CN113624886A - Method for measuring concentration of triethylamine in air of workplace - Google Patents
Method for measuring concentration of triethylamine in air of workplace Download PDFInfo
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Abstract
The invention discloses a method for measuring triethylamine concentration in air of a workplace. Because triethylamine is hydrolyzed into alkalescence, the triethylamine in the air of the workplace is adsorbed and collected by the acidic silica gel tube, and the adsorption efficiency of the triethylamine in the air of the workplace is improved. The acidic silica gel tube adsorbs triethylamine in the air of the collection workplace and combines headspace sampling for gas chromatography analysis, the conventional process of ultrasonic analysis by sulfuric acid and neutralization by adding alkali liquor is avoided, the test flow is simplified, and the service life of the instrument is prolonged.
Description
Technical Field
The invention belongs to the technical field of organic amine detection, and particularly relates to a method for determining triethylamine concentration in air of a workplace.
Background
The existing detection standard of triethylamine concentration in air of workplace is 'GBZ/T300.136-2017 determination of toxic substances in air of workplace 136 th part of trimethylamine, diethylamine and triethylamine', in the prior art, an alkaline silicone tube is adopted to collect triethylamine in air of adsorption workplace, silica gel is poured into an analytical bottle, 2mL of sulfuric acid is added for sealing and ultrasonic analysis is carried out for 20min, 0.5mL of analytical solution is taken out of a test tube, 0.5mL of sodium hydroxide solution is added for neutralization, and then analysis is carried out by a gas chromatograph (a chromatographic column is a packed column).
However, the existing detection technology often has the following problems: 1. because triethylamine is ionized to be alkalescent, the collection and adsorption efficiency of an alkaline silica gel tube is not high; 2. triethylamine in the air of a workplace is adsorbed by using alkaline silica gel, the silica gel is taken out by using a collected silica gel tube, sulfuric acid is added for ultrasonic analysis, and then alkali liquor is added for neutralization: the operation is complicated and long-time consuming, and if the neutralization is not good, the acid and the alkali have great damage to the sample inlet and the chromatographic column of the gas chromatograph, and the service life of the instrument is shortened.
Disclosure of Invention
Aiming at the problems, the invention aims to provide a method for measuring the concentration of triethylamine in air of a workplace, which effectively improves and simplifies the experimental process and reduces the detection limit of the method.
In order to realize the purpose, the following technical scheme is adopted:
a method for measuring triethylamine concentration in air of a workplace adopts an acidic silica gel tube to adsorb and collect triethylamine in the air of the workplace, and carries out gas chromatography analysis on the collected triethylamine in a headspace sampling mode.
Preferably, the gas chromatography analysis of the collected triethylamine by means of headspace sampling comprises the following steps:
s1, placing the acidic silica gel with the collected triethylamine into a headspace bottle to prepare a sample to be detected;
s2, taking a group of triethylamine standard solutions with concentration gradients, taking the concentration as a horizontal coordinate, taking a chromatographic peak area corresponding to the concentration as a vertical coordinate, and establishing a standard curve;
s3, setting parameters of headspace sample injection and parameters of a gas chromatograph, performing gas chromatographic analysis on the sample to be detected by adopting headspace sample injection based on the standard curve, and determining the content of triethylamine in the sample to be detected;
s4, calculating the triethylamine concentration in the air of the workplace according to the gas chromatography analysis result, wherein the formula is as follows:
wherein rho is the concentration of triethylamine in the air of a workplace in mg/m3(ii) a C is the content of triethylamine in the acidic silica gel tube, and is microgram; v is the sampling volume, L; coThe content of triethylamine in the blank silicone tube is μ g.
Preferably, the parameters of the headspace sampling comprise: the heating equilibrium temperature is 80 ℃; the balance time is 20 min; the temperature of the sampling needle is 100 ℃; the temperature of the transmission line is 110 ℃; the volume of the quantitative loop injection is 1 mL.
Preferably, the parameters of the gas chromatograph include: the temperature of a sample inlet is 220 ℃; the sample introduction mode is split, and the split ratio is 5: 1; the column flow rate is 1.25 mL/min; the temperature of the column incubator is programmed to 50 ℃, the temperature is kept for 2min, and then the temperature is raised to 150 ℃ at the speed of 10 ℃/min; detector temperature 280 ℃, hydrogen flow: 30mL/min, workplace air flow: 300 mL/min.
Preferably, the preparing of the sample to be detected specifically comprises: and (3) putting the acidic silica gel with the collected triethylamine into a headspace bottle, and adding sodium chloride, a sodium hydroxide solution and ammonia water to obtain a mixed solution with the pH value of more than 12.
Preferably, the sodium chloride is firstly burned in a muffle furnace at 400 ℃ for 4h, placed in a dryer for cooling, and then added into a headspace bottle.
Preferably, the acid silica gel tube is a solvent-resolved silica gel tube, and is filled with 100-200mg of acid silica gel.
Preferably, the step of adsorbing and collecting triethylamine in the air of the workplace by using an acidic silica gel tube specifically comprises the following steps: a15-min workplace air sample is collected by an air sampler of a workplace by using an acid silicone tube at a flow rate of 500mL/min, and then two ends of the acid silicone tube are sealed.
Preferably, the set of triethylamine standard solutions with concentration gradients comprises the following concentrations: 0.5. mu.g, 1.0. mu.g, 2.5. mu.g, 5.0. mu.g, 10.0. mu.g, 20.0. mu.g.
Preferably, the gas chromatographic analysis employs a capillary chromatography column.
The invention has the following beneficial effects: because triethylamine is hydrolyzed into alkalescence, the triethylamine in the air of the workplace is adsorbed and collected by the acidic silica gel tube, and the adsorption efficiency of the triethylamine in the air of the workplace is improved. The acidic silica gel tube adsorbs triethylamine in the air of the collection workplace and combines headspace sampling for gas chromatography analysis, the conventional process of ultrasonic analysis by sulfuric acid and neutralization by adding alkali liquor is avoided, the test flow is simplified, and the service life of the instrument is prolonged. The addition of ammonia inhibited the ionization of triethylamine in water. When the air and the liquid of the sample are balanced at the top working site, triethylamine can be more easily volatilized to the gas phase part, and the detection limit of the method is reduced. The glass wool in the glass liner tube of the gas chromatograph sample inlet is taken out, so that the absorption of the instrument to triethylamine can be effectively reduced, and the linear correlation coefficient of the standard curve is better.
Additional features and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims hereof.
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In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and those skilled in the art can also obtain other drawings according to the drawings without creative efforts.
FIG. 1 shows a standard graph according to an embodiment of the invention;
FIG. 2 shows a sample chromatogram according to an embodiment of the invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below, and it is obvious that the described embodiments are a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Determination of toxic substances in air of workplace of GBZ/T300.136-2017 workplace, 136 th part of trimethylamine, diethylamine and triethylamine in the specification, when the sampling volume is 7.5L, the detection limit concentration of triethylamine is 0.16mg/m3In the patent, the detection limit of the measuring instrument is determined according to the standard requirement of HJ168-2020, and the detection limit concentration of triethylamine is 0.07mg/m3。
Example 1:
a method for determining triethylamine concentration in air of a workplace comprises the following steps:
1. the following reagents and materials were prepared: water for experiment: secondary distilled water or water prepared by pure water equipment; sodium hydroxide: the top grade is pure; sodium chloride: before use, the mixture is burned in a muffle furnace at 400 ℃ for 4h, placed in a dryer to be cooled to room temperature, and transferred to a ground glass bottle for storage; ammonia water: rho is 0.91 g/mL; sodium hydroxide solution: w (naoh) 40%, 40g of sodium hydroxide (1.2) was weighed out and dissolved in 60mL of water; triethylamine: carrying out chromatographic purification; triethylamine standard solution: 500 mg/L;
2. instruments and devices:
silicone tube: dissolving in solvent, and adding 200mg/100mg acidic silica gel;
workplace air sampler: the flow range is 0.1-1L/min;
gas chromatograph: a split-flow non-split-flow sample inlet is arranged, and a hydrogen Flame Ionization Detector (FID) is arranged;
quartz capillary chromatographic column: DB-1(30m × 0.32mm × 5.0 μm);
a headspace autosampler;
a headspace bottle: 22mL of sealing gasket and sealing cover with polytetrafluoroethylene coating;
3. collecting samples: a workplace air sampler is used for collecting 15min workplace air samples at sampling points by using an acid silicone tube at a flow rate of 500 mL/min. Sealing two ends of the acidic silicone tube immediately after sampling;
4. sample preparation: taking out the acidic silica gel, cutting the acidic silica gel tube by using a grinding wheel from the middle of the acidic silica gel tube, pouring the acidic silica gel tube into a headspace bottle, respectively and sequentially adding 10mL of experimental water, 4g of sodium chloride, 500 mu L of sodium hydroxide solution and 100 mu L of ammonia water, immediately sealing, preparing into a sample to be detected, and shaking uniformly to be detected.
5. Adopting the headspace automatic sample injector to send the sample to be detected into the gas chromatograph, and setting parameters of the headspace automatic sample injector: heating equilibrium temperature: 80 ℃; the balance time is as follows: 20 min; temperature of the sampling needle: 100 ℃; transmission line temperature: 110 ℃; quantitative loop sample injection volume: 1 mL;
setting parameters of a gas chromatograph: sample inlet temperature: 220 ℃; and (3) sample introduction mode: splitting, wherein the splitting ratio of the flow rate of the carrier gas column to the splitting flow rate is 5: 1; column flow rate: 1.25 mL/min; temperature programmed in a column oven: keeping at 50 deg.C for 2min, and increasing to 150 deg.C at a speed of 10 deg.C/min; detector (FID) temperature: 280 ℃, hydrogen flow rate: 30mL/min, workplace air flow: 300 mL/min.
6. And (3) establishing a standard curve, namely respectively taking a proper amount of triethylamine standard solution, diluting the triethylamine standard solution to 10mL by using a proper amount of pure water, and preparing a standard series of at least 5 concentration points, wherein the mass concentrations of triethylamine are respectively 0.5 mu g, 1.0 mu g, 2.5 mu g, 5.0 mu g, 10.0 mu g and 20.0 mu g. Then respectively adding 4g of sodium chloride, 500 mu L of sodium hydroxide solution and 100 mu L of ammonia water, immediately sealing and shaking up. According to the instrument conditions, samples are sequentially injected from low concentration to high concentration, a standard curve is established by taking the concentration (mg/L) of a standard series as an abscissa and taking the peak area of a chromatographic peak corresponding to the concentration as an ordinate, and as shown in figure 1, the slope m of the curve is 33.02166 and the intercept is 9.03546;
7. and (3) determination of a sample:
testing the sample prepared in the step 4 according to the analysis conditions of an instrument;
8. calculating the triethylamine concentration in the air of the workplace according to the test result in the step 7:
wherein ρ: concentration of triethylamine in the air of the workplace in mg/m3(ii) a C: the content of triethylamine in the adsorption tube is mu g; v: sample volume, L. Through determination, the concentration of triethylamine in the air of the workplace is less than the detection limit. And then, carrying out standard addition measurement on the air sample of the workplace, wherein the standard addition amount is 1 ug. Through determination, a sample chromatogram is shown in fig. 2, the peak area of triethylamine is 46.7462, and the triethylamine content is 1.142ug calculated according to a standard curve. When the sampling volume is 7.5L, the concentration is 0.15mg/m3。
Because triethylamine is hydrolyzed into alkalescence, the acidic silica gel tube is used for adsorbing and collecting triethylamine in air of a workplace, and the adsorption efficiency is higher compared with that of an alkaline adsorption tube. When samples are processed, the collected silica gel is poured into a 20mL headspace bottle, a proper amount of alkali liquor is added to adjust the pH to be more than 12, a proper amount of ammonia water is added to inhibit ionization of triethylamine, the samples are extracted after being balanced by a headspace automatic sampler, and gas chromatograph analysis is carried out, so that the triethylamine can be more easily volatilized to the gas phase part of the headspace bottle when the samples are balanced in the headspace, and the detection limit of the method is reduced.
And the headspace sample injection is adopted, the pH value of the analytic solution is not required to be adjusted, the operation is simpler, more convenient and safer, the instrument can be better protected, and the service life of the instrument is prolonged.
The capillary column is used for replacing the packed column, so that the packed column is not used for measurement, and if other organic compounds are detected in the work, the capillary column needs to be replaced by the instrument, so that the operation is troublesome, the operation is simple and convenient, and the detection limit of the method can be reduced.
In conclusion, triethylamine is hydrolyzed to be alkalescent, and the acidic silica gel tube is used for adsorbing and collecting triethylamine in the air of a workplace, so that the adsorption efficiency of the triethylamine in the air of the workplace is improved. The acidic silica gel tube adsorbs triethylamine in the air of the collection workplace and combines headspace sampling for gas chromatography analysis, the conventional process of ultrasonic analysis by sulfuric acid and neutralization by adding alkali liquor is avoided, the test flow is simplified, and the service life of the instrument is prolonged. The addition of ammonia inhibited the ionization of triethylamine in water. When the air and the liquid of the sample are balanced at the top working site, triethylamine can be more easily volatilized to the gas phase part, and the detection limit of the method is reduced. The glass wool in the glass liner tube of the gas chromatograph sample inlet is taken out, so that the absorption of the instrument to triethylamine can be effectively reduced, and the linear correlation coefficient of the standard curve is better.
Although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions of the embodiments of the present invention.
Claims (10)
1. A method for determining triethylamine concentration in air of a workplace is characterized in that an acidic silica gel tube is adopted to adsorb and collect triethylamine in the air of the workplace, and a headspace sampling mode is used for carrying out gas chromatography analysis on the collected triethylamine.
2. The method of claim 1, wherein the step of performing gas chromatography analysis on the collected triethylamine by headspace sampling comprises the steps of:
s1, placing the acidic silica gel tube with the collected triethylamine into a headspace bottle to prepare a sample to be detected;
s2, taking a group of triethylamine standard solutions with concentration gradients, taking the concentration as a horizontal coordinate, taking a chromatographic peak area corresponding to the concentration as a vertical coordinate, and establishing a standard curve;
s3, setting parameters of headspace sample injection and parameters of a gas chromatograph, performing gas chromatographic analysis on the sample to be detected by adopting headspace sample injection based on the standard curve, and determining the content of triethylamine in the sample to be detected;
s4, calculating the triethylamine concentration in the air of the workplace according to the gas chromatography analysis result, wherein the formula is as follows:
wherein rho is the concentration of triethylamine in the air of the workplace; c is the content of triethylamine in the acidic silicone tube; v is the sampling volume; coThe content of triethylamine in the blank silicone tube is shown.
3. The method of determining triethylamine concentration in the air of a workplace of claim 2, wherein the parameters of the headspace sample injection comprise: the heating equilibrium temperature is 80 ℃; the balance time is 20 min; the temperature of the sampling needle is 100 ℃; the temperature of the transmission line is 110 ℃; the volume of the quantitative loop injection is 1 mL.
4. The method of determining triethylamine concentration in workplace air according to claim 2, wherein the parameters of the gas chromatograph include: the temperature of a sample inlet is 220 ℃; the sample introduction mode is split, and the split ratio is 5: 1; the column flow rate is 1.25 mL/min; the temperature of the column incubator is programmed to 50 ℃, the temperature is kept for 2min, and then the temperature is raised to 150 ℃ at the speed of 10 ℃/min; detector temperature 280 ℃, hydrogen flow: 30mL/min, workplace air flow: 300 mL/min.
5. The method for determining triethylamine concentration in the air of a workplace according to claim 2, wherein the preparing of the sample to be tested specifically comprises: and (3) putting the acidic silica gel with the collected triethylamine into a headspace bottle, and adding sodium chloride, a sodium hydroxide solution and ammonia water to obtain a mixed solution with the pH value of more than 12.
6. The method for determining triethylamine concentration in air at work place according to claim 5, wherein said sodium chloride is burned in a muffle furnace at 400 ℃ for 4h, placed in a dryer for cooling, and then added into a headspace bottle.
7. The method for determining triethylamine concentration in air of work place as claimed in claim 1, wherein said acidic silica gel tube is solvent-resolved silica gel tube, and contains 100-200mg of acidic silica gel.
8. The method for determining triethylamine concentration in the air of the workplace according to claim 1, wherein the step of collecting triethylamine in the air of the workplace by using acid silica gel tube adsorption specifically comprises the following steps: a15-min workplace air sample is collected by an air sampler of a workplace by using an acid silicone tube at a flow rate of 500mL/min, and then two ends of the acid silicone tube are sealed.
9. The method of claim 2, wherein the concentration gradient of triethylamine standard solution comprises the following concentrations: 0.5. mu.g, 1.0. mu.g, 2.5. mu.g, 5.0. mu.g, 10.0. mu.g, 20.0. mu.g.
10. The method of determining triethylamine concentration in the workplace air according to any one of claims 1 to 9, wherein said gas chromatography uses a capillary chromatography column.
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| CN112684037A (en) * | 2020-12-09 | 2021-04-20 | 杭州中一检测研究院有限公司 | Detection method for determining organic amine in ambient air and waste gas |
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