Determination of soil cyanide and total cyanide isonicotinic acid-pyrazolone spectrophotometric method (3)

Six, analysis and testing

(1) Drawing of standard curve

Take 8 25mL colorimetric tubes with plugs, add cyanide standard solution 0mL, 0.

(2) Measurement of sample

Take 10.

(3) Blank test

Pipette 10mL of the blank sample to be tested, and measure the absorbance in the same way as the standard solution is drawn

Seven, calculation and presentation of results

(1) Result calculation

Content of the sample (mg / kg), cyanide ion to (the CN ^- ) meter, (1) is calculated according to the formula:

In the formula, w——the content of cyanide or total cyanide (dry weight), mg/kg;

A-the absorbance of the sample;

A _b ——Blank absorbance;

a——The intercept of the calibration curve;

b―The slope of the calibration curve;

m——weigh the mass of the sample, g;

w _dm —— dry matter content in the sample, %;

V ₁ ——Sampling volume of the sample, mL;

V ₂ ——Volume of distillate, mL

(2) Results presentation

When the measurement result is less than 1mg/kg, the result shall retain two decimal places; when the measurement result is greater than or equal to 1mg/kg, the result shall retain three significant digits

8.

(1) The cyanide and total cyanide content of the blank test should be less than the detection limit of the method

(2) At least 10% parallel samples should be made for each batch of samples, and the relative deviation between cyanide and total cyanide should be less than 20%

(3) At least 10% standard addition should be made for each batch of samples, and the standard addition recovery rate of cyanide and total cyanide should be controlled between 70% and 120%

(4) The configuration of the standard series must be at least 5 points, and the correlation coefficient of the standard curve must be greater than or equal to 0.

Nine, matters needing attention

Hydrogen cyanide is volatile, so in the process of sample determination, every step must be operated quickly and operated in a fume hood, and the bottle cap should be tightly closed at any time

Related links: Determination of soil cyanide and total cyanide isonicotinic acid-pyrazolone spectrophotometry (2)