GB/T 36384-2018Determination of mercury in inorganic chemical product—Atomic fluorescence spectrometry (English PDF)

7.1 Pre-cleaning of Glass Instruments

Before usage, glass vessels and PTFE digestion inner tank, which are about to be used in test, shall be soaked in nitric acid solution for 24 h. Then, use water to rinse them.

7.2 Preparation of Test Solutions

Test solutions shall be prepared in accordance with the stipulation in relevant product standards.

7.3 Sample Pre-treatment Method

Sample pre-treatment method shall refer to Appendix A.

7.4 Standard Curve Drawing

Respectively transfer 0.00 mL, 2.00 mL, 4.00 mL, 6.00 mL and 8.00 mL of mercury standard using solution; place them into 5 100 mL volumetric flasks. Respectively add 5 mL of hydrochloric acid; dilute to the constant volume, then, mix it up. In this series of solutions, mercury (Hg) mass concentration shall respectively be 0.00 µg/L, 1.00 µg/L, 2.00 µg/L, 3.00 µg/L and 4.00 µg/L. Standard solutions can also be prepared in accordance with the practically determined mercury content.

After the instrument is stabilized, use potassium borohydride (or sodium borohydride) solution as the reducing agent; take hydrochloric acid solution as the carrier solution.

Under the optimal working conditions of the instrument, determine the fluorescence value of the standard solution. Take the measured fluorescence value as the y- coordinate; take the corresponding mercury mass concentration (µg/L) as the x- coordinate; draw a standard curve.

7.5 Test

A.1 Open Container Digestion Method

Heat up and digest samples and reagents on a heating plate or electric furnace through an open container.

A.2 Sealed Container Digestion Method

In a sealed container (generally, PTFE material), use acid or other reagents to conduct wet digestion under raised temperature and pressure.

A.3 Microwave Digestion Method

Under the effect of microwave and the condition of sealed pressurization, mix up sample and acid, till they are completely digested.

A.4 Alkali Melting Method

Use alkali melting reagents, such as lithium metaborate, lithium tetraborate, sodium carbonate, sodium hydroxide, sodium peroxide, and corresponding fluoride of potassium salt and alkali metal (for example, potassium bifluoride); mix up with sample; melt them at high temperature.