WS/T 635-2018Determination of urinary arsenic speciation - liquid chromatography-atomic fluorescence spectrometry (English PDF)

5.7 Reference material. Arsenite (AsO3)

3-), arsenate (AsO4

3-), monomethyl arsenic (CH4AsO3-), dimethyl arsenic (C2H6AsO2 all are certified standard substances.

6.1 Current Carrying, Hydrochloric Acid Solution (7 93)

Measure 70 mL of hydrochloric acid and dilute to 1000 mL with pure water.

6.2 reducing agent (20 g/L potassium borohydride solution - 3.5 g/L potassium hydroxide solution) Weigh 3.5 g of potassium hydroxide dissolved in 900 mL of pure water, add 20 g of potassium borohydride, dilute to 1000 mL with pure water, mix uniform.

6.3 Formic acid solution (10 90)

Dilute 10 mL of formic acid to 100 mL with pure water.

6.4 Mobile phase (15 mmol/L diammonium phosphate solution)

Weigh 1.98 g of diammonium hydrogen phosphate dissolved in 1000 mL of pure water, adjust the pH to 6.0 with formic acid solution (10 90), ultrasonic degassing 5 min, spare.

6.5 Arsenic Form Standard Solution Preparation

6.5.1 Standard storage solution of arsenic form [rho(As)=10.0 mg/L]. accurately weigh the appropriate amount of arsenite, arsenate, monomethyl arsenic and dimethyl Four kinds of arsenic standard materials of arsenic, prepared with pure water to prepare arsenic form standard stock solution with arsenic concentration of 10.0 mg/L, placed at 4 °C Store in the refrigerator.

6.5.2 Arsenic form mixed standard solution [rho(As)=1.0 mg/L]. accurately transfer 10.0 mg/L of four kinds of arsenic single standard stock solutions respectively Place 1.00 mL in a 10 mL volumetric flask and dilute to volume with pure water.

6.5.3 Arsenic form mixing standard use series solution [rho(As)=0~100.0 µg/L]. accurately transfer a certain amount of 1.0 mg/L arsenic form Standard solution, diluted with pure water to 0.0 µg/L, 2.0 µg/L, 5.0 µg/L, 10.0 µg/L, 50.0 µg/L, 100.0 µg/L the arsenic form mixed standard series uses the solution, which is currently used.

8.1 Pretreatment of the sample

Take 1 mL of uniform urine sample diluted 3 times with pure water, filter with 0.45 µm water filter and measure on the machine. If there is a precipitate in the urine sample, the urine sample was centrifuged for 10 min (8000 r/min), and a certain amount of supernatant was taken according to the above method. If the arsenic form concentration in the sample exceeds the upper limit of the standard curve is determined by diluting the urine sample to a certain ratio.

8.2 Liquid Chromatography Reference Conditions

8.2.1 Column conditions. anion exchange column (column length 250 mm, inner diameter 4.1 mm), or equivalent column. Anion exchange chromatography Bracelet (column length 25 mm, inner diameter 2.3 mm), or equivalent column.

8.2.2 Mobile phase composition. 15 mmol/L diammonium hydrogen phosphate solution (pH = 6.0) as mobile phase, 1.0 mL/min flow rate elution, sample the product is 100 µL.

8.3 Atomic Fluorescence Detection Reference Conditions

The reference conditions for atomic fluorescence detection are as follows.

-- Photomultiplier tube negative high voltage. 280 V;

- arsenic hollow cathode lamp total current. 90 mA;

--Auxiliary cathode lamp current. 40 mA;

-- atomization method. flame atomization;

-- atomizer temperature. medium temperature;

- Argon carrier gas flow rate. 300 mL/min;

-- Argon shielding gas flow. 600 mL/min;

-- reducing agent. 20 g/L potassium borohydride solution - 3.5 g/L potassium hydroxide solution;

- Current carrying. hydrochloric acid solution (7 93).

8.4 Determination of the standard curve

A series of solutions using 100 µL of four kinds of arsenic in a standard mixing solution were sequentially injected into the liquid chromatography-atomic fluorescence spectrometer.

The line is separated and detected, and a chromatogram is obtained, which is characterized by retention time. The concentration of arsenic in the standard series solution is plotted on the abscissa.

Or the peak area is the ordinate and a standard curve is drawn. The standard solution chromatogram is shown in Figure A.1 of Appendix A.

8.5 Determination of sample solution

Pipette 100 µL of the sample solution into a liquid chromatography-atomic fluorescence spectrometer for analysis to obtain a chromatogram, which is determined by the retention time.

Sex. The content of arsenic in the sample solution was obtained from the standard curve. The chromatogram of the sample solution is shown in Figure A.2.

10.1 Detection limit

In this method, the detection limits of arsenite, monomethyl arsenic and dimethyl arsenic are both 0.5 µg/L, and the limit of quantification is 1.5 µg/L; the detection limit of arsenate at 0.8 µg/L, the limit of quantification is 2.4 µg/L.

10.2 Precision

Six laboratories performed 6 repeated measurements on urine samples containing arsenic in the form of 6.0 µg/L to 400.0 µg/L, and the relative standard deviations were less than 5.0%.

10.3 Accuracy

Accuracy of arsenic morphological components in urine and standardization of recovery methods, and the samples of different concentrations determined by 6 laboratories were added back to the standard.

The yield is between 80% and 120%.