HJ 694-2014Water Quality - Determination of Mercury, Arsenic, Selenium, Bismuth and Antimony - Atomic Fluorescence Spectrometry (English PDF)

5.1 The elements in acidic medium, that can react with potassium borohydride and

generate hydride, would affect each other and produce interference; adding thiourea

+ ascorbic acid solution (6.20) can substantially eliminate the interference.

5.2 Copper and other transition metals that are above a certain concentration may

interfere to the determination; adding thiourea + ascorbic acid solution (6.20) can

eliminate most of the interference. Under the experimental conditions of this Standard,

samples containing less than 100mg/L of Cu2+, less than 50mg/L of Fe2+, less than

1mg/L of Co2+, less than 10mg/L of Pb2+ (5mg/L for selenium), and less than 150mg/L

of Mn2+ (2mg/L for selenium) do not affect the determination.

5.3 Common anions do not interfere to the determination.

5.4 Physical interference elimination. Select two-layer-structure quartz tube atomizer;

with the outer and inner layers filled with argon gas, form a protective outer layer to

isolate air, so that the ground-state atom of determined elements do not collide with

oxygen and nitrogen in the air, so as to reduce the fluorescence quenching effect on

the determination.

6.1 Hydrochloric acid: rho(HCl) = 1.19g/ml, guarantee reagent.

6.2 Nitric acid: rho(HNO3) = 1.42g/ml, guarantee reagent.

6.3 Perchloric acid: rho(HClO4) = 1.68g/ml, guarantee reagent.

6.4 Hydrogen sodium hydride (NaOH).

6.5 Potassium borohydride (KBH4).

6.6 Thiourea (CH4N2S).

6.7 Ascorbic acid (C6H8O6).

6.8 Potassium dichromate (K2Cr2O7): guarantee reagent.

6.9 Mercuric chloride (HgCl2): guarantee reagent.

6.10 Arsenic trioxide (As2O3): guarantee reagent.

6.11 Selenium powder: high-purity (the mass fraction is more than 99.99%).

6.12 Bismuth: high-purity (the mass fraction is more than 99.99%).

6.13 Antimony trioxide (Sb2O3), guarantee reagent.

6.14 Hydrochloric acid solution: 1 + 1.

6.15 Hydrochloric acid solution: 5 + 95.

6.16 Nitric acid solution: 1 + 1.

6.17 Hydrochloric acid - nitric acid solution

Weigh 300ml of hydrochloric acid (6.1) and 100ml of nitrate (6.2) respectively; add to

400ml of water; mix well.

6.18 Mixture acid of nitric acid - perchloric acid

Prepare by mixing an equal volumes of nitric acid (6.2) and perchloric acid (6.3).

Prepare it when it is to be used.

6.19 Reducing agents

6.19.1 Potassium borohydride Solution A

Weigh 0.5g of sodium hydroxide (6.4); dissolve in 100ml of water; add 1.0g of

potassium borohydride (6.5); mix well. This solution is used for the determination of

mercury; prepare it when it is to be used; stored in a plastic bottle.

6.19.2 Potassium borohydride solution B

Weigh 0.5g of sodium hydroxide (6.4); dissolve in 100ml of water; add 2.0g of

potassium borohydride (6.5); mix well. This solution is used for the determination of

arsenic, selenium, bismuth, and antimony; prepare it when it is to be used; stored in a

plastic bottle.

Note: It can also use potassium hydroxide, potassium borohydride to prepare reducing agents.

6.20 Thiourea - ascorbic acid solution

Weigh 5.0g of sulfur urea (6.6) and ascorbic acid (6.7) respectively; dissolve with

100ml of water; mix well. Prepare it at the day of determination.

6.21 Mercury standard solution

6.21.1 Mercury standard fixative

Weigh 0.5g of potassium dichromate (6.8) and dissolve in 950ml of water; add 50ml of

nitric acid (6.2); mix well.

6.21.2 Mercury standard stock solution: rho(Hg) = 100mg/L.

Purchase the commercially available certified reference materials; or weigh 0.1354g

of mercuric chloride (6.9) that has been placed on a silica dryer overnight; transfer into

a 1000ml flask after dissolved with a small amount of mercury standard fixative

(6.21.1); dilute with mercury standard fixative (6.21.1) to the mark; mix well. Store in a

glass bottle. It can be stored at 4°C for 2 years.

6.21.3 Mercury standard intermediate solution: rho(Hg) = 1.00mg/L.

Pipette 5.00ml of mercury standard solution (6.21.2) into a 500ml volumetric flask;

add 50ml of hydrochloric acid (6.14); use mercury standard fixative (6.21.1) to dilute to

the mark; mix well. Store in a glass bottle. It can be stored at 4°C for 100 d [Translator:

days].

6.21.4 Mercury standard using solution: rho(Hg) = 10.0g/L.

Pipette 5.00ml of mercury standard intermediate solution (6.21.3) into a 500ml

volumetric flask; add 50ml of hydrochloric acid (6.14); dilute with water to the mark;

mix well. Store in a glass bottle. Prepare it when it is to be used.

6.22 Arsenic standard solution

6.22.1 Arsenic standard stock solution: rho(As) = 100mg/L.

Purchase the commercially available certified reference materials; or weigh 0.1320g

of guarantee-reagent arsenic trioxide (6.10) that has been dried at 105°C for 2h;

dissolve in 5ml of 1mol/L sodium hydroxide solution; use 1mol/L hydrochloric acid to

neutralize until phenolphthalein red fades off; transfer into a 1000ml volumetric flask;

dilute with water to the mark; mix well. Store in a glass bottle. It can be stored at 4°C

for 2 years.

6.22.2 Arsenic intermediate standard solution: rho(As) = 1.00mg/L.

Pipette 5.00ml of arsenic standard stock solution (6.22.1) into a 500ml volumetric

flask; add 100ml of hydrochloric acid (6.14); dilute with water to the mark ; mix well. It

can be stored at 4°C for 1 year.

6.22.3 Arsenic standard using solution: rho(As) = 100µg/L.

Pipette 10.00ml of arsenic standard intermediate solution (6.22.2) into a 100ml

volumetric flask; add 20ml of hydrochloric acid (6.14); dilute with water to the mark;

mix well. It can be stored at 4°C for 30 d.

6.23 Selenium standard solution

6.23.1 Selenium standard stock solution: rho(Se) = 100mg/L.

Purchase the commercially available certified reference materials; or weigh 0.1000g

of high-purity selenium powder (6.11) in a 100ml beaker; add 20ml of nitric acid (6.2);

heat at a low temperature to dissolve; cool to room temperature; transfer into a

1000ml volumetric flask; dilute with water to the mark; mix well. Stored in a glass

bottle. It can be stored at 4°C for 2 years.

6.23.2 Selenium standard intermediate solution: rho(Se) = 1.00mg/L.

Pipette 5.00ml of selenium standard stock solution (6.23.1) into a 500ml volumetric

flask; add 150ml of hydrochloric acid (6.14); dilute with water to the mark; mix well. It

can be stored at 4°C for 100 d.

6.23.3 Selenium standard using solution: rho(Se) = 10.0µg/L.

Pipette 5.00ml of selenium standard intermediate solution (6.23.2) into a 500ml

volumetric flask; add 150ml of hydrochloric acid (6.14); dilute with water to the mark;

mix well. Prepare it when it is to be used.

6.24 Bismuth standard solution

6.24.1 Bismuth standard stock solution: rho(Bi) = 100mg/L.

Purchase the commercially available certified reference materials; or weigh 0.1000g

of high-purity mental bismuth (6.12) in a 100ml beaker; add 20ml of nitric acid (6.2);

heat at a low temperature to dissolve completely; cool down; transfer into a 1000ml

volumetric flask; dilute with water to the mark; mix well. Store in a glass bottle. It can

be stored at 4°C for 2 years.

6.24.2 Bismuth standard intermediate solution: rho(Bi) = 1.00mg/L.

Pipette 5.00ml of bismuth stock standard solution (6.24.1) into a 500ml volumetric

flask; add 100ml of hydrochloric acid (6.14); dilute with water to the mark; mix well. It

can be stored at 4°C for 1 year.

6.24.3 Bismuth standard using solution: rho(Bi) = 100µg/L.

Pipette 10.00ml of bismuth standard intermediate solution (6.24.2) into a 100ml

volumetric flask; add 20ml of hydrochloric acid (6.14); dilute with water to the mark;

mix well. Prepare it when it is to be used.

6.25 Antimony standard solution

6.25.1 Antimony standard stock solution: rho(Sb) = 100mg/L.

Purchase the commercially available certified reference materials; or weigh 0.1197g

of antimony trioxide (6.13) that has been dried at 105°C for 2h; dissolve in 80ml of

hydrochloric acid (6.1); transfer into a 1000ml volumetric flask; add 120ml of

hydrochloric acid (6.1); dilute with water to the mark; mix well. Stored in a glass bottle.

It can be stored at 4°C for 2 years.

6.25.2 Antimony standard intermediate solution: rho(Sb) = 1.00mg/L.

Pipette 5.00ml of antimony standard stock solution (6.25.1) into a 500ml volumetric

flask; add 100ml of hydrochloric acid (6.14); dilute with water to the mark; mix well. It

can be stored at 4°C for 1 year.

6.25.3 Antimony standard using solution: rho(Sb) = 100µg/L.

Pipette 10.00ml of antimony standard intermediate solution (6.25.2) into a 100ml

volumetric flask; add 20ml of hydrochloric acid (6.14); dilute with water to the mark;

mix well. Prepare it when it is to be used.

6.26 Argon: purity >= 99.999%.

7.1 Atomic fluorescence spectrometer: Instrument performance indicators shall

comply with specifications of GB/T 21191.

7.2 Element light (mercury, arsenic, selenium, bismuth, antimony).

7.3 Thermostat heating plate.

7.4 Thermostatic water bath device: temperature control accuracy is ±1°C.

7.5 Filtration device: water-system microporous filter membrane with a pore size of

0.45µm.

7.6 Analytical balance: accuracy is 0.0001g.

7.7 Sample container: hard glass bottles or polyethylene bottles (barrels).

7.8 Commonly used laboratory ware: grade-A glass gauges and glassware that

comply with the national standard.

8.1 Sample collection

Sample collection is conducted by referring to the relevant specifications of HJ/T 91

and HJ/T 164. Soluble samples and total quantity samples are collected separately.

8.2 Sample preservation

Sample preservation is conducted by referring to the relevant specifications of HJ

493.

8.2.1 Filterable mercury, arsenic, selenium, bismuth, antimony samples

Filter the sample with 0.45µm filter membrane (7.5) as soon as possible after sample

collection; discard the initial 50ml of filtrate; clean sample bottle with a small amount of

the filtrate; collect the filtrate in the sample bottle. Determine mercury samples; if the

water sample is neutral, add hydrochloric acid in a ratio of adding 5ml of hydrochloric

acid (6.1) per liter of water sample; determine arsenic, selenium, antimony, bismuth

samples; add hydrochloric acid in a ratio of adding 2ml of hydrochloric acid (6.1) per

liter of water sample. Sample preservation period is 14 d.

8.2.2 Total quantity samples of mercury, arsenic, selenium, bismuth, antimony

Except that samples are not filtered after collection, other treatment methods and

preservation period are same as 8.2.1.

8.3 Sample preparation

8.3.1 Mercury

Weigh 5.0ml of mixed sample (8.2.1) or (8.2.2) in a 10ml colorimetric tube; add 1ml of

hydrochloric acid - nitric acid solution (6.17); put on a stopper and mix well; place in

boiling water bath to heat to dissolve for 1h; shake for 1 to 2 times during heating, and

open the stopper to deflate. Cool down; dilute with water to the mark; mix well for test.

8.3.2 Arsenic, selenium, bismuth, antimony

Weigh 50.0ml of mixed sample (8.2.1) or (8.2.2) in a 150ml conical flask; add 5ml of

mixture acid of nitric acid - perchloric acid (6.18); heat on a heating plate until white

smoke emits; cool down. Then add 5ml of hydrochloric acid solution (6.14); heat until

brown smoke disappears; transfer into a 50ml volumetric flask after cooling down;

diluted with water to constant volume; mix well for test.

8.3.3 Blank samples

Use water to replace the sample, prepare blank samples according to the steps of 8.3.

9.1 Instrument adjustment

Adjust the instrument to the optimal working condition according to instrument's

instructions for use. Reference measurement conditions are shown in Table 1.

Table 1 Reference measurement conditions

Elements

Negative

high

voltage/

Light

current/

mA

Atomizer

preheat

temperature/

°C

Carrier

gas flow/

(ml/min)

Shielding

gas flow/

(ml/min)

Integration

method

Hg 240~280 15~30 200 400 900~1000 Peak area

As 260~300 40~60 200 400 900~1000 Peak area

Se 260~300 80~100 200 400 900~1000 Peak area

Sb 260~300 60~80 200 400 900~1000 Peak area

Bi 260~300 60~80 200 400 900~1000 Peak area

9.2 Calibration

9.2.1 Preparation of calibration standard series

9.2.1.1 Mercury

Pipette respectively 0ml, 1.00ml, 2.00ml, 5.00ml, 7.00ml, 10.00ml of mercury

standard using solution (6.21.4) in 100ml volumetric flasks; add 10.0ml of hydrochloric

acid - nitric acid solution respectively; dilute with water to the mark; mix well.

9.2.1.2 Arsenic

Pipette respectively 0ml, 0.50ml, 1.00ml, 2.00ml, 3.00ml, 5.00ml of arsenic standard

using solution (6.22.3) in 50ml volumetric flasks; add respectively 10ml of hydrochloric

acid solution (6.14) and 10ml of thiourea - ascorbic acid solution (6.20); place at room

temperature for 30min (when room temperature is lower than 15°C, place in 30°C

water bath for 30min); dilute with water to constant volume; mix well.

9.2.1.3 Selenium

Pipette respectively 0ml, 2.00ml, 4.00ml, 6.00ml, 8.00ml, 10.00ml of selenium

standard using solution (6.23.3) in 50ml volumetric flasks; add 10ml of hydrochloric

acid solution (6.14) respectively; dilute with water to constant volume; mix well.

9.2.1.4 Bismuth

Pipette respectively 0ml, 0.50ml, 1.00ml, 2.00ml, 3.00ml, 5.00ml of bismuth standard

using solution (6.24.3) in 50ml volumetric flasks; add 10ml of hydrochloric acid

solution (6.14) respectively; dilute with water to constant volume; mix well.

9.2.1.5 Antimony

Pipette respectively 0ml, 0.50ml, 1.00ml, 2.00ml, 3.00ml, 5.00ml of antimony standard

using solution (6.25.3) in 50ml volumetric flasks; add respectively 10ml of hydrochloric

acid solution (6.14) and 10ml of thiourea - ascorbic acid solution (6.20); place at room

temperature for 30min (when room temperature is lower than 15°C, place in 30°C

water bath for 30min); dilute with water to constant volume; mix well.

Mass concentrations of mercury, arsenic, selenium, bismuth, antimony standard

series are shown in Table 2.

Table 2 Mass concentrations of standard series Unit: µg/L

Elements Mass concentrations of standard series

Hg 0 0.10 0.20 0.50 0.70 1.00

As 0 1.0 2.0 4.0 6.0 10.0

Se 0 0.4 0.8 1.2 1.6 2.0

Bi 0 1.0 2.0 4.0 6.0 10.0

Sb 0 1.0 2.0 4.0 6.0 10.0

9.2.2 Drawing of calibration curves

9.2.2.1 Mercury

Reference to measurement conditions (9.1) or use self-determined optimal

measurement conditions; use hydrochloric acid solution (6.15) as the carrier; use

potassium borohydride solution A (6.19.1) as the reducing agent; determine the

atomic fluorescence intensity of mercury standard series from low to high

concentration; take the atomic fluorescence intensity as ordinate and the mass

concentration of mercury as abscissa, to draw the calibration curve.

9.2.2.2 Arsenic, selenium, bismuth, antimony

Reference to measurement conditions (9.1) or use self-determined optimal

measurement conditions; use hydrochloric acid solution (6.15) as the carrier; use

potassium borohydride solution B (6.19.2) as the reducing agent; determine the

atomic fluorescence intensity of each element standard series from low to high

concentration; take the atomic fluorescence intensity as ordinate and the mass

concentration of the corresponding elements as abscissa, to draw the calibration

curve.

9.3 Sample determination

9.3.1 Mercury

Determine the atomic fluorescence intensity of the sample (8.3.1) according to the

same conditions of drawing calibration curves. For samples that exceed the high

concentration points of the calibration curve, determine again after diluting its

digestion solution, the dilution multiple is f.

9.3.2 Arsenic, antimony

Weigh 5.0ml of sample (8.3.2) in a 10ml colorimetric tube; add 2ml of hydrochloric

acid solution (6.14) and 2ml of thiourea - ascorbic acid solution (6.20); place at room

temperature for 30min (when room temperature is lower than 15°C, place in 30°C

water bath for 30min); dilute with water to constant volume; mix well; determine

according to the same conditions of drawing calibration curves. For samples that

exceed the high concentration points of the calibration curve, determine again after

diluting its digestion solution, the dilution multiple is f.

9.3.3 Selenium, bismuth

Weigh 5.0ml of sample (8.3.2) in a 10ml colorimetric tube; add 2ml of hydrochloric

acid solution (6.14); dilute with water to constant volume; mix well; determine

according to the same conditions of drawing calibration curves. For samples that

exceed the high concentration points of the calibration curve, determine after diluting

its digestion solution, the dilution multiple is f.

9.4 Blank test

Determine the blank sample according to the same procedure of determination (9.2).

10.1 Result calculation

The mass concentration rho of the determined element in the sample is calculated

according to equation (1):

Where:

rho - The mass concentration of the determined element in the sample, µg/L;

rho1 - The mas concentration of the determined element in the sample obtained from

the calibration curve, µg/L;

f - Sample dilution multiple (if the sample has been diluted);

V1 - The constant volume of sample after pipetted, ml;

V - The volume of pipetted sample, ml.

10.2 Result presentation

When the determination result of mercury is less than 1µg/L, retain to two decimal

places; when the determination result of mercury is greater than 1µg/L, retain three

significant figures.

When the determination result of arsenic, smashing, bismuth, antimony is less than

10µg/L, retain to one decimal place; when the determination result of arsenic,

smashing, bismuth, antimony is greater than 10µg/L, retain three significant figures.

11.1 Precision

Six laboratories have tested the unified sample that contains mercury, arsenic,

selenium, bismuth, antimony of different concentration levels. Test results of method

precision are shown in Table A.1.

Six laboratories have determined the unified sample that contains mercury of four

kinds of concentrations, i.e. 0.10µg/L, 0.20µg/L, 0.40µg/L, and 0.80µg/L. The relative

standard deviations among laboratories are 3.3%~10.9%, 2.0%~7.5%, 1.5%~3.7%,

and 1.5%~2.9% respectively; the relative standard deviations among laboratories are

8.5%, 2.8%, 1.9%, and 1.4%; the repeatability limits are 0.03µg/L, 0.03µg/L, 0.03µg/L,

and 0.05µg/L; the reproducibility limits are 0.03µg/L, 0.03µg/L, 0.04µg/L, and

0.06µg/L.

Six laboratories have determined the unified sample that contains arsenic of three

kinds of concentrations, i.e. 1.0µg/L, 4.0µg/L, and 8.0µg/L. The relative standard

deviations among laboratories are 6.0%~7.0%, 2.3%~5.4%, and 0.9%~3.4%; the

relative standard deviations among laboratories are 4.1%, 1.6%, and 1.5%; the

repeatability limits are 0.2µg/L, 0.4µg/L, and 0.5µg/L; the reproducibility limits are

0.2µg/L, 0.4µg/L, and 0.6µg/L.

Six laboratories have determined the unified sample that contains selenium of three

kinds of concentrations, i.e. 1.0µg/L, 2.0µg/L, and 8.0µg/L. The relative standard

deviations among laboratories are 4.1%~8.9%, 1.2%~4.9%, and 0.3%~3.6%; the

relative standard deviations among laboratories are 4.1%, 2.6%, and 2.7%; the

repeatability limits are 0.2µg/L, 0.2µg/L, and 0.6µg/L; the reproducibility limits are

0.2µg/L, 0.2µg/L, and 0.8µg/L.

Six laboratories have determined the unified sample that contains bismuth of three

kinds of concentrations, i.e. 0.5µg/L, 2.0µg/L, and 4.0µg/L. The relative standard

deviations among laboratories are 4.8%~8.0%, 2.8%~4.7%, and 2.7%~4.0%; the

relative standard deviations among laboratories are 4.5%, 3.6%, and 1.5%; the

repeatability limits are 0.1µg/L, 0.2µg/L, and 0.4µg/L; the reproducibility limits are

0.1µg/L, 0.3µg/L, and 0.4µg/L.

Six laboratories have determined the unified sample that contains mercury of four

kinds of concentrations, i.e. 0.5µg/L, 1.0µg/L, 2.0µg/L, and 4.0µg/L. The relative

standard deviations among laboratories are 6.4%~11.6%, 3.9%~6.7%, 3.2%~4.7%,

and 1.7%~3.8%; the relative standard deviations among laboratories are 4.4%, 4.5%,

2.6%, and 2.7%; the repeatability limits are 0.1g/L, 0.1g/L, 0.2g/L, and 0.3g/L; the

reproducibility limits are 0.1µg/L, 0.2µg/L, 0.2µg/L, and 0.4µg/L.

11.2 Accuracy

Six laboratories have tested the certifie...

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