Determination of Plasticizer Present in Pvc Sheets Using Soxhlet Extraction and Gc- Ms
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PRACTICE 4: DETERMINATION OF PLASTICIZER PRESENT IN PVC SHEETS USING SOXHLET EXTRACTION AND GC- MS
Practical activity of the Área of Toxicología Universidad Miguel Hernández de Elche Environmental Analytic Methods
OVERVIEW
You will perform a Soxhlet (solid-liquid) extraction with ethanol from a PVC sheet containing bis (2- ethylhexyl) adipate as a plasticizer. After that, the presence of this compound in the extract will be confirmed through GC-MS. Finally, the concentration of the extracted plasticizer will be determined by GC-MS using standard solutions of the plasticizer in chromatograms run with an appropriate internal standard.
OBJECTIVES
To familiarize the students with solid-liquid extraction by Soxhlet
To familiarize the students with the techniques of identification of analytes using gas chromatography coupled to mass spectrometry.
To familiarize the students with the concept of chromatographic internal standard.
To familiarize the students with the quantification of chemicals using chromatographic techniques.
PRECAUTIONS
Specific precautions for this activity
Attention: when working with organic solvents do it with extreme caution and always wear gloves. Organic solvent waste must be deposited in shells intended for this purpose and that will be located in places that indicate the teachers.
The GC-MS device is very sensible device and must be always operated in presence of the teacher. Never run an operation on the system (hardware or software) without supervision.
General precautions for working in the laboratory
General safety rules in any laboratory must be followed. In addition, any specific safety rule in relationship with the activity to be developed must be also followed.
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In case of doubt you must always contact the teacher or head of the laboratory. You must report any anomaly that you realize as damaged material or hazard to other users.
Each student will find in his work place a dossier with the prospectus "Your health comes first" and "Standards of safety and health in laboratories" as well as the brochure edited by the Environmental Office entitled "Information for students in laboratory practice". Moreover, a folder will be available to students in the laboratory with the international safety cards of all chemicals employed in this practice.
EXPERIMENTAL PROCEDURE
1 To weigh approximately 3 g of PVC paste and divided into thin slices with a scalpel.
2 To extract with approximately 100 ml of ethanol during around 18 hours in a Soxhlet extractor.
3 To dry in an oven the extracted PVC and afterwards to weight the resulting material.
4 Measure the final volume of ethanol extract (after it reached room temperature).
5 To dilute the ethanol extract 1:30 yielding a resulting solution containing 50 µM 2-ethyl hexanol.
6 To inject into the GC-MS 5 µl of the resulting extract using the following method:
The program of chromatographic separation shall be as follows:
COLUMN: Zebron (Phenomenex)-Multiresidue 1; 30 m de length; 0.25 mm inner diameter and 0.25 µm particle size. INJECTOR TEMPERATURE: 280 °C TEMPERATURE PROGRAM IN THE OVEN: Step 1: 50-280 °C at 40 °C/minute; step 2: 2.5 minutes a 280 °C. TOTAL FLOW: 24 ml/minute (constant) FLOW IN THE COLUMN: 1.0 ml/minute INJECTION MODE: splitless (without flow division). INJECTION VOLUME: 5 µl
The mass spectrometer detection program shall be as follows:
TEMPERATURE IN THE IONIZATION SOURCE: 230 °C QUADRUPOLE TEMPERATURE: 150 °C RECORDING DATA MODE: SCAN: m/z = 40-375 SIM: m/z = 57, 129 DETECTOR OFF: 3.5 min DETECTOR ON: 7.5 min SOLVENT DELAY: 2.75 minutes
7 To confirm the presence of the plasticizer bis (2-ethylhexyl) adipate by comparing retention times and mass spectra of the problem chromatogram with the chromatogram of the standard displayed below.
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8 To prepare samples the standard bis (2-ethylhexyl) adipate at 150, 100, 75, 50, 25 and 10 µM concentrations in the presence of 50 µM 2-ethyl hexanol as internal standard. Proceed as indicated below.
Vial [µM] µl plasticizer 500 µM µl internal standard 500 µM µl ethanol 1 250 500 100 400 2 200 400 100 500 3 150 350 100 550 4 100 200 100 700 5 75 150 100 750 6 50 100 100 800 7 25 50 100 850 8 10 20 100 880
9 To inject and run calibration samples and the problem solution using a method identical to described above but working in SIM mode monitoring m/z = 129 signal (for plasticizer bis (2- ethylhexyl) adipate and m/z = 57 signal (for internal standard for 2-ethyl hexanol).
FINAL REPORT
To calculate the percentage of bis (2-ethylhexyl) adipate in original PVC sheet using: 1) the PVC sheet weight loss; (2) the concentration of plasticizer in the extract.
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A (2) signal (1)
345678 TIME (minutes)
B 57
signal 83 41 70 43 5556 69 84 98 42 4445 71 82 97 99 112
m / z
C 129
signal 112 147 5557 70 4143 83 101 241 259
m/z Chromatogram and mass spectra of solutions containing 2-ethyl hexanol and bis (2-ethylhexyl) adipate. The chromatogram (panel A) corresponds to a mixture of 500 μM plasticizer and 50 µM internal standard injected and run according to the method described above. Peak 1 (3.1 retention time minutes) corresponds to the internal standard 2-ethyl hexanol while that peak 2 (7.91 retention time minutes) corresponds to the plasticizer bis (2-ethyl hexyl) adipate. B and C panels offer spectra of masses of peaks 1 and 2, respectively, recorded in SCAN mode.
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