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8/2/2019 Determination of Volatiles and PCB's in Transformer Oil Final (1)
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Determination of Volatiles & PCBs
in Transformer Oil by GC/PID
Pittcon March 11, 2012
Paper # 220-16P
Dr. J.N. Driscoll
PID Analyzers, LLC
Sandwich, MAhttp://www.hnu.com
1PID Analyzers, LLC; Sandwich MAhttp://www.hnu.com
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Introduction
Methods were needed to measure volatiles andsemivolatiles (PCBs in used transformer oil).
Initially two columns were used but the methodwas simplified so that only a single column wasnecessary.
The method selected for the volatiles washeadspace
The method for PCBs was dilution followed by sdirect injection
These methods will be described in the followingslides
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Photoionization Detector
R + h = R + + e-
where
R= molecule
h = a photon with an
energy > IP of R
R+ = positive ion
e- = electron
Process
PID
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PID Photo
PID
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GC Conditions Volatiles
PID Analyzers- Model GC322 with PID
GC conditions
Injector- 80C
Oven- Isothermal 60oC
Column 30M x 0.53 mm 0.5 m film Restek RTX-5
Carrier: N2
Flow 7 cc/min, 10 cc/min makeup
Sample size: 1 cc gas-
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GC322
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Headspace Procedure
Using a 40 mL VOA vial-
Add 25-30 mL of transformer oil & seal cap tightly
Heat in oven @60C for 15 min
Remove from oven
Let stand for 15-20 min
Using a 1 cc gas syringe remove a sample through
the septum & inject into GC
Inject a second 1 cc sample
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Determination of Waiting time before
HS sampling
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Blank Transformer oil- Headspace
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Headspace 5 min after removal from
oven
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Headspace 15 min after removal from
oven
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PCBs in Transformer Oil
PID Analyzers- Model GC322 with PID
GC conditions
Injector- 250oC
Oven- Temp. Prog. 160oC for 1 min, 10oC/min
To 225oC, hold 2 min.
Column 30M x 0.53 mm m film Restek R
Carrier: He
Flow 8.5 cc/min, 10 cc/min makeup
Sample size: 0.2uL sample + 0.2 uL hexane (dilution)
Total analysis Time (with cool down): 13 min.
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PID Response PID Sensitivity for Organic Compounds
Sensitivity increases as carbon number increases For n-alkanes, SM= 0.715n-0.457 where SM = molar sensitivity
relative to benzene (benzene= 1.0) and n = carbon number
Sensitivity for alkanes < alkenes < aromatics
Sensitivity for alkanes < alcohols esters < aldehydes < ketones
Sensitivity for cyclic compounds > non cyclic compounds
Sensitivity for branched compounds > non branched compounds
Sensitivity for fluorine substituted < chlorine substituted < brominesubstituted < iodine substituted
For substituted benzenes, ring activators (electron releasinggroups) increase sensitivity
For substituted benzenes, ring deactivators ( electron withdrawinggroups) decrease sensitivity (exception: halogenated benzenes)
PID
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PID Response to PCBs Where Benzene
Sensitivity = 1.0
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1 ppm Arochlor 1016 in hexane -PID
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ppm Arochlor 1016 in Transformer Oil
Arochlor 1016 in transformer oil25 ppm Clean Transformer Oil blank
*1000
-50
-45
-40
-35
-30
-25
-20
-15
-10
-5
0
0:00 2:00 4:00 6:00 8:00 10:00
min
1 2 3 4
*10000
-10
-5
0
5
10
15
0:00 2:00 4:00 6:00 8:00 10:00
min
1
2 34
5
6 7 8 910111213141516 17181920
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Statistics for 25 ppm PCBs in Oil
Total Area
32,379,272.00
41,605,638.00
38,087,952.00
33,710,864.00
41,825,388.00
37,521,823 -ave
4372870-std dev
11.7 CV% 5 replicates
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Comparison of GC/PID chromatograms of PCBs @ 25 ppm
in Transformer Oil
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Conclusions
Two methods were developed using the same
column but with different techniques.
The volatiles required 15 minutes of heating in a
VOC vial before analysis. The analysis time was 3min. the precision was +/- 5%
The SVOC sample was diluted 1:1 with hexane
and injected. We could recognize the differencebetween various PCBs using the PID. The
precision of the method was +/- 11% at 25 ppm.