JJF 1567-2016Calibration Specification for Phosphate Analyzers (English PDF)

1 Scope (1)

2 References (1)

3 Overview (1)

4 Metering characteristics (1)

5 Calibration conditions (2)

6 Calibration items and calibration methods (2)

7 Expression of calibration results (3)

8 Recurrence time interval (4)

Appendix A Preparation method of color reagent (5)

Appendix B Phosphate Analyzer Calibration Record Format (for reference) (6)

Appendix C Calibration Certificate Inside Format (for reference) (7)

Appendix D Analysis of Uncertainty of Calibration Results for Indication Error of Phosphate Analyzer (8)

Introduction

This specification to JJF 1071-2010 "national measurement calibration standard preparation rules", JJF 1001-2011 "General Measurement Terms and Definitions "and JJF 1059.1-2012" Measurement Uncertainty Assessment and Representation "for basic specifications to develop.

In the development of this specification, with reference to the GB/T 6913-2008 "boiler water and cooling water analysis method phosphoric acid Determination of salts "and DL/T 502.13-2006" Water vapor analysis methods for thermal power plants Part 13. Phosphate Determination (spectrophotometric method) "part of the content.

This specification is the first release.

Standard for Phosphate Analyzer Calibration

1 Scope

This specification applies to the calibration of a phosphate analyzer (colorimetric method).

2 reference file

This specification refers to the following documents.

GB/T 6682 Analytical laboratory water specifications and test methods Water vapor analysis methods for thermal power plants - Part 13. Determination of phosphates (points) Photometric method) for dated references, only the dated edition applies to this specification; references that are not dated , The latest version (including all modifications) applies to this specification.

3 Overview

Phosphate analyzer is used to determine the phosphate content of water (represented by PO43-). The principle is in the acid in the medium water samples, phosphates form molybdenum vanadium molybdate complexes with molybdate and metavanadate, and then use photoelectric the color principle is measured according to Lambert-Beer's law.

Phosphate analyzer (hereinafter referred to as instrument) mainly by the light source, light collimation unit, sample chamber, signal detection transmission System and display and processing systems and other components. The structure of the diagram shown in Figure 1.

Figure 1 Schematic diagram of the structure of the phosphate analyzer

4 measurement characteristics the instrument performance requirements are shown in Table 1.

Table 1 Phosphate analyzer metering performance requirements

Metrological performance indicators Instrument zero drift (30min) ± 0.2mg/L the maximum permissible error of the instrument is ± 2% FS Instrument measurement repeatability <= 1%

Table 1 (continued)

Metrological performance indicators Instrument indication stability (30min) ± 1% FS Note. All of the above indicators are not used for qualifying, only reference.

5 calibration conditions

5.1 Environmental conditions

5.1.1 Ambient temperature. (15 ~ 35) °C

5.1.2 Relative humidity. not more than 85%

5.1.3 Power supply. voltage (220 ± 22) V, frequency (50 ± 0.5) Hz, or meet the requirements of the instrument.

5.2 Measurement standards and other equipment

5.2.1 Determination of phosphate composition in water Standard substance. A national standard material should be used, relative expansion uncertainty Better than 1.0% (k = 2).

5.2.2 Stopwatch. Minimum scale value 0.1s.

5.2.3 glass measuring device. single-line capacity bottle 1000mL, single-line pipette 10mL, are A-level.

Above the use of measuring instruments should be effective traceability.

6 calibration items and calibration methods

6.1 Instrument zero drift Until the instrument boot warm-up stability, in normal working condition, with deionized water to clean the instrument sample pool, and to go Ion water as a zero solution, color reaction after injection into the sample pool, record the initial value of the instrument c0. After every 5min remember Recorded instrument indication c0i, continuous observation 30min, according to formula (1) calculated zero drift, take the absolute value of the maximum deltac0 for the instrument Zero drift.

deltac0 = c0i-c0 (1) where.

deltac0 --- instrument zero drift, mg/L;

c0i --- instrument i show, mg/L;

c0 --- initial value of the instrument, mg/L.

6.2 Instrument indication error when the instrument is warmed up, it is in the normal working condition and the instrument is carried out according to the instruction manual.

quasi. Within the calibration range of the instrument, 20%, 40%, 80% of the corresponding phosphate concentration Solution, after the color reaction followed by injection into the instrument sample pool, each concentration point measurement 3 times, record the instrument indication. press Equation (2) calculates the indication error deltac for each concentration point. For other ranges of multi-range instruments, refer to the above method to calibrate.

deltac =

c-cs

R × 100%

Where.

deltac --- instrument indication error,%;

c - the average of the three measurements of the instrument, mg/L;

cs --- standard value of phosphate solution, mg/L;

R --- Instrument calibration range, mg/L.

6.3 Instrument measurement repeatability Until the instrument boot warm-up stability, in the normal working condition, select the instrument range of 80% concentration of phosphate concentration Standard solution, the color reaction into the instrument after the sample pool, continuous measurement 6 times, read the instrument display, according to type (3) Calculate its repeatability delta.

delta =

(ci-c) 2

100% (3)

Where.

delta - instrument measurement repeatability,%;

ci --- the instrument measured the first i, mg/L;

c - the average of the 6 measurements, mg/L;

n - number of measurements, n = 6.

6.4 Instrument indication stability to be instrumented preheat stable, in normal working condition, with deionized water to clean the instrument sample pool, optional instrument Range of 80% concentration of phosphate standard solution, the color reaction into the instrument after the sample pool, record the initial value of the instrument cD.

After every 5min record instrument indication cDi, continuous observation 30min, according to formula (4) calculated the value of stability, the maximum value of deltacD for the instrument shows the value of stability.

deltacD =

cDi-cD

R × 100%

Where.

deltacD --- instrument indication stability,%;

cDi --- instrument i measured, mg/L;

cD --- initial indication of the instrument, mg/L;

R --- Instrument calibration range, mg/L.

7 The expression of the calibration results the calibration results should be reflected in the calibration certificate. The calibration certificate shall include at least the following information.

a) Title. "Calibration Certificate";

b) laboratory name and address;

c) where the calibration is made (if the address is different from the laboratory);

d) the identity of the certificate (such as number), the identity of each page and the total number of pages;

e) the name and address of the customer;

f) the description and identification of the school object;

g) The date of calibration, if relevant to the validity and application of the calibration results, shall indicate the object to be calibrated Date of receipt

h) If the test results of the calibrated results are relevant to the application of the calibration results,

i) the identification of the technical specifications on which the calibration is based, including the name and code;

k) description of the calibration environment;

l) Calibration results and their measurement uncertainty;

m) a description of the deviation from the calibration specification;

n) the signature, title or equivalent mark of the certificate or calibration report issuer;

o) The result of the calibration is valid only for the school object;

p) No part of the reproduction of the certificate without the written approval of the laboratory.

8 re-school time interval the recommended calibration cycle of the instrument should not exceed 1 year (12 months), due to the length of the re-school time interval by the instrument Use, users, instruments and other factors, therefore, the use of units according to the actual situation of their own decision to re-school time interval. You should always calibrate when replacing important parts or have doubts about the performance of the instrument.

Appendix A

Preparation method of color reagent the coloring agent used in the calibration process is configured as follows.

Ammonium molybdate, ammonium metavanadate, concentrated sulfuric acid are analytical or analytical pure above, the water used for the preparation of the solution must be Ion water.

Preparation of molybdenum - vanadic acid coloring reagent A.1.1 When preparing the color reagent, weigh 50 g of ammonium molybdate and 2.5 g of ammonium metavanadate in 400 mL of deionized Water.

A.1.2 amount of 195mL concentrated sulfuric acid (density of 1.84g/cm3), in constant stirring slowly added to 250mL Deionized water and cooled to room temperature.

A.1.3 The solution of A.1.2 was poured into a solution of A.1.1 and diluted to 1 L with deionized water.

Appendix B

Phosphate Analyzer Calibration Record Format (for reference) Principal. Certificate Number.

Manufacturer. Instrument Model.

Instrument Name. Factory Number. Unique Identification Number.

Calibration basis. Temperature. Relative humidity.

1 indication error. instrument range value.

Standard solution number 1 2 3 4 PO43- concentration standard value/(mg/L) PO43- concentration measurement mg/L Average value of measurement/(mg/L) Indication error /%

2 Measure repeatability.

Number of measurements 1 2 3 4 5 6 Average repeatability /% Instrument measurements/(mg/L) 3 zero drift.

Continuous observation time/min 0 5 10 15 20 25 30 zero drift Instrument measurements/(mg/L) 4 indication stability.

Continuous observation time/min 0 5 10 15 20 25 30 Maximum drift stability /% Instrument measurements/(mg/L)

5 Insulation resistance.

Calibrator. Date.

Appendix C.

Calibration certificate page format (for reference)

1 Appearance.

2 indication error.

3 Measure repeatability.

4 zero drift.

5 indication stability.

6 Insulation resistance.

Appendix D

Evaluation of Uncertainty in Calibration Result of Indication Error of Phosphate Analyzer D.1 Overview D.1.1 measurement principle in acidic water samples, phosphates form molybdenum vanadium molybdate complexes with molybdate and metavanadate, Determination of Phosphate by Acid Spectrometer (Spectrophotometry).

D.1.2 Measurement method After the instrument is stabilized, calibrate the instrument according to the instruction manual. Within the instrument calibration range, select the amount 20%, 40%, 80% of the phosphate standard solution, after the color reaction in turn into the instrument measurement pool, each Concentration point measurement 3 times, record the instrument display value, at each point 3 times the average measured as the concentration point of the measured value, press (D.1) Calculate the indication error.

D.1.3 Standard substances and calibration objects Standard substance. GB W (E) 081228 Determination of phosphate component in water Standard substance, nominal 1000mg/L, the relative uncertainty is 0.6%, k = 2.

Calibration object. This measurement used phosphate analyzer model HK-218, range (0 ~ 20) mg/L, the calibration range is (0 ~ 20) mg/L.

Taking the 40% (8mg/L) concentration point calibration process as an example, the uncertainty evaluation was carried out.

D.2 measurement model deltac = c-cs R × 100% (D.1) where.

deltac --- instrument indication error,%;

c - the average of the three measurements of the instrument, mg/L;

cs --- standard value of phosphate solution, mg/L;

R --- Instrument calibration range, mg/L.

D.3 Standard Uncertainty Estimation u2r (deltac) = ddeltac dc u2 (c) ddeltac dcs u2 (cs) (D.2) Calculate the sensitivity of each variable according to the following formula.

ddeltac

ddeltac

dcs = -

D.3.1 Sources and assessment of standard uncertainty D.3.1.1 Class A assessment of standard uncertainty Class A Uncertainty is derived from the repetitive performance of the instrument measurement, which can be obtained by continuous measurement, using the Class A method assessment. The measurement, select 8mg/L point repeated measurements 6 times, the results are as follows (mg/L). 7.62,7.73, 7.68, 7.81, 7.67, 7.82. The average value of 7.72mg/L, according to the Bessel formula, a single measurement test standard Quasi-deviation s.

(ci-c) 2

0.08 mg/L (D.4)

In the actual measurement, the average of the three measurements is taken as the measurement result, so.

0.08 mg/L

= 0.046 mg/L

Expressed as relative standard uncertainty.

ur (c) =

0.046 mg/L

8mg/L =

0.58%

D.3.1.2 Class B assessment of standard uncertainty.

It can be seen from the analysis, the instrument error of the B class of uncertainty from the standard value of the standard and standard solution preparation the introduction of the uncertainty.

D.3.1.2.1 Relative standard uncertainty introduced by reference material it can be seen from the certificate, the calibration of the water used in the phosphate composition of the standard material standard concentration of 1000mg/L, the relative expansion uncertainty is 0.6%, k = 2, so.

usb =

2 = 0.30%

D.3.1.2.2 Relative standard uncertainty introduced using 10 mL pipette

1) Preparation of 8mg/L calibration solution. Remove the 8mL sample, volume to 1000mL. According to JJG196-2006 "Common glass measuring device", A-level 10mL pipette maximum allowable error of ± 0.05mL, according to the uniform distribution of consideration, then u101 = 0.05 mL = 0.029 mL

2) Uncertainties introduced by temperature changes According to the general provisions of the maximum temperature change of ± 5 °C, according to the uniform distribution of consideration, check the table that the expansion of water the number of 2.1 × 10-4/°C, glass expansion coefficient of 9.75 × 10-6/°C (negligible), the temperature caused by the wrong the degree is.

u102 =

10 × 2.1 × 10-4 × 5

= 0.006 (mL)

10mL pipette introduction of the uncertainty from the above two parts, the result is.

u10 = 0.0292 0.0062 = 0.030 (mL) Relative standard uncertainty.

urel10 =

0.030

10 × 100% = 0.3%

D.3.1.2.3 Relative standard uncertainty introduced using a 1000 mL volumetric flask

1) Preparation of 8mg/L calibration solution. Remove the 8mL sample, volume to 1000mL. According to JJG196-2006 "Common glass measuring device", A-level 1000mL volumetric flask maximum allowable error of ± 0.40mL, according to uniform distribution test Consider, then u10001 = 0.40 mL = 0.23 mL

2) Uncertainties introduced by temperature changes in accordance with the general provisions of the maximum temperature change of ± 5 °C, according to uniform distribution considerations, check the table, the water expansion coefficient is 2.1 × 10-4/° C, the expansion coefficient of the glass is 9.75 × 10-6/° C (negligible), then the temperature is uncertain Degrees.

u10002 =

1000 × 2.1 × 10-4 × 5 = 0.61 (mL) 1000mL volumetric flask introduced the uncertainty from the above two parts, the result is.

u1000 = 0.232 0.612 = 0.64 (mL) Relative standard uncertainty.

urel1000 =

0.64

1000 × 100% = 0.064% D.3.1.3 Class B synthetic standard uncertainty usrel = (0.3%) 2 (0.3%) 2 (0.064%) 2 = 0.42% u (cs) = 8 × 0.42% = 0.034 (mg/L) D.3.1.4 List of standard uncertainties

Table D.1 List of standard uncertainties

Uncertainty of standard uncertainty Standard Uncertainty % mg/L ci ci ui /% u (c) Measurement repeatability 0.58 0.046 1/20 0.23 u (cs) usb standard substance 0.3 urel10 10mL pipette 0.3 urel1000 1000mL volumetric flask 0.064 0.034 -1/20 -0.17 D.3.2 Synthetic relative standard Uncertainty.

u2r (deltac) =

ddeltac

u2 (c)

ddeltac

dcs

u2 (cs)

× 0.0462

× 0.0342

ur (deltac) = 0.3%

D.4 Relative expansion uncertainty of indication error Take k = 2, Ur = 2 × 0.3% = 0.6% the results of this measurement are. deltac = 7.72-8 20 × 100 = -1.4% , Ur = 0.6%, k = 2.

Similarly, the concentration of 4mg/L, 16mg/L to assess the final results are as follows.

Measuring point 8mg/L. deltac = -1.4%, Ur = 0.6%, k = 2;

Measuring point 4mg/L. deltac = -1.6%, Ur = 0.4%, k = 2;

Measuring point 16mg/L. deltac = -0.7%, Ur = 0.8%, k = 2.