FID detection is DB-624.

7. The detection method according to claim 1, characterized in that: The FID condition in the GC-FID detection satisfies at least one of (a) to (d): (a) The heater temperature is 245-255°C; (b) Air flow rate is 395-405 mL / min; (c) Hydrogen gas flow rate is 25-35 mL / min; (d) The tail gas is high-purity nitrogen, and the tail gas flow rate is 20-30 mL / min.

8. The detection method according to claim 1, characterized in that The sample solution for GC-FID detection is prepared by the following preparation method: 0.3-0.5g of offset printing ink is mixed with n-heptane internal standard solution and ethanol, and after ultrasonic extraction for 10-20min, the upper clear liquid is taken and filtered to obtain the sample solution; the n-heptane internal standard solution is a mixture of n-heptane and chromatographic grade ethanol.

9. The detection method according to claim 8, characterized in that: The concentration of the n-heptane internal standard solution is 15000 mg / L, and the amount added is 200 μL; the amount added of the ethanol is 9.8 mL.

10. The detection method according to claim 1, characterized in that: n-Tetradecane was used as a volatile organic compound time marker; the concentration of the n-tetradecane solution was 50 mg / L, and the solution matrix was chromatographic grade ethanol.

11. The detection method according to claim 1, characterized in that: The offset printing ink comprises at least one of heat-set rotary offset printing ink, sheet-fed offset printing ink, cold-set rotary offset printing ink and energy-curable offset printing ink.

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