GB/T 5009.1-2003 General principles for physical and chemical parts of food hygiene inspection methods

This standard specifies the basic principles and requirements for the physical and chemical part of food hygiene inspection methods. This standard applies to the physical and chemical part of food hygiene inspection methods. GB/T 5009.1-2003 General principles for the physical and chemical part of food hygiene inspection methods GB/T5009.1-2003 Standard download decompression password: www.bzxz.net

ICS67.040
National Standard of the People's Republic of China
GB/T5009.1—-2003
Replaces GB/T5009.1—19S6
Methods of food hygienic analysis--Physical and chemical section-General principles2003-08-11 Issued
Ministry of Health of the People's Republic of China
Standardization Administration of China
2004-01-01 Implementation
GB/T5009.1—2003
This standard replaces GB/T5009.1-1996 "General principles for physical and chemical parts of food hygiene inspection methods" Compared with GB/T5009.1-1996, the main modifications of this standard are as follows: The structure of the original standard has been modified in accordance with GB/T20001.4—2001 "Standard Preparation Rules Part 4: Chemical Analysis Methods".
Appendix A of this standard is a normative appendix, and Appendix B and Appendix C are informative appendices. This standard is proposed and managed by the Ministry of Health of the People's Republic of China. This standard is drafted by the Food Hygiene Supervision and Inspection Institute of the Ministry of Health. This standard was first issued in 1985, revised for the first time in 1996, and this is the second revision. 1 Scope
Food hygiene inspection methods
Physical and chemical part
This standard specifies the basic inspection principles and requirements for the physical and chemical part of food hygiene inspection methods. This standard applies to the physical and chemical part of food hygiene inspection methods. 2 Normative references
GB/T5009.1—2003
The clauses in the following documents become the clauses of this standard through reference in this standard. For all dated referenced documents, all subsequent amendments (excluding errata) or revisions are not applicable to this standard. However, parties to an agreement based on this standard are encouraged to study whether the latest versions of these documents can be used. For undated referenced documents, the latest version shall apply to this standard. GB/T601 Preparation of standard titration solutions for chemical reagents GB/T602 Preparation of standard solutions for determination of impurities GB/T5009.3—2003 Determination of moisture in foods Determination of fat in foods GB/T5009.6—2003 GB/T5009.20—2003 Determination of organophosphorus pesticide residues in foods GB/T5009.26--20031 Determination of N-nitrosamines in foods GB/T5009.34—2003 Determination of sulfite in foods GB/T8170 Rules for rounding off values ​​JF1027 Measurement error and data processing t||3 General requirements for test methods
3.1 Weighing: The accuracy of weighing operations performed using a balance shall be expressed by the significant digits of the value, such as "weigh 20.0g accurately to ±0.1g"; "weigh 20.00g..." means weighing accurately to ±0.01g. 3.2 Accurate weighing: The accuracy of weighing operations performed using a balance is ±0.0001g. 3.3 Constant weight: Under specified conditions, the difference in mass measured after two consecutive drying or burning shall not exceed the specified range. 3.4 Measuring: The operation of taking liquid substances with a measuring cylinder or measuring cup. 3.5 Absorption: The operation of taking liquid substances with a pipette or graduated pipette." refers to weighing
3.6 The accuracy of the volume measured by glass measuring instruments such as burettes, pipettes, volumetric flasks, graduated pipettes, colorimetric tubes, etc. used in the test shall comply with the accuracy requirements of national standards for glass measuring instruments of this volume. 3.7 Blank test: The result obtained by parallel operation using exactly the same analytical steps, reagents and dosage (except for the dosage of standard titrant in titration method) except that no sample is added. It is used to deduct the reagent background in the sample and calculate the detection limit of the test method. 4 Selection of test method
4.1 If there are more than two test methods for standard method, they can be selected according to the conditions available, with the first method as the arbitration method. 4.2 When several parallel methods are set according to the scope of application in the standard method, the appropriate method should be selected according to the scope of application. In GB/T5009.3, GB/T5009.6, GB/T5009.20, GB/T5009.26, and GB/T5009.34, due to the different scopes of application of the methods, the first method is in a parallel relationship with other methods (not an arbitration method). In addition, standard methods that do not specify the first method are also in a parallel relationship with other methods.
5 Requirements for reagents and basic expression methods for their solution concentrations 5.1 The water used in the test method, unless otherwise specified, refers to distilled water or deionized water. When the solvent used to prepare the solution is not specified, it refers to aqueous solution.
5.2 When the specific concentrations of sulfuric acid, nitric acid, hydrochloric acid, and ammonia water are not specified in the test method, they refer to the concentrations of commercially available reagent specifications (see Appendix C). 5.3 Drops of liquid: refers to the amount of a drop of distilled water flowing from a standard dropper. At 20°C, 20 drops are approximately equivalent to 1mL. 5.4 Requirements for preparing solutions
5.4.1 The purity of the reagents and solvents used in preparing solutions should meet the requirements of the analysis project. Chemical reagents of different grades should be selected according to the analysis task, analysis method, and requirements for the accuracy of the analysis results. 5.4.2 Reagent bottles should be made of hard glass. Generally, alkali solutions and metal solutions are stored in polyethylene bottles. Reagents that need to be protected from light should be stored in brown bottles. 5.5 Methods for expressing solution concentrations
5.5.1 The expression of the concentration of standard titration solutions (see Appendix B) shall comply with the requirements of GB/T601. 5.5.2 Standard bath solutions are mainly used to determine the content of impurities and shall comply with the requirements of GB/T602. 5.5.3 The mixed mass fractions of several solid reagents or the mixed volume fractions of liquid reagents can be expressed as (1+1), (4+2+1), etc. 5.5.4 The concentration of a solution may be given on the basis of mass fraction or volume fraction, and the expression should be “the mass (or volume) fraction is 0.75\ or “the mass (or volume) fraction is 75%”. The mass and volume fractions may also be expressed in the form of 5ug/g or 4.2mL/m respectively. 5.5.5 The concentration of a solution may be expressed in mass or volume units, in grams per liter or in appropriate multiples thereof (g/L or mg/mL, etc.).
5.5.6 If a solution is prepared by diluting another specific solution, it should be expressed according to the following convention: “Dilution V.-V\ means that a specific solution with a volume of V is diluted in a certain way, The total volume of the final mixture is V2; "Dilution Vi+V, \ means adding a specific solution with a volume of V. to a solution with a volume of Vz (1+1), (2+5), etc. 6 Representation of temperature and pressure
6.1 Generally, temperature is expressed in degrees Celsius, written as ℃; or in degrees Kelvin, written as K (Kelvin = degrees Celsius + 273.15). 6.2 The unit of pressure is Pascal, expressed as Pa (kPa, MPa). 1atm=760mmHg
=101325Pa=101.325kPa=0.101325MPa (atm is standard atmospheric pressure, mmHg is millimeters of mercury) 7 Requirements for instruments and equipment
7.1 Glass measuring instruments
7.1.1 The burettes, pipettes, volumetric flasks, graduated pipettes, colorimetric tubes and other glass measuring instruments used in the test methods shall be calibrated and inspected in accordance with relevant national regulations and procedures.
7.1.2 Glass measuring instruments and glassware shall be thoroughly cleaned before use. For the washing method and preparation of washing liquid, please refer to Appendix C. 7.2 Temperature control equipment
The muffle furnace, constant temperature drying oven, constant temperature water bath and other instruments used in the test methods shall be tested and calibrated in accordance with relevant national regulations. 7.3 Measuring instruments
Balance, acidity meter, thermometer, spectrophotometer, Chromatographs and other instruments should be tested, verified and calibrated in accordance with relevant national regulations. 7.4 The instruments listed in the test method
are the main instruments required by the method. Common laboratory instruments are no longer listed. 8 Sample requirements
8.1 When sampling, attention should be paid to the production date, batch number, representativeness and uniformity of the sample (except for adulterated food and food poisoning samples). The quantity collected should be able to reflect the sanitary quality of the food and meet the sample quantity requirements of the test items. Three copies should be prepared for inspection, re-inspection, reference or arbitration. Generally, each bulk sample should be no less than 0.5kg. 8.2 The sampling container should be made of hard glass bottles or polyethylene products according to the test items. 8.3 Liquid and semi-fluid food and beverages such as vegetable oil, fresh milk, wine or other beverages, if contained in large barrels or large cans, should be fully mixed before sampling. The samples should be placed in three clean containers. GB/T5009.1-2003 8.4 Grain and solid food should take partial samples from different parts of the upper, middle and lower layers of each batch of food, mix them and take diagonal samples according to the quartering method, mix them several times and finally take representative samples 8.5 Meat, aquatic products and other foods should take samples from different parts or mix them according to the requirements of the analysis items. 8.6 Canned, bottled or other small packaged foods should be randomly sampled according to the batch number. The number of samples for the same batch number should not be less than 6 for packages with more than 250g and not less than 10 for packages with less than 250g. 8.7 The sample collection of adulterated food and food poisoning should be typical. 8.8 Storage of samples after inspection: Generally, samples should be kept for one month after the inspection is completed in case of re-inspection when necessary. Perishable foods shall not be kept, and they shall be sealed and kept in their original state as much as possible. Inspection sampling generally refers to taking edible parts, which are calculated based on the sample inspected. 8.9 Products with sensory disqualification do not need to undergo physical and chemical inspections and are directly judged as disqualified products. 9 Inspection requirements
9.1 Inspections shall be carried out strictly in accordance with the analytical steps specified in the standard method, and protective measures shall be taken for unsafe factors (poisoning, explosion, corrosion, burns, etc.) during the test.
9.2 Physical and chemical inspection laboratories shall implement analytical quality control. 9.3 Inspection personnel shall fill in inspection records. 10 Presentation of analysis results
10.1 The calculation of measured values ​​and the rounding of significant figures shall comply with the provisions of GB/T8170 and JF1027. For technical parameters and data processing, see Appendix A.
10.2 Expression of results: Report the arithmetic mean of the measured values ​​of the parallel samples, and report the calculated results to the number of decimal places or significant digits. The number of significant digits of the measured value should meet the requirements of the hygiene standards. 10.3 The units of the sample measured values ​​should use legal measurement units. 10.4 If the analysis result is below the detection limit of the method, the analysis result can be expressed as "not detected", but the detection limit value should be indicated. GB/T5009.1—2003
A.1 Sensitivity provisions
Appendix A
(Normative Appendix)
Technical parameters and data processing in the test method The slope (6) in the regression equation of the standard curve is taken as the method sensitivity (refer to Chapter A.5), that is, the response value of the unit physical quantity. A.2 Detection limit
The mass or concentration corresponding to the standard deviation of 3 times the blank value (number of measurements n≥20) is called the detection limit. A.2.1 Chromatography (GC.HPLC)
Assume: the lowest response value of the chromatograph is S=3N (N is the instrument noise level), then the detection limit is calculated according to formula (A.1). Detection limit = lowest response value S
Where:
b—slope in the standard curve regression equation, response value/μg or response value/ng; S—is 3 times the instrument noise, that is, the minimum substance signal that the instrument can identify. A.2.2 Absorption and fluorescence methods
According to the provisions of the International Union of Pure and Applied Chemists (IUPAC). A.2.2.1 Total reagent blank response value
The total reagent blank response value is calculated according to formula (A.2). X,-X.+Ks
Where:
--response value of blank of all reagents (adjust zero point with solvent according to 3.7);X
X:--average value of blank solution measured n times (n≥20);standard deviation of blank values ​​n times;
K coefficient determined according to a certain confidence level.
A.2.2.2 Detection limit
The detection limit is calculated according to formula (A.3).
Where:
Detection limit;
XL,X,K,5,b—-same as formula (A2) notes; generally 3.
A.3 Precision
The degree of agreement of each measured value of the same sample is precision. A.3.1 Determination
In a certain laboratory, when the same operation method is used to determine the same stable sample, the factors that are allowed to vary include the operator, time, reagents, instruments, etc. The relative deviation between the measured values ​​is the accuracy of the method in the laboratory. 6
A.3.2 Representation
A.3.2.1 Relative deviation
Relative deviation is calculated according to formula (A.4).
Where:
X,——the measured value of a certain time;
x ​​is the average value of the measured values.
Relative deviation (%)=
The relative error of parallel samples is calculated according to formula (A.5). X,-X
-×100
Relative error of parallel samples (%)=
A.3.2.2 Standard deviation
A.3.2.2.1 Arithmetic mean: The arithmetic mean of multiple determinations can be calculated according to formula (A,6). X-X+X+...Www.bzxZ.net
Wherein:
x—the arithmetic mean of n repeated determinations; the number of repeated determinations,
GB/T5009.1—-2003
.(A.5)
.....(A, 6)
Xnth determination value in n determinations.
A,3.2.2.2 Standard deviation: It reflects the magnitude of random error, expressed as standard deviation (S), and calculated according to formula (A7). x.)/n
wherein:
the arithmetic mean of the results of n repeated measurements; n
number of repeated measurements;
X, the ith measurement value in n measurements;
S-standard deviation.
A.3.2.3Relative standard deviation
Relative standard deviation is calculated according to formula (A.8). RSD-
wherein:
Relative standard deviation;
S, X -same as A. 3.2.2.2.
A.4Accuracy
The degree to which the measured mean value is consistent with the true value. S
.(A.7)
A.4.1 Determination
A certain stable sample is spiked with a known amount of a standard substance (the amount of the standard substance is taken as the true value). The sample and the spiked sample are measured at the same time; the error between the spiked sample and the standard substance after deducting the sample value is the accuracy of the method. A.4.2 The accuracy of the method is expressed by the recovery rate. The recovery rate of the added standard substance is calculated according to formula (A.9). 7
GB/T5009.1—2003
Where:
The recovery rate of the added standard substance,
The amount of the added standard substance;
X, the measured value of the spiked sample;
X. The measured value of the unspiked sample.
A.5 Calculation of linear regression equation
P=XX×100%
When drawing the standard curve, the linear regression equation can be used for calculation, and then the curve can be drawn based on the calculation result. The formula for calculating the linear regression equation using the least squares method is shown in equations (A.10) to (A.13). y=a+bx
a-2x(2-(2x(2x)
b = (2)-(2x(2)
n2x-(2x)2
n(XY)-(EX)(EY)
n>x(2x)ny-()
Independent variable, is the value on the horizontal axis,
dependent variable, is the value on the vertical axis;
slope of a straight line,
intercept of the straight line on the Y axis;
measured value:
correlation coefficient of the regression line.
A.6 significant figures
...(A, 10 )
（A11)
.....( A. 13 )
The quantities measured directly or indirectly in food physical and chemical testing are generally expressed in numbers, but they are different from "numbers" in mathematics and only represent the approximate value of the measurement. Only one suspicious digit is retained in the measured value, such as 0.0123 and 1.23 both have three significant digits. When the \0\ at the end of the number is not a significant digit, it should be rewritten as multiplying by 10\. For example, 24600 has three significant digits and should be written as 2.46×10. A.6.1 Operation rules
A.6.1.1 Unless otherwise specified, the general suspicious number represents an error of 1 unit at the end. A.6.1.2 In complex operations, one more significant digit is retained in the intermediate process, and the final result must take the appropriate number of digits. 3 The number of digits retained after the decimal point of the result of addition and subtraction calculations should be the same as the number of digits after the decimal point of the numbers participating in the operation A.6.1.3
The number of significant digits retained for the result of multiplication and division calculations should be the same as the number with the least number of significant digits among the numbers participating in the calculation, "A, 6.2 After the number of significant digits is determined according to the accuracy of the instrument in the method determination, the calculation is performed first, and the value after the calculation is rounded off. A.7 Rules for rounding off numbers
A.7.1 Among the numbers to be discarded, if the first digit on the left is less than 5 (not including 5), it is discarded, that is, the last digit to be retained remains unchanged.
For example; round 14.2432 to retain one decimal place. Before rounding
After rounding
GB/T5009.1-2003
A, 7.2 Among the numbers to be discarded, if the first digit on the left is less than 5 (not including 5), it is discarded, that is, the last digit to be retained remains unchanged.
For example; round 14.2432 to retain one decimal place. Before rounding
After rounding
GB/T5009.1-2003
A, 7.2 Among the numbers to be discarded, if the first digit on the left is less than 5 (not including 5), it is discarded, that is, the last digit to be retained remains unchanged. If a number is greater than 5 (not including 5), it is rounded up by one, that is, the last digit to be retained is increased by one. For example: 26.4843 is rounded to one decimal place. Before rounding
After rounding
A.7.3 Among the numbers to be discarded, if the first digit on the left is equal to 5 and the digits on the right are not all zero, it is rounded up by one, that is, the last digit to be retained is increased by one
For example: 1.0501 is rounded to one decimal place. Before rounding
After rounding
A.7.4 Among the numbers to be discarded, if the first digit on the left is equal to 5 and the digits on the right are all zero, the last digit to be retained is odd, if it is an odd number, it is rounded up by one, if it is an even number (including 0"), it is not rounded up. For example: The following numbers are rounded to one decimal place. Before rounding
After rounding
A.7.5 If the number to be discarded is more than two digits, it shall not be rounded off multiple times in succession. The result shall be rounded off once according to the above provisions based on the size of the first digit to the left of the number to be discarded. For example: rounding 15.4546 to an integer.
The correct approach is:
Before rounding
The incorrect approach is:
Before rounding
First rounding
Second rounding
After rounding
Third rounding
Fourth rounding (result)
GB/T 5009.1—2003
Appendix B
(Informative appendix)
Standard titration solution
The preparation and calibration of certain standard titration solutions in the test methods shall be carried out in accordance with the following provisions and shall comply with the requirements of GB/T601. B.1 Standard hydrochloric acid titration solution
B.1.1 Preparation
B.1.1.1 Standard hydrochloric acid titration solution Cc (HCI) = 1mol/LJ: Measure 90mL of hydrochloric acid, add appropriate amount of water and dilute to 1000mL. B.1.1.2 Standard hydrochloric acid titration solution [c (HCI) = 0.5mol/L: Measure 45mL of hydrochloric acid, add appropriate amount of water and dilute to 1000mL. B.1.1.3 Standard hydrochloric acid titration solution (c (HCI) = 0.1moL/L): Measure 9mL of hydrochloric acid, add appropriate amount of water and dilute to 1000mL. B.1.1.4 Bromocresol green-methyl red mixed indicator solution: Measure 30mL of bromocresol green ethanol solution (2g/L), add 20mL of methyl red ethanol solution (1g/L), and mix well.
B.1.2 Calibration
B.1.2.1 Hydrochloric acid standard titration solution Lc (HCI) = 1 mol/LJ: Accurately weigh about 1.5 g of standard anhydrous sodium carbonate dried to a constant amount at 270℃ ~ 300℃, add 50 mL of water to dissolve it, add 10 drops of bromocresol green-methyl red mixed indicator solution, and titrate with this solution until the solution changes from green to purple-red, boil for 2 minutes, cool to room temperature, and continue to titrate until the solution changes from green to dark purple. B.1.2.2 Hydrochloric acid standard solution Lc (HC1) = 0.5 mol/LJ: Operate according to B.1.2.1, but change the standard anhydrous sodium carbonate amount to about 0.8 g. B.1.2.3 Hydrochloric acid standard solution [c (HC1) = 0.1 mol/LJ: Operate according to B.1.2.1, but change the standard anhydrous sodium carbonate amount to about 0.15 g. B.1.2.4 Perform a reagent blank test at the same time.
B.1.3 Calculation
The concentration of the hydrochloric acid standard titration solution is calculated according to formula (B.1). m
Gl = (V,-V)× 0. 053 0
Wherein:
cl—-actual concentration of the hydrochloric acid standard titration solution, in moles per liter (mol/L); m
mass of the standard anhydrous sodium carbonate, in grams (g); Vi the amount of the hydrochloric acid standard solution, in milliliters (mL); V.
-amount of the hydrochloric acid standard solution used in the reagent blank test, in milliliters (mL); (B.1)
The mass of the standard anhydrous sodium carbonate equivalent to 1.00mL of the hydrochloric acid standard titration solution (c(HCI)=1mol/L), in grams (g).
B.2 Hydrochloric acid standard titration solution Ce(HCI)=0.02mol/L, e(HCI)=0.01mol/L) Take the hydrochloric acid standard solution Cc(HCI)=0.1mol/L)(B.1.1.3) and dilute it with water before use. Recalibrate the concentration if necessary. B.3 Standard sulfuric acid titration solution
B.3.1 Preparation
B.3.1.1 Standard sulfuric acid titration solution (c(1/2H,SO,)=1mol/LJ: Measure 30mL of sulfuric acid, slowly inject it into an appropriate amount of water, cool to room temperature, dilute with water to 1000mL, and mix well. B.3.1.2 Standard sulfuric acid titration solution (c(1/2H.SO.)=0.5mol/L): Follow the procedures of B.3.1.1, but change the amount of sulfuric acid to 15mL. B.3.1.3 Standard sulfuric acid titration solution Cc(1/2H,SO.)=0.1mol/L): Follow the procedures of B.3.1.1, but change the amount of sulfuric acid to 3mL. 10
B.3.2 Calibration
B.3.2.1 Standard sulfuric acid titration solution [c(1/2H,SO,）=1.0mol/L): operate according to B.1.2.1. B.3.2.2 Standard sulfuric acid titration solution Cc(1/2H.SO,）=0.5mol/L): operate according to B.1.2.2. B.3.2.3 Standard sulfuric acid titration solution Cc(1/2H,SO,）=0.1mol/L): operate according to B.1.2.3. B.3.3 Calculation
The concentration of standard sulfuric acid titration solution is calculated according to formula (B.2). m
c2=(VV,)×0.0530
Wherein:
C2—actual concentration of sulfuric acid standard titration solution, in moles per liter (mol/L); m
grams of standard anhydrous sodium carbonate, in grams (g); Vi—amount of sulfuric acid standard solution, in milliliters (mL); V,-amount of sulfuric acid standard solution in the reagent blank test, in milliliters (mL); CB/T5009.1—2003
—mass of standard anhydrous sodium carbonate equivalent to 1.00mL sulfuric acid standard solution [c(1/2H,SO,）=1mol/L), in grams (g).
B.4 Standard titration solution of sodium hydroxide
B.4.1 Preparation
B.4.1.1 Saturated sodium hydroxide solution: Weigh 120g sodium hydroxide, add 100mL water, shake to dissolve into saturated solution, cool and place in a polyethylene plastic bottle, seal, leave for several days, and set aside after clarification. B.4.1.2 Standard sodium hydroxide solution (Cc (NaOH) = 1mol/L): Take 56mL of clear saturated sodium hydroxide solution, add appropriate amount of freshly boiled cold water to 1000mL, shake well. B.4.1.3 Standard sodium hydroxide solution (Cc (NaOH) = 0.5mol/L): Operate as in B.4.1.2, but take 28mL of clear saturated sodium hydroxide solution instead.
B.4.1.4 Sodium hydroxide standard solution [c(NaOH)=0.1mol/L): Operate as in B.4.1.2, but pipette 5.6mL of the clear saturated sodium hydroxide solution instead.
B.4.1.5 Phenol indicator solution: Weigh 1g of phenolphthalein and dissolve it in an appropriate amount of ethanol and then dilute to 100mL. B.4.2 Calibration
B.4.2.1 Sodium hydroxide standard solution (c(NaOH)=1mol/L): Accurately weigh about 6g of standard potassium hydrogen phthalate dried to a constant amount at 105℃~110℃, add 80mL of freshly boiled cold water to dissolve it as much as possible, add 2 drops of phenol indicator solution, and titrate with this solution until the solution turns pink and does not fade for 0.5min. B.4.2.2 Standard sodium hydroxide solution (c(NaOH) = 0.5 mol/L): Operate as in B.4.2.1, but change the amount of standard potassium hydrogen phthalate to about 3 g.
B.4.2.3 Standard sodium hydroxide solution Cc(NaOH) = 0.1mol/L): Operate as in B.4.2.1, but change the amount of standard potassium hydrogen phthalate to about 0.6g.
B.4.2.4 Perform a blank test at the same time.
B.4.3 Calculation
The concentration of the sodium hydroxide standard titration solution is calculated according to formula (B.3). In the formula:
cs=(V,-V,)×0.2042
is the actual concentration of the standard sodium hydroxide titration solution, in moles per liter (mol/L); m
is the mass of the benchmark potassium hydrogen phthalate, in grams (g); V is the amount of the standard sodium hydroxide solution used, in milliliters (mL); (B.3)
GB/T5009.1—2003
is the amount of the standard sodium hydroxide solution used in the blank test, in milliliters (mL); 0.2042
is the mass of the benchmark potassium hydrogen phthalate equivalent to 1.00mL of the standard sodium hydroxide titration solution (c(NaOH)=1mol/L), in grams (g).
B.5 Standard sodium hydroxide titration solution (c(NaOH)=0.02mol/L, c(Na0H)=0.01mol/L) Take the standard sodium hydroxide solution (c(NaOH)=0.1mol/L) and dilute it with freshly boiled cold water before use. If necessary, use the standard hydrochloric acid titration solution (c(HCI)=0.02.mol/L, c(HCl)=0.01mol/L) to calibrate the concentration. B.6 Standard potassium hydroxide titration solution (c(KOH)=0.1mol/L) B.6.1 Preparation
Weigh 6g potassium hydroxide, add freshly boiled cold water to dissolve, dilute to 1000mL, and mix. B.6.2 Calibration
Perform according to B.4.2.3 and B.4.2.4.
B.6.3 Calculation
Calculate according to formula (B.3) in B.4.3.
B.7 Potassium permanganate standard titration solution (c(1/5KMnO,)=0.1mol/L)B.7.1 Preparation
Weigh about 3.3g potassium permanganate and add 1000mL water. Boil for 15min. Stopper and let stand for more than 2d, filter with a vertical melting funnel, and place in a brown bottle with a glass stopper and seal it for storage. B.7.2 Calibration
Accurately weigh about 0.2g of reference sodium oxalate dried to a constant weight at 110℃. Add 250mL of freshly boiled cold water and 10mL of sulfuric acid, and stir to dissolve. Quickly add about 25mL of potassium permanganate solution, wait until it fades, heat to 65℃, and continue to titrate with potassium permanganate solution until the solution turns slightly red, and keep it without fading for 0.5min. At the end of the titration, the solution temperature should not be lower than 55°C. Perform a blank test at the same time. B.7.3 Calculate the concentration of the potassium permanganate standard titration solution according to formula (B.4). m
C4 =(V,-V.)× 0. 067 0
Wherein:
The actual concentration of the potassium permanganate standard titration solution, in moles per liter (mol/L): The mass of the reference sodium oxalate, in grams (g); V, the amount of the potassium permanganate standard solution, in milliliters (mL); V, the amount of the potassium permanganate standard solution used in the reagent blank test, in milliliters (mL); *(B.4)
0.0670-The mass of the reference sodium oxalate equivalent to 1.00mL of the potassium permanganate standard titration solution (c(1/5KMnO.)=1mol/L), in grams (g).
B.8 Potassium permanganate standard titration solution [c(1/5KMnO,)=0.01mol/L] Take potassium permanganate standard solution Cc(1/5KMnO,)=0.1mol/LJ and dilute it before use. Recalibrate the concentration if necessary. B.9 Oxalic acid standard titration solution [c(1/2H,Cz02H,0)=0.1mol/L] B.9.1 Preparation
Weigh about 6.4g oxalic acid, add appropriate amount of water to dissolve it and dilute to 1000mL, mix well. 12
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