Scope of application
When the sampling volume of the extract is 45 mL, the detection limits of methyl mercury and ethyl mercury are 0.
01 ng/L and 0.
02 ng/L, respectively
Second, the principle of the method
The extract was distilled with a distillation apparatus, and the distillate was derivatized with sodium tetrapropyl boride and measured by an alkyl mercury analyzer
Qualitatively by retention time and quantified by external standard method
Reagents and materials
Unless otherwise specified, analytical reagents conforming to national standards are used for analysis, and the experimental water is newly prepared ultrapure water or distilled water
(1) Hydrochloric acid : pure superior grade
(2) Copper sulfate : analytically pure
(3) Acetic acid : pure superior grade
(4) Sodium acetate : excellent grade pure
(5) Sodium tetrapropyl boride: analytically pure
0 g of sodium tetrapropyl boride in 100 mL of KOH solution with a mass fraction of 2% at 0°C, shake well, and dispense into 4 mL brown glass bottles, and then immediately place them in a refrigerator at -18°C for storage and use Temporarily thaw before
(6) Standard solution: standard solution of methylmercury and ethylmercury, ρ=1.
00mg/L, and the solvent is pure water
(7) Concentrated sulfuric acid: pure superior grade
(8) Concentrated nitric acid: pure superior grade
(9) Extractant: Add a mixture of concentrated sulfuric acid and concentrated nitric acid with a mass ratio of 2:1 to ultrapure water (about 2 drops of 1L water) to make the pH 3.
Four, instruments and equipment
(1) Alkyl mercury analyzer: It consists of a purge and trap system, a gas chromatograph, a thermal cracking system, and a cold atomic fluorescence spectrometer
(2) Distillation instrument: fraction collection device with ice bath
(3) Flip the oscillator
(1) Preparation of leaching solution
(2) Steaming letter
Accurately measure 45mL pure water (or sample, need to add 0.
4% HC1) in a distillation flask, add 100mL saturated CuSO 4 solution, add 4.
4mL ultrapure water and 0.
6mL acetic acid/sodium acetate buffer solution with pH 6.
0 to the receiving flask ( 2mol/L), distill at 125°C for 3.
5~4h, distill out about 80% of the distillate (35~36mL), the distillate receiving flask should be placed in a water tank with an ice bath
Pour all the distillate into a 42 mL sample bottle, then add 50 μm of sodium tetrapropyl boride for derivatization, and analyze it on the machine after 20 minutes