Method for determining formaldehyde and acetaldehyde in propylene glycol

Abstract

The invention discloses a method for determining formaldehyde and acetaldehyde in propylene glycol, which comprises the following steps: (1) preparing a contrast solution: dissolving formaldehyde and acetaldehyde standard substances in water to obtain a formaldehyde and acetaldehyde mixed solution, adding a propylene glycol sample into the obtained formaldehyde and acetaldehyde mixed solution, and uniformly mixing to obtain the contrast solution; (2) preparation of a test solution: taking a propylene glycol sample to be detected, and adding water to dilute the propylene glycol sample to obtain the test solution; (3) chromatographic measurement: carrying out headspace sampling on the obtained contrast solution and the test solution, and determining by adopting a gas chromatograph; and (4) content calculation: calculating the content of formaldehyde and acetaldehyde in the propylene glycol sample to be detected according to a standard addition method. The detection method disclosed by the invention is high in sensitivity, good in repeatability and precision, rapid, efficient, simple and convenient, is suitable for determination of formaldehyde and acetaldehyde in propylene glycol, and can effectively supervise production and ensure the stability of product quality.

Description

Technical Field

[0001] The invention belongs to the technical field of analytical chemistry, and in particular relates to a method for determining formaldehyde and acetaldehyde in propylene glycol. Background Art

[0002] The chemical name of propylene glycol is 1,2-propylene glycol. Due to its good hygroscopicity and non-toxicity, it is widely used in the food, medicine, and cosmetics industries as an antifreeze agent, moisturizer, lubricant, and solvent. In the food industry, it is mainly used as a food emulsifier and an excellent solvent for condiments and pigments; in the cosmetics field, propylene glycol, as an emollient component in skin care products, can be miscible with spices, so it is a good solvent, softener, and wetting agent for cosmetics; in the pharmaceutical industry, it is often used as a solvent, softener, and excipient for the manufacture of various ointments and salves. Propylene glycol is a good auxiliary agent for the manufacture of various pastes, vitamins, softeners, excipients, and medical injections. Propylene glycol is also used in eye drops and the content is indicated. For example, the ingredients of the commercially available Siran eye drops are 0.4% polyethylene glycol 400 and 0.3% propylene glycol. Other literature reports that propylene glycol is used in eye drops, indicating that the eye drops contain 0.1-1.0% propylene glycol.

[0003] The main synthesis processes of propylene glycol include hydration, 1,2-dichloropropane synthesis, ester exchange reaction, glycerol catalytic hydrogenolysis process, propylene carbonate direct saponification hydrolysis process and other processes.

[0004] Propylene glycol is included in the Chinese Pharmacopoeia Volume IV, the United States Pharmacopoeia and the European Pharmacopoeia. The specific impurities involved include ethylene glycol, diethylene glycol, triethylene glycol, dipropylene glycol and tripropylene glycol. The acidity, oxidizing substances and reducing substances of propylene glycol are also controlled. Based on the degradation mechanism of propylene glycol, the literature reports that propylene glycol may be degraded into aldehydes and ketones. The present invention studies the genotoxic impurities formaldehyde and acetaldehyde that may be produced by the degradation of propylene glycol that are not studied in the above standards. There are currently two methods for determining aldehydes reported in the literature (GB14571-2008): one is ultraviolet-visible spectrophotometry, the principle of which is to use 3-methyl-2-benzothiazolone hydrazone hydrochloride solution as a color developer, add an oxidant solution (ferric chloride hexahydrate and aminosulfonic acid solution), and detect the absorbance at a wavelength of 620nm with a UV spectrophotometer; the other is pre-column derivatization high-performance liquid chromatography, the principle of which is that aldehydes and 2,4-dinitrophenylhydrazine react to generate hydrazones with strong absorption at specific wavelengths, and the different carbon chain lengths in the aldehydes can be separated at C8 or C18. The existing method determines aldehydes of all structures and cannot distinguish the structure and type of aldehydes. In addition, a complex sample pretreatment process is required in the determination. Summary of the invention

[0005] The primary object of the present invention is to provide a method for determining formaldehyde and acetaldehyde in propylene glycol, so as to achieve high-sensitivity qualitative and / or quantitative determination of formaldehyde and acetaldehyde in propylene glycol.

[0006] To this end, the present invention provides the following technical solutions.

[0007] One aspect of the present invention provides a method for determining formaldehyde and acetaldehyde in propylene glycol, the method comprising the following steps:

[0008] (1) Reference solution: dissolving formaldehyde and acetaldehyde standards in water to obtain a formaldehyde-acetaldehyde mixed solution, adding propylene glycol sample to the obtained formaldehyde-acetaldehyde mixed solution and mixing well to obtain a reference solution;

[0009] (2) Test solution: Take the propylene glycol sample to be tested and dilute it with water to obtain the test solution;

[0010] (3) Chromatographic measurement: The obtained control solution and the test solution are injected into the headspace and measured by gas chromatography;

[0011] (4) Content calculation: Calculate the content of formaldehyde and acetaldehyde in the propylene glycol sample to be tested by the standard addition method.

[0012] As a preferred embodiment of the present invention, in step (1), in the control solution: the formaldehyde concentration is 5-100 μg / ml, the acetaldehyde concentration is 5-100 μg / ml, and the propylene glycol concentration is 0.5-1 g / ml.

[0013] As a preferred embodiment of the present invention, in step (2), the concentration of the propylene glycol sample to be tested in the test solution is 0.5-1 g / ml.

[0014] As a preferred embodiment of the present invention, in step (3), the stationary phase in the gas chromatograph uses a gas chromatography system, the detector is a flame ionization detector, and the temperature is 240-260°C.

[0015] As a preferred embodiment of the present invention, in step (3), the gas chromatography conditions are: a capillary column is used as the chromatographic column, the injection port temperature is 140-160°C, the column flow rate is 3.0-4.5 ml / min, and the split ratio is 3:1-5:1.

[0016] As a preferred embodiment of the present invention, the capillary column uses 100% dimethylpolysiloxane or 5% phenyl-95% dimethylpolysiloxane as the stationary liquid.

[0017] By means of the above technical solution, the present invention has at least the following advantages:

[0018] The gas chromatography method for directly determining formaldehyde and acetaldehyde in propylene glycol proposed by the present invention is simple to prepare and does not require pretreatment. The method is also compared with a pre-column derivatization high performance liquid chromatography method in the literature. The results show that the recovery rate of the pre-column derivatization method is relatively low when determining formaldehyde and acetaldehyde in propylene glycol (about 70% for formaldehyde and about 50% for acetaldehyde). It is speculated that the recovery rate is low due to the matrix effect of propylene glycol. The self-developed method does not require complex pretreatment, does not use organic solvents, and has good sensitivity. The gas chromatography method adopts the standard addition method for quantification, and the recovery rate of the method is good, indicating that the method is suitable for the determination of formaldehyde and acetaldehyde in propylene glycol.

[0019] The detection method of the invention has high sensitivity, good repeatability and precision, and is quick, efficient and simple. It is suitable for the determination of formaldehyde and acetaldehyde in propylene glycol, and can effectively supervise production and ensure the stability of product quality.

[0020] The above description is only an overview of the technical solution of the present invention. In order to more clearly understand the technical means of the present invention and implement it according to the contents of the specification, the preferred embodiments of the present invention are described in detail as follows. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is the reference spectrum of the 50 μg / ml formaldehyde acetaldehyde solution in Example 1;

[0022] Figure 2 This is the detection diagram of formaldehyde and acetaldehyde in the propylene glycol test solution in Example 1;

[0023] Figure 3 is the formaldehyde standard curve;

[0024] Figure 4 The standard curve of acetaldehyde. DETAILED DESCRIPTION

[0025] In order to make the technical means, creative features, objectives and effects of the present invention easy to understand, the technical solutions in the embodiments of the present invention will be clearly and completely described below in combination with the embodiments of the present invention. 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.

[0026] Unless otherwise specified, the percentage content involved in the present invention refers to mass percentage for solid-liquid mixing and solid-solid mixing, and refers to volume percentage for liquid-liquid mixing.

[0027] Unless otherwise specified, the percentage concentrations referred to in the present invention all refer to final concentrations, which refer to the percentage of the added component in the system after the addition of the component.

[0028] The temperature parameters in the present invention, if not specifically limited, allow for both constant temperature treatment and treatment within a certain temperature range. The constant temperature treatment allows the temperature to fluctuate within the precision range controlled by the instrument.

[0029] Unless otherwise specified, the experimental methods used in the following examples are all conventional methods.

[0030] Unless otherwise specified, the materials and reagents used in the following examples can be obtained from commercial sources.

[0031] The detection method of the present invention adopts a gas chromatography system.

[0032] (1) Preparing a control solution: dissolving formaldehyde and acetaldehyde standards in water to obtain a formaldehyde-acetaldehyde mixed solution, adding a propylene glycol sample to the obtained formaldehyde-acetaldehyde mixed solution, and mixing them evenly to obtain a control solution; in the obtained control solution, the formaldehyde concentration is 5 to 100 μg / ml, the acetaldehyde concentration is 5 to 100 μg / ml, and the propylene glycol concentration is 0.5 to 1 g / ml.

[0033] (2) Test solution: Take a propylene glycol sample to be tested, dilute it with water, and obtain a test solution; the concentration of the propylene glycol sample to be tested in the obtained test solution is 0.5-1 g / ml.

[0034] (3) Chromatographic measurement: The obtained control solution and the test solution are injected into the headspace and measured by gas chromatography; the detector of the gas chromatograph used is a flame ionization detector, and the standard addition method is used for quantification, wherein the chromatographic conditions are:

[0035] a. 100% methyl polysiloxane is the fixing liquid;

[0036] b. The chromatographic column temperature is programmed temperature method;

[0037] c. The injection port temperature is 150-165°C;

[0038] d. Detector temperature is 250-275°C;

[0039] e. The carrier gas is nitrogen or helium, with a flow rate of 3.0-4.5 ml / min;

[0040] f. The split ratio is 3:1 to 5:1.

[0041] (4) Content calculation: Calculate the content of formaldehyde and acetaldehyde in the propylene glycol sample to be tested by the standard addition method.

[0042]

[0043] Wherein, Ax is the peak area of ​​formaldehyde or acetaldehyde in the test solution;

[0044] mx is the weight of the test sample in g;

[0045] Ais is the peak area of ​​formaldehyde or acetaldehyde in the control sample;

[0046] mis is the weight of the control solution (g);

[0047] ΔCis is the concentration of the control solution of known concentration added to the control sample in μg / ml;

[0048] Vis is the volume of control solution added to the control solution in ml.

[0049] The gas chromatography method is carried out in accordance with the General Rules for Gas Chromatography 0521 of Part IV of the 2020 Edition of the Chinese Pharmacopoeia.

[0050] Embodiment 1:

[0051] Preparation of control solution: Take appropriate amount of formaldehyde and acetaldehyde standard products, add water, and quantitatively dilute to make formaldehyde and acetaldehyde solutions with a concentration of 50μg / ml each. Take 1g of propylene glycol sample, accurately weigh it, place it in an empty bottle, add 1ml of the above formaldehyde and acetaldehyde solution, and seal it to obtain the control solution.

[0052] Preparation of test solution: Take 1 g of propylene glycol sample, weigh it accurately, place it in an empty bottle, add 1 ml of water, and seal it as the test solution.

[0053] The obtained control solution and the test solution were injected into the headspace and measured by gas chromatography. The chromatographic conditions were as follows: a capillary column with 100% dimethyl polysiloxane (Agilent CP-SIL5CB or similar polarity) as the stationary liquid was used as the chromatographic column (50m×0.53mm, 5.0μm), the column temperature was 50℃, maintained for 5 minutes, increased to 180℃ at a rate of 5℃ each, and then increased to 250℃ at a rate of 30℃ per minute, maintained for 5 minutes; the injection port temperature was 150℃; the split ratio was 5:1; the detector temperature was 250℃.

[0054] Content calculation: Calculate the content of formaldehyde and acetaldehyde in the propylene glycol sample to be tested by the standard addition method. The specific calculation formula is:

[0055]

[0056] Wherein, Ax is the peak area of ​​formaldehyde or acetaldehyde in the test solution;

[0057] mx is the weight of the test sample in g;

[0058] Ais is the peak area of ​​formaldehyde or acetaldehyde added to the control sample;

[0059] mis is the weight of the control sample in g;

[0060] ΔCis is the concentration of the control solution of known concentration added to the control sample in μg / ml;

[0061] Vis is the volume of control solution added to the control sample (ml).

[0062] The chromatogram of the obtained reference solution is shown in Figure 1 The chromatogram of the test solution is shown in Figure 2 .

[0063] Example 2: Determination of detection limit and quantification limit

[0064] Take the formaldehyde and acetaldehyde mixed solution prepared in Example 1, add water to dilute to a concentration of 0.6 μg / ml. Accurately weigh 1 g of propylene glycol sample, place it in a headspace bottle, add 1 ml of the above formaldehyde and acetaldehyde solution, seal it, and obtain a quantitative limit solution. The obtained quantitative limit solution is headspace injected according to the method described in Example 1 and measured by gas chromatograph. The results show that the signal-to-noise ratio of the formaldehyde and acetaldehyde chromatographic peak is ≥10.

[0065] Take the formaldehyde and acetaldehyde mixed solution prepared in Example 1, add water to dilute to a concentration of 0.3 μg / ml. Accurately weigh 1 g of propylene glycol sample, place it in a headspace bottle, add 1 ml of the above formaldehyde and acetaldehyde solution, seal it, and obtain a detection limit solution. The obtained detection limit solution is headspace injected according to the method described in Example 1 and measured by gas chromatograph. The results show that the signal-to-noise ratio of the formaldehyde and acetaldehyde chromatographic peak is ≥3.

[0066] The above results show that when the concentration of the propylene glycol sample to be tested is 1 g / ml, the formaldehyde and acetaldehyde content of 0.00003% can be detected and 0.00006% can be accurately quantified. This result shows that the detection method of the present invention has good sensitivity.

[0067] Example 3: Determination of linear range

[0068] Take an appropriate amount of the formaldehyde acetaldehyde mixed solution prepared in Example 1, add water to dilute to prepare formaldehyde acetaldehyde mixed solutions with concentrations of 0.6, 25, 50, 75, 100, and 125 μg / ml, respectively. Take 1 g of propylene glycol sample, add 1 ml of the above-mentioned formaldehyde acetaldehyde mixed solution of different concentrations, seal, and obtain corresponding control solutions with different formaldehyde acetaldehyde concentrations. The obtained control solution is headspace injected according to the method described in Example 1, and measured by gas chromatograph. With concentration C (μg / ml) as the horizontal coordinate and chromatographic peak area A as the vertical coordinate, linear regression is performed.

[0069] Acceptance criteria: With concentration as the abscissa X and peak area as the ordinate Y: the correlation coefficient (r) must not be less than 0.995, the Y-axis intercept should be within 10% of the 100% response value, and the RSD of the response factor ≤ 10%.

[0070] The linear curve of formaldehyde and acetaldehyde is as follows Figure 3 and 4 As shown. Figure 3 As shown in Figure 1, the formaldehyde standard curve equation is: y = 0.0646x + 0.0207, R = 0.9998. Figure 4 As shown, the equation of the acetaldehyde standard curve is: y=0.0878x-0.0476, R=1.0000.

[0071] The above results show that when the concentration of formaldehyde and acetaldehyde is between 0.6 and 125 μg / ml, the peak area has a good linear relationship with the concentration, and the correlation coefficient r values ​​are 0.9998 and 1.0000 respectively. The Y-axis intercept should be within 10% of the 100% response value, and the RSD of the response factor is ≤10%.

[0072] Example 4: Precision Experiment

[0073] Take appropriate amount of formaldehyde and acetaldehyde standard products, add water, and quantitatively dilute to prepare formaldehyde and acetaldehyde solutions with a concentration of 50 μg / ml each. Take 1g of propylene glycol sample, place it in a headspace bottle, and add 1ml of the above formaldehyde and acetaldehyde solution to obtain a control solution. According to the method described in Example 1, 6 bottles of headspace sampling were performed continuously as the injection precision.

[0074] Take 1g of the propylene glycol sample to be tested, weigh it accurately, place it in an empty bottle, add 1ml of water, seal it, and use it as the test solution. Prepare 6 copies in parallel.

[0075] Repeated experiments were performed by different experimenters at different times as intermediate precision.

[0076] The results showed that the RSD of the formaldehyde peak area of ​​the injection precision of the present invention was 3.2%, and the RSD of the acetaldehyde peak area was 1.3%. No formaldehyde or acetaldehyde was detected in the 12 propylene glycol samples in terms of repeatability and intermediate precision.

[0077] Example 5: Recovery determination

[0078] Take appropriate amount of formaldehyde and acetaldehyde standards, add water, and quantitatively dilute to prepare formaldehyde and acetaldehyde mixed solutions with concentrations of 25, 50, and 75 μg / ml respectively.

[0079] Take 1g of propylene glycol sample, weigh accurately, place in an empty bottle, add 1ml of the above-mentioned formaldehyde and acetaldehyde solutions of each concentration, seal, and obtain solutions with different formaldehyde and acetaldehyde concentrations as test solutions with different levels of sample recovery. Test each sample according to the method described in Example 1, perform 3 replicates for each level, and calculate the recovery amount and recovery rate.

[0080] Acceptance criteria: Recovery between 85-110% and RSD not exceeding 15%.

[0081] The results show that the formaldehyde recovery rate and acetaldehyde recovery rate of the present invention are both between 97% and 103%, and RSD is less than 2%. The above results indicate that the detection method of the present invention has good accuracy.

[0082] Example 6: Durability test

[0083] a. Change the chromatographic column

[0084] The difference from Example 1 is that: the chromatographic column is replaced with a filler of similar polarity for determination (5% phenyl-95% dimethylpolysiloxane as the stationary phase CP-SIL 8CB).

[0085] The results show that after replacing the chromatographic column, the separation degree of formaldehyde and acetaldehyde was measured to be 9.58, and no formaldehyde and acetaldehyde were detected in the test sample under the same conditions as the original conditions. The slight adjustment of the polarity of the chromatographic column has little effect on the present invention.

[0086] b. Change the flow rate

[0087] The difference from Example 1 is that the column flow rate of the chromatographic column is changed to 3.6 and 4.4 ml / min for measurement.

[0088] The results show that after changing the flow rate, the separation degrees of formaldehyde and acetaldehyde were measured to be 9.92 and 9.66 respectively, and no formaldehyde and acetaldehyde were detected in the test samples under the same conditions as the original conditions. The slight change in column flow rate has little effect on the present invention.

[0089] c. Change column temperature

[0090] The difference from Example 1 is that the initial column temperature is changed to 45°C and 55°C for measurement.

[0091] The results show that after changing the initial column temperature, the separation degrees of formaldehyde and acetaldehyde are 11.09 and 8.61 respectively, and no formaldehyde and acetaldehyde are detected in the test samples under the same conditions as the original conditions. The slight change of column temperature has little effect on the present invention.

[0092] Example 7: Measurement results of actual samples

[0093] Three batches of propylene glycol samples were tested according to the method described in Example 1. The results showed that no formaldehyde or acetaldehyde was detected in all the propylene glycol samples.

[0094] It can be seen that the present invention can detect the content of formaldehyde and acetaldehyde in propylene glycol conveniently, quickly, sensitively and efficiently.

[0095] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Although the present invention has been disclosed as a preferred embodiment as above, it is not used to limit the present invention. Any technician familiar with this profession can make some changes or modifications to equivalent embodiments of equivalent changes by using the methods and technical contents disclosed above without departing from the scope of the technical solution of the present invention. However, any simple modification, equivalent change and modification made to the above embodiments according to the technical essence of the present invention without departing from the content of the technical solution of the present invention still fall within the scope of the technical solution of the present invention.

Claims

1. A method for determining formaldehyde and acetaldehyde in propylene glycol, characterized in that: The method comprises the following steps: (1) Reference solution: Dissolve formaldehyde and acetaldehyde standards in water to obtain a formaldehyde-acetaldehyde mixed solution, add propylene glycol sample to the obtained formaldehyde-acetaldehyde mixed solution, mix well, and obtain a reference solution; (2) Test solution: Take the propylene glycol sample to be tested and dilute it with water to obtain the test solution; (3) Chromatographic measurement: The obtained control solution and the test solution are injected into the headspace and measured by gas chromatography; (4) Content calculation: Calculate the content of formaldehyde and acetaldehyde in the propylene glycol sample according to the standard addition method.

2. The method according to claim 1, characterized in that In step (1), in the control solution: the formaldehyde concentration is 5-100 µg / ml, the acetaldehyde concentration is 5-100 µg / ml, and the propylene glycol concentration is 0.5-1 g / ml.

3. The method according to claim 1, characterized in that In step (2), the concentration of the propylene glycol sample to be tested in the test solution is 0.5~1g / ml.

4. The method according to claim 1, characterized in that: In step (3), the stationary phase in the gas chromatograph uses a gas chromatography system, the detector is a flame ionization detector, and the temperature is 240-260°C.

5. The method according to claim 1, characterized in that In step (3), the gas chromatography conditions are: a capillary column is used as the chromatographic column, the injection port temperature is 140-160°C, the column flow rate is 3.0-4.5 ml / min, and the split ratio is 3:1-5:

1.

6. The method according to claim 5, characterized in that The capillary column uses 100% dimethyl polysiloxane or 5% phenyl-95% dimethyl polysiloxane as the stationary liquid.

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