1 Scope
The wood part of GB/T6324 specifies the test method for the determination of trace sulfur in organic liquid products by the microcoulometric method
.
This part of GB/T6324 is applicable to samples with sulfur content in the range of 0.
5 mg/kg to 1000 mg/kg in organic liquid products
.
2 Normative references
The clauses in the following documents become the clauses of this part through the reference of the wooden part of GB/T6324
.
For dated reference documents, all subsequent amendments (excluding errata content) or revisions do not apply to this section.
However, all parties who have reached an agreement based on this section are encouraged to study whether the latest versions of these documents can be used
.
For undated reference documents, the latest version is applicable to this section
.
GB/T6682-1992 Analysis laboratory water specifications and test methods (neqISO3696; 1987)
GB/T8170-1987 Numerical rounding rules
3 Principles of the method
Samples gasification gasification zone cracking tubes and mixed with a carrier gas mixed into the combustion section and combusting with oxygen, the sulfur is converted into sulfur dioxide , with the carrier gas into the titration cell together with the triiodide ion in the electrolyte (the I .
3 - ) occurs The following response:
The I .
3 - + SO .
4 + H 2 O → SO .
3 + 3I - + 2H +
Titration cell triiodide ion (the I .
3 - ) concentration decreases, indicating - the indication of the reference electrode and this change and given bias, compared to the input signal microcoulombs this amplifier, the output voltage is applied to and amplified To the electrolysis electrode, the following reaction occurs at the electrolysis anode:
3I - → the I .
3 - + 2E
Triiodide ion is consumed (the I .
3 - ) supplemented, the consumption of electricity is the time integral of the electrolysis current, the sulfur content in the samples is calculated according to the Faraday's laws of electrolysis
.
4 Reagents
Unless otherwise specified, only use reagents confirmed to be analytically pure and secondary water specified in GB/T6682-1992 in the analysis.
4.
1 Carrier gas: nitrogen, argon or gas, the volume fraction is not less than 99.
5%
.
4.
2 Oxygen; the volume fraction is not less than 99.
5%
.
4.
3 Electrolyte 1; take 0.
5g potassium iodide , add a little water to dissolve, add 4mL acetic acid solution (1+9), dilute with water to 1000mL, put it in a brown bottle, store in a dark and cool place, the use period should not exceed one month, applicable Samples with halogen content less than 60ug/mL, total nitrogen content less than 100ug/mL, and heavy metals (nickel, vanadium, lead, etc.
) content less than 500mg/kg
.
4.
4 Electrolyte 2; take 0.
5g potassium iodide and 0.
6g sodium azide , dissolve in 500mL water, add 5mL glacial acetic acid , dilute to 1000mL with water, put it in a brown bottle, store in a dark and cool place, the use period should not exceed one month
.
Suitable for samples with halogen content less than 10 times the sulfur content, total nitrogen content less than 1000 times the sulfur content, and heavy metals (nickel, vanadium, lead, etc.
) content less than 500mg/kg
.
4.
5 Standard material: Dibenzothiophene (C 6 H 4 C 6 H 4 S), thiophene (C 4 H 4 S) or dibutyl disulfide (C 4 H 9 C 4 H 9 S 2 ), etc.
, quality The score is not less than 98%
.
4.
6 Solvent: isooctane , n-heptane , or hexadecane and the like
.
The integrated value of the solvent without sulfur under the detection conditions is displayed
.
4.
7 Standard stock solution (sulfur content about 1000ng/uL); add a small amount of solvent into a 100mL volumetric flask, weigh out about 0.
58g of standard substance dibenzothiophene (or about 0.
26g for thiophene, about 0.
28g for dibutyl disulfide) , Accurate to 0.
1mg, quantitatively transfer the full-volume bottle towel, dilute to the mark with a solvent, the sulfur content C of the standard stock solution, the value is expressed in ng/uL, calculated according to formula (1):
Where:
m—The value of the mass of the reference material, in grams (g);
n—The mass fraction of sulfur in the reference material;
V 1 —The value of the volume of the solvent, in milliliters (mL) (V 1 =100)
.
4.
8 Standard solution: Use a solvent to dilute the standard stock solution into a series of concentration sulfur standard solutions.
The concentration is represented by C 1 and the unit is ug/uL.
Standard solutions that meet the requirements can also be purchased
.
