CN103399011A - Measuring method of content of cyanoacetic acid product - Google Patents

Abstract

The invention relates to a measuring method of content of a cyanoacetic acid product. The measuring method is characterized in that the measurement for an cyanoacetic acid product with mass percentage concentration of at least 30% is carried out by the following steps: adding excessive alkali liquor into a Kjeldahl flask; accurately weighing a certain amount of the cyanoacetic acid product, heating up for hydrolysis and distillation after the adding; absorbing the distilled ammonia gas by an excessive boric acid solution; using a methyl red-methylene blue mixed indictor and an acid standard titration solution for titration; and calculating the content of cyanoacetic acid in a sample. The measuring method is high in accuracy, good in precision, low in analysis cost and suitable for accurate measurement of content of the cyanoacetic acid product.

Description

A kind of assay method of cyanoacetic acid product content

Technical field

The present invention relates to the mensuration of cyanoacetic acid product, relate in particular to a kind of assay method of cyanoacetic acid product content.

Background technology

Cyanoacetic acid, another name cyanoacetic acid, cyanoacetic acid, its fusing point is 70 ℃, moderate toxicity, water-soluble, ethanol, ether, be slightly soluble in benzene, chloroform, meets the alkali salify, is a kind of important medicine, pesticide intermediate.It can chloroacetic acid, sodium cyanide, sodium carbonate are raw material, by neutralization, cyaniding, acidifying, makes.At present commercially available cyanoacetic acid has the specification product of following multiple mass percent concentration: 95% (crystal), 80%, 70%, 60%, 30% etc.In these products, the Accurate Determining of cyanoacetic acid content is synthetic significant to next step medicine and agricultural chemicals.

At present, the assay method of cyanoacetic acid content adopts direct alkalimetry and high performance liquid chromatography to measure usually.Wherein, directly alkalimetry is the total acid in working sample, in cyanoacetic acid, but because a synthetic in the end step of cyanoacetic acid forms with the mineral acid acidifying, the mineral acid of residual existence in its sample, the final content results of measuring is more higher than actual value by making; And the employing high performance liquid chromatography, although measurement result is accurate, needs high performance liquid chromatograph, also needs the standard items of known accurate content, and its analysis cost is higher.

Summary of the invention

The object of the present invention is to provide a kind of assay method of cyanoacetic acid product content, this assay method accuracy is high, and precision is good, and analysis cost is low, is suitable for the Accurate Determining of cyanoacetic acid product content.

The object of the present invention is achieved like this:

A kind of assay method of cyanoacetic acid product content, it is characterized in that, it is for mass percent concentration, to be at least 30% cyanoacetic acid product, the mensuration of carrying out according to following steps: first excessive alkali lye is joined in kjeldahl flask, accurately take again a certain amount of cyanoacetic acid product, add rear heating hydrolysis distillation, the ammonia that distills out is absorbed with excessive BAS, use again methyl red-methylenum careuleum mixed indicator, with the accurate volumetric soiutions titration of acidity scale, finally calculate the content of cyanoacetic acid in sample.

The said determination method is based on organic cyanogen and alkali reaction generation ammonia in sample.In order to prevent that ammonia from overflowing in advance, take first to add after alkali the order that adds the cyanoacetic acid product sample.

In said process, for making distillation, in 40min, complete and can obtain accurate result, not causing again simultaneously reagent waste, adopting mass percent concentration is that 6.5% sodium hydroxide solution is hydrolyzed.

Above-mentioned mass percent concentration is that the addition of 6.5% sodium hydroxide solution is 300mL, and according to the specification of cyanoacetic acid product, to make cyano-containing acetic acid in the cyanoacetic acid product sample that correspondence adds be 0.9～1.0g.The concentration of alkali lye and total amount are directly related with cyanogen root total amount in sample.Alkali number used is too small, and the hydrolysis of cyanogen root is incomplete or hydrolysis rate is slow; Too much not only waste reagent, and be unfavorable for the carrying out of reacting balance.

During mensuration, in advance nitrogen ball and condenser pipe are linked together, under the liquid level of the BAS of the other end mouth of pipe insertion 200g/L of condenser pipe, after the cyanoacetic acid product sample adds, connect immediately kjeldahl flask and nitrogen ball, then add thermal distillation.

In above-mentioned still-process, adopt first slowly heating, the elution speed of controlling ammonia is 2～3mL/min, more than after 10 minutes, again elution speed being brought up to 5mL/min.The speed that its distillation incipient stage ammonia produces, in 10 minutes, most ammonia is distilled out of, and this speed is controlled and has been guaranteed that the ammonia that steams can be absorbed fully by boric acid.

More detailed says, the assay method of a kind of cyanoacetic acid product content disclosed by the invention, is characterized in that, it specifically carries out according to following steps:

in advance nitrogen ball and condenser pipe are linked together, under the liquid level of the BAS of the other end mouth of pipe insertion 200g/L of condenser pipe, getting afterwards the 300mL mass percent concentration and be 6.5% sodium hydroxide solution adds in the kjeldahl flask of 500mL, add beaded glass number, accurately add again cyanoacetic acid product sample 1～3g, and according to its specification, make cyano-containing acetic acid 0.9～1.0g in the cyanoacetic acid product sample that adds, claim accurate to 0.0002g, after connecting kjeldahl flask and nitrogen ball, kjeldahl flask is heated, originally slowly heating, the elution speed of controlling ammonia is 2～3mL/min, more than after 10 minutes, again elution speed being brought up to 5mL/min, during to distillate 200mL, the condensation mouth of pipe is shifted out to the BAS liquid level, with the litmus red test paper check condensation mouth of pipe, have or not ammonia to emit, while without ammonia, emitting, stopped heating, otherwise till continuing to be distilled to again and detecting when without ammonia, emitting, afterwards the condensation mouth of pipe is shifted out to the BAS liquid level, with steam flush condenser pipe inwall after 1 minute, water rinses condensation mouth of pipe outer wall, in the BAS that has absorbed ammonia, add methyl red-2 of methylenum careuleum mixed indicators, with

when for the sulfuric acid standard titration solution of 0.5mol/L, being titrated to green and becoming lavender, record the consumption of sulfuric acid standard titration solution, finally according to following formula, calculate the content results of cyanoacetic acid in sample:

${\mathrm{NCCH}}_2\mathrm{COOH}(\%)=\frac{c_{\frac{1}{2}{H}_2{\mathrm{SO}}_4}V\×85.06/1000}{m}\×100$

In formula:

For the actual concentrations of sulfuric acid standard titration solution, unit is mole every liter (mol/L);

V is the consumption of sulfuric acid standard titration solution, and unit is milliliter (mL);

85.06 be the molal weight of cyanoacetic acid, unit is every mole of gram (g/mol);

M is the accurate numerical value of sample mass, and unit is gram (g).

The present invention has following beneficial effect:

The invention discloses a kind of short-cut method of cyanoacetic acid assay, it adopts under alkali condition, make the cyano group in the cyanoacetic acid sample be subjected to pyrohydrolysis to generate ammonia, in the kjeldahl determination device, react and distill, the ammonia that steams absorbs with BAS, take methyl red-methylenum careuleum as indicator, the ammonia that steams with the accurate solution titration of acidity scale, thus calculate cyanoacetic acid content.The relative standard deviation RSD=0.04% of its sample determination result (n=6), recovery of standard addition 98.63%; Basically identical with content and its result of HPLC method mensuration comparison that this method is measured.In addition, the method is easy and simple to handle, favorable reproducibility, result precision is high, precision is good, and do not need with valuable instrument, analysis cost is low, is applicable to the cyanoacetic acid product content and measures, and also is suitable for other and under alkali condition, is subjected to the heat energy complete hydrolysis to produce the assay of organic cyanides of ammonia.

Embodiment

Below by embodiment, the present invention is specifically described; but following examples are only for being further detailed the present invention; can not be interpreted as the restriction to its protection domain, the person skilled in the art in this field can make some nonessential improvement and adjustment to the present invention according to foregoing.

Embodiment 1

a kind of assay method of cyanoacetic acid product content, it specifically carries out according to following steps: in advance nitrogen ball and condenser pipe are linked together, under the liquid level of the BAS of the other end mouth of pipe insertion 200g/L of condenser pipe, getting afterwards the 300mL mass percent concentration and be 6.5% sodium hydroxide solution adds in the kjeldahl flask of 500mL, add 10 of beaded glasses, accurately adding specification is 95% cyanoacetic acid product sample 1.0056g again, connect kjeldahl flask and nitrogen ball, with the adjustable electric furnace of 1500W, kjeldahl flask is heated, originally slowly heating, the elution speed of control ammonia is 2～3mL/min approximately, more than after 10 minutes, again elution speed being brought up to 5mL/min, during to the about 200mL of distillate, the condensation mouth of pipe is shifted out to the BAS liquid level, with the litmus red test paper check condensation mouth of pipe, there is ammonia to emit, continue distillation extremely detected while without ammonia, emitting in 5 minutes again, stopped heating, afterwards the condensation mouth of pipe is shifted out to the BAS liquid level, with steam flush condenser pipe inwall after 1 minute, water rinses condensation mouth of pipe outer wall, in the BAS that has absorbed ammonia, add methyl red-2 of methylenum careuleum mixed indicators, with

when for the sulfuric acid standard titration solution of 0.5mol/L, being titrated to green and becoming lavender, the consumption that consumes the sulfuric acid standard titration solution is 22.44mL, finally according to the content results of cyanoacetic acid in following formula counting yield sample:

${\mathrm{NCCH}}_2\mathrm{COOH}(\%)=\frac{c_{\frac{1}{2}{H}_2{\mathrm{SO}}_4}V\×85.06/1000}{m}\×100$

$=\frac{0.5012\×22.44\×85.06}{1000\×1.0056}\×100$

$=95.13$

In formula:

For the actual concentrations of sulfuric acid standard titration solution, unit is mole every liter (mol/L);

V is the consumption of sulfuric acid standard titration solution, and unit is milliliter (mL);

85.06 be the molal weight of cyanoacetic acid, unit is every mole of gram (g/mol);

M is the accurate numerical value of sample mass, and unit is gram (g).

Embodiment 2

A kind of assay method of cyanoacetic acid product content, it specifically carries out according to the operation steps described in embodiment 1, its product specification is 30%, the quality of taking is 2.9935g (fluid sample), sulfuric acid standard titration solution concentration is 0.5012mol/L, consumed 21.06mL, the mass percent concentration that result calculates cyanoacetic acid in this product is 29.99%.

Embodiment 3

A kind of assay method of cyanoacetic acid product content, it specifically carries out according to the operation steps described in embodiment 1, its product quality is 1.5516g (fluid sample), sulfuric acid standard titration solution concentration is 0.5012mol/L, consumed 22.50mL, the mass percent concentration that result calculates cyanoacetic acid in this product is 61.82%.

Embodiment 4 (reappearance experiment)

A kind of assay method of cyanoacetic acid product content, it is the same cyanoacetic acid product that adopts in embodiment 1, accurately take respectively six parts, and according to the operation steps described in embodiment 1, the content of cyanoacetic acid in product sample is divided and carries out respectively measurement and calculation six times, and its concrete data that record see the following form 1:

Table 1

Conclusion: in this example, by to same product replication six times, record the average content 95.19% of cyanoacetic acid, RSD=0.04%, this assay method reappearance as a result are very good.

Embodiment 5 (recovery testu)

A kind of assay method of cyanoacetic acid product content, it is totally 6 parts of cyanoacetic acid product samples that adopt the known quality percent concentration that accurately takes different size, be placed in respectively the kjeldahl flask of 6 500mL, adding respectively more high-purity cyanoacetic acid reagent of known quality percent concentration 98.0% is standard items, according to the operation steps described in embodiment 1, measure, calculate respectively its recovery, its concrete experimental data sees the following form 2:

Table 2

Visible: this method is measured the content of cyanoacetic acid in product, and the recovery is between 97.88～99.19%, and average recovery rate is 98.63%, and its recovery is high.

In addition, mass percent concentration is denoted as >=98.0% cyanoacetic acid high purity reagent adopts the described step of embodiment 1 to detect, and result shows that the quality percentage composition of its cyanoacetic acid is 98.08%.

By experiment numbers proportion by subtraction in above-mentioned table 2, be the mass percent concentration data that 1,3 and 5 product detects gained, with the result that adopts high-performance liquid chromatographies to measure these three kinds of products, compare, result obtains following table 3:

Table 3

More visible by this method measurement result and high effective liquid chromatography for measuring result: the relative deviation of the result of the mass percent concentration of the products of different specifications that two kinds of methods detect respectively is below 0.3%, illustrate that both results are basically identical, also show that this method accuracy is high.

Embodiment 6

A kind of assay method of cyanoacetic acid product content, it is that the employing specification is that 98.0% high-purity cyanoacetic acid product reagent is detected object, and add the sodium hydroxide solution 300mL of seven different mass percent concentrations described in following table, according to the operation steps described in embodiment 1, content to cyanoacetic acid in product carries out respectively measurement and calculation, to investigate the concentration of required sodium hydroxide solution, its concrete data that record see the following form 4:

Table 4

Experiment shows: the sample of cyano-containing acetic acid 1g, the sodium hydroxide solution total amount is 300mL in flask, when the mass percent concentration of sodium hydroxide solution is not less than 6%, can in 40min, distill complete, average distillation rate 5mL/min, and result is accurate.Therefore no matter this assay method requires solid sample or fluid sample, when the amount of sample was equivalent to cyanoacetic acid 0.9～1.0g, the mass percent concentration of determining sodium hydroxide solution was 6.5%, can guarantee like this in 40min, to be hydrolyzed and to distill complete, and result is accurate, saves again reagent.

Claims (7)

1. the assay method of a cyanoacetic acid product content, it is characterized in that, it is for mass percent concentration, to be at least 30% cyanoacetic acid product, the mensuration of carrying out according to following steps: first excessive alkali lye is joined in kjeldahl flask, accurately take again a certain amount of cyanoacetic acid product, add rear heating hydrolysis distillation, the ammonia that distills out is absorbed with excessive BAS, use again methyl red-methylenum careuleum mixed indicator, with the accurate volumetric soiutions titration of acidity scale, finally calculate the content of cyanoacetic acid in sample.

2. the assay method of cyanoacetic acid product content according to claim 1 is characterized in that: it is 6.5% sodium hydroxide solution that described alkali lye adopts mass percent concentration.

3. the assay method of cyanoacetic acid product content according to claim 2, it is characterized in that: described mass percent concentration is that the addition of 6.5% sodium hydroxide solution is 300mL, and according to the specification of cyanoacetic acid product, to make the cyanoacetic acid product sample cyano-containing acetic acid that correspondence adds be 0.9～1.0g.

4. the assay method of according to claim 1-3 arbitrary described cyanoacetic acid product contents, it is characterized in that: while measuring, in advance nitrogen ball and condenser pipe are linked together, under the liquid level of the BAS of the other end mouth of pipe insertion 200g/L of condenser pipe, after the cyanoacetic acid product adds, connect immediately kjeldahl flask and nitrogen ball, then add thermal distillation.

5. the assay method of according to claim 1-3 arbitrary described cyanoacetic acid product contents, it is characterized in that: in described still-process, adopt first slowly heating, the elution speed of controlling ammonia is 2～3mL/min, more than after 10 minutes, again elution speed being brought up to 5mL/min.

6. the assay method of cyanoacetic acid product content according to claim 4 is characterized in that: in described still-process, adopt first slowly heating, the elution speed of controlling ammonia is 2～3mL/min, more than after 10 minutes, again elution speed being brought up to 5mL/min.

7. the assay method of cyanoacetic acid product content according to claim 1, is characterized in that, it specifically carries out according to following steps:

in advance nitrogen ball and condenser pipe are linked together, under the liquid level of the BAS of the other end mouth of pipe insertion 200g/L of condenser pipe, getting afterwards the 300mL mass percent concentration and be 6.5% sodium hydroxide solution adds in the kjeldahl flask of 500mL, add beaded glass number, accurately add again cyanoacetic acid product sample 1～3g, and according to its specification, make cyano-containing acetic acid 0.9～1.0g in the sample that adds, claim accurate to 0.0002g, after connecting kjeldahl flask and nitrogen ball, kjeldahl flask is heated, originally slowly heating, the elution speed of controlling ammonia is 2～3mL/min, more than after 10 minutes, again elution speed being brought up to 5mL/min, to distillate at least during 200mL, the condensation mouth of pipe is shifted out to the BAS liquid level, with the litmus red test paper check condensation mouth of pipe, have or not ammonia to emit, while without ammonia, emitting, stopped heating, otherwise till continuing to be distilled to again and detecting when without ammonia, emitting, afterwards the condensation mouth of pipe is shifted out to the BAS liquid level, with steam flush condenser pipe inwall after 1 minute, water rinses condensation mouth of pipe outer wall, in the BAS that has absorbed ammonia, add methyl red-2 of methylenum careuleum mixed indicators, with

when for the sulfuric acid standard titration solution of 0.5mol/L, being titrated to green and becoming lavender, record the consumption of sulfuric acid standard titration solution, finally according to following formula, calculate the content results of cyanoacetic acid in sample:

${\mathrm{NCCH}}_2\mathrm{COOH}(\%)=\frac{c_{\frac{1}{2}{H}_2{\mathrm{SO}}_4}V\×85.06/1000}{m}\×100$

In formula:

For the actual concentrations of sulfuric acid standard titration solution, unit is mole every liter (mol/L);

V is the consumption of sulfuric acid standard titration solution, and unit is milliliter (mL);

85.06 be the molal weight of cyanoacetic acid, unit is every mole of gram (g/mol);

M is the accurate numerical value of sample mass, and unit is gram (g).