Method for detecting total phosphorus content in phosphorus flame retardant

Abstract

The invention discloses a method for detecting the total phosphorus content in a phosphorus flame retardant, which is characterized by comprising the following steps: preparing a phosphorus standard working solution and drawing a working curve; preparing a solution to be detected; weighing a to-be-detected sample, adding the digestion solution, and heating and digesting; cooling, adding distilled water, and continuously heating and digesting; cooling, transferring to a 50mL volumetric flask by using distilled water, diluting to a scale, and uniformly shaking to obtain a blank solution; transferring a predetermined volume from the blank solution into a 50mL volumetric flask, adding a color developing agent for color development, diluting with distilled water to a scale, uniformly shaking, and standing for a predetermined time to obtain a solution to be detected; the color developing agent comprises a dilute sulfuric acid solution, an ammonium ferrous sulfate solution and an ammonium molybdate solution; determining the phosphorus content of the to-be-determined solution; measuring the absorbance of the blank solution and the to-be-measured solution under a preset wavelength; and calculating the phosphorus content of the to-be-detected sample. The detection method can be used for detecting the content of the phosphorus element in the phosphorus flame retardant and related esterification liquid, the detection lower limit is lower, and the detection accuracy and precision are higher.

Description

Technical Field

[0001] The present specification relates to the technical field of chemical analysis and detection, and in particular to a method for detecting the total phosphorus content in a phosphorus-based flame retardant. Background Art

[0002] Polyester fiber is the most widely used and highest-yield material in the chemical fiber industry. Its excellent mechanical properties, wrinkle resistance and light resistance make it widely used in clothing, home textiles, carpet base fabrics and industrial fabrics. However, the limiting oxygen index (LOI) of PET material is only 20%, which is a flammable material. Therefore, flame retardant modification of PET material has important practical significance. Phosphorus-based flame retardant is a low-toxic, low-smoke and high-efficiency flame retardant, and has a good effect on improving the color and dyeing properties of fibers. The flame retardant effect of phosphorus-based flame retardants is determined by their total phosphorus content, and the detection of the phosphorus content in flame retardants is crucial.

[0003] In the Chinese patent application number CN201810227779.9, "A method for detecting the total phosphorus content in phosphate flame retardants", ammonium vanadium molybdate is selected as a color developer to detect samples with a phosphorus content greater than 50% in phosphate flame retardants. However, this detection method is based on the high phosphorus content in flame retardants, and cannot accurately test the esterification liquid with a low phosphorus content at various stages in the polyester production process. Summary of the invention

[0004] In view of the deficiencies in the prior art, one purpose of this specification is to provide a method for detecting the total phosphorus content in phosphorus-based flame retardants, which can detect the phosphorus content in phosphorus-based flame retardants and related esterification liquids, has a low detection limit, and has high detection accuracy and precision.

[0005] To achieve the above purpose, the present specification provides a method for detecting the total phosphorus content in a phosphorus-based flame retardant, comprising the following steps:

[0006] Prepare a phosphorus standard working solution and draw a working curve; the phosphorus standard working solution is prepared from potassium dihydrogen phosphate, distilled water and dilute sulfuric acid; measure the absorbance values ​​of the phosphorus standard working solution of different concentrations at a predetermined wavelength, and draw the working curve according to the measured absorbance values ​​and the concentration of the phosphorus standard working solution;

[0007] Prepare a test solution; weigh a first predetermined mass m of the test sample, add a digestion solution and heat to digest; add distilled water after cooling and continue heating to digest; transfer to a 50mL volumetric flask with distilled water after cooling, dilute to the scale and shake well to serve as a blank solution; transfer a predetermined volume V from the blank solution to a 50mL volumetric flask, add a color developer to develop color, dilute to the scale with distilled water and shake well, and place for a predetermined time to obtain the test solution; the color developer includes a dilute sulfuric acid solution, an ammonium ferrous sulfate solution and an ammonium molybdate solution;

[0008] Determine the phosphorus content of the solution to be tested; determine the absorbance of the blank solution and the solution to be tested at the predetermined wavelength, subtract the absorbance of the blank solution from the measured absorbance of the solution to be tested to obtain an actual absorbance, and find out the phosphorus content corresponding to the actual absorbance on the working curve as the phosphorus content of the solution to be tested;

[0009] Calculate the phosphorus content of the sample to be tested; use the formula Z is the phosphorus content of the sample to be tested expressed as mass fraction, in %; C p is the phosphorus content of the solution to be tested, in mg; m is the first predetermined mass of the sample to be tested, in mg; V is the predetermined volume of the solution removed from the blank solution, in mL.

[0010] As a preferred embodiment, in the step of preparing the solution to be tested, the step of preparing the developer comprises:

[0011] Prepare the dilute sulfuric acid solution; add 125 mL of concentrated sulfuric acid to 800 mL of distilled water, cool and transfer into a 1000 mL volumetric flask, add distilled water to the mark, and shake well;

[0012] The ammonium molybdate solution is prepared by adding 50 g of ammonium molybdate to 400 mL of distilled water, heating until completely dissolved to obtain a first solution, and after cooling slightly, adding the first solution to 500 mL of cooled 4.5 mol / L sulfuric acid solution under stirring to obtain a second solution, and after the second solution is cooled, transferring it into a 1000 ml volumetric flask, adding distilled water to the scale, and shaking well;

[0013] Prepare the ammonium ferrous sulfate solution; weigh 25g of ammonium ferrous sulfate and add it to a 250mL beaker, add distilled water, stir to dissolve the ammonium ferrous sulfate to obtain a third solution, filter the third solution into a 250mL volumetric flask, add 0.5mL to 1.0mL of 2.25mol / L sulfuric acid, and dilute to the scale with distilled water.

[0014] As a preferred embodiment, in the step of preparing the phosphorus standard working solution, accurately weigh dry potassium dihydrogen phosphate, dissolve it in distilled water, add 0.5-1.0 mL of dilute sulfuric acid, shake well, dilute to the scale with distilled water, and shake well again to obtain the phosphorus standard working solution.

[0015] As a preferred embodiment, the potassium dihydrogen phosphate is dried in an oven at 110°C to constant weight, and after cooling, 0.4394g of potassium dihydrogen phosphate is accurately weighed, washed into a 1000mL volumetric flask with distilled water from a small funnel, 0.5-1.0mL of 2.25mol / L sulfuric acid is added, shaken well, diluted to the scale with distilled water, and shaken again to obtain a 100μg / mL phosphorus standard working solution.

[0016] As a preferred implementation, in the step of preparing the solution to be tested, the first predetermined mass m is 4-10 mg.

[0017] As a preferred embodiment, in the step of preparing the solution to be tested, adding the digestion solution for heating and digestion includes: adding concentrated sulfuric acid and nitric acid, and heating with an alcohol lamp until yellow smoke is completely eliminated and white smoke is emitted; adding distilled water after cooling and continuing to heat and digestion includes: adding 0.5 to 1.0 mL of distilled water after cooling, and continuing to heat until white smoke is emitted.

[0018] As a preferred embodiment, in the step of preparing the solution to be tested, the predetermined volume V is 5 mL.

[0019] As a preferred implementation, in the step of preparing the solution to be tested, the predetermined time is 15 minutes.

[0020] As a preferred embodiment, in the steps of preparing a phosphorus standard working solution and drawing a working curve and determining the phosphorus content of the solution to be tested, the predetermined wavelength is 750 nm.

[0021] As a preferred embodiment, in the step of preparing the test solution, for the same test sample, weigh another test sample of a second predetermined mass n, and perform the same operation as the test sample of the first predetermined mass m, calculate the phosphorus content of the second predetermined mass n of the test sample as Y, and take the arithmetic mean of Z and Y as the phosphorus content of the test sample, and the phosphorus content of the test sample is expressed to two decimal places.

[0022] Beneficial effects:

[0023] The method for detecting the total phosphorus content in the phosphorus-based flame retardant provided in the present embodiment is to prepare a phosphorus standard working solution and draw a working curve, and prepare a test solution according to the test sample, and the color developer is selected from a dilute sulfuric acid solution, an ammonium ferrous sulfate solution and an ammonium molybdate solution. After the phosphorus content of the test solution is determined, the phosphorus content of the test sample is calculated. The operation is simple and the cost is low. The phosphorus content in the phosphorus-based flame retardant and related esterification liquid can be detected, and the detection limit is low, and the detection precision and accuracy are high.

[0024] In the detection method, the linear coefficient of the working curve of the phosphorus standard working solution is 0.9996, the detection limit of the blank sample is 0.017ug / mL, the RSD (relative standard deviation) of the reproducibility detection of 6 parallel samples is 0.0381%, and the recovery rate of 6 spike additions ranges from 97% to 104%.

[0025] With reference to the following description and the accompanying drawings, the specific embodiments of the present invention are disclosed in detail, indicating the manner in which the principles of the present invention can be adopted. It should be understood that the embodiments of the present invention are not limited in scope thereby.

[0026] Features described and / or illustrated with respect to one embodiment may be used in the same or similar manner in one or more other embodiments, combined with features in other embodiments, or substituted for features in other embodiments.

[0027] It should be emphasized that the term “include / comprises” when used herein refers to the presence of features, integers, steps or components, but does not exclude the presence or addition of one or more other features, integers, steps or components. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without paying creative labor.

[0029] Figure 1 This is a flow chart of the steps of a method for detecting the total phosphorus content in a phosphorus-based flame retardant provided in this embodiment. DETAILED DESCRIPTION

[0030] In order to enable those skilled in the art to better understand the technical solutions in the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0031] It should be noted that when an element is referred to as being "disposed on" another element, it may be directly on the other element or there may be another element centered thereon. When an element is considered to be "connected to" another element, it may be directly connected to the other element or there may be another element centered thereon at the same time. The terms "vertical", "horizontal", "left", "right" and similar expressions used herein are for illustrative purposes only and do not represent the only implementation method.

[0032] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used herein in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The term "and / or" used herein includes any and all combinations of one or more related listed items.

[0033] See also Figure 1 The present application provides a method for detecting the total phosphorus content in a phosphorus-based flame retardant, comprising the following steps:

[0034] Step S10: prepare phosphorus standard working solution and draw a working curve.

[0035] Specifically, the phosphorus standard working solution is prepared from potassium dihydrogen phosphate, distilled water and dilute sulfuric acid. The absorbance values ​​of the phosphorus standard working solution of different concentrations are measured at a predetermined wavelength, and the working curve is drawn according to the measured absorbance values ​​and the concentration of the phosphorus standard working solution.

[0036] In the step of preparing the phosphorus standard working solution, accurately weigh dry potassium dihydrogen phosphate, add distilled water to dissolve it, then add 0.5-1.0 mL of dilute sulfuric acid, shake well, dilute to the scale with distilled water, and shake well again to obtain the phosphorus standard working solution.

[0037] More specifically, the preparation of the phosphorus standard working solution is as follows: the potassium dihydrogen phosphate is dried in an oven at 110° C. to constant weight, then cooled in a dryer, 0.4394 g of potassium dihydrogen phosphate is accurately weighed, washed into a 1000 mL volumetric flask with distilled water from a small funnel, 0.5 to 1.0 mL of 2.25 mol / L sulfuric acid is added, shaken well, diluted to the scale with distilled water, and shaken again to obtain a 100 μg / mL phosphorus standard working solution.

[0038] In the step of drawing the working curve, the predetermined wavelength is preferably 750 nm. The correlation coefficient R2 of the working curve of the phosphorus standard working solution is 0.9996, and the slope is 0.1264.

[0039] Step S20: preparing a solution to be tested.

[0040] There is no requirement for the order of step S20 and step S10, and both can be performed simultaneously.

[0041] Specifically, after weighing the first predetermined mass m of the sample to be tested, add the digestion solution and heat to digest; add distilled water after cooling and continue to heat to digest; transfer to a 50mL volumetric flask with distilled water after cooling, shake up after diluting to the scale, as a blank solution; pipette a predetermined volume V from the blank solution to a 50mL volumetric flask, add a color developer to develop color, shake up after diluting to the scale with distilled water, and place the solution to be tested after a predetermined time. The color developer includes a dilute sulfuric acid solution, an ammonium ferrous sulfate solution, and an ammonium molybdate solution. The selection of the color developer can make the detection limit of the present application lower. If ammonium ferrous sulfate is replaced with ascorbic acid, the solution to be tested is detected at 750nm, and the test result has poor repeatability, which is invalid experimental data.

[0042] The principle of preparing the test solution is: accurately weigh the test sample and place it in a Kjergler flask, add strong acid for digestion, cool, adjust the volume, dilute, and color, and then measure the absorbance with an ultraviolet visible spectrophotometer (UV-Vis).

[0043] In this embodiment, the first predetermined mass m is preferably 4 mg to 10 mg.

[0044] In the step of preparing the solution to be tested, adding the digestion solution for heating and digestion includes: adding concentrated sulfuric acid and nitric acid, and heating with an alcohol lamp until yellow smoke disappears and white smoke emerges. Adding distilled water after cooling and continuing to heat and digestion includes: adding 0.5-1.0 mL of distilled water after cooling, and continuing to heat until white smoke emerges.

[0045] In the step of preparing the solution to be tested, the predetermined volume V is preferably 5 mL. The predetermined time is preferably 15 min.

[0046] In step S20, the preparation step of the developer includes:

[0047] (1) preparing the dilute sulfuric acid solution; adding 125 mL of concentrated sulfuric acid to 800 mL of distilled water, cooling and transferring the mixture into a 1000 mL volumetric flask, adding distilled water to the mark, and shaking well;

[0048] (2) preparing the ammonium molybdate solution; adding 50 g of ammonium molybdate to 400 mL of distilled water, heating until completely dissolved to obtain a first solution, and after cooling slightly, adding the first solution to 500 mL of cooled 4.5 mol / L sulfuric acid solution under stirring to obtain a second solution, and after the second solution is cooled, transferring it into a 1000 mL volumetric flask, adding distilled water to the mark, and shaking well;

[0049] (3) Prepare the ammonium ferrous sulfate solution; weigh 25 g of ammonium ferrous sulfate and add it to a 250 mL beaker, add distilled water, stir to dissolve the ammonium ferrous sulfate, and obtain a third solution. Filter the third solution into a 250 mL volumetric flask, add 0.5 mL to 1.0 mL of 2.25 mol / L sulfuric acid to prevent hydrolysis, and dilute to the mark with distilled water. The ammonium ferrous sulfate solution is unstable and should be prepared and used immediately.

[0050] Step S30: Determine the phosphorus content of the solution to be tested.

[0051] Specifically, the absorbance of the blank solution and the solution to be tested is measured at the predetermined wavelength, the actual absorbance is obtained by subtracting the absorbance of the blank solution from the measured absorbance of the solution to be tested, and the phosphorus content corresponding to the actual absorbance is found on the working curve as the phosphorus content of the solution to be tested.

[0052] In step S30, the predetermined wavelength is preferably 750 nm. Since 750 nm is the maximum absorption wavelength, 750 nm is selected as the predetermined wavelength. If the selected wavelength is 825 nm, the detection limit is 0.034 ug / mL, which is higher than the detection limit (0.017 ug / mL) at 750 nm. Therefore, the selection of the predetermined wavelength of 750 nm can make the detection limit of the present application lower.

[0053] Step S40: Calculate the phosphorus content of the sample to be tested.

[0054] Specifically, use the formula Z is the phosphorus content of the sample to be tested expressed as mass fraction, in %; C p is the phosphorus content of the solution to be tested, in mg; m is the first predetermined mass of the sample to be tested, in mg; V is the predetermined volume of the solution removed from the blank solution, in mL.

[0055] In step S40, for the same sample to be tested, another sample to be tested of a second predetermined mass n is weighed (i.e., for each sample to be tested, two parallel samples are selected: a sample to be tested of a first predetermined mass m and a sample to be tested of a second predetermined mass n), and the same operation as that of the first predetermined mass m is performed on the sample to be tested, and the phosphorus content of the second predetermined mass n is calculated as Y, and the arithmetic mean of Z and Y is taken as the phosphorus content of the sample to be tested, and the phosphorus content of the sample to be tested is expressed to two decimal places.

[0056] The relative deviation allowed for the determination result of the total phosphorus content calculated in step S40 is 2%.

[0057] The method for detecting the total phosphorus content in the phosphorus-based flame retardant provided in the present embodiment is to prepare a phosphorus standard working solution and draw a working curve, and prepare a test solution according to the test sample, and the color developer is selected from a dilute sulfuric acid solution, an ammonium ferrous sulfate solution and an ammonium molybdate solution. After the phosphorus content of the test solution is determined, the phosphorus content of the test sample is calculated. The operation is simple and the cost is low. The phosphorus content in the phosphorus-based flame retardant and related esterification liquid can be detected, and the detection limit is low, and the detection precision and accuracy are high.

[0058] In the detection method, the linear coefficient of the working curve of the phosphorus standard working solution is 0.9996, the detection limit of the blank solution is 0.017ug / mL, the RSD (relative standard deviation) of the reproducibility detection of 6 parallel samples is 0.0381%, and the recovery rate range of 6 spike additions is 97% to 104%.

[0059] In a specific embodiment, the preparation of the test solution includes: 1) weighing 4-10 mg (accurate to 0.00001 g) of the test sample into a gram flask; 2) adding concentrated sulfuric acid and nitric acid, heating with an alcohol lamp until the yellow smoke is gone and white smoke is emitted, and cooling; 3) adding 0.5-1.0 mL of distilled water, and continuing to heat until white smoke is emitted; 4) after cooling, transferring to a 50 mL volumetric flask with distilled water, diluting to the scale, shaking well, and serving as a blank solution (a blank experiment can be performed at the same time, that is, measuring the absorbance of the blank solution at a wavelength of 750 nm); 5) using a graduated pipette to accurately transfer 5 mL of the blank solution to a 50 mL volumetric flask; 6) adding dilute sulfuric acid, ammonium ferrous sulfate and ammonium molybdate solution to develop color, diluting to the scale with distilled water, shaking well, and leaving for 15 minutes to obtain the test solution.

[0060] When determining the phosphorus content of the test solution, first calibrate to zero with distilled water, then use a 1 cm cuvette to measure the absorbance of the blank solution and the test solution at a wavelength of 750 nm, subtract the absorbance of the blank solution from the measured absorbance of the test solution, and find out the corresponding phosphorus content from the working curve.

[0061] In this embodiment, when preparing the phosphorus standard working solution and drawing the working curve, 0.1 mL, 0.2 mL, 0.5 mL, 0.7 mL, 1.0 mL, 1.2 mL, and 1.5 mL of the 100 μg / mL phosphorus standard working solution are accurately pipetted and placed in 50 mL volumetric flasks, respectively, and 3 mL of 2.25 mol / L sulfuric acid, 10 mL of ammonium molybdate solution, and 5 mL of ammonium ferrous sulfate solution are added in sequence, diluted to the scale with distilled water, and fully mixed. Phosphorus standard samples of different concentrations are obtained, as shown in Table 1 below:

[0062] Table 1 Phosphorus standard working solution volume and concentration

[0063]

[0064] Methodological investigation

[0065] (1) Method detection limit test: Prepare a blank solution according to step (1) and perform 11 blank solution repeatability tests at 750 nm. The result is a mean of 0.015, a standard deviation of 0.0007, and a detection limit of 0.017 ug / mL.

[0066] The detection limit is calculated and expressed as follows:

[0067] In general testing, the confidence factor of the detection limit is 3, that is, 3 times the standard deviation divided by the slope of the absorbance curve in the low concentration range, and the detection limit is calculated according to the following formula:

[0068]

[0069] Where: C L is the detection limit; M is the slope of the standard curve in the low concentration range; S b is the standard deviation of the blank solution; k is the confidence factor, which is generally 2 to 3, and is 3 here.

[0070] According to the working curve of phosphorus standard working solution, M = 0.1264, so the detection limit C L It is 3×0.0007 / 0.1264=0.017ug / mL.

[0071] (2) Method reproducibility test: Accurately weigh 6 parts of phosphorus-based flame retardant, prepare a solution to be tested for phosphorus content according to step S20, and measure its absorbance at 750 nm. The average value is 14.16%, the standard deviation is 0.0054, and the RSD is 0.0381%, indicating that the method has good reproducibility.

[0072] (3) Method spike recovery test: Take an appropriate amount of the sample solution with measured phosphorus content, conduct 6 parallel tests, add an appropriate amount of phosphorus standard working solution, prepare the phosphorus content test solution according to step S20, measure its absorbance at 750nm, and calculate the recovery rate according to the standard curve regression equation and the spike recovery calculation formula. The recoveries of the spiked samples ranged from 97% to 104%, indicating that the method had good accuracy.

[0073] In this embodiment, the instruments and equipment used are as follows:

[0074] 1. When measuring absorbance, use an ultraviolet visible spectrophotometer (UV-Vis), such as the UV-2700i produced by Shimadzu Instruments (Suzhou) Co., Ltd.;

[0075] 2. Alcohol lamp;

[0076] 3. Electronic balance: MS204TS / 02, accurate to 0.01mg;

[0077] 4. Gram flask: 50mL;

[0078] 5. Volumetric flask: 50mL, Grade A;

[0079] 6. Pipette: 1.0, 2.0, 5.0, 10.0mL;

[0080] 7. Beaker: 100mL;

[0081] 8. Cuvette: 1cm.

[0082] To ensure that the glassware was phosphorus-free, all glassware used was soaked in dilute acid to remove phosphorus.

[0083] The reagents and standards used in this example, unless otherwise specified, the water involved in the detection process all meet the specifications of grade 3 water in GB / T 6682, and the purity of the reagents used in the analysis (such as concentrated sulfuric acid, nitric acid, ammonium molybdate, ammonium ferrous sulfate, potassium dihydrogen phosphate) are all analytically pure.

[0084] It should be noted that, in the description of this specification, the terms "first", "second", etc. are only used for descriptive purposes and to distinguish similar objects. There is no order of precedence between the two, and they cannot be understood as indicating or implying relative importance. In addition, in the description of this specification, unless otherwise specified, the meaning of "plurality" is two or more.

[0085] Any numerical value cited herein includes all values ​​of lower and upper values ​​that increase by one unit from the lower limit to the upper limit, and there is at least a two-unit interval between any lower value and any higher value. For example, if the value of the quantity of a component or a process variable (such as temperature, pressure, time, etc.) is stated to be from 1 to 90, preferably from 20 to 80, and more preferably from 30 to 70, the purpose is to illustrate that values ​​such as 15 to 85, 22 to 68, 43 to 51, 30 to 32 are also explicitly listed in the specification. For values ​​less than 1, one unit is appropriately considered to be 0.0001, 0.001, 0.01, 0.1. These are merely examples that are intended to be clearly expressed, and it can be considered that all possible combinations of numerical values ​​listed between the lowest value and the highest value are clearly stated in the specification in a similar manner.

[0086] Unless otherwise specified, all ranges include the endpoints and all numbers between the endpoints. "About" or "approximately" used with a range applies to both endpoints of the range. Thus, "about 20 to 30" is intended to cover "about 20 to about 30", including at least the specified endpoints.

[0087] All articles and references disclosed, including patent applications and publications, are incorporated herein by reference for all purposes. The term "consisting essentially of..." to describe a combination should include the identified elements, ingredients, parts or steps and other elements, ingredients, parts or steps that do not substantially affect the basic novel characteristics of the combination. The use of the terms "comprising" or "including" to describe a combination of elements, ingredients, parts or steps herein also contemplates embodiments that consist essentially of these elements, ingredients, parts or steps. By using the term "may", it is intended to indicate that any attribute described that "may" include is optional.

[0088] Multiple elements, ingredients, parts or steps can be provided by a single integrated element, ingredient, part or step. Alternatively, a single integrated element, ingredient, part or step can be divided into separate multiple elements, ingredients, parts or steps. The disclosure "one" or "an" used to describe an element, ingredient, part or step is not intended to exclude other elements, ingredients, parts or steps.

[0089] It should be understood that the above description is for illustration and not for limitation. Many embodiments and many applications beyond the examples provided will be apparent to those skilled in the art upon reading the above description. Therefore, the scope of the present teachings should not be determined with reference to the above description, but should be determined with reference to the appended claims and the full scope of equivalents possessed by such claims. For the purpose of comprehensiveness, all articles and references, including disclosures of patent applications and publications, are incorporated herein by reference. The omission of any aspect of the subject matter disclosed herein in the preceding claims is not intended to be a waiver of the subject matter, nor should it be considered that the inventors did not consider the subject matter to be part of the disclosed inventive subject matter.

Claims

1. A method for detecting the total phosphorus content in a phosphorus-based flame retardant, characterized in that: The following steps are involved: Prepare a phosphorus standard working solution and draw a working curve; the phosphorus standard working solution is prepared from potassium dihydrogen phosphate, distilled water and dilute sulfuric acid; measure the absorbance values ​​of the phosphorus standard working solution of different concentrations at a predetermined wavelength, and draw the working curve according to the measured absorbance values ​​and the concentration of the phosphorus standard working solution; Prepare a test solution; weigh a first predetermined mass m of the test sample, add a digestion solution and heat to digest; add distilled water after cooling and continue heating to digest; transfer to a 50mL volumetric flask with distilled water after cooling, dilute to the scale and shake well to serve as a blank solution; transfer a predetermined volume V from the blank solution to a 50mL volumetric flask, add a color developer to develop color, dilute to the scale with distilled water and shake well, and place for a predetermined time to obtain the test solution; the color developer includes a dilute sulfuric acid solution, an ammonium ferrous sulfate solution and an ammonium molybdate solution; Determining the phosphorus content of the solution to be tested; Determine the absorbance of the blank solution and the solution to be tested at the predetermined wavelength, subtract the absorbance of the blank solution from the measured absorbance of the solution to be tested to obtain an actual absorbance, and find out the phosphorus content corresponding to the actual absorbance on the working curve as the phosphorus content of the solution to be tested; Calculating the phosphorus content of the sample to be tested; Using the formula Z is the phosphorus content of the sample to be tested expressed as mass fraction, in %; C p is the phosphorus content of the solution to be tested, in mg; m is the first predetermined mass of the sample to be tested, in mg; V is the predetermined volume of the solution removed from the blank solution, in mL.

2. The method for detecting the total phosphorus content in a phosphorus-based flame retardant according to claim 1, characterized in that: In the step of preparing the solution to be tested, the step of preparing the developer comprises: Prepare the dilute sulfuric acid solution; add 125 mL of concentrated sulfuric acid to 800 mL of distilled water, cool and transfer into a 1000 mL volumetric flask, add distilled water to the mark, and shake well; The ammonium molybdate solution is prepared by adding 50 g of ammonium molybdate to 400 mL of distilled water, heating until completely dissolved to obtain a first solution, and after cooling slightly, adding the first solution to 500 mL of cooled 4.5 mol / L sulfuric acid solution under stirring to obtain a second solution, and after the second solution is cooled, transferring it into a 1000 ml volumetric flask, adding distilled water to the scale, and shaking well; Prepare the ammonium ferrous sulfate solution; weigh 25g of ammonium ferrous sulfate and add it to a 250mL beaker, add distilled water, stir to dissolve the ammonium ferrous sulfate to obtain a third solution, filter the third solution into a 250mL volumetric flask, add 0.5mL to 1.0mL of 2.25mol / L sulfuric acid, and dilute to the scale with distilled water.

3. The method for detecting the total phosphorus content in a phosphorus-based flame retardant according to claim 1, characterized in that: In the step of preparing the phosphorus standard working solution, accurately weigh dry potassium dihydrogen phosphate, add distilled water to dissolve it, add 0.5-1.0 mL of dilute sulfuric acid, shake well, dilute to the scale with distilled water, and shake well again to obtain the phosphorus standard working solution.

4. The method for detecting the total phosphorus content in a phosphorus-based flame retardant according to claim 3, characterized in that: The potassium dihydrogen phosphate was dried in an oven at 110° C. to constant weight, and after cooling, 0.4394 g of potassium dihydrogen phosphate was accurately weighed, and washed into a 1000 mL volumetric flask with distilled water from the funnel, and 0.5 to 1.0 mL of 2.25 mol / L sulfuric acid was added, and after shaking, it was diluted to the scale with distilled water, and then shaken again to obtain a 100 μg / mL phosphorus standard working solution.

5. The method for detecting the total phosphorus content in a phosphorus-based flame retardant according to claim 1, characterized in that: In the step of preparing the solution to be tested, the first predetermined mass m is 4-10 mg.

6. The method for detecting the total phosphorus content in a phosphorus-based flame retardant according to claim 1, characterized in that: In the step of preparing the solution to be tested, adding the digestion solution for heating and digestion includes: adding concentrated sulfuric acid and nitric acid, and heating with an alcohol lamp until yellow smoke disappears and white smoke emerges; adding distilled water after cooling and continuing to heat and digestion includes: adding 0.5-1.0 mL of distilled water after cooling, and continuing to heat until white smoke emerges.

7. The method for detecting the total phosphorus content in a phosphorus-based flame retardant according to claim 1, characterized in that: In the step of preparing the solution to be tested, the predetermined volume V is 5 mL.

8. The method for detecting the total phosphorus content in a phosphorus-based flame retardant according to claim 1, characterized in that: In the step of preparing the solution to be tested, the predetermined time is 15 minutes.

9. The method for detecting the total phosphorus content in a phosphorus-based flame retardant according to claim 1, characterized in that: In the steps of preparing a phosphorus standard working solution and drawing a working curve and determining the phosphorus content of the solution to be tested, the predetermined wavelength is 750 nm.

10. The method for detecting the total phosphorus content in a phosphorus-based flame retardant according to claim 1, characterized in that: In the step of preparing the test solution, for the same test sample, weigh another test sample of a second predetermined mass n, and perform the same operation as the test sample of the first predetermined mass m on it, calculate the phosphorus content of the second predetermined mass n of the test sample as Y, and take the arithmetic mean of Z and Y as the phosphorus content of the test sample, and the phosphorus content of the test sample is expressed to two decimal places.

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