A method for determining the content of ethylene glycol and diethylene glycol in laundry beads by gas chromatography

Abstract

The present invention belongs to the technical field of chemical detection, and discloses a method for determining the content of ethylene glycol and diethylene glycol in laundry beads by gas chromatography. The detection method of the present invention comprises the following steps: weighing the laundry beads, dissolving them in methanol after crushing, fixing the volume, and then ultrasonically extracting, centrifuging, filtering, and diluting to obtain a sample solution to be tested; subjecting the sample solution to be tested to gas chromatography-mass spectrometry detection to determine whether it contains ethylene glycol and diethylene glycol; conducting gas chromatography detection to obtain the area of ​​the chromatographic peaks of ethylene glycol and diethylene glycol, bringing them into the standard working curve, and obtaining the concentration of ethylene glycol and diethylene glycol, and calculating the content of ethylene glycol and diethylene glycol in the laundry beads. The present invention can accurately measure the content of ethylene glycol and diethylene glycol components, promote a more standardized market for laundry beads products, reduce the addition of components toxic to the human body, such as ethylene glycol and diethylene glycol, in production, and better protect the rights and interests of consumers.

Description

Technical Field

[0001] The invention relates to the technical field of chemical detection, and in particular to a method for determining the contents of ethylene glycol and diethylene glycol in laundry beads by gas chromatography. Background Art

[0002] As a new generation of concentrated laundry detergent products, laundry beads have excellent functions such as decontamination, sterilization, care, and fragrance. Their concentrated ingredients are environmentally friendly and meet the national requirements for energy conservation and emission reduction. In recent years, the production and sales volume has exploded. Laundry beads are low-water formulas. Compared with concentrated laundry detergents, a large amount of solvents are required to replace water. The surface active ingredients are generally above 65%, which is at a relatively high level. Therefore, the industry standard QB / T 5658-2021 "Laundry Beads" only strictly requires detergency performance, and no longer requires indicators for active content. However, the quality of laundry beads on the market varies. The commonly used organic solvents in the formula are low-toxic or non-toxic propylene glycol and glycerin. Some companies use relatively low-priced ethylene glycol, diethylene glycol, and industrial glycerin containing diethylene glycol as solvents, and even add excessive amounts of such toxic solvents to replace active ingredients as fillers, infringing on consumer rights. Among them, there have been many diethylene glycol poisoning incidents in history, and the main manifestations of poisoning are renal failure, liver damage, and central nervous system damage.

[0003] Therefore, in order to promote a more standardized market for laundry detergent beads and safeguard the rights and interests of consumers, it is urgently necessary to provide a method for determining the content of ethylene glycol and diethylene glycol in laundry detergent beads. Summary of the invention

[0004] The purpose of the present invention is to provide a method for determining the content of ethylene glycol and diethylene glycol in laundry beads by gas chromatography, so as to promote more standardized production of laundry beads products in the market and better protect the rights and interests of consumers.

[0005] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0006] The present invention provides a method for determining the contents of ethylene glycol and diethylene glycol in laundry beads by gas chromatography, comprising the following steps:

[0007] (1) Sample preparation: weigh the laundry beads, crush them, dissolve them in methanol, fix the volume, and then ultrasonically extract, centrifuge, filter, and dilute them to obtain the sample solution to be tested;

[0008] (2) Qualitative analysis: The sample solution is subjected to gas chromatography-mass spectrometry detection to determine whether ethylene glycol and diethylene glycol are contained in the sample solution by the retention time and relative ion abundance ratio of ethylene glycol and diethylene glycol, respectively;

[0009] (3) Gas chromatography analysis: The sample liquid is subjected to gas chromatography detection, and the retention time and the area of ​​the chromatographic peak are recorded to obtain the areas of the chromatographic peaks of ethylene glycol and diethylene glycol respectively;

[0010] (4) Quantitative analysis: The areas of the chromatographic peaks of ethylene glycol and diethylene glycol obtained in step (3) are respectively inserted into the standard working curves of ethylene glycol and diethylene glycol, and the concentrations of ethylene glycol and diethylene glycol in the sample solution are calculated respectively;

[0011] (5) Content calculation: The contents of ethylene glycol and diethylene glycol in the laundry beads are calculated according to the concentrations of ethylene glycol and diethylene glycol obtained in step (4), respectively, and the calculation formula is as follows:

[0012]

[0013] Wherein, X: the content of ethylene glycol and diethylene glycol in the laundry beads, mg / kg;

[0014] c: The concentration of ethylene glycol and diethylene glycol in the sample solution, μg / mL;

[0015] m: the mass of the laundry beads, g;

[0016] k: dilution factor of the sample solution to be tested;

[0017] V: The fixed volume of the laundry beads, mL.

[0018] Furthermore, in the above-mentioned method for determining the content of ethylene glycol and diethylene glycol in laundry beads by gas chromatography, in the step (1), the frequency of ultrasound is 30 to 50 kHz, the time of ultrasound is 25 to 40 min, the speed of centrifugation is 7500 to 8500 r / min, the time of centrifugation is 8 to 15 min, and the filter membrane specification is 0.2 to 0.45 μm.

[0019] Furthermore, in the above-mentioned method for determining the content of ethylene glycol and diethylene glycol in laundry beads by gas chromatography, a standard working curve is drawn before the qualitative analysis in step (2), and the method is as follows: take appropriate amounts of 10.0 μg / mL, 20.0 μg / mL, 50.0 μg / mL, 100.0 μg / mL, and 500.0 μg / mL of mixed standard solutions of ethylene glycol and diethylene glycol, perform gas chromatography detection on them respectively, record the retention time and the area of ​​the chromatographic peak, and draw standard working curves of ethylene glycol and diethylene glycol with the area of ​​the chromatographic peak as the ordinate and the concentration as the abscissa.

[0020] Furthermore, in the above-mentioned method for determining the content of ethylene glycol and diethylene glycol in laundry beads by gas chromatography, the conditions for the gas chromatography detection in the method of drawing the standard working curve and the gas chromatography detection in the step (3) are as follows: the chromatographic column is a 30×0.53mm×1.00μm HP-INNOWAX quartz capillary chromatographic column, the carrier gas is nitrogen with a purity of >99.99%, a constant flow mode is adopted, the flow rate is 2.0mL / min, the combustion-supporting gases are hydrogen and air, the flow rate of hydrogen is 40mL / min, the flow rate of air is 400mL / min, the injection port temperature is 240°C, the detector temperature is 250°C, the injection mode is split injection, the split ratio is 10:1, and the injection volume is 1μL.

[0021] Furthermore, in the above-mentioned method for determining the content of ethylene glycol and diethylene glycol in laundry beads by gas chromatography, the programmed temperature conditions for the gas chromatography detection in the method of drawing the standard working curve and the gas chromatography detection in the step (3) are as follows: the initial temperature of the chromatographic column is 140°C, maintained for 5 minutes, heated to 150°C at a rate of 10°C / min, maintained for 5 minutes, then heated to 180°C at a rate of 20°C / min, maintained for 10 minutes, and finally heated to 240°C at a rate of 30°C / min, maintained for 35 minutes.

[0022] Furthermore, in the above-mentioned method for determining the content of ethylene glycol and diethylene glycol in laundry beads by gas chromatography, the conditions for gas chromatography detection in step (2) are as follows: the chromatographic column is a 30×0.32mm×0.25μm SH-Rtx-Wax quartz capillary chromatographic column, the carrier gas is helium with a purity of >99.99%, a constant flow mode is adopted, the flow rate is 2.0mL / min, the injection port temperature is 240°C, the injection method is split injection, the split ratio is 10:1, and the injection volume is 1μL.

[0023] Furthermore, in the above-mentioned method for determining the content of ethylene glycol and diethylene glycol in laundry beads by gas chromatography, the programmed temperature conditions for gas chromatography detection in step (2) are as follows: the initial temperature of the chromatographic column is 80°C, maintained for 5 minutes, heated to 150°C at a rate of 10°C / min, maintained for 5 minutes, then heated to 180°C at a rate of 20°C / min, maintained for 10 minutes, and finally heated to 240°C at a rate of 30°C / min, maintained for 35 minutes.

[0024] Furthermore, in the above-mentioned method of determining the content of ethylene glycol and diethylene glycol in laundry beads by gas chromatography, the conditions for mass spectrometry detection in step (2) are: the ionization mode is an electron bombardment source, the ionization energy is 70 eV, the ion source temperature is 200°C, the interface temperature is 240°C, the solvent delay time is 3 min, the scanning mode is full scan, and the scanning range m / z is 30 to 300.

[0025] It can be seen from the above technical solution that compared with the prior art, the present invention has the following beneficial effects:

[0026] The present invention uses gas chromatography-mass spectrometry to confirm whether ethylene glycol and diethylene glycol are present in laundry beads, and then uses the external standard method of gas chromatography-hydrogen flame ionization detector to perform separation and quantitative testing, accurately measuring the content of ethylene glycol and diethylene glycol components, promoting a more standardized market for laundry beads products, reducing the addition of components toxic to the human body, such as ethylene glycol and diethylene glycol, in production, and better protecting the rights and interests of consumers. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required to be used in the description of the embodiments or the prior art are briefly introduced below.

[0028] Figure 1 The gas chromatogram of a mixed standard solution of 103.36μg / mL ethylene glycol and 98.50μg / mL diethylene glycol;

[0029] Figure 2 is the standard working curve of ethylene glycol;

[0030] Figure 3 is the standard working curve of diethylene glycol;

[0031] Figure 4 The gas chromatogram of the sample liquid to be tested in Example 1;

[0032] Figure 5 The gas chromatogram of the sample solution after dilution 500 times in Example 1;

[0033] Figure 6 The gas chromatogram of the sample liquid to be tested in Example 2;

[0034] Figure 7 The gas chromatogram of the sample solution after dilution 100 times in Example 2;

[0035] Figure 8 The gas chromatogram of the sample liquid to be tested in Example 3;

[0036] Fig. 9 The gas chromatogram of the sample solution after dilution 500 times in Example 3;

[0037] Fig.10 This is the gas chromatogram of the sample liquid to be tested in Example 4. DETAILED DESCRIPTION

[0038] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0039] Reagents and Materials:

[0040] Methanol: chromatographic grade;

[0041] Ethylene glycol standard sample: purity ≥99%;

[0042] Diethylene glycol standard sample: purity ≥99%;

[0043] Mixed standard stock solution of ethylene glycol and diethylene glycol: accurately weigh 0.5 g (accurate to 0.1 mg) of ethylene glycol standard sample and diethylene glycol standard sample into a 100 mL volumetric flask, dissolve with methanol and make up to the mark; the content of ethylene glycol and diethylene glycol in this solution is 5 mg / mL;

[0044] Mixed standard working solution of ethylene glycol and diethylene glycol: Accurately pipette the mixed standard stock solution of ethylene glycol and diethylene glycol, and prepare mixed standard working solutions with concentrations of 10.0 μg / mL, 20.0 μg / mL, 50.0 μg / mL, 100.0 μg / mL, and 500.0 μg / mL with methanol;

[0045] Filter membrane: 0.45 μm, organic phase.

[0046] Sample preparation:

[0047] Weigh the laundry beads sample (accurate to 0.001g), cut its outer membrane with clean and dry scissors to let the internal solution flow out, rinse the scissors with appropriate amount of methanol in small amounts multiple times, add methanol in small amounts multiple times to dissolve the sample, transfer it to a 50mL volumetric flask after dissolution, and make up to the scale, shake well, ultrasonically extract for 30min under 40kHz conditions, centrifuge at 8000r / min for 10min, take appropriate amount of clear liquid, filter it through a 0.45μm filter membrane, dilute it, and obtain the sample solution to be tested.

[0048] Standard working curve drawing:

[0049] Take appropriate amounts of 10.0 μg / mL, 20.0 μg / mL, 50.0 μg / mL, 100.0 μg / mL, and 500.0 μg / mL of ethylene glycol and diethylene glycol mixed standard solutions, respectively, and perform gas chromatography detection, record the retention time and the area of ​​the chromatographic peak, as shown in Table 1, and draw standard working curves of ethylene glycol and diethylene glycol with the area of ​​the chromatographic peak as the ordinate and the concentration as the abscissa, respectively, as shown in Table 1. Figure 2 , Figure 3shown.

[0050] Table 1. Preparation of working curves of ethylene glycol and diethylene glycol standard solutions

[0051]

[0052] The conditions for gas chromatography detection are as follows: the chromatographic column is a 30×0.53mm (inner diameter)×1.00μm HP-INNOWAX quartz capillary chromatographic column, the carrier gas is nitrogen with a purity of>99.99%, the constant flow mode is adopted, the flow rate is 2.0mL / min, the auxiliary gas is hydrogen and air, the flow rate of hydrogen is 40mL / min, the flow rate of air is 400mL / min, the injection port temperature is 240°C, the detector temperature is 250°C, the injection mode is split injection, the split ratio is 10:1, and the injection volume is 1μL;

[0053] The programmed temperature conditions were as follows: the initial temperature of the chromatographic column was 140°C, maintained for 5 min, then increased to 150°C at a rate of 10°C / min, maintained for 5 min, then increased to 180°C at a rate of 20°C / min, maintained for 10 min, and finally increased to 240°C at a rate of 30°C / min, maintained for 35 min.

[0054] Reasons for choosing the above continuous heating conditions:

[0055] Since the present invention uses HP-INNOWAX capillary chromatographic column 30×0.53mm (inner diameter)×1.00μm for testing, the parameters of gas chromatography detection refer to the content of GB / T 32115-2015. In GB / T 32115-2015, the program temperature conditions are: the initial column temperature is 40°C, maintained for 5min, heated to 150°C at a rate of 10°C / min, maintained for 10min, and then heated to 250°C at a rate of 30°C / min, maintained for 5min. Since the retention time of the target ethylene glycol and diethylene glycol is greatly extended in the standard, the retention time of ethylene glycol is greater than 30min, and the retention time of diethylene glycol is greater than 50min, which takes a long time. When the sample is actually detected, the components are many and complex, and the target is easily interfered by other components. The conditions set by the standard are adopted, the efficiency is low, and the sample components are easily left in the chromatographic column, affecting the analysis of other samples. Therefore, the present invention readjusts the programmed temperature conditions and the chromatographic column flow rate and keeps other conditions unchanged, which can effectively reduce the adverse effects of the above test and improve the detection efficiency.

[0056] Qualitative analysis:

[0057] The sample solution is subjected to gas chromatography-mass spectrometry detection, and the relative ion abundance ratios of ethylene glycol and diethylene glycol are respectively determined, as shown in Table 2 and Table 3, to determine whether the sample solution contains ethylene glycol and diethylene glycol;

[0058] The conditions for gas chromatography detection are as follows: the chromatographic column is a 30×0.32mm (inner diameter)×0.25μm SH-Rtx-Wax quartz capillary column, the carrier gas is helium with a purity of >99.99%, the constant flow mode is adopted, the flow rate is 2.0mL / min, the injection port temperature is 240°C, the injection method is split injection, the split ratio is 10:1, and the injection volume is 1μL;

[0059] The programmed temperature conditions were as follows: the initial temperature of the column was 80 °C, maintained for 5 min, then increased to 150 °C at a rate of 10 °C / min, maintained for 5 min, then increased to 180 °C at a rate of 20 °C / min, maintained for 10 min, and finally increased to 240 °C at a rate of 30 °C / min, maintained for 35 min;

[0060] The conditions for mass spectrometry detection were as follows: the ionization mode was electron bombardment source, the ionization energy was 70 eV, the ion source temperature was 200°C, the interface temperature was 240°C, the solvent delay time was 3 min, the scanning mode was full scan, and the scanning range was m / z 30-300.

[0061] Table 2. Relative abundance ratio of glycol ions

[0062]

[0063] Table 3. Relative abundance ratio of diethylene glycol ions

[0064]

[0065] Gas chromatography analysis:

[0066] The sample liquid is subjected to gas chromatography detection. The detection conditions and programmed temperature conditions are consistent with those for drawing the standard working curve. The retention time and the area of ​​the chromatographic peak are recorded to obtain the areas of the chromatographic peaks of ethylene glycol and diethylene glycol, respectively.

[0067] Quantitative analysis:

[0068] The areas of the chromatographic peaks of ethylene glycol and diethylene glycol are respectively introduced into the standard working curves of ethylene glycol and diethylene glycol, and the concentrations of ethylene glycol and diethylene glycol in the sample solution to be tested are calculated respectively.

[0069] Content calculation:

[0070] The contents of ethylene glycol and diethylene glycol in the laundry beads are calculated according to the concentrations of ethylene glycol and diethylene glycol, respectively, and the calculation formula is as follows:

[0071]

[0072] Wherein, X: the content of ethylene glycol and diethylene glycol in the laundry beads, mg / kg;

[0073] c: The concentration of ethylene glycol and diethylene glycol in the sample solution, μg / mL;

[0074] m: the mass of the laundry beads, g;

[0075] k: dilution factor of the sample solution to be tested;

[0076] V: The fixed volume of the laundry beads, mL.

[0077] In the present invention, the recovery rates of the ethylene glycol and diethylene glycol contents in the laundry beads determined by gas chromatography are both 95%.

[0078] In the present invention, the detection limits of ethylene glycol and diethylene glycol in the laundry beads by gas chromatography are both 3 mg / kg.

[0079] Example 1

[0080] The name of the sample to be tested in this embodiment is: Dettol 9X sterilizing laundry beads; the specification is 384g (32 beads).

[0081] This embodiment provides a method for determining the content of ethylene glycol and diethylene glycol in laundry beads by gas chromatography, comprising the following steps:

[0082] (1) Sample preparation: Weigh the laundry beads sample, which weighs 13.1811 g. Cut the outer membrane into pieces to allow the internal solution to flow out. Add methanol in small amounts and multiple times to dissolve the sample. After dissolution, transfer the sample to a 50 mL volumetric flask and adjust the volume to the mark. Shake well. Ultrasonic extraction at 40 kHz for 30 min. Centrifuge at 8000 r / min for 10 min. Take an appropriate amount of the clear solution and filter it through a 0.45 μm filter membrane to obtain the sample solution to be tested.

[0083] (2) Qualitative analysis: The sample solution was subjected to gas chromatography-mass spectrometry. After analysis, ethylene glycol was not identified based on the retention time and relative ion abundance ratio, so ethylene glycol was not measured; the chromatographic peak of diethylene glycol was identified, and its relative ion abundance ratios were:

[0084] Diethylene glycol: 45:75:76=100:26:14;

[0085] (3) Gas chromatography analysis: The sample liquid is subjected to gas chromatography and the retention time and the area of ​​the chromatographic peak are recorded. Figure 4 As shown, the chromatographic peak area of ​​ethylene glycol in the sample solution to be tested is obtained as A=0;

[0086] Dilute the sample solution 500 times and perform gas chromatography again. Figure 5 As shown, the chromatographic peak area of ​​diethylene glycol in the sample solution is A=43.5;

[0087] (4) Quantitative analysis: The areas of the chromatographic peaks of ethylene glycol and diethylene glycol obtained in step (3) were respectively inserted into the standard working curves of ethylene glycol and diethylene glycol, and the concentrations of ethylene glycol and diethylene glycol were calculated to be c1 (μg / mL) = 2.00 and c2 (μg / mL) = 88.50, respectively.

[0088] (5) Content calculation: Calculate the content of diethylene glycol in the laundry beads based on the concentrations of ethylene glycol and diethylene glycol obtained in step (4).

[0089] Diethylene glycol

[0090]

[0091] Example 2

[0092] The name of the sample to be tested in this embodiment is: Mama's Choice Natural Plant Soap 4-in-1 Laundry Detergent Beads; the specification is 405ml (45 pieces).

[0093] This embodiment provides a method for determining the content of ethylene glycol and diethylene glycol in laundry beads by gas chromatography, comprising the following steps:

[0094] (1) Sample preparation: Weigh the laundry beads sample, which weighs 10.3585 g. Cut the outer membrane to make the internal solution flow out. Add methanol in small amounts and multiple times to dissolve the sample. After dissolution, transfer it to a 50 mL volumetric flask and adjust the volume to the mark. Shake well. Ultrasonic extraction at 40 kHz for 30 min. Centrifuge at 8000 r / min for 10 min. Take an appropriate amount of the clear solution and filter it through a 0.45 μm filter membrane to obtain the sample solution to be tested.

[0095] (2) Qualitative analysis: The sample solution is subjected to gas chromatography-mass spectrometry. After analysis, the chromatographic peaks of ethylene glycol and diethylene glycol are identified based on the retention time and relative ion abundance ratio. The relative ion abundance ratios are:

[0096] Ethylene glycol: 31:33:62=100:41:5,

[0097] Diethylene glycol: 45:75:76=100:28:15;

[0098] (3) Gas chromatography analysis: The sample liquid is subjected to gas chromatography and the retention time and the area of ​​the chromatographic peak are recorded. Figure 6 As shown, the chromatographic peak area of ​​ethylene glycol in the sample solution is obtained as A=21.4;

[0099] Dilute the sample solution 100 times and perform gas chromatography again. Figure 7 As shown, the chromatographic peak area of ​​diethylene glycol in the sample solution is A=203.9;

[0100] (4) Quantitative analysis: The areas of the chromatographic peaks of ethylene glycol and diethylene glycol obtained in step (3) were respectively inserted into the standard working curves of ethylene glycol and diethylene glycol, and the concentrations of ethylene glycol and diethylene glycol were calculated to be c1 (μg / mL) = 45.77 and c2 (μg / mL) = 407.90, respectively.

[0101] (5) Content calculation: Calculate the contents of ethylene glycol and diethylene glycol in the laundry beads according to the concentrations of ethylene glycol and diethylene glycol obtained in step (4):

[0102] Ethylene glycol

[0103]

[0104] Diethylene glycol

[0105]

[0106] Example 3

[0107] The name of the sample to be tested in this embodiment is: La Natural 4-in-1 Laundry Detergent Colloid Beads; the specification is 100 ml (10 beads).

[0108] This embodiment provides a method for determining the content of ethylene glycol and diethylene glycol in laundry beads by gas chromatography, comprising the following steps:

[0109] (1) Sample preparation: Weigh the laundry beads sample, which weighs 11.2115 g. Cut the outer membrane to make the internal solution flow out. Add methanol in small amounts and multiple times to dissolve the sample. After dissolution, transfer it to a 50 mL volumetric flask and adjust the volume to the mark. Shake well. Ultrasonic extraction at 40 kHz for 30 min. Centrifuge at 8000 r / min for 10 min. Take an appropriate amount of the clear solution and filter it through a 0.45 μm filter membrane to obtain the sample solution to be tested.

[0110] (2) Qualitative analysis: The sample solution is subjected to gas chromatography-mass spectrometry. After analysis, the chromatographic peaks of ethylene glycol and diethylene glycol are identified based on the retention time and relative ion abundance ratio. The relative ion abundance ratios are:

[0111] Ethylene glycol: 31:33:62=100:43:5,

[0112] Diethylene glycol: 45:75:76=100:29:15;

[0113] (3) Gas chromatography analysis: The sample liquid is subjected to gas chromatography and the retention time and the area of ​​the chromatographic peak are recorded. Figure 8 As shown, the chromatographic peak area of ​​ethylene glycol in the sample solution is obtained as A=11.8;

[0114] Dilute the sample solution 500 times and perform gas chromatography again. Fig. 9As shown, the chromatographic peak area of ​​diethylene glycol in the sample solution is A=31.1;

[0115] (4) Quantitative analysis: The areas of the chromatographic peaks of ethylene glycol and diethylene glycol obtained in step (3) were respectively substituted into the standard working curves of ethylene glycol and diethylene glycol, and the concentrations of ethylene glycol and diethylene glycol were calculated to be c1 (μg / mL) = 26.13 and c2 (μg / mL) = 63.81, respectively.

[0116] (5) Content calculation: Calculate the contents of ethylene glycol and diethylene glycol in the laundry beads according to the concentrations of ethylene glycol and diethylene glycol obtained in step (4):

[0117] Ethylene glycol

[0118]

[0119] Diethylene glycol

[0120]

[0121] Example 4

[0122] The name of the sample to be tested in this embodiment is: Liby concentrated bacteria-free laundry detergent beads; the specification is 320 grams (40 beads).

[0123] This embodiment provides a method for determining the content of ethylene glycol and diethylene glycol in laundry beads by gas chromatography, comprising the following steps:

[0124] (1) Sample preparation: Weigh the laundry beads sample, which weighs 8.2568 g. Cut the outer membrane to make the internal solution flow out. Add methanol in small amounts and multiple times to dissolve the sample. After dissolution, transfer the sample to a 50 mL volumetric flask and adjust the volume to the mark. Shake well. Ultrasonic extraction at 40 kHz for 30 min. Centrifuge at 8000 r / min for 10 min. Take an appropriate amount of the clear solution and filter it through a 0.45 μm filter membrane to obtain the sample solution to be tested.

[0125] (2) Qualitative analysis: The sample solution was subjected to gas chromatography-mass spectrometry. After analysis, ethylene glycol and diethylene glycol were not identified based on retention time and relative ion abundance ratio;

[0126] (3) Gas chromatography analysis: The sample liquid is subjected to gas chromatography and the retention time and the area of ​​the chromatographic peak are recorded. Fig.10 As shown, the chromatographic peak area of ​​ethylene glycol in the sample solution is A=0, and the chromatographic peak area of ​​diethylene glycol is A=0;

[0127] (4) Quantitative analysis: The areas of the chromatographic peaks of ethylene glycol and diethylene glycol obtained in step (3) were respectively inserted into the standard working curves of ethylene glycol and diethylene glycol, and the concentrations of ethylene glycol and diethylene glycol were calculated to be c1 (μg / mL) = 2.00 and c2 (μg / mL) = 1.88, respectively.

[0128] Since ethylene glycol and diethylene glycol were not detected in the qualitative test, it can be considered that the sample does not contain ethylene glycol and diethylene glycol.

[0129] The above embodiments illustrate that the detection method of the present invention can accurately measure the content of ethylene glycol and diethylene glycol components, promote a more standardized market for laundry detergent beads, reduce the addition of components toxic to the human body, such as ethylene glycol and diethylene glycol, during production, and better protect the rights and interests of consumers.

[0130] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for determining the content of ethylene glycol and diethylene glycol in laundry beads by gas chromatography, characterized in that: The following steps are involved: (1) Sample preparation: weigh the laundry beads, crush them, dissolve them in methanol, fix the volume, and then ultrasonically extract, centrifuge, filter, and dilute them to obtain the sample solution to be tested; (2) Qualitative analysis: The sample solution is subjected to gas chromatography-mass spectrometry detection to determine whether ethylene glycol and diethylene glycol are contained in the sample solution by the retention time and relative ion abundance ratio of ethylene glycol and diethylene glycol, respectively; (3) Gas chromatography analysis: The sample liquid is subjected to gas chromatography detection, and the retention time and the area of ​​the chromatographic peak are recorded to obtain the areas of the chromatographic peaks of ethylene glycol and diethylene glycol respectively; (4) Quantitative analysis: The areas of the chromatographic peaks of ethylene glycol and diethylene glycol obtained in step (3) are respectively inserted into the standard working curves of ethylene glycol and diethylene glycol, and the concentrations of ethylene glycol and diethylene glycol in the sample solution are calculated respectively; (5) Content calculation: The contents of ethylene glycol and diethylene glycol in the laundry beads are calculated according to the concentrations of ethylene glycol and diethylene glycol obtained in step (4), respectively, and the calculation formula is as follows: Wherein, X: the content of ethylene glycol and diethylene glycol in the laundry beads, mg / kg; c: The concentration of ethylene glycol and diethylene glycol in the sample solution, μg / mL; m: the mass of the laundry beads, g; k: dilution factor of the sample solution to be tested; V: fixed volume of laundry beads, mL; The conditions for gas chromatography detection in step (2) are as follows: the chromatographic column is a 30×0.32mm×0.25μm SH-Rtx-Wax quartz capillary chromatographic column, the carrier gas is helium with a purity of >99.99%, a constant flow mode is adopted, the flow rate is 2.0mL / min, the injection port temperature is 240°C, the injection method is split injection, the split ratio is 10:1, and the injection volume is 1μL; The programmed temperature conditions for gas chromatography detection in step (2) are as follows: the initial temperature of the chromatographic column is 80°C, maintained for 5 minutes, then heated to 150°C at a rate of 10°C / min, maintained for 5 minutes, then heated to 180°C at a rate of 20°C / min, maintained for 10 minutes, and finally heated to 240°C at a rate of 30°C / min, maintained for 35 minutes; The mass spectrometry detection conditions in step (2) are as follows: the ionization mode is an electron bombardment source, the ionization energy is 70 eV, the ion source temperature is 200° C., the interface temperature is 240° C., the solvent delay time is 3 min, the scanning mode is full scan, and the scanning range m / z is 30 to 300; The conditions for gas chromatography detection in step (3) are as follows: the chromatographic column is a 30×0.53mm×1.00μm HP-INNOWAX quartz capillary chromatographic column, the carrier gas is nitrogen with a purity of >99.99%, the constant flow mode is adopted, the flow rate is 2.0mL / min, the auxiliary combustion gases are hydrogen and air, the flow rate of hydrogen is 40mL / min, the flow rate of air is 400mL / min, the injection port temperature is 240°C, the detector temperature is 250°C, the injection mode is split injection, the split ratio is 10:1, and the injection volume is 1μL; The programmed temperature conditions for gas chromatography detection in step (3) are as follows: the initial temperature of the chromatographic column is 140°C, maintained for 5 minutes, then heated to 150°C at a rate of 10°C / min, maintained for 5 minutes, then heated to 180°C at a rate of 20°C / min, maintained for 10 minutes, and finally heated to 240°C at a rate of 30°C / min, maintained for 35 minutes.

2. A method for determining the content of ethylene glycol and diethylene glycol in laundry beads by gas chromatography as claimed in claim 1, characterized in that: In the step (1), the frequency of ultrasound is 30-50 kHz, the time of ultrasound is 25-40 min, the speed of centrifugation is 7500-8500 r / min, the time of centrifugation is 8-15 min, and the specification of the filter membrane is 0.2-0.45 μm.

3. A method for determining the content of ethylene glycol and diethylene glycol in laundry beads by gas chromatography as claimed in claim 1, characterized in that: Before the qualitative analysis in step (2), a standard working curve is drawn as follows: appropriate amounts of 10.0 μg / mL, 20.0 μg / mL, 50.0 μg / mL, 100.0 μg / mL, and 500.0 μg / mL mixed standard solutions of ethylene glycol and diethylene glycol are taken, respectively, and gas chromatography detection is performed, and the retention time and the area of ​​the chromatographic peak are recorded, and standard working curves of ethylene glycol and diethylene glycol are drawn with the area of ​​the chromatographic peak as the ordinate and the concentration as the abscissa.

4. A method for determining the content of ethylene glycol and diethylene glycol in laundry beads by gas chromatography as claimed in claim 3, characterized in that: The conditions for gas chromatography detection in the method for drawing the standard working curve are as follows: the chromatographic column is a 30×0.53mm×1.00μm HP-INNOWAX quartz capillary chromatographic column, the carrier gas is nitrogen with a purity of >99.99%, a constant flow mode is adopted, the flow rate is 2.0mL / min, the auxiliary combustion gases are hydrogen and air, the flow rate of hydrogen is 40mL / min, the flow rate of air is 400mL / min, the injection port temperature is 240°C, the detector temperature is 250°C, the injection mode is split injection, the split ratio is 10:1, and the injection volume is 1μL.

5. A method for determining the content of ethylene glycol and diethylene glycol in laundry beads by gas chromatography as claimed in claim 3 or 4, characterized in that: The programmed temperature conditions for gas chromatography detection in the method for drawing the standard working curve are as follows: the initial temperature of the chromatographic column is 140°C, maintained for 5 minutes, then heated to 150°C at a rate of 10°C / min, maintained for 5 minutes, then heated to 180°C at a rate of 20°C / min, maintained for 10 minutes, and finally heated to 240°C at a rate of 30°C / min, maintained for 35 minutes.

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