CN115598226A

CN115598226A - Application of ultra-fast gas-phase electronic nose in fatty acid detection

Info

Publication number: CN115598226A
Application number: CN202110767949.4A
Authority: CN
Inventors: 柳新荣; 邢志强; 费亚男
Original assignee: Jiahe Food Industry Co ltd
Current assignee: Jiahe Food Industry Co ltd
Priority date: 2021-07-07
Filing date: 2021-07-07
Publication date: 2023-01-13
Also published as: WO2023279749A1; CN116194768A

Abstract

The invention relates to an application of an ultra-fast gas-phase electronic nose in fatty acid detection. The application thinks for the first time that ultra-fast gaseous phase electronic nose is used for detecting fatty acid to through the optimization to the scheme, can realize separating qualitative to 32 kinds and above fatty acid methyl ester. The method has the advantages of short detection time, and can save more than 65% of time compared with the national standard method, and the use of fatty acid methyl ester single standard is not needed, so that the purchase cost of the standard product can be saved.

Description

Application of ultra-fast gas-phase electronic nose in fatty acid detection

Technical Field

The invention particularly relates to an application of an ultra-fast gas-phase electronic nose in fatty acid detection.

Background

At present, when the qualitative detection is carried out on the fatty acid in the food, a gas chromatograph is usually adopted, a plurality of fatty acid methyl ester standard solution mixed samples and a single fatty acid methyl ester sample are simultaneously adopted as standard substances, the price of the single fatty acid methyl ester sample is higher, and when the gas chromatograph is adopted for detection at present, the detection time is longer, and about 85min is usually required.

Disclosure of Invention

Aiming at the defects in the prior art, the invention aims to provide the application of the ultra-fast gas-phase electronic nose in detecting fatty acid methyl ester, which has the advantages of fast detection and no need of using a single expensive fatty acid methyl ester sample.

In order to achieve the purpose, the invention adopts the technical scheme that:

the invention provides an application of an ultra-fast gas-phase electronic nose in fatty acid detection.

Preferably, the ultra-fast gas-phase electronic nose comprises a first chromatographic column and a second chromatographic column, and the polarity of the first chromatographic column and the polarity of the second chromatographic column are different.

Preferably, the length of the first chromatographic column and the length of the second chromatographic column are each greater than 10m.

Further preferably, the length of the first chromatographic column and the length of the second chromatographic column are each greater than 15m.

More preferably, the length of the first chromatographic column and the length of the second chromatographic column are each equal to or greater than 20m.

Preferably, the length of the first chromatographic column and the length of the second chromatographic column are respectively less than or equal to 30m.

Preferably, the first chromatographic column is a polar column and the second chromatographic column is a non-polar column.

Preferably, when the ultra-fast gas-phase electronic nose is used for detecting fatty acid, the method comprises the step of methyl esterifying a sample.

Preferably, when the ultra-fast gas phase electronic nose is used for detecting fatty acid, the method comprises the step of establishing a relation between retention time or retention index of each fatty acid methyl ester and corresponding fatty acid methyl ester on the first chromatographic column and the second chromatographic column by taking a mixture of a plurality of fatty acid methyl esters as a standard substance and taking an n-alkane standard solution as a calibrator

Further preferably, the normal paraffin standard solution comprises nC 7-nC 17 normal paraffin standard solution and/or nC 10-nC 40 normal paraffin standard solution.

Further preferably, the specific method for establishing the relationship between each fatty acid methyl ester and the retention time or retention index of the corresponding fatty acid methyl ester on the first chromatographic column and the second chromatographic column comprises the following steps:

(1) Determining and analyzing the mixture of the fatty acid methyl esters by using the ultra-fast gas-phase electronic nose;

(2) The ultra-fast gas-phase electronic nose is adopted to carry out determination analysis on the normal alkane standard solution;

(3) And calibrating the results of the mixture of the plurality of fatty acid methyl esters by using the results of the normal paraffin standard solution, and then respectively qualifying the mixture of the plurality of fatty acid methyl esters by using an AroChemBase database to obtain the relation between the retention time or retention index of each fatty acid methyl ester and the corresponding fatty acid methyl ester on the first chromatographic column and the second chromatographic column.

Further preferably, when the ultrafast gas phase electronic nose is used for detecting fatty acid, the method further comprises calibrating the chromatographic peak of the sample by using a normal alkane standard solution, converting the retention time into a retention index, and then performing qualitative analysis on the compound by using an AroChemBase database, and/or comparing the retention time or the retention index with a corresponding list of the retention time or the retention index of each fatty acid methyl ester with the corresponding fatty acid methyl ester on the first chromatographic column and the second chromatographic column.

Preferably, when the ultra-fast gas-phase electronic nose is adopted for detection, the sample introduction duration is controlled to be 25-30 s, the carrier gas constant-current purging speed is controlled to be 0.8-1 mL/min, and/or the shunt speed of the trap is controlled to be 1-8 mL/min, and/or the trap trapping duration is controlled to be 30-35 s, and/or the initial temperature of the chromatographic column at 50 ℃ is controlled to be 5-100 s, and/or the temperature of the chromatographic column is controlled to be 80-150 ℃ according to 0.3-0.5 ℃/s, the temperature is kept for 200-300 s, then the temperature is increased to 250 ℃ according to 0.2-0.5 ℃/s, and the temperature is kept for 300-500 s.

The second aspect of the invention provides a method for detecting fatty acid, which utilizes an ultra-fast gas-phase electronic nose for detection.

Due to the application of the technical scheme, compared with the prior art, the invention has the following advantages:

the application thinks for the first time that ultra-fast gaseous phase electronic nose is used for detecting fatty acid methyl ester to through the optimization to the scheme, can realize separating qualitative to 32 kinds and above fatty acid methyl ester. The method has short detection time, can save more than 65% of time compared with the national standard method, does not need to use fatty acid methyl ester single standard, and can save the purchase cost of the standard product.

Drawings

FIG. 1 is a raw gas chromatogram of a mixture of 37 fatty acid methyl esters of example 1;

FIGS. 2 and 3 are chromatograms obtained by enlarging FIG. 1;

FIG. 4 is a qualitative representation of the compounds in the sample of example 1;

FIG. 5 is a raw gas chromatogram of a mixture of 37 fatty acid methyl esters of example 2;

FIG. 6 is an enlarged view of the original gas chromatogram of the mixture of 37 fatty acid methyl esters of example 2, corrected with a standard solution of C7-C17 n-alkanes, shown by retention indices;

FIGS. 7 and 8 are enlarged views of the original gas chromatograms of the 37 fatty acid methyl esters of example 2, which are shown by using retention indexes after being corrected with C10-C40 n-alkane standard solutions;

FIG. 9 is the results of the characterization of the compounds in the sample of example 2;

FIG. 10 is a raw gas chromatogram of the mixture of 37 fatty acid methyl esters of example 3;

FIGS. 11 and 12 are enlarged views of FIG. 10;

FIG. 13 is a raw gas chromatogram of a mixed standard of 37 fatty acid methyl esters of comparative example 1;

FIGS. 14 and 15 are enlarged views of FIG. 13;

FIG. 16 is a raw gas chromatogram of a mixed standard of 37 fatty acid methyl esters of comparative example 2;

fig. 17 and 18 are enlarged views of fig. 16;

FIG. 19 is a raw gas chromatogram of a mixed standard of 37 fatty acid methyl esters of comparative example 3;

FIGS. 20 and 21 are enlarged views of FIG. 19;

FIG. 22 is a raw gas chromatogram of a mixed standard of 37 fatty acid methyl esters of comparative example 4;

FIG. 23 is a raw gas chromatogram of a methyl esterified sample of an application example;

FIG. 24 is an enlarged view of a sample and the standard of example 2 shown in terms of retention index after calibration with a C10-C40 normal paraffin standard solution;

FIG. 25 shows the qualitative results of compounds in the methyl esterification sample using the ultrafast gas phase electronic nose method;

FIG. 26 is a graph of the detection of the methyl esterified sample by GC-MC;

FIG. 27 shows the qualitative results of the GC-MC method for methyl esterification of the compounds in the samples.

Detailed Description

The inventor firstly thinks of combining the electronic nose generally used for detecting food flavor with gas phase, detecting fatty acid in food, daily chemical products and the like, and using a carbon mark combined with an AroChemBase database to qualify the result.

Furthermore, the invention optimizes the conditions to ensure that the proposal of the application can carry out the treatment of butyric acid, caproic acid, caprylic acid, capric acid, undecanoic acid, dodecanoic acid, tridecanoic acid, tetradecanoic acid, cis-9-tetradecenoic acid, pentadecanoic acid, cis-10-pentadecaenoic acid, hexadecanoic acid, cis-9-hexadecenoic acid methyl ester, heptadecanoic acid, cis-10-heptadecenoic acid, octadecanoic acid, eicosanoic acid, cis-6, 9, 12-octadecatrienoic acid, cis-11-eicosenoic acid, cis-9, 12, 15-octadecatrienoic acid, heneicosylic acid, cis-11, 14-eicosadienoic acid, docosanoic acid and cis, the detection of cis, cis-8, 11, 14-eicosatrienoic acid, cis-11, 14, 17-eicosatrienoic acid, cis-5, 8,11, 14-eicosatetraenoic acid, tricosa, cis-13, 16-docosadienoic acid, tetracosenoic acid, cis-5, 8,11,14, 17-eicosapentaenoic acid, cis-15-tetracosenoic acid, cis-4, 7,10,13,16, 19-docosahexaenoic acid and the like can be determined, whereby the saturated fatty acid in a substance, for example, the fatty acid composition of extremely hydrogenated fats and oils (hydrogenated soybean oil, hydrogenated coconut oil, hydrogenated palm kernel oil and the like) and the presence or absence of the above-exemplified fatty acid in a substance can be verified.

The present invention will be further described with reference to the following examples. However, the present invention is not limited to the following examples. The implementation conditions adopted in the embodiments can be further adjusted according to different requirements of specific applications, and the implementation conditions not mentioned are conventional conditions in the industry or recommended conditions of corresponding equipment or devices. The technical features according to the embodiments of the present invention may be combined with each other as long as they do not conflict with each other. The raw materials and equipment used in the examples were all commercially available.

Example 1

The method adopts an ultra-fast gas-phase electronic nose (Heracles NEO) to perform measurement and analysis on the mixed standard of 37 fatty acid methyl esters specified by national standard:

(1) Respectively installing an mxt-wax chromatographic column and an mxt-5 chromatographic column with the length of 20 meters on the ultra-fast gas electronic nose Heracles;

(2) Diluting a mixed standard of 37 fatty acid methyl esters to the mass concentration of 1% by using n-pentane, transferring 1 mu L of sample into a 2mL liquid sample injection bottle, placing the liquid sample injection bottle on an automatic sample injector device, performing measurement analysis according to the experimental conditions shown in Table 1, and performing data processing by using AlphaSoft V2020;

(3) The retention times of the 37 fatty acid methyl esters mixed standard were converted into retention indices using normal alkane standard solutions (nC 7-nC 17) and (nC 10-nC 40) calibrated according to the experimental conditions shown in Table 1, and then the compounds were qualitatively analyzed by AroChemBase database.

TABLE 1

The original gas chromatogram of the mixture of 37 fatty acid methyl esters detected in this example is shown in FIG. 1, and the enlarged chromatogram of FIG. 1 is shown in FIGS. 2 and 3. As can be seen from FIGS. 1 to 3, the fatty acid methyl ester mixture showed 34 peaks (chromatographic peaks with peak area > 10000 were selected) on a polar column of 20m length. The AroChemBase database was used to characterize the compounds in the samples, and the compounds contained are shown in figure 4.

The retention index of a compound refers to a quantitative value that measures the degree to which a compound is retained on a chromatographic column using n-alkanes as standards on a certain stationary phase. The retention index of a compound is constant for the stationary phase of the column, i.e. the retention index of a certain compound of the same column is constant. The retention index of the compound can be obtained by calculating the retention time of the n-alkane and the retention time of the compound, and the effect of characterizing the compound without standard substances can be achieved by utilizing the different retention indexes of the two chromatographic columns.

In the compound qualitative process, a total of two alkane calibration solutions are used. Two kinds of C7-C17 and C10-C40. The retention indices were calibrated to 700-1700 and 1800-2800, respectively, to facilitate qualitative work on subsequent compounds.

The retention indices of the fractions indicated by

numbers

21, 25, 26 and 33 in FIG. 4, which were not collected in Arochemase, were presumed to be the substance in question, based on their order of appearance and the comparison of the chromatographic peaks on the two columns.

The components shown as 24, 27, 28, 29 and 34 in fig. 4 retain index-related information only on the non-polar columns in the database. It is assumed that these are likely to be the above at this retention index, based on their order of appearance.

According to the analysis, about 34 obvious fatty acid methyl ester compounds of the Heracles electronic nose peak when a WAX chromatographic column with the length of 20m is selected, and the Heracles electronic nose has good separation degree.

The use of the Arochembase database enables qualitative analysis of the compound composition of the samples.

Heracles NEO has high analysis speed and high sensitivity, has various data analysis tools such as quality control models and the like, and can be used as a method for quickly detecting up to 34 fatty acid methyl esters.

Example 2

The test method was substantially the same as in example 1 except for the experimental conditions, which are shown in Table 2.

TABLE 2

Fig. 5 shows a raw gas chromatogram of 37 mixed standard fatty acid methyl esters detected in this example, fig. 6 shows an enlarged view of retention indexes after calibration with a C7-C17 normal alkane standard solution for the raw gas chromatogram of 37 mixed standard fatty acid methyl esters, and fig. 7 and 8 show an enlarged view of retention indexes after calibration with a C10-C40 normal alkane standard solution for the raw gas chromatogram of 37 mixed standard fatty acid methyl esters. As can be seen from FIGS. 5 to 8, the fatty acid methyl ester mixtures showed 34 peaks on a polar column of 20m length (chromatographic peaks with peak area > 10000 were selected). In comparison with the test method of example 1, this time by reducing the carrier gas purge rate and the temperature programming rate, the optimization of the peak profile is improved a little, but the number of chromatographic peaks is not increased. 26 and 30 can be completely separated and independently generate peaks at the time, but 29 and 31 are influenced, and the peaks generated by the peak generation situation of the comparative example 1 obviously reduce the impurity peaks with the response value of less than 500000 at the time, and do not exclude the impurities in the standard product of the example 1. When the new standard is analyzed by the previous method, the impurity peak is obviously reduced, and 29 and 31 are not separated, so that the impurity in the standard influences the previous peak-appearing result.

The AroChemBase database was used to characterize the compounds in the samples, and the compounds contained are shown in figure 9.

Example 3

The test method was substantially the same as in example 1 except for the experimental conditions, which are shown in Table 3.

TABLE 3

The original gas chromatogram of the mixture of 37 fatty acid methyl esters detected in this example is shown in fig. 10, the enlarged diagram of fig. 10 is shown in fig. 11 and fig. 12, and it can be seen that the peak number is 34, most substances are well separated, and part of chromatographic peaks are not completely separated (as indicated by the marks in the boxes), but do not affect the substance qualitative.

Comparative example 1

The detection method is substantially the same as that of example 1 except for experimental conditions, which are shown in Table 4.

TABLE 4

The original gas chromatogram of the mixture of 37 fatty acid methyl esters detected in the comparative example is shown in fig. 13, and fig. 14 and 15 are enlarged views of fig. 13, and it can be seen that the number of peaks is about 20, and the number of peaks is less when the substances co-flow is larger, which is not favorable for the later-stage substance characterization.

Comparative example 2

The detection method is substantially the same as that of example 1 except for experimental conditions, which are shown in Table 5.

TABLE 5

The raw gas chromatogram of the mixture of 37 fatty acid methyl esters detected in this comparative example is shown in fig. 16, and fig. 17 and 18 are enlarged views of fig. 16, from which it can be seen that the number of peaks is 34, but the degree of separation is not good (as indicated by the box mark), possibly interfering with the qualitative results.

Comparative example 3

The detection method is substantially the same as that of example 1 except for experimental conditions, which are shown in Table 6.

TABLE 6

The original gas chromatogram of the mixture of 37 fatty acid methyl esters detected in this comparative example is shown in fig. 19, and fig. 20 and 21 are enlarged views of fig. 19, from which it can be seen that the number of peaks is about 33, most of the separation degrees are good, the individual separation degrees are poor, and co-current may exist, which may interfere with the qualitative determination of the substance.

Comparative example 4

The detection method is basically the same as that of example 1, except that: the length of the column in this example was 10 meters.

The raw gas chromatogram of the mixture of 37 fatty acid methyl esters detected in this example is shown in FIG. 22, and the peak number of this example on a 10m long polar column was only 28 (chromatographic peaks with peak area > 3000 were selected).

Application example

The hydrogenated coconut oil was methyl esterified using a 5% sulfuric acid-methanol solution method and then the sample was tested using ultra fast gas phase electronic nose Heracles as in example 2.

The original gas chromatogram of the sample detected in this example is shown in FIG. 23, and the enlarged view of the sample and the standard of example 2, which is shown by the retention index after calibration with the standard solution of C10-C40 n-alkane, is shown in FIG. 24. As can be seen from FIG. 23, the number of peaks of the methyl-esterified sample excluding the solvent on the polar column of 20m length was 7 (chromatographic peaks with peak area > 8000 were selected).

The compounds in the samples were characterized using the AroChemBase database and the compounds contained are shown in figure 25.

The methyl esterification sample is detected by GC-MC at the same time, the detection map is shown in figure 26, and the qualitative result map is shown in figure 27. Through comparison, the detection result of the Heracles adopting the ultra-fast gas-phase electronic nose is consistent with the detection result of the GC-MC, and therefore, the detection method can accurately and quickly detect the methyl esterification sample.

The above-mentioned embodiments are provided only for illustrating the technical idea and features of the present invention, and the purpose thereof is to enable those skilled in the art to understand the content of the present invention and to implement the present invention, and not to limit the protection scope of the present invention by this, and all equivalent changes or modifications made according to the spirit of the present invention should be covered in the protection scope of the present invention.

Claims

1. The application of the ultra-fast gas-phase electronic nose in detecting fatty acid.

2. Use according to claim 1, characterized in that: the ultra-fast gas-phase electronic nose comprises a first chromatographic column and a second chromatographic column, wherein the first chromatographic column and the second chromatographic column have different polarities.

3. Use according to claim 2, characterized in that: the length of the first chromatographic column and the length of the second chromatographic column are each greater than 10m.

4. Use according to claim 3, characterized in that: the length of the first chromatographic column and the length of the second chromatographic column are each greater than 15m.

5. Use according to claim 2, characterized in that: the first chromatographic column is a polar column and the second chromatographic column is a non-polar column.

6. Use according to claim 1, characterized in that: when the ultra-fast gas phase electronic nose is adopted for detection, the sample introduction duration is controlled to be 25-30 s, the carrier gas constant-current purging speed is controlled to be 0.8-1 mL/min, and/or the shunt speed of the trap is controlled to be 1-8 mL/min, and/or the trap trapping duration is controlled to be 30-35 s, and/or the initial temperature of the chromatographic column at 50 ℃ is controlled to be 5-100 s, and/or the chromatographic column is controlled to be heated to 80-150 ℃ according to 0.3-0.5 ℃/s, kept for 200-300 s, then heated to 250 ℃ according to 0.2-0.5 ℃/s, and kept for 300-500 s.

7. Use according to claim 1, characterized in that: when the ultra-fast gas-phase electronic nose is used for detecting fatty acid, the method comprises the step of methyl esterifying a sample; and/or, the method comprises the step of establishing a relation between the retention time or retention index of each fatty acid methyl ester and the corresponding fatty acid methyl ester on the first chromatographic column and the second chromatographic column by taking a mixture of a plurality of fatty acid methyl esters as a standard substance and taking an n-alkane standard solution as a calibrator.

8. Use according to claim 7, characterized in that: the normal alkane standard solution comprises nC 7-nC 17 normal alkane standard solution and/or nC 10-nC 40 normal alkane standard solution.

9. Use according to claim 7, characterized in that: the specific method for establishing the relationship between each fatty acid methyl ester and the retention time or retention index of the corresponding fatty acid methyl ester on the first chromatographic column and the second chromatographic column comprises the following steps:

(3) And calibrating the result of the mixture of the plurality of fatty acid methyl esters by using the result of the normal alkane standard solution, and then respectively qualifying the mixture of the plurality of fatty acid methyl esters by using an AroChemBase database to obtain the relation between the retention time or retention index of each fatty acid methyl ester and the corresponding fatty acid methyl ester on the first chromatographic column and the second chromatographic column.

10. Use according to claim 7, characterized in that: when the ultra-fast gas-phase electronic nose is used for detecting fatty acid, the method also comprises the steps of calibrating a chromatographic peak of the sample by using a normal alkane standard solution, converting retention time into a retention index, and then carrying out qualitative analysis on a compound by using an AroChemBase database, and/or comparing the retention time or the retention index with a corresponding list of the relationship between the retention time or the retention index of each fatty acid methyl ester and the corresponding fatty acid methyl ester on the first chromatographic column and the second chromatographic column.

11. A method for detecting fatty acid, which is characterized in that: which utilizes an ultra-fast gas-phase electronic nose for detection.