determination of volatiles and pcb's in transformer oil final (1)

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.

determination of volatiles and pcb's in transformer oil final (1)

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