CN105954462B - Solid moisture standards material and preparation method thereof - Google Patents
Solid moisture standards material and preparation method thereof Download PDFInfo
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- CN105954462B CN105954462B CN201610296929.2A CN201610296929A CN105954462B CN 105954462 B CN105954462 B CN 105954462B CN 201610296929 A CN201610296929 A CN 201610296929A CN 105954462 B CN105954462 B CN 105954462B
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N31/00—Investigating or analysing non-biological materials by the use of the chemical methods specified in the subgroup; Apparatus specially adapted for such methods
- G01N31/16—Investigating or analysing non-biological materials by the use of the chemical methods specified in the subgroup; Apparatus specially adapted for such methods using titration
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N1/00—Sampling; Preparing specimens for investigation
- G01N1/28—Preparing specimens for investigation including physical details of (bio-)chemical methods covered elsewhere, e.g. G01N33/50, C12Q
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N1/00—Sampling; Preparing specimens for investigation
- G01N1/28—Preparing specimens for investigation including physical details of (bio-)chemical methods covered elsewhere, e.g. G01N33/50, C12Q
- G01N2001/2893—Preparing calibration standards
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Abstract
A kind of solid moisture standards material and preparation method thereof, including step：(1) preparation of solid moisture standards material candidate；(2) standard substance candidate uniformity testing；(3) standard substance candidate stability test；(4) definite value of standard substance；(5) uncertainty evaluation.Compared with prior art, moisture standards material of the present invention can regulate and control the moisture of standard substance by adjusting the mass ratio of the P-methoxybenzoic acid of low moisture content and two hydration sodium tartrates of high moisture content, moisture can arbitrarily regulate and control in the range of (0.1%~5%), have flexibility.Described solid moisture standards material has good uniformity and stability.Described standard substance both can be used for the calibration of karl Fischer titration, can be used for the checking of karl Fischer moisture measuring method.
Description
Technical field
The present invention relates to a kind of solid moisture standards material and preparation method thereof, is that a kind of moisture is adjustable, uniform
Solid moisture standards material.
Background technology
Karl Fischer titration is used for the moisture for measuring solid and fluid sample, is the specificity method of moisture measurement,
It is widely used in the water content detection of food, medicine and petrochemicals.Karl Fischer titration includes karl Fischer coulomb
Method and karl Fischer volumetric method.Either coulometry or volumetric method, it is required for the standard substance of known moisture levels to calibrate.
Although coulometry can directly calculate sample moisture according to electrolysis electricity, because electrolytic efficiency and karl Fischer are anti-
Systematic error caused by the side reaction answered, the true moisture of moisture and sample directly calculated have certain deviation, it is necessary to use moisture mark
The relative error of indication and correction factor of quasi- substance-measuring method, to be modified to unknown sample moisture measurement result.Card
Er Feixiu volumetric methods calculate sample moisture according to the titration volumes of titrant, and the titer of titrant needs to use known water
Divide the standard substance calibration of content.Moisture standards material is additionally operable to card in addition to the calibration for karl Fischer titration
The checking of Er Feixiu titrations.Particularly when sample moisture is low, when measurement result repeatability and poor accuracy, it is necessary to
The standard substance of known moisture levels, measurement of comparison value and standard substance asserting value are measured, calculates the error of indication, verification method is
It is no accurate.
Moisture standards material can be divided into two classes, liquid moisture standards material and solid moisture standards material by matrix difference.
The matrix of liquid moisture standards material is the mixed solution of organic solvent and water, and moisture is in (0.01%~4.76%) model
Enclose.Solid moisture standards material is generally using the pure compound containing the crystallization water as matrix, such as two hydration sodium tartrates, a hydration lemon
Lemon acid potassium and a Lactose hydrate, its moisture are respectively 15.66%, 5.55% and 5.05%.Pure compound containing the crystallization water
Uniform moisture, value are stable.But the compound containing the crystallization water, its moisture are typically larger than 5%.Detection field is badly in need of low at present
The solid moisture standards material of moisture (0.1%~5%), calibration and measurement side for karl Fischer moisture titration
The checking of method.
The content of the invention
Moisture standards material relatively low and uniform it is an object of the invention to provide a kind of moisture, stable and its system
Preparation Method.
To reach the purpose of foregoing invention, the technical solution adopted by the present invention is：A kind of solid moisture standards material and its
Preparation method, it is characterised in that comprise the following steps：
(1) preparation of solid moisture standards material candidate：Using P-methoxybenzoic acid and two hydration sodium tartrates as original
Material prepares the candidate sample of multiple solid moisture standards materials；
(2) standard substance candidate uniformity testing：If the uniform sexual satisfaction requirement of standard substance candidate, is carried out down
The stability test of one step；If standard substance candidate uniformity is unsatisfactory for requiring, candidate sample is further mixed,
Distribution, uniformity testing, until the requirement of uniform sexual satisfaction；
(3) standard substance candidate stability test：If the stable sexual satisfaction requirement of moisture, is carried out in next step
Standard substance definite value；If the stability of moisture is unsatisfactory for requiring, whole candidate samples are poured out, mixed again
Afterwards, Packaging Bottle is changed, is redistributed, adjustment candidate preserves damp condition, according to above-mentioned steps, carries out stability inspection again
Test, until stablizing sexual satisfaction requirement；
(4) definite value of standard substance：Two groups of samples are randomly selected in above-mentioned standard material candidate, use karr respectively
Take not coulomb moisture titration and karl Fischer capacity moisture titration measures the moisture of two groups of samples, with card taking that
Take the not moisture result of coulometry and the average value of karl Fischer volumetric method result as moisture standards material；
(5) uncertainty evaluation：Evaluate the moisture and uncertainty for the moisture standards material that place is prepared.
The specific method of the preparation of described step (1) solid moisture standards material candidate comprises the following steps：
1. raw material P-methoxybenzoic acid is put into three-dimensional motion mixer, taken out after mixing；Using karl Fischer storehouse
Logical sequence method measures the moisture of P-methoxybenzoic acid；Using the moisture of the hydration sodium tartrate of Karl Fischer coulometric determination measurement two
Content；
2. taking about 2kg P-methoxybenzoic acid, two hydration sodium tartrates of certain mass are added, for preparing solid water
Divide standard substance；The addition quality of two hydration sodium tartrates calculates according to equation below：
In above formula：
m2--- the quality of two hydration sodium tartrates；
m1--- the quality of P-methoxybenzoic acid；
X --- the target moisture content of solid moisture standards material；
x1--- the moisture of P-methoxybenzoic acid；
x2--- the moisture of two hydration sodium tartrates；
3. above-mentioned P-methoxybenzoic acid and two are hydrated to the mixture of sodium tartrates, after being mixed with three-dimensional motion mixer
Take out, be assigned in 300-500 tool lid Brown Glass Brown glass bottles and jars only, every bottle of sample quality 4-6g, as solid moisture standards material
Candidate sample.
The specific method of described step (2) standard substance candidate uniformity testing：
10-20 bottles are randomly selected from the candidate of above-mentioned solid moisture standards material, are surveyed with Karl Fischer coulometric determination
Its moisture is measured, every bottle at least measures 2 times, according to ISO directive/guides 35《The general statistical principle of standard substance --- identification》Meter
Statistic F is calculated, if F values are not more than prescribed limits, the uniform sexual satisfaction requirement of description standard material candidate, can be carried out next
Walk stability test；If F values are more than prescribed limits, description standard material candidate uniformity is unsatisfactory for requiring, by whole times
Select thing sample to pour out, mixed again with three-dimensional motion mixer, distributed, uniformity testing, until the requirement of uniform sexual satisfaction.
The specific method of described step (3) standard substance candidate stability test comprises the following steps：
1. randomly selecting more bottles from above-mentioned standard material candidate sample, its water is measured with Karl Fischer coulometric determination
Point, every bottle at least measures 2 times, records moisture average value；
2. after at one section, its moisture is measured with Karl Fischer coulometric determination again, records the moisture repeatedly measured
Average value；
3. according to ISO directive/guides 35《The general statistical principle of standard substance --- identification》Moisture measurement result is counted, if
The directive/guide requirement of the stable sexual satisfaction of moisture, can carry out described step (4) standard substance definite value；If moisture
Stability be unsatisfactory for the directive/guide requirement, then whole candidate samples are poured out, again mix after, change Packaging Bottle, divide again
Match somebody with somebody, adjustment candidate preserves damp condition, and stability test is carried out again according to above-mentioned steps, is led until stablizing sexual satisfaction ISO
Then 35 requirement.
The specific method of described step (5) uncertainty evaluation is：According to ISO directive/guides 35《Standard substance --- assert
General statistical principle》The not true of the moisture measurement result of Karl Fischer coulometric determination and karl Fischer volumetric method is evaluated respectively
Fixed degree, and the uncertainty that the uncertainty of Certified Reference Material Homogeneity introducing and stability introduce, and the side synthesized with variance
Method obtains the combined standard uncertainty of moisture standards material；The moisture of the final moisture standards material for drawing preparation and its
Uncertainty.
The uncertainty of described Karl Fischer coulometric determination measurement result by A classes uncertainty and B classes uncertainty by
Formula is 2-in-1 into obtaining；A class relative uncertainty degrees (u1,r,A) it is equal to the relative standard deviation of measurement result；B class relative uncertainty degrees
(u1,r,B) come from the quality of sample, Faradaic current and time, the system deviation of measurement result；
The uncertainty of described karl Fischer volumetric method measurement result by A classes uncertainty and B classes uncertainty by
The synthesis of formula 3 obtains；A class relative uncertainty degrees (u2,r,A) it is equal to the relative standard deviation of measurement result；B class relative uncertainty degrees
(u2,r,B) come from the quality of sample, the volume of titrant and the moisture of moisture standards material etc.；
The relative standard uncertainty of the moisture of moisture standards material is calculated according to formula 4, wherein, ur,HIt is standard
The relative uncertainty degree that material uniformity introduces, ur,stabIt is the relative uncertainty degree that standard substance stability introduces.According to formula
5 calculate the relative expanded uncertainty (spreading factor k=2) of the moisture of moisture standards material；
Ur=kur,c (5)
Method with karl Fischer coulomb moisture titration measurement moisture is according to karl Fischer principle, that is, is existed
In anhydrous solvent, iodine, sulfur dioxide and water according to material amount ratio 1:1:1 reaction；Reactant iodine molecule is obtained by anode electrolysis
Arrive；According to Faraday's law, by the amount of the material of electrolysis electricity calculating iodine, so as to calculate moisture in unknown sample；
When measuring P-methoxybenzoic acid, sample size 0.3g；During the hydration sodium tartrate of measurement two, sample size 20mg；Electrode used therein
For without septum electrode, electrolyte is the Hydranal Coulomat AG type anolytes of Sigma companies.
Method with karl Fischer capacity moisture titration measurement moisture is according to karl Fischer principle, without water-soluble
In agent, iodine, sulfur dioxide and water according to material amount ratio 1:1:1 reaction；Contain iodine in titrant；Contain two in titration solvent
Sulfur oxide；The titer of titrant is determined using the standard substance of known moisture levels, i.e. the titration solvent of unit volume is disappeared
The quality of the water of consumption, unit mg/mL.
Compared with the existing pure material containing the crystallization water is the solid moisture standards material of matrix, moisture mark of the present invention
Quasi- material can be hydrated the matter of sodium tartrates by adjusting the P-methoxybenzoic acid of low moisture content and the two of high moisture content
The moisture than regulating and controlling standard substance is measured, moisture can arbitrarily regulate and control in the range of (0.1%~5%), have flexibility.Institute
The solid moisture standards material stated has good uniformity and stability.Described standard substance both can be used for karr expense
The not calibration of titration, it can be used for the checking of karl Fischer moisture measuring method.
Embodiment
A kind of solid moisture standards material of the present invention and preparation method thereof, comprises the following steps：
1. raw material P-methoxybenzoic acid is put into three-dimensional motion mixer, taken out after mixing 10min.Taken using karr
The not moisture of coulometry measurement P-methoxybenzoic acid.Using the hydration sodium tartrate of Karl Fischer coulometric determination measurement two
Moisture.
2. taking about 2kg P-methoxybenzoic acid, two hydration sodium tartrates of certain mass are added, for preparing solid water
Divide standard substance.The addition quality of two hydration sodium tartrates calculates according to equation below.
In above formula：
m2--- the quality of two hydration sodium tartrates；
m1--- the quality of P-methoxybenzoic acid；
X --- the target moisture content of solid moisture standards material；
x1--- the moisture of P-methoxybenzoic acid；
x2--- the moisture of two hydration sodium tartrates.
3. by above-mentioned P-methoxybenzoic acid and the mixture of two hydration sodium tartrates, mixed with three-dimensional motion mixer
Taken out after 30min, be assigned in 400 tool lid Brown Glass Brown glass bottles and jars onlys (every bottle of sample quality about 5g) and be used as solid moisture standards material
Candidate.
4. standard substance candidate uniformity testing：15 are randomly selected from the candidate of above-mentioned solid moisture standards material
Bottle, its moisture is measured with Karl Fischer coulometric determination, every bottle measures 2 times, according to ISO directive/guides 35《Standard substance --- recognize
Fixed general statistical principle》Counting statistics amount F, if F values are not more than prescribed limits, description standard material candidate uniformity expires
Foot requires, can carry out next step stability test；If F values are more than prescribed limits, description standard material candidate uniformity
It is unsatisfactory for requiring, all 400 bottles of candidates is poured out, mixed again with three-dimensional motion mixer, are distributed, uniformity testing, directly
To the requirement of uniform sexual satisfaction.
5. standard substance candidate stability test：3 bottles are randomly selected from above-mentioned standard material candidate, uses karr
Expense stops coulometry and measures its moisture, and every bottle measures 2 times, records moisture average value；1 month, 2 months, 3 months, 6 months and 12
After month, its moisture is measured with Karl Fischer coulometric determination again, records moisture average value.According to ISO directive/guides 35《Reference material
The general statistical principle of matter --- identification》Moisture measurement result is counted, if the directive/guide requirement of the stable sexual satisfaction of moisture,
Next step standard substance definite value can be carried out；, will all 400 bottles if the stability of moisture is unsatisfactory for the directive/guide requirement
Candidate is poured out, and after mixing again, is changed Packaging Bottle, is redistributed.Adjust candidate and preserve damp condition, according to above-mentioned step
Suddenly, stability test is carried out again, until stablizing the requirement of sexual satisfaction ISO directive/guides 35.
6. the definite value of standard substance：In in above-mentioned 400 standard substance candidates, 15 bottles are randomly selected, uses karr
Expense stops coulomb moisture titration and measures its moisture, and every bottle is surveyed 2 times.In addition, randomly selecting 10 bottles again, held with karl Fischer
Amount moisture titration measures its moisture, and every bottle is surveyed 1 time.Coulometry and the average value of volumetric method result are taken as moisture standards
The moisture result of material.
7. uncertainty evaluation：According to ISO directive/guides 35《The general statistical principle of standard substance --- identification》Evaluate respectively
The uncertainty of the moisture measurement result of coulometry and volumetric method, and the uncertainty and stably that Certified Reference Material Homogeneity introduces
Property introduce uncertainty, and with variance synthesize method obtain the combined standard uncertainty of moisture standards material.Finally, give
Go out the moisture and its uncertainty of the moisture standards material of preparation.
The step 1. in P-methoxybenzoic acid, analysis it is pure, No. CAS is：100-09-4.
The step 1. in two hydration sodium tartrates, analysis it is pure, No. CAS is：6106-24-7.
The step 1. in three-dimensional motion mixer, staving has multi-direction motion, mixing various materials
During, flowing and diffusion are accelerated, while avoid the machine of generally mixing with because of material density caused by centrifugal action
Segregation and accumulation phenomenon, mix no dead angle, can effectively ensure the uniformity of mixed material.
The step 1. in Karl Fischer coulometric determination, according to karl Fischer principle, i.e., in anhydrous solvent, iodine,
Sulfur dioxide and water according to material amount ratio 1:1:1 reaction；Reactant iodine molecule is obtained by anode electrolysis.Determined according to faraday
Rule, the amount of the material of iodine is calculated by electrolysis electricity, so as to calculate moisture in unknown sample.Measurement is to methoxybenzene first
When sour, sample size 0.3g；During the hydration sodium tartrate of measurement two, sample size 20mg.Electrode used therein is without septum electrode, electrolysis
Liquid is the Hydranal Coulomat AG type anolytes of Sigma companies.
The step 6. in karl Fischer volumetric method, according to karl Fischer principle, i.e., in anhydrous solvent, iodine,
Sulfur dioxide and water according to material amount ratio 1:1:1 reaction；Contain iodine in titrant；Contain sulfur dioxide in titration solvent.
Determine the titer of titrant using the standard substance of known moisture levels, i.e. the water that the titration solvent of unit volume is consumed
Quality, unit mg/mL.
The step 7. in, the uncertainty of coulometry measurement result is obtained by A classes uncertainty and B class uncertainty combinations
To (formula 2).A class relative uncertainty degrees (u1,r,A) it is equal to the relative standard deviation of measurement result；B class relative uncertainty degrees
(u1,r,B) come from the quality of sample, Faradaic current and time, the system deviation of measurement result etc..Volumetric method measurement result is not
Degree of certainty is obtained (formula 3) by A classes uncertainty and B class uncertainty combinations.A class relative uncertainty degrees (u2,r,A) it is equal to measurement
As a result relative standard deviation；B class relative uncertainty degrees (u2,r,B) come from the quality of sample, the volume and moisture mark of titrant
Moisture of quasi- material etc..The relative standard uncertainty of the moisture of moisture standards material is calculated according to formula 4.Its
In, ur,HBe Certified Reference Material Homogeneity introduce relative uncertainty degree, ur,stabIt is the relatively not true of standard substance stability introducing
Fixed degree.The relative expanded uncertainty (spreading factor k=2) of the moisture of moisture standards material is calculated according to formula 5.
Ur=kur,c (5)
Here is two specific embodiments of the present invention.
1st, embodiment 1：Prepare the solid moisture standards material that moisture is 1%.
According to the step 1. and 2., 2.050kg P-methoxybenzoic acid is mixed with three-dimensional motion mixer.With card
Er Feixiu coulometries measure the moisture of P-methoxybenzoic acid.The average value of measurement result is 0.014%.Use karl Fischer
The moisture of the hydration sodium tartrate of coulometry measurement two, measurement result average value is 15.66%.Being calculated according to formula (1) to add
Two hydration sodium tartrates quality should be 137.9g.Therefore, the water of 137.9g bis- is added into 2.050kg P-methoxybenzoic acid
Close sodium tartrate.After 3. mixture is mixed with three-dimensional motion mixer according to the step, 400 brown tool lid glass are assigned to
In glass bottle, every bottle of about 5g containing mixture.
15 bottles are 4. randomly selected according to the step, its moisture is measured with Karl Fischer coulometric determination, sampling amount 0.3g,
Every bottle measures 2 times.It is 2.26 to count value F, less than critical value F0.05 (14,15)(F0.05 (14,15)=2.42) standard substance, is shown
It is uniform.3 bottles are 5. randomly selected according to the step, its moisture is measured with Karl Fischer coulometric determination, sampling amount 0.3g,
Every bottle measures 2 times.Statistical result shows that standard substance is stable.
15 bottles are 6. randomly selected according to the step, its moisture is measured with Karl Fischer coulometric determination, sampling amount 0.3g,
Every bottle measures 2 times.The average value of moisture measurement result is 0.986%, standard deviation 0.007%, and relative standard deviation is
0.68%.10 bottles are 6. randomly selected according to the step, its moisture is measured with karl Fischer volumetric method, sampling amount 0.3g,
Every bottle measures 1 time.The average value of moisture measurement result is 0.992%, standard deviation 0.005%, and relative standard deviation is
0.50%.Take the moisture asserting value of coulometry and the average value of volumetric method (0.999%) for solid moisture standards material.
The uncertainty of solid moisture standards material is 7. evaluated according to the step.
Ur=kur,c=2 × 0.99%=1.98% ≈ 2.0%
U=0.999% × 2.0%=0.020% (k=2)
The A class relative uncertainty degrees (u of coulometry1,r,A) it is 0.68%, B class relative uncertainty degrees (u1,r,B) it is 0.18%,
Synthetic standards relative uncertainty degree (u1,c) it is 0.70%.The A class relative uncertainty degrees (u of volumetric method2,r,A) it is 0.50%, B class phases
To uncertainty (u2,r,B) it is 0.18%, synthetic standards relative uncertainty degree (u2,c) it is 0.53%.Between moisture standards material bottle
Relative uncertainty degree (the u that even property introducesr,H) it is 0.42%, the relative uncertainty degree that moisture standards material stability introduces
(ur,stab) it is 0.19%.Therefore, the standard relative uncertainty degree (u of the moisture of moisture standards materialr,c) it is 0.99%, expand
Open up relative uncertainty degree (Ur) it is that 2.0% (k=2) expanded uncertainty (U) is 0.020% (k=2).
Finally, the solid moisture standards substance moisture content content of preparation is 0.999%, expanded uncertainty 0.02%.
2nd, embodiment 2：Prepare the solid moisture standards material that moisture is 0.1%.
According to the step 1. and 2., 2.001kg P-methoxybenzoic acid is mixed with three-dimensional motion mixer.With card
Er Feixiu coulometries measure the moisture of P-methoxybenzoic acid.The average value of measurement result is 0.014%.Use karl Fischer
The moisture of the hydration sodium tartrate of coulometry measurement two, measurement result average value is 15.66%.Being calculated according to formula (1) to add
Two hydration sodium tartrates quality should be 11.06g.Therefore, the water of 11.06g bis- is added into 2.001kg P-methoxybenzoic acid
Close sodium tartrate.After 3. mixture is mixed with three-dimensional motion mixer according to the step, 400 brown tool lid glass are assigned to
In glass bottle, every bottle of about 5g containing mixture.
15 bottles are 4. randomly selected according to the step, its moisture is measured with Karl Fischer coulometric determination, sampling amount 0.3g,
Every bottle measures 2 times.It is 0.95 to count value F, less than critical value F0.05 (14,15)(F0.05 (14,15)=2.42) standard substance, is shown
It is uniform.3 bottles are 5. randomly selected according to the step, its moisture is measured with Karl Fischer coulometric determination, sampling amount 0.3g,
Every bottle measures 2 times.Statistical result shows that standard substance is stable.
15 bottles are 6. randomly selected according to the step, its moisture is measured with Karl Fischer coulometric determination, sampling amount 0.3g,
Every bottle measures 2 times.The average value of moisture measurement result is 0.0877%, standard deviation 0.0013%, and relative standard deviation is
1.46%.10 bottles are 6. randomly selected according to the step, its moisture is measured with karl Fischer volumetric method, sampling amount 0.3g,
Every bottle measures 1 time.The average value of moisture measurement result is 0.0870%, standard deviation 0.0011%, and relative standard deviation is
1.26%.Take the moisture asserting value of coulometry and the average value of volumetric method (0.0874%) for solid moisture standards material.
The uncertainty of solid moisture standards material is 7. evaluated according to the step.
Ur=kur,c=2 × 2.15%=4.3%
U=0.0874% × 4.3%=0.0038% (k=2)
The A class relative uncertainty degrees (u of coulometry1,r,A) it is 1.46%, B class relative uncertainty degrees (u1,r,B) it is 0.18%,
Synthetic standards relative uncertainty degree (u1,c) it is 1.47%.The A class relative uncertainty degrees (u of volumetric method2,r,A) it is 1.26%, B class phases
To uncertainty (u2,r,B) it is 0.18%, synthetic standards relative uncertainty degree (u2,c) it is 1.27%.Between moisture standards material bottle
Relative uncertainty degree (the u that even property introducesr,H) it is 0.77%, the relative uncertainty degree that moisture standards material stability introduces
(ur,stab) it is 0.49%.Therefore, the standard relative uncertainty degree (u of the moisture of moisture standards materialr,c) it is 2.15%, expand
Open up relative uncertainty degree (Ur) it is that 4.3% (k=2) expanded uncertainty (U) is 0.0038% (k=2).
Finally, the solid moisture standards substance moisture content content of preparation is 0.0874%, expanded uncertainty 0.0038%.
Claims (4)
1. a kind of preparation method of solid moisture standards material, it is characterised in that comprise the following steps：
(1) preparation of solid moisture standards material candidate：Using P-methoxybenzoic acid and two hydration sodium tartrates as raw material system
It is standby go out multiple solid moisture standards materials candidate sample；
(2) standard substance candidate uniformity testing：If the uniform sexual satisfaction requirement of standard substance candidate, is carried out in next step
Stability test；If standard substance candidate uniformity is unsatisfactory for requiring, candidate sample is further mixed into splitting or integrating
Match somebody with somebody, uniformity testing, until the requirement of uniform sexual satisfaction；
(3) standard substance candidate stability test：If the stable sexual satisfaction requirement of moisture, carries out next step standard
Material definite value；If the stability of moisture is unsatisfactory for requiring, whole candidate samples are poured out, after mixing again, more
Transducer package bottle, is redistributed, and adjustment candidate preserves damp condition, according to above-mentioned steps, carries out stability test again, until
Stable sexual satisfaction requirement；
(4) definite value of standard substance：Two groups of samples are randomly selected in above-mentioned standard material candidate, use karl Fischer respectively
Coulomb moisture titration and karl Fischer capacity moisture titration measure the moisture of two groups of samples, with taking karl Fischer
The moisture result of coulometry and the average value of karl Fischer volumetric method result as moisture standards material；
(5) uncertainty evaluation：Evaluate the moisture and uncertainty for the moisture standards material that place is prepared；
The specific method of the preparation of step (1) solid moisture standards material candidate comprises the following steps：
1. raw material P-methoxybenzoic acid is put into three-dimensional motion mixer, taken out after mixing；Using Karl Fischer coulometric determination
Measure the moisture of P-methoxybenzoic acid；Moisture using the hydration sodium tartrate of Karl Fischer coulometric determination measurement two contains
Amount；
2. taking about 2kg P-methoxybenzoic acid, two hydration sodium tartrates of certain mass are added, for preparing solid water minute mark
Quasi- material；The addition quality of two hydration sodium tartrates calculates according to equation below：
In above formula：
m2--- the quality of two hydration sodium tartrates；
m1--- the quality of P-methoxybenzoic acid；
X --- the target moisture content of solid moisture standards material, %；
x1--- the moisture of P-methoxybenzoic acid, %；
x2--- the moisture of two hydration sodium tartrates；
3. by above-mentioned P-methoxybenzoic acid and the mixture of two hydration sodium tartrates, taken after being mixed with three-dimensional motion mixer
Go out, be assigned in 300-500 tool lid Brown Glass Brown glass bottles and jars only, every bottle of sample quality 4-6g, the time as solid moisture standards material
Select thing sample；
The specific method of step (2) standard substance candidate uniformity testing：
10-20 bottles are randomly selected from the candidate of above-mentioned solid moisture standards material, it is measured with Karl Fischer coulometric determination
Moisture, every bottle at least measures 2 times, according to ISO directive/guides 35《The general statistical principle of standard substance --- identification》Calculate system
F is measured, if F values are not more than prescribed limits, the uniform sexual satisfaction requirement of description standard material candidate, can be carried out steady in next step
Qualitative reaction；If F values are more than prescribed limits, description standard material candidate uniformity is unsatisfactory for requiring, by whole candidates
Sample is poured out, and is mixed again with three-dimensional motion mixer, distribution, uniformity testing, until the requirement of uniform sexual satisfaction；
The specific method of step (3) standard substance candidate stability test comprises the following steps：
1. randomly selecting more bottles from above-mentioned standard material candidate sample, its moisture is measured with Karl Fischer coulometric determination, often
Bottle at least measures 2 times, records moisture average value；
2. after at one section, its moisture is measured with Karl Fischer coulometric determination again, the moisture repeatedly measured is recorded and is averaged
Value；
3. according to ISO directive/guides 35《The general statistical principle of standard substance --- identification》Moisture measurement result is counted, if moisture
The directive/guide requirement of the stable sexual satisfaction of content, then carry out step (4) standard substance definite value；If the stability of moisture is discontented with
Foot directive/guide requirement, then pour out whole candidate samples, after mixing again, changes Packaging Bottle, redistributes, adjusts candidate
Damp condition is preserved, stability test is carried out again according to above-mentioned steps, until stablizing the requirement of sexual satisfaction ISO directive/guides 35；
The specific method of step (5) uncertainty evaluation is：According to ISO directive/guides 35《The general statistical of standard substance --- identification
Principle》The uncertainty of the moisture measurement result of Karl Fischer coulometric determination and karl Fischer volumetric method is evaluated respectively, and
The uncertainty that the uncertainty and stability that Certified Reference Material Homogeneity introduces introduce, and the method synthesized with variance obtains moisture
The combined standard uncertainty of standard substance；The moisture and its uncertainty of the final moisture standards material for drawing preparation.
2. the preparation method of solid moisture standards material according to claim 1, it is characterised in that
The uncertainty of described Karl Fischer coulometric determination measurement result is by A classes uncertainty and B classes uncertainty by formula 2
Synthesis obtains；A class relative uncertainty degrees (u1,r,A) it is equal to the relative standard deviation of measurement result；B class relative uncertainty degrees
(u1,r,B) come from the quality of sample, Faradaic current and time, the system deviation of measurement result；
The uncertainty of described karl Fischer volumetric method measurement result is by A classes uncertainty and B classes uncertainty by formula 3
Synthesis obtains；A class relative uncertainty degrees (u2,r,A) it is equal to the relative standard deviation of measurement result；B class relative uncertainty degrees
(u2,r,B) come from the quality of sample, the volume of titrant and the moisture of moisture standards material etc.；
The relative standard uncertainty of the moisture of moisture standards material is calculated according to formula 4, wherein, ur,HIt is standard substance
The relative uncertainty degree that uniformity introduces, ur,stabIt is the relative uncertainty degree that standard substance stability introduces；Counted according to formula 5
Calculate the relative expanded uncertainty of the moisture of moisture standards material, spreading factor k=2 therein；
Ur=kur,c (5)。
3. the preparation method of solid moisture standards material according to claim 1, it is characterised in that with karl Fischer storehouse
The method of logical sequence moisture titration measurement moisture is according to karl Fischer principle, i.e., in anhydrous solvent, iodine, sulfur dioxide
Amount ratio 1 with water according to material:1:1 reaction；Reactant iodine molecule is obtained by anode electrolysis；According to Faraday's law, pass through
Electrolysis electricity calculates the amount of the material of iodine, so as to calculate moisture in unknown sample；When measuring P-methoxybenzoic acid, enter
Sample amount is 0.3g；During the hydration sodium tartrate of measurement two, sample size 20mg；Electrode used therein is to be without septum electrode, electrolyte
The Hydranal Coulomat AG type anolytes of Sigma companies.
4. the preparation method of solid moisture standards material according to claim 1, it is characterised in that held with karl Fischer
The method for measuring moisture titration measurement moisture is that in anhydrous solvent, iodine, sulfur dioxide and water are pressed according to karl Fischer principle
According to the amount ratio 1 of material:1:1 reaction；Contain iodine in titrant；Contain sulfur dioxide in titration solvent；Contained using known moisture
The titer of the standard substance measure titrant of amount, the i.e. quality for the water that the titration solvent of unit volume is consumed, unit mg/
mL。
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| US7122376B2 (en) * | 2001-11-01 | 2006-10-17 | Facet Analytical Services And Technology, Llc | Calibration standards, methods, and kits for water determination |
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