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J . N . D R I S C O L L , & J . L . M A C L A C H L A N , P I D A N A LY Z E R S , L L C , S A N D W I C H , M A

&

S TA N L E Y S T E A R N S , VA L C O I N S T R U M E N T S , I N C . , H O U S T O N , T X

HTTP : / /WWW.HNU .COM

AC S NAT IONAL MEET ING, PH IL . , PA AUG. 2012

Monitoring and identification of hazardous air pollutants by fast

capillary gas chromatography with PID/FID detection

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What are Hazardous Air Pollutants (HAP’s)?

There are 187 hazardous air pollutants that range from gases such as ETO to semivolatiles like biphenyl that has a BP of 255.oC

EPA has issued rules & regulations covering more than 80 categories of major industrial sources, such as chemical plants, oil refineries, aerospace manufacturers, and steel mills, as well as categories of smaller sources, such as dry cleaners, & commercial sterilizers

Monitoring of these species will be necessary to comply with EPA regulations

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Introduction

Much of the previous work on “fast GC” utilized short (5M) thin film capillary columns to elute solutes quickly and the result is rapid but inferior separations because of the short column. New technology developed at Valco’s capillary column development center where VICI takes polyimide-coated fused silica (FST) and removes the polyimide layer. Then the (FST) is electroplated with nickel. As a result of the superior heat transfer of the electroplated nickel, we are able to rapidly and efficiently heat and achieve excellent resolution for a 30M capillary column.

These columns can be programmed faster (hundreds of degrees/min)- save 50-90%

The columns can be reliably started a few degrees above ambient These columns cool down faster because of their low mass so savings>

50% Stearns et al (J. Chromat.) have looked at high MW HC but we are

looking at applications for gases & semivolatiles with thick film (5-10m) capillary columns

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Resistively Heated Column

There are two types: a wire wrapped- where a Ni wire is wrapped with a

fused silica column and covered with an insulator B. where the column is coated with Ni then coated

with polyimideThe performance of the latter is somewhat better but

the former has a lower costThese are available in short (5M) or long (30M) capillary

columns in a variety of bonded liquid phasesThey are also available as PLOT column with various

Hayesep packings

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Photo GC 301 C

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Applications

Our applications at PID are in lower MW HC up to C6 solvents and semivolatiles. Here we have to start just above to ambient, a difficult task for most GC’s, w/o subamb. We were able to start @ 23oC (reproducibly), hold 1 min, then prog. to 200oC (at 40C/min.) & hold for 1-2min. to complete. With a thick film column (5 m), we could easily separate gases and light solvents.

For larger molecules, we would need a thin film 0.5 m resistively heated column.

Since these columns can be controlled separately, it is possible to have two different columns and two detectors running at the same time.

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Fast GC Chromatogram for C1 to C6 alkanes

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PID/FID Ratios (f) # of Double Bonds

PID/FID Series Schematic

PID FID Ratios

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Complex LNG sample GC PID/FID (Packed column)

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PID FID Rations for LNG Sample

Peak # Type PH-PID PH-FID PID/FIDRatio

1 IP> 10.2 eV NR OR --

2 IP> 10.2 eV NR OR --

3 IP> 10.2 eV NR OR --

4 Aliphatic 220 54 4

5 Aliphatic 180 57 3.2

6 Aliphatic 88 17 5.1

7 Olefin 52 4 13

8 Aliphatic 104 17 6.1

9 Aromatic- Bz 256 5 51.2

10 Aromatic- Tol

308 4 77

11 Aromatic 132 3 44

12 Aromatic 64 2 32

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PID/FID Capillary Chromatograms of Aromatics

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PID/FID Ratios (note PID scale is set 80x less sensitive than the FID)

# Component PID FID PID/FID Ratio

1 toluene 33 28 94

2 ethyl benzene

20 37 43.2

3 m- xylene 28 36 62

4 tmbenz 39 35 89

5 styrene 27 38 78

6 i prop Tol 15 32 37.5

7 1,2,4 TMT 19 36 42

8 but benz 23 39 47

9 br- benz 29 18 128

10 1,2,4 TMB 13 12 87

11 1,2,3 TMB 12 12 80

12 naphthalene 26 29 72

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Solvents (BTX + MeOH) GC-PID/FID

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Conclusions

We have shown that with low MW HC- there is a >50% reduction in analysis times

There are eight different ramps that can be programmed so that separations can be improved in different sections of the chromatograms

Although we have worked with thick films, these columns are available with thin films for high MW compounds and with PLOT columns for separation of low MW gases. Note that two columns can be run simultaneously for volatiles & semivolatiles or polar and non polar compounds to expand the detection of multiple compounds

PID/FID analyses provides an opportunity to positively identify the solutes during the analytical process. Note the large differences in PID/FID rations in slide #12. These can be used for positive identification of a HAP in the chromatogram