1 Scope
This standard specifies the method for the determination of polydimethylsiloxane in animal and vegetable fats and oils.
This standard is applicable to the determination of polydimethylsiloxane in animal and vegetable fats and oils.
Method I Inductively Coupled Plasma Atomic Emission Spectrometry
2 Principle
The polydimethylsiloxane in the specimen is extracted by 1# aviation kerosene, the silicon content in specimen extracting solution is determined with inductively coupled plasma atomic emission spectrometer and quantitation is realized by external standard method.
3 Reagents and Materials
Unless otherwise specified, the reagents adopted in this method are all analytically pure. The water is Grade 1 water specified in GB/T 6682.
3.1 Reagents
3.1.1 1# aviation kerosene (or the organic solvent that may serve as direct injection sample of inductively coupled plasma atomic emission spectrometer and can dissolve polydimethylsiloxane).
3.1.2 Hydrochloric acid (HCl).
3.1.3 Hydrochloric acid solution (1.37mol/L): measure 114mL of hydrochloric acid and bring the volume with water to 1 000mL.
3.2 Standard substance
Polydimethylsiloxane [(CH3)3SiO(C2H6SiO)nSi(CH3)3, CAS: 63148-62-9], with the purity greater than or equal to 99.0%.
3.3 Preparation of standard solution
3.3.1 Standard stock solution of polydimethylsiloxane (1 000μg/mL): accurately weigh 100.0mg of polydimethylsiloxane and put it into a 50mL beaker, dissolve it with 1# aviation kerosene, then transfer it to a 100mL volumetric flask, bring the volume to the scale and then shake well. This solution may be stored in refrigerator at 4℃ for 12 months.
3.3.2 Standard working solution of polydimethylsiloxane: weigh 5g (to the nearest of 0.01g) of vegetable oils or animal oils or blank fats and oils of hydrogenated vegetable oil (blank fats and oils are those commercially available and free from polydimethylsiloxane) and put it into a 10mL volumetric flask, place those to be melted to 70℃ water bath kettle and dilute with 2mL~3mL of 1# aviation kerosene; transfer 0μL, 40μL, 100μL, 200μL, 300μL and 500μL of standard stock solution of polydimethylsiloxane respectively, bring the volume to the scale with 1# aviation kerosene and shake well. Obtain the standard working solution of polydimethylsiloxane of 0μg/mL, 4μg/mL, 10μg/mL, 20μg/mL, 30μg/mL and 50μg/mL with vegetable oil or animal oil or hydrogenated vegetable oil as substrate. Fats and oils easy for solidification shall be placed into 70℃ water bath and be immediately determined after they are taken out.
4 Instruments and Apparatus
4.1 Inductively coupled plasma atomic emission spectrometer: with organic sampling system.
4.2 Balance: with sensibility of 0.1mg.
4.3 Swirl mixer.
4.4 Ultrasonic oscillator: with heating and temperature regulating device.
4.5 Volumetric flask: 10mL, 25mL and 100mL.
4.6 Plastic centrifuge tube: 15mL and 50mL.
5 Analytical Procedures
5.1 Specimen preparation
Weigh 5g (to the nearest of 0.01g) of specimen and put it into a 25mL volumetric flask, add into 15mL of 1# aviation kerosene and sufficiently mix it well; place it into 70℃ water bath, carry out the ultrasonic extraction for 2h and bring the volume to the scale with 1# aviation kerosene. Then, transfer it to a 50mL plastic centrifuge tube, add into 15mL of 1.37mol/L hydrochloric acid again, sufficiently mix it well and keep it still for layering in water bath; take 10mL of supernatant to a 15mL plastic centrifuge tube for standby application and carry out the reagent blank test simultaneously. Fats and oils easy for solidification shall be placed into 70℃ water bath and be immediately determined after they are taken out.
5.2 Reference conditions of apparatus
They are detailed in Table A.1.
5.3 Plotting of standard curve
Respectively pipet the standard series working solutions into the inductively coupled plasma atomic emission spectrometer, determine the corresponding emission intensity, and plot the standard curve by taking the concentration of polydimethylsiloxane in standard working solution as horizontal coordinate and emission intensity value as longitudinal coordinate.
5.4 Determination of specimen solution
Pipet the blank and specimen solution into inductively coupled plasma atomic emission spectrometer, determine the emission intensity value and obtain the concentration (μg/mL) of polydimethylsiloxane in to-be-determined solution according to the standard curve.
1 Scope
2 Principle
3 Reagents and Materials
4 Instruments and Apparatus
5 Analytical Procedures
6 Expression of Analysis Results
7 Precision
8 Others
9 Principle
10 Reagents and Materials
11 Instruments and Apparatus
12 Analytical Procedures
13 Expression of Analysis Results
14 Precision
15 Others
Appendix A Reference Conditions of Apparatus
