Principle
In the presence of copper salt, carbon disulfide reacts with diethylamine to produce yellowish brown copper diethylaminodithiocarbamate, which is measured by spectrophotometer at 430 nm wavelength. The reaction formula is as follows:
CS2+2NH(C2H5)2—-(C2H5)2N一CS2H·NH(C2H5)2
2[(C2H5)2N-CS-SH.NH(C2H5)2]+Cu(CH3COO)2→[(C2H5)2N-CS+S]2Cu+2CH3COOH+2NH(C2H5)2
CS2+2NH(C2H5)2—-(C2H5)2N一CS2H·NH(C2H5)2
2[(C2H5)2N-CS-SH.NH(C2H5)2]+Cu(CH3COO)2→[(C2H5)2N-CS+S]2Cu+2CH3COOH+2NH(C2H5)2
Instruments and reagents
Macylab V-1500spectrophotometer
Colorimetric tube with stopper :10 mL with scale, corrected.
Bubble absorption tube; Large (height 225 mm, branch width 80 mm).
Washing cylinder :250 nL.
Gas flowmeter. Air pump.
Prepare a 1cm absorption tank.
The reagents used in the analysis are all in line with the national standard analysis reagent distilled water or deionized water.
Solution of lead acetate: Weigh 10 g lead acetate [Pb(CH3COO)2·3H20] and dissolve in 90 mL distilled water, add 5 mL glacial acetic acid and 10 ml glycerol, and mix thoroughly.
Absorbent solution; Weigh 10mg copper acetate [Cu(CH2COO)2·H20] into a 50 mL small beaker, add a small amount of anhydrous ethanol, stir with a glass rod, dissolve and transfer to a 500 mL volumetric flask, wash the beaker with anhydrous ethanol for 2~3 times, put all the liquid into the volumetric flask, add 5 mL triethanolamine, mix thoroughly, and add 2 more Dilute mL diethylamine to scale with anhydrous ethyl yeast, mix well and store in refrigerator 2-5 ℃.
Carbon disulfide standard storage solution; Add about 10 mL of anhydrous ethanol into a 25mL volumetric bottle, close the cork tightly, and weigh accurately on the analytical balance, then add 1 to 2 drops of analytical pure carbon disulfide, quickly plug, weigh again, dilute with anhydrous ethanol to the scale, shake well, calculate the concentration of carbon disulfide standard reserve solution according to the difference subtractive method, and store in the refrigerator 2-5 ℃.
Carbon disulfide standard liquid; Carbon disulfide standard reserve solution was diluted to 100 ug/mnL with anhydrous ethanol. Preparation before use.
Colorimetric tube with stopper :10 mL with scale, corrected.
Bubble absorption tube; Large (height 225 mm, branch width 80 mm).
Washing cylinder :250 nL.
Gas flowmeter. Air pump.
Prepare a 1cm absorption tank.
The reagents used in the analysis are all in line with the national standard analysis reagent distilled water or deionized water.
Solution of lead acetate: Weigh 10 g lead acetate [Pb(CH3COO)2·3H20] and dissolve in 90 mL distilled water, add 5 mL glacial acetic acid and 10 ml glycerol, and mix thoroughly.
Absorbent solution; Weigh 10mg copper acetate [Cu(CH2COO)2·H20] into a 50 mL small beaker, add a small amount of anhydrous ethanol, stir with a glass rod, dissolve and transfer to a 500 mL volumetric flask, wash the beaker with anhydrous ethanol for 2~3 times, put all the liquid into the volumetric flask, add 5 mL triethanolamine, mix thoroughly, and add 2 more Dilute mL diethylamine to scale with anhydrous ethyl yeast, mix well and store in refrigerator 2-5 ℃.
Carbon disulfide standard storage solution; Add about 10 mL of anhydrous ethanol into a 25mL volumetric bottle, close the cork tightly, and weigh accurately on the analytical balance, then add 1 to 2 drops of analytical pure carbon disulfide, quickly plug, weigh again, dilute with anhydrous ethanol to the scale, shake well, calculate the concentration of carbon disulfide standard reserve solution according to the difference subtractive method, and store in the refrigerator 2-5 ℃.
Carbon disulfide standard liquid; Carbon disulfide standard reserve solution was diluted to 100 ug/mnL with anhydrous ethanol. Preparation before use.
Sample
Sample collection: The water samples were collected from 250 mL small-mouth glass bottles with ground glass stopper. During sampling, the water samples were collected and immersed 20~30 cm below the water surface, so that the water would rise from the bottom and overflow the mouth of the bottle. The glass ground bottle cap was plugged to prevent bubbles in the bottle and aeration.
Preservation of samples; The collected samples should be analyzed immediately. If the analysis needs to be delayed, the samples must be stored at 2~5℃ for two days.
Preservation of samples; The collected samples should be analyzed immediately. If the analysis needs to be delayed, the samples must be stored at 2~5℃ for two days.
6 Measurement Procedure
Aeration absorption device
All glassware shall be installed according to the procedure in Figure 1, and silicone rubber tubes shall be connected at the interface to make the two glass tubes contact with each other.
Draw calibration curve
Add 100 mL distilled water and 100 ug/mL carbon disulfide standard liquid to eight sets of aeration absorption device washing cylinders respectively :0.00, 0.10,0.20,0.40, 0.60,0.80,1.00,1.20 mL. Connect two live core gas sampling tubes for each set of aeration washing cylinders in series according to Figure 1. Add 10 mL of lead acetate solution into the first sampling tube and 10 mL of carbon disulfide absorption solution into the second sampling tube. Connect the air pump and gas flowmeter, and control the flow rate of about 100 mL/min. Aerate for 1 h. Transfer the absorbent solution into a 10 mL stopper colorimetric tube with constant volume.
Spectrophotometry
At the wavelength of 430 nm, the absorbance of the absorbent solution in the colorimetric tube with stopper was measured by using 1 cm absorption tank with anhydrous ethanol as reference.
By deducting the absorbance Ab value of reagent blank (zero concentration) from the value of absorbance As measured by a series of calibration liquid, the corrected absorbance Ar is obtained. The corrected absorbance Ar is taken as the ordinate, and the carbon disulfide content W(g) is taken as the horizontal coordinate to draw the calibration curve, or the regression equation is calculated by the least square method. The concentration is “zero”, which is not involved in the calculation
Ar=- bW+a·┉┉┉┉┉┉（1）
By deducting the absorbance Ab value of reagent blank (zero concentration) from the value of absorbance As measured by a series of calibration liquid, the corrected absorbance Ar is obtained. The corrected absorbance Ar is taken as the ordinate, and the carbon disulfide content W(g) is taken as the horizontal coordinate to draw the calibration curve, or the regression equation is calculated by the least square method. The concentration is “zero”, which is not involved in the calculation
Ar=- bW+a·┉┉┉┉┉┉（1）
Trial assay
Take 100 mL water sample in the wash cylinder (if the content of carbon disulfide in the water sample is high, it can be diluted with distilled water) and connect the aeration absorption device according to Figure 1 for spectrophotometry.
computational formula
The absorbance Ar of carbon disulfide in the sample was calculated by equation (2).
Ar=As-Ab·┉┉┉┉┉┉（2）
As-—sample absorbance
Ab—Blank absorbance。
The content of carbon disulfide w(ug) in the sample can be obtained from the curve or calculated according to Equation (3).
Ar=As-Ab·┉┉┉┉┉┉（2）
As-—sample absorbance
Ab—Blank absorbance。
The content of carbon disulfide w(ug) in the sample can be obtained from the curve or calculated according to Equation (3).
┉┉┉┉┉┉（3）
The concentration of C(mg/L) in the sample was calculated by equation (4).
┉┉┉┉┉┉（4）
Where :Vr — sample volume,mL.
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