A method for constructing selective retention index for flame photometric detectors

Abstract

The present invention discloses a method for constructing a selective retention index suitable for a flame photometric detector, which belongs to the field of chromatographic analysis and is used to construct the selective retention index of a compound. The selective retention index calibration liquid uses n-hexane as a solvent, and the 7 components it contains are evenly distributed on the time axis. According to the peak position of the analyte in the chromatogram, different mathematical models are used to construct the selective retention index of 113 compounds. The deviation between the selective retention index and the retention index in the database is 0 to 19 retention index units. Within the deviation range allowed for qualitative analysis (0 to 20 retention index units), the selective retention index can be directly compared with the retention index in the database to qualitatively characterize the analyte. This invention solves the problem of no response of normal alkane series compounds on flame photometric detectors and broadens the application of retention index qualitative analysis on selective detectors.

Description

Technical Field

[0001] The invention relates to a method for constructing a selective retention index suitable for a flame photometric detector, belongs to the field of chromatographic analysis, and is used for constructing the selective retention index of a compound. Background Art

[0002] Gas chromatography has the advantages of high resolution, good inertness, high sensitivity, and the ability to perform selective detection, and has become the most widely used analytical technique for the analysis of volatile organic compounds.

[0003] In gas chromatography, qualitative analysis is typically performed by comparison with reference standards. However, in on-site analysis, the analyte is often unknown, and some reference standards are difficult to obtain. When reference standards are unavailable, qualitative analysis can be performed using literature values. The primary basis for qualitative analysis using literature values ​​is retention parameters, including absolute retention time, relative retention time, and retention index. Currently, the most widely used is the retention index. Using the retention index as a qualitative indicator complements and overcomes the shortcomings of relative retention time, making it far more reliable than absolute and relative retention times. To date, the retention index is considered one of the most valuable and comprehensive qualitative indices and has become a standard qualitative method.

[0004] The retention index of the analyte needs to be calibrated using a series of n-alkane retention index calibration solutions. The retention index of n-alkanes is specified as 100 times the number of carbon atoms in the alkane molecule, such as the retention index of n-hexane is 600, the retention index of n-pentadecane is 1500, and so on. Equation 1 is the retention index calculation formula under linear temperature programming conditions:

[0005]

[0006] Among them C n and C n+1 = the number of carbon atoms in the normal alkanes eluted before and after the analyte; t R(x) is the retention time of the analyte; t R(n) and t R(n+1) =Contains C n and C n+1 Retention time of n-alkanes with a carbon number of 1.

[0007] Currently, n-alkane retention index calibrants are the most commonly used retention index standards and have been used as auxiliary identification aids in gas chromatography-mass spectrometry. However, the use of n-alkane retention index calibrants presents the following challenges: theoretically, the closer the structural similarity between the analyte and n-alkanes, the better the reproducibility. However, n-alkanes are non-polar compounds, while most CW-related compounds and pesticides are polar, which impacts the reproducibility of results. Most CW-related compounds and pesticides contain elements such as sulfur and phosphorus, and therefore are often detected using highly sensitive selective detectors. However, n-alkanes are not detectable on selective detectors used for trace analysis (for example, FPDs are highly sensitive to phosphorus atoms but have no response to hydrocarbons). Therefore, retention indices for CW-related compounds and pesticides cannot be constructed using n-alkane retention index calibrants, limiting their application in the analysis of CW-related compounds and pesticides. Therefore, selecting non-n-alkane compounds as reference standards can both improve the reproducibility of test results and broaden the application of retention index qualitative analysis on selective detectors. Summary of the Invention

[0008] The present invention aims to solve the problem that retention index calibration solutions of normal alkanes series do not respond on a flame photometric sulfur-phosphorus detector, and therefore cannot construct retention indices for chemical weapons-related compounds and pesticides; provide a method for constructing a selective retention index suitable for a flame photometric detector, develop a selective retention index calibration solution suitable for a gas chromatography-flame photometric sulfur-phosphorus detector, use this as a reference standard to construct the selective retention index of an analyte, and broaden the application of retention index qualitative analysis on selective detectors.

[0009] The present invention solves the above-mentioned problem by adopting a technical solution, a method for constructing a selective retention index suitable for a flame photometric detector, and the steps are as follows:

[0010] Step 1: Selection of solvent for selective retention index calibration solution

[0011] 0.1 to 0.5 μL of a phosphate triester compound was taken and added to 10.0 mL of n-hexane or dichloromethane to prepare a phosphate triester compound solution with a concentration of 10.0 to 50.0 μg / mL. Chromatograms of the phosphate triester compound in n-hexane, dichloromethane, and both solvents were collected using a Trace GC 2000 FPD gas chromatograph. n-hexane was used as the solvent for the final selective retention index calibration solution. The phosphate triester compound was trimethyl phosphate, triethyl phosphate, tributyl phosphate, or tris(2-ethylhexyl) phosphate.

[0012] Step 2: Determination of sulfur / phosphorus compound solution

[0013] Using n-hexane as a solvent, sulfur / phosphorus compounds were prepared into solutions with a concentration of 5.0 to 20.0 μg / mL by a stepwise dilution method. A Trace 1310 gas chromatograph was used as an analytical instrument. The retention times of the sulfur / phosphorus compounds were collected and ranked from low to high. The first to sixth compounds with the lowest retention times were selected as the first components of a selective retention index calibrant. The retention times were theoretically spaced at intervals of 2.8+0.1n, with n=0 to 26. The theoretical retention times of the remaining components, i.e., expected values, were calculated. The compounds closest to the expected values ​​were selected, and the standard deviations (SD) of the retention time intervals were calculated. The one or two solutions with the lowest standard deviations were selected as alternative solutions. The selected selective retention index calibrant finally contained seven components, namely, allyl methyl sulfide, methyl propyl disulfide, phenethyl sulfide, tripropyl phosphate, diheptyl sulfide, methyl isofenphos, and tri(2-ethylhexyl) phosphate. The seven components were evenly distributed throughout the entire time axis.

[0014] Step 3: Determination of the relative content of each component in the selective retention index calibration solution

[0015] Preparation of a 1 / 100 volume ratio single component stock solution: 10 μL of each of allyl methyl sulfide, methyl propyl disulfide, phenethyl sulfide, tripropyl phosphate, diheptyl sulfide, and tri(2-ethylhexyl) phosphate were added to 990 μL of n-hexane solution to prepare a 1 / 100 volume ratio single component stock solution. Due to its high viscosity, isofenphos-methyl was prepared to a concentration of 10 mg / mL, i.e., a 1 / 100 volume ratio single component stock solution. Using n-hexane as the solvent, tripropyl phosphate was prepared to a concentration of 1.0 μg / mL. Based on the 1.0 μg / mL concentration of tripropyl phosphate, the concentrations of the other components were adjusted to 1.0 to 40.0 μg / mL. A selectivity retention index calibrant was prepared so that the signal generated by the sulfur-containing compounds in the selectivity retention index calibrant in the P channel was equivalent to the signal generated by the phosphorus-containing compounds.

[0016] Step 4: Stability Study of Selective Retention Index Calibrator

[0017] Prepare a stock solution of the selective retention index calibrant according to the relative concentration of each component. Place the stock solution of the selective retention index calibrant at room temperature for 1 to 6 months for stability study. Dilute 100-fold with n-hexane before use.

[0018] Step 5: Construction of the Selective Retention Index of the Analyte

[0019] Take 100-200 μL of retention index calibration solution and add the analyte to the retention index calibration solution to make the concentration of the analyte 1.0-10.0 μg / mL. Use gas chromatography-flame photometric sulfur-phosphorus detector to collect the retention times of the analyte and the two components before and after the peak position of the analyte in the retention index calibration solution. According to the peak position of the analyte and the following different mathematical models, the selective retention index of the analyte is constructed:

[0020] (1) The peak position is before the first component, and the selectivity retention index is constructed using formula 2:

[0021] RI x =697-125*(t R(1) -t R(x) ) Formula 2

[0022] (2) The peak position is between the first component and the second component, and the selectivity retention index is constructed using formula 3:

[0023]

[0024] (3) The peak position is between the second and third components, and the selectivity retention index is constructed using formula 4:

[0025]

[0026] (4) The peak position is between the third and fourth components, and the selectivity retention index is constructed using formula 5:

[0027]

[0028] (5) The peak position is between the 4th and 5th components, and the selectivity retention index is constructed using formula 6:

[0029]

[0030] (6) The peak position is between the fifth and sixth components, and the selectivity retention index is constructed using formula 7:

[0031]

[0032] (7) The peak position is between the 6th and 7th components, and the selectivity retention index is constructed using formula 8:

[0033]

[0034] (8) The peak position is after the 7th component, and the selectivity retention index is constructed using formula 9:

[0035] RI x =2448+85.5*(tR(x) -t R(7) ) Formula 9

[0036] When using retention indices for qualitative analysis of unknowns, the deviation between the experimentally measured retention index and the retention index in the database is required to be within 20 retention index units. Using the present invention, selective retention indices for 113 compounds were constructed. The constructed retention indices and the retention indices in the database are shown in Table 1.

[0037] Table 1 Selective retention index of compounds and retention index in the database

[0038]

[0039]

[0040]

[0041] Note: RI0: retention index in the database;

[0042] RI B : Selective retention index constructed according to this patent;

[0043] *: Retention index data are derived from the OCAD database;

[0044] #: Retention index data comes from the NIST database;

[0045] ◎: Retention index is derived from the VGWD database.

[0046] Beneficial effects of the present invention:

[0047] (1) The selective retention index calibration solution uses n-hexane as the solvent. Trisphosphate compounds of the same concentration have higher responses and better peak shapes in n-hexane. The solvent peak produced by n-hexane is smaller and has less impact on low-boiling point substances. Compared with chlorinated solvents, n-hexane is easier to handle.

[0048] (2) The selective retention index calibration solution contains 7 components, all of which contain sulfur and / or phosphorus elements and have good responses on both the P and S channels of the gas chromatography-flame photometry sulfur-phosphorus detector.

[0049] (3) The seven components in the selective retention index calibrant are evenly distributed over the entire time axis, and the retention time interval between two adjacent components is 3.1 to 3.7 min.

[0050] (4) The concentrations of the seven components in the selectivity retention index ranged from 1.0 to 40.0 μg / mL, and the signals generated in the P channel were comparable.

[0051] (5) The stock solution of the selective retention index calibration solution prepared according to the relative concentrations of each component was placed at room temperature for 0 to 6 months. No interaction occurred between the components, and the stock solution of the selective retention index calibration solution could exist stably.

[0052] (6) By recording the retention times of the two components adjacent to the peak position of the analyte and the retention index calibrant, the selective retention indices of 114 compounds were constructed according to the peak position of the analyte using different mathematical models. The deviation of the constructed selective retention index from the retention index in the NIST database or the OCAD database was 0 to 19 retention index units, while the retention index deviation allowed in qualitative analysis was 0 to 20 retention index units. The constructed selective retention index could be directly compared with the database to qualitatively identify the analyte. BRIEF DESCRIPTION OF THE DRAWINGS

[0053] Figure 1 Chromatogram of trimethyl phosphate in n-hexane at a concentration of 10.0 μg / mL

[0054] In the figure: the horizontal axis is the retention time min, and the vertical axis is the chromatographic peak intensity;

[0055] Retention time (RT) = 4.84 min, chromatographic peak height (Intensity) = 3.29 × 10 0 .

[0056] Figure 2 Chromatogram of trimethyl phosphate in dichloromethane at a concentration of 10.0 μg / mL

[0057] In the figure: the horizontal axis is the retention time min, and the vertical axis is the chromatographic peak intensity;

[0058] Retention time (RT) = 5.30 min, chromatographic peak height (Intensity) = 2.16 × 10 0 .

[0059] Figure 3 Chromatogram of triethyl phosphate in n-hexane at a concentration of 10.0 μg / mL

[0060] In the figure: the horizontal axis is the retention time min, and the vertical axis is the chromatographic peak intensity;

[0061] Retention time (RT) = 7.12 min, chromatographic peak height (Intensity) = 1.27 × 10 1 .

[0062] Figure 4 Chromatogram of triethyl phosphate in dichloromethane at a concentration of 10.0 μg / mL

[0063] In the figure: the horizontal axis is the retention time min, and the vertical axis is the chromatographic peak intensity;

[0064] Retention time (RT) = 7.30 min, chromatographic peak height (Intensity) = 6.93 × 10 0 .

[0065] Figure 5 Chromatogram of tributyl phosphate in n-hexane at a concentration of 10.0 μg / mL

[0066] In the figure: the horizontal axis is the retention time min, and the vertical axis is the chromatographic peak intensity;

[0067] Retention time (RT) = 12.95 min, chromatographic peak height (Intensity) = 3.47 × 10 1 .

[0068] Figure 6 Chromatogram of tributyl phosphate in dichloromethane at a concentration of 10.0 μg / mL

[0069] In the figure: the horizontal axis is the retention time min, and the vertical axis is the chromatographic peak intensity;

[0070] Retention time (RT) = 13.10 min, chromatographic peak height (Intensity) = 1.29 × 10 1 .

[0071] Figure 7 Chromatogram of trihexyl phosphate in n-hexane at a concentration of 10.0 μg / mL

[0072] In the figure: the horizontal axis is the retention time min, and the vertical axis is the chromatographic peak intensity;

[0073] Retention time (RT) = 18.29 min, chromatographic peak height (Intensity) = 8.48 × 10 0 .

[0074] Figure 8 Chromatogram of trihexyl phosphate in dichloromethane at a concentration of 10.0 μg / mL

[0075] In the figure: the horizontal axis is the retention time min, and the vertical axis is the chromatographic peak intensity;

[0076] Retention time (RT) = 18.30 min, chromatographic peak height (Intensity) = 4.32 × 10 0 .

[0077] Figure 9 Chromatogram of tri(2-ethylhexyl) phosphate in n-hexane at a concentration of 10.0 μg / mL

[0078] In the figure: the horizontal axis is the retention time min, and the vertical axis is the chromatographic peak intensity;

[0079] Retention time (RT) = 20.41 min, chromatographic peak height (Intensity) = 1.97 × 10 1 .

[0080] Figure 10 Chromatogram of tri(2-ethylhexyl) phosphate in dichloromethane at a concentration of 10.0 μg / mL

[0081] In the figure: the horizontal axis is the retention time min, and the vertical axis is the chromatographic peak intensity;

[0082] Retention time (RT) = 20.47 min, chromatographic peak height (Intensity) = 1.19 × 10 1 .

[0083] Figure 11 Retention time distribution of 42 sulfur / phosphorus compounds on Trace1310

[0084] In the figure: the horizontal axis is the retention time min;

[0085] The retention times (RT) of the 42 compounds are as follows: t R(1) =3.15min; t R(2) =4.20min; t R(3) =4.68min; t R(4) =4.72min; t R(5) =4.94min; t R(6) =5.82min; t R(7) =5.96min; t R(8) =7.28min; t R(9) =7.81min; t R(10) =7.82min; t R(11) =7.97min; t R(12) =9.37min; t R(13) =10.36min; t R(14) =10.37min; t R(15) =10.71min; t R(16) =10.80min;t R(17) =11.28min; t R(18) =11.71min; t R(19) =11.84min; t R(20) =11.89min; t R(21) =12.34min; t R(22) =12.68min; t R(23)=13.20min;t R(24) =13.28min; t R(25) =14.38min; t R(26) =15.75min; t R(27) =16.03min;t R(28) =16.41min; t R(29) =17.46min; t R(30) =17.53min; t R(31) =18.06min;t R(32) =18.85min; t R(33) =19.24min; t R(34) =19.38min; t R(35) =20.26min;t R(36) =21.31min; t R(37) =21.71min; t R(38) =22.93min; t R(39) =22.94min;t R(40) =25.15min; t R(41) =25.20min;t R(42) =25.32min.

[0086] Figure 12 Response of the Selective Retention Index Calibrator in the P Channel at 1 Month

[0087] In the figure: the horizontal axis is the retention time min, and the vertical axis is the chromatographic peak intensity;

[0088] The retention times (RT) of the 7 components are: t R(1) =4.67min; t R(2) =7.96min; t R(3) =11.29min; t R(4) =14.38min; t R(5) =18.04min; t R(6) =21.67min; t R(7) =25.14min.

[0089] The chromatographic peak heights (Intensity) of the 7 components are as follows: I R(1) =6.13×10 2 ;I R(2) =5.68×10 2 ;I R(3) =7.72×10 2 ;I R(4) =7.08×10 2 ;I R(5)=7.07×10 2 ;I R(6) =8.39×10 2 ;I R(7) =8.77×10 2 .

[0090] Figure 13 Response of the Selective Retention Index Calibrator in the S Channel at 1 Month

[0091] In the figure: the horizontal axis is the retention time min, and the vertical axis is the chromatographic peak intensity;

[0092] The retention times (RT) of the 7 components are: t R(1) =4.67min; t R(2) =7.96min; t R(3) =11.28min; t R(4) =14.38min; t R(5) =18.06min;t R(6) =21.69min; t R(7) =25.14min.

[0093] The chromatographic peak heights (Intensity) of the 7 components are as follows: I R(1) =3.99×10 3 ;I R(2) =3.87×10 3 ;I R(3) =5.38×10 3 ;I R(4) =1.80×10 1 ;I R(5) =4.88×10 3 ;I R(6) =2.31×10 1 ;I R(7) =1.86×10 1 .

[0094] Figure 14 P channel chromatogram after adding selective retention index calibration solution to methyl ethyl sulfide

[0095] In the figure: the horizontal axis is the retention time min, and the vertical axis is the chromatographic peak intensity;

[0096] The retention times (RT) of the eight compounds are as follows: t R(x) =4.19min; t R(1) =4.67min; t R(2) =7.96min; t R(3) =11.28min; t R(4) =14.38min; tR(5) =18.04min; t R(6) =21.67min; t R(7) =25.15min. t R(x) represents the retention time of ethyl methyl sulfide, t R(n) Represents the retention time of the nth component in the retention index calibrant.

[0097] The chromatographic peak heights (Intensity) of the 8 compounds are as follows: R(x) =1.68×10 2 ;I R(1) =2.99×10 2 ;I R(2) =3.32×10 2 ;I R(3) =3.65×10 2 ;I R(4) =4.86×10 2 ;I R(5) =4.11×10 2 ;I R(6) =5.00×10 2 ;I R(7) =6.01×10 2 I R(x) Represents the chromatographic peak height of methyl ethyl sulfide, I R(n) Represents the chromatographic peak height of the nth component in the retention index calibrant.

[0098] Figure 15 P channel chromatogram of ethyl methylphosphonate after adding selective retention index calibration solution

[0099] In the figure: the retention times (RT) of the 8 compounds are: t R(1) =4.68min; t R(x) =5.49min; t R(2) =7.97min; t R(3) =11.28min; t R(4) =14.38min; t R(5) =18.04min; t R(6) =21.66min;t R(7) =25.14min. t R(x) represents the retention time of ethyl methylphosphonate, t R(n) Represents the retention time of the nth component in the retention index calibrant;

[0100] The chromatographic peak heights (Intensity) of the 8 compounds are as follows: R(1) =8.60×10 2 ;I R(x)=2.43×10 3 ;I R(2) =7.85×10 2 ;I R(3) =9.87×10 2 ;I R(4) =6.74×10 2 ;I R(5) =9.60×10 2 ;I R(6) =9.20×10 2 ;I R(7) =1.03×10 3 I R(x) Represents the chromatographic peak height of ethyl methylfluorophosphonate, I R(n) Represents the chromatographic peak height of the nth component in the retention index calibrant.

[0101] Figure 16 Chromatogram of P channel after Tabun was added with selective retention index calibration solution

[0102] In the figure: the retention times (RT) of the 8 compounds are: t R(1) =4.66min; t R(2) =7.97min; t R(x) =10.86min; t R(3) =11.29min; t R(4) =14.38min; t R(5) =18.05min; t R(6) =21.67min; t R(7) =25.14min. t R(x) represents the retention time of the tabun, t R(n) Represents the retention time of the nth component in the retention index calibrant;

[0103] The chromatographic peak heights (Intensity) of the 8 compounds are as follows: R(1) =7.11×10 2 ;I R(2) =7.68×10 2 ;I R(x) =1.11×10 3 ;I R(3) =1.06×10 3 ;I R(4) =1.05×10 3 ;I R(5) =9.86×10 2 ;I R(6) =1.07×10 3 ;I R(7) =1.21×10 3 IR(x) Represents the chromatographic peak height of Tabun, I R(n) Represents the chromatographic peak height of the nth component in the retention index calibrant.

[0104] Figure 17 Chromatogram of P channel after adding dichlorvos to the selective retention index calibration solution

[0105] In the figure: the retention times (RT) of the 8 compounds are: t R(1) =4.67min; t R(2) =7.97min; t R(3) =11.29min; t R(x) =12.68min; t R(4) =14.38min; t R(5) =18.05min; t R(6) =21.67min; t R(7) =25.14min. t R(x) represents the retention time of dichlorvos, t R(n) Represents the retention time of the nth component in the retention index calibrant;

[0106] The chromatographic peak heights (Intensity) of the 8 compounds are as follows: R(1) =6.77×10 2 ;I R(2) =8.24×10 2 ;I R(3) =1.18×10 3 ;I R(x) =1.42×10 3 ;I R(4) =1.12×10 3 ;I R(5) =1.14×10 3 ;I R(6) =1.11×10 3 ;I R(7) =1.28×10 3 I R(x) Represents the chromatographic peak height of dichlorvos, I R(n) Represents the chromatographic peak height of the nth component in the retention index calibrant.

[0107] Figure 18 P channel chromatogram after adding trimethylsilyloxyethyl ethyl sulfone to the selectivity retention index calibration solution

[0108] In the figure: the retention times (RT) of the 8 compounds are: t R(1) =4.64min; t R(2) =8.02min; t R(3)=11.29min; t R(4) =14.39min; t R(x) =14.65min; t R(5) =18.05min; t R(6) =21.67min; t R(7) =25.14min. t R(x) represents the retention time of trimethylsilyloxyethyl ethyl sulfone, t R(n) Represents the retention time of the nth component in the retention index calibrant;

[0109] The chromatographic peak heights (Intensity) of the 8 compounds are as follows: R(1) =3.95×10 2 ;I R(2) =1.12×10 3 ;I R(3) =1.16×10 3 ;I R(4) =1.08×10 3 ;I R(x) =2.30×10 3 ;I R(5) =1.29×10 3 ;I R(6) =1.12×10 3 ;I R(7) =1.39×10 3 I R(x) Represents the chromatographic peak height of trimethylsilyloxyethyl ethyl sulfone, I R(n) Represents the chromatographic peak height of the nth component in the retention index calibrant.

[0110] Figure 19 The response of VEX in the P channel after adding the selective retention index calibrant

[0111] In the figure: the retention times (RT) of the 8 compounds are: t R(1) =4.67min; t R(2) =7.96min; t R(3) =11.28min; t R(4) =14.38min; t R(5) =18.04min; t R(x) =18.22min; t R(6) =21.67min; t R(7) =25.14min. t R(x) represents the retention time of VX, t R(n) Represents the retention time of the nth component in the retention index calibrant;

[0112] The chromatographic peak heights (Intensity) of the 8 compounds are as follows: R(1) =6.51×10 2 ;I R(2) =5.81×10 2 ;I R(3) =7.38×10 2 ;I R(4) =8.53×10 2 ;I R(5) =7.12×10 2 ;I R(x) =1.71×10 3 ;I R(6) =8.49×10 2 ;I R(7) =9.87×10 2 I R(x) Represents the chromatographic peak height of VEX, I R(n) Represents the chromatographic peak height of the nth component in the retention index calibrant.

[0113] Figure 20 Response of trithion in P channel after adding selective retention index calibration solution

[0114] In the figure: the retention times (RT) of the 8 compounds are: t R(1) =4.67min; t R(2) =7.97min; t R(3) =11.28min; t R(4) =14.38min; t R(5) =18.05min; t R(6) =21.67min; t R(x) =24.21min; t R(7) =25.14min. t R(x) represents the retention time of trithion, t R(n) Represents the retention time of the nth component in the retention index calibrant;

[0115] The chromatographic peak heights (Intensity) of the 8 compounds are as follows: R(1) =6.93×10 2 ;I R(2) =7.53×10 2 ;I R(3) =1.02×10 3 ;I R(4) =1.06×10 3 ;I R(5) =9.69×10 2 ;I R(6) =1.05×10 3;I R(x) =9.79×10 2 ;I R(7) =1.18×10 3 I R(x) Represents the chromatographic peak height of trithion, I R(n) Represents the chromatographic peak height of the nth component in the retention index calibrant.

[0116] Figure 21 Response of coumaphos in the P channel after adding selective retention index calibrant

[0117] In the figure: the retention times (RT) of the 8 compounds are: t R(1) =4.66min; t R(2) =7.96min; t R(3) =11.29min; t R(4) =14.38min; t R(5) =18.04min; t R(6) =21.67min; t R(7) =25.14min;t R(x) =27.82min. t R(x) represents the retention time of coumaphos, t R(n) Represents the retention time of the nth component in the retention index calibrant;

[0118] The chromatographic peak heights (Intensity) of the 8 compounds are as follows: R(1) =7.30×10 2 ;I R(2) =6.79×10 2 ;I R(3) =8.96×10 2 ;I R(4) =9.32×10 2 ;I R(5) =9.03×10 2 ;I R(6) =9.29×10 2 ;I R(7) =1.19×10 3 ;I R(x) =4.21×10 2 I R(x) Represents the chromatographic peak height of coumaphos, I R(n) Represents the chromatographic peak height of the nth component in the retention index calibrant. DETAILED DESCRIPTION

[0119] The present invention is further described in detail below with reference to specific embodiments.

[0120] (1) Preparation of Selective Retention Index Calibration Solution

[0121] Take 150 μL of 1 / 100 volume ratio of allyl methyl sulfide mother solution, take 60 μL of 1 / 100 volume ratio of methyl propyl disulfide mother solution, take 100 μL of 1 / 100 volume ratio of phenylethyl sulfide mother solution, take 5 μL of 1 / 100 volume ratio of tripropyl phosphate mother solution, take 200 μL of 1 / 100 volume ratio of diheptyl sulfide mother solution, take 8 μL of 1 / 100 volume ratio of methyl isothioate mother solution, take 20 μL of 1 / 100 volume ratio of tri(2-ethylhexyl) phosphate mother solution to prepare 543 μL of retention index calibrant B mother solution.

[0122] (2) Preparation of selective retention index calibrant: Take 100 μL of the stock solution of selective retention index calibrant and dilute it 100 times with n-hexane to prepare 10.0 mL of selective retention index calibrant.

[0123] Example 1

[0124] Construction of Selective Retention Index for Ethyl Methyl Sulfide

[0125] Take 180 μL of selective retention index calibration solution, add 20 μL of methyl ethyl sulfide / n-hexane solution with a volume ratio of 1 / 10000, and analyze it using Trace 1310 gas chromatograph. The chromatogram of channel P is as follows: Figure 14 shown.

[0126] Determination results: The peak position of methyl ethyl sulfide is before the first component. The selectivity retention index is constructed using formula 2: t R(x) =4.19min, t R(1) =4.67min, RI x =697-125*(4.67-4.19)=637.

[0127] The retention index of ethyl methyl sulfide in the NIST database is 638, which is 1 retention index unit different from the retention index in the database. Within the allowable deviation range of qualitative analysis (0 to 20 retention index units), the selective retention index can be directly compared with the retention index in the database to qualitatively identify the analyte.

[0128] Example 2

[0129] Construction of Selective Retention Index for Ethyl Methylfluorophosphonate

[0130] Take 200 μL of the selective retention index calibration solution, add 1 μL of 1 mg / mL methylphosphonofluoroethyl ester / dichloromethane solution, and analyze using a Trace 1310 gas chromatograph. The chromatogram of the P channel is as follows: Figure 15 shown.

[0131] Determination results: The peak position of ethyl methylphosphonate is between the first component and the second component. The selectivity retention index is constructed using formula 3: t R(1) =4.68min, t R(x) =5.49min, t R(2) =7.97min,

[0132] RI x =697+249*(5.49-4.68) / (7.97-4.68)=758.

[0133] The retention index of ethyl methylphosphonate in the NIST database is 755, which is 3 retention index units different from the retention index in the database. This is within the allowable deviation range for qualitative analysis (0 to 20 retention index units). The selective retention index can be directly compared with the retention index in the database to qualitatively identify the analyte.

[0134] Example 3

[0135] Construction of Tabun Selective Retention Index

[0136] Take 200 μL of selective retention index calibration solution, add 0.1 μL of 2 mg / mL tabun / acetonitrile solution, and analyze using Trace 1310 gas chromatograph. The chromatogram of channel P is as follows: Figure 16 shown.

[0137] Measurement results: The peak position of the tower collapse is between the second component and the third component. The selectivity retention index is constructed using formula 4: t R(2) =7.97min, t R(x) =10.86min, t R(3) =11.29min,

[0138] RI x =946+214*(10.86-7.97) / (11.29-7.97)=1132.

[0139] The retention index in the OCAD database is 1133, which differs by 1 retention index unit. Within the allowable deviation range of qualitative analysis (0 to 20 retention index units), the selective retention index can be directly compared with the retention index in the database to qualitatively identify the analyte.

[0140] Example 4

[0141] Construction of the Selective Retention Index of Dichlorvos

[0142] Take 200 μL of selective retention index calibration solution, add 5 μL of 100 μg / mL dichlorvos / acetone solution, and analyze using Trace 1310 gas chromatograph. The chromatogram of channel P is as follows: Figure 17 shown.

[0143] Determination results: The peak position of dichlorvos is between the third and fourth components. The selectivity retention index is constructed using formula 5: t R(3) =11.29min, t R(x) =12.68min, t R(4) =14.38min,

[0144] RI x =1160+219*(12.68-11.29) / (14.38-11.29)=1259.

[0145] The retention index of dichlorvos in the NIST database is 1263, which is 4 retention index units different from the previous one. Within the allowable deviation range of qualitative analysis (0 to 20 retention index units), the selective retention index can be directly compared with the retention index in the database to qualitatively identify the analyte.

[0146] Example 5

[0147] Construction of Selective Retention Index of Trimethylsilyloxyethyl Ethyl Sulfone

[0148] Take 150 μL of the selective retention index calibration solution, add 50 μL of a 100 μg / mL trimethylsilyloxyethyl ethyl sulfone / dichloromethane solution, and analyze using a Trace 1310 gas chromatograph. The chromatogram of the P channel is as follows: Figure 18 shown.

[0149] Determination results: The peak position of trimethylsilyloxyethyl ethyl sulfone is between the 4th component and the 5th component. The selectivity retention index is constructed using formula 6: t R(4) =14.39min, t R(x) =14.65min, t R(5) =18.05min,

[0150] RI x =1379+317*(14.65-14.39) / (18.05-14.39)=1402.

[0151] The retention index of trimethylsilyloxyethyl ethyl sulfone in the NIST database is 1405, which differs by 3 retention index units. This is within the allowable deviation range for qualitative analysis (0 to 20 retention index units). The selective retention index can be directly compared with the retention index in the database to qualitatively identify the analyte.

[0152] Example 6

[0153] Construction of Selective Retention Index for Ethyl S-2-Diisopropylaminoethyl Methylphosphonothioate

[0154] Take 200 μL of selective retention index calibration solution, add 0.2 μL of 2 mg / mL Viagra / acetonitrile solution, and analyze using Trace 1310 gas chromatograph. The chromatogram of channel P is as follows: Figure 19 shown.

[0155] Measurement results: The peak position of VEX is between the 5th and 6th components. The selectivity retention index is constructed using formula 7: t R(5) =18.04min, t R(x) =18.22min, t R(6) =21.67min,

[0156] RI x =1696+366*(18.22-18.04) / (21.67-18.04)=1714.

[0157] The retention index of VIX in the OCAD database is 1713, which differs by 1 retention index unit. Within the allowable deviation range of qualitative analysis (0 to 20 retention index units), the selective retention index can be directly compared with the retention index in the database to qualitatively identify the analyte.

[0158] Example 7

[0159] Construction of the Selective Retention Index of Trithion

[0160] Take 200 μL of selective retention index calibration solution, add 5 μL of 100 μg / mL trithion / acetone solution, and analyze using Trace 1310 gas chromatograph. The chromatogram of P channel is as follows: Figure 20 shown.

[0161] Determination results: The peak position of trithion is between the 6th and 7th components. The selectivity retention index is constructed using formula 8: t R(6) =21.67min, t R(x) =24.21min, t R(7) =25.14min,

[0162] RI x =2062+386*(24.21-21.67) / (25.14-21.67)=2344.

[0163] The retention index of trithion in the NIST database is 2337, which is 7 retention index units different from the previous one. Within the allowable deviation range of qualitative analysis (0 to 20 retention index units), the selective retention index can be directly compared with the retention index in the database to qualitatively identify the analyte.

[0164] Example 8

[0165] Construction of the Selective Retention Index for Coumaphos

[0166] Take 200 μL of selective retention index calibration solution, add 5 μL of 100 μg / mL coumaphos / acetone solution, and analyze using Trace 1310 gas chromatograph. The chromatogram of P channel is as follows: Figure 21 shown.

[0167] Measurement results: The peak position is after the 7th component. The selectivity retention index is constructed using formula 9: t R(7) =25.14min, t R(x) =27.82min, RI x =2448+85.5*(27.82-25.14)=2677.

[0168] The retention index of coumaphos in the NIST database is 2669, which is 8 retention index units different from the retention index in the database. Within the allowable deviation range of qualitative analysis (0 to 20 retention index units), the selective retention index can be directly compared with the retention index in the database to qualitatively identify the analyte.

Claims

1. A method for constructing a selective retention index suitable for a flame photometric detector, characterized in that The construction method steps are as follows: Step 1: Selection of solvent for selective retention index calibration solution 0.1 to 0.5 μL of a phosphate triester compound is added to 10.0 mL of n-hexane or dichloromethane to prepare a phosphate triester compound solution with a concentration of 10.0 to 50.0 μg / mL. Chromatograms of the phosphate triester compound in n-hexane, dichloromethane, and two solvents are collected using a Trace GC 2000FPD gas chromatograph. The final selective retention index calibration solution uses n-hexane as the solvent. The phosphate triester compound is trimethyl phosphate, triethyl phosphate, tributyl phosphate, or tris(2-ethylhexyl) phosphate. Step 2: Determination of sulfur / phosphorus compound solution Using n-hexane as a solvent, sulfur / phosphorus compounds were prepared into solutions with a concentration of 5.0 to 20.0 μg / mL by a stepwise dilution method. A Trace 1310 gas chromatograph was used as an analytical instrument. The retention times of the sulfur / phosphorus compounds were collected and ranked from low to high. The first to sixth compounds with the lowest retention times were selected as the first components of a selective retention index calibrant. The retention times were theoretically spaced at intervals of 2.8+0.1n, with n=0 to 26. The theoretical retention times of the remaining components, i.e., expected values, were calculated. The compounds closest to the expected values ​​were selected, and the standard deviations (SD) of the retention time intervals were calculated. The one or two solutions with the lowest standard deviations were selected as alternative solutions. The selected selective retention index calibrant finally contained seven components, namely, allyl methyl sulfide, methyl propyl disulfide, phenethyl sulfide, tripropyl phosphate, diheptyl sulfide, methyl isofenphos, and tri(2-ethylhexyl) phosphate. The seven components were evenly distributed throughout the entire time axis. Step 3: Determination of the relative content of each component in the selective retention index calibration solution Preparation of a 1 / 100 volume ratio single component stock solution: 10 μL of each of allyl methyl sulfide, methyl propyl disulfide, phenethyl sulfide, tripropyl phosphate, diheptyl sulfide, and tri(2-ethylhexyl) phosphate were added to 990 μL of n-hexane solution to prepare a 1 / 100 volume ratio single component stock solution. Due to its high viscosity, isofenphos-methyl was prepared to a concentration of 10 mg / mL, i.e., a 1 / 100 volume ratio single component stock solution. Using n-hexane as the solvent, tripropyl phosphate was prepared to a concentration of 1.0 μg / mL. Based on the 1.0 μg / mL concentration of tripropyl phosphate, the concentrations of the other components were adjusted to 1.0 to 40.0 μg / mL. A selectivity retention index calibrant was prepared so that the signal generated by the sulfur-containing compounds in the selectivity retention index calibrant in the P channel was equivalent to the signal generated by the phosphorus-containing compounds. Step 4: Stability Study of Selective Retention Index Calibrator Prepare a stock solution of the selective retention index calibrant according to the relative concentration of each component. Place the stock solution of the selective retention index calibrant at room temperature for 1 to 6 months for stability study. Dilute 100-fold with n-hexane before use. Step 5: Construction of the Selective Retention Index of the Analyte Take 100-200 μL of retention index calibration solution and add the analyte to the retention index calibration solution to make the concentration of the analyte 1.0-10.0 μg / mL. Use gas chromatography-flame photometric sulfur-phosphorus detector to collect the retention times of the analyte and the two components before and after the peak position of the analyte in the retention index calibration solution. According to the peak position of the analyte and the following different mathematical models, the selective retention index of the analyte is constructed: (1) The peak position is before the first component, and the selectivity retention index is constructed using formula 1: RI x = 697 - 125*(t R(1) - t R(x) ) Equation 1 (Undefined letters in the formula, the same below) (2) The peak position is between the first component and the second component, and the selectivity retention index is constructed using formula 2: (3) The peak position is between the second and third components, and the selectivity retention index is constructed using formula 3: (4) The peak position is between the third and fourth components, and the selectivity retention index is constructed using formula 4: (5) The peak position is between the 4th and 5th components, and the selectivity retention index is constructed using formula 5: (6) The peak position is between the fifth and sixth components, and the selectivity retention index is constructed using formula 6: (7) The peak position is between the 6th and 7th components, and the selectivity retention index is constructed using formula 7: (8) The peak position is after the 7th component, and the selectivity retention index is constructed using formula 8: RI x = 2448 + 85.5 * (t R(x) - t R(7) ) Equation 8 When using retention indices for qualitative analysis of unknowns, the deviation between the experimentally measured retention index and the retention index in the database is required to be within 20 retention index units. Selective retention indices for 113 compounds were constructed. The retention indices and the retention indices in the database are shown in Table 1: Table 1 Selective retention index of compounds and retention index in the database Note: RI0: Retention index in the database; RI B : The selective retention index constructed according to claim 1; *: Retention index data are derived from the OCAD database; #: Retention index data comes from the NIST database; ◎: Retention index is derived from the VGWD database.

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