The detection of environmentally important polychlorinated aromatics by ion mobility spectrometry (IMS) was investigated. Single polychlorinated biphenyl (PCB) isomers (congeners) having five or more chlorine atoms were reliably detected in isooctane solution at levels of 35 ng with a Barringer IONSCAN ion mobility spectrometer operating in negative mode; limits of detection (LOD) were extrapolated to be in the low ng region. Mixtures of up to four PCB congeners, showing characteristic multiple peaks, and complex commercial mixtures of PCBs (Aroclors) were also detected. Detection of Aroclors in transformer oil was suppressed by the presence of the antioxidant BHT (2,6-di-t-butyl4-methylphenol) in the oil. The wood preservative pentachlorophenol (PCP) was easily detected in recycled wood shavings at levels of 52 ppm with the IONSCAN; the LOD was extrapolated to be in the low ppm region

Ritchie, Robert K.

Rudolph, Andreas

English

NASA Technical Reports Server

N95- 33279
ENVIRONMENTAL APPLICATIONS FOR
ION MOBILITY SPECTROMETRY
Robert K. Ritchie and Andreas Rudolph
Barringer Research Limited
304 Carlingview Drive, Rexdale, ON, Canada M9W 5G2
ABSTRACT
The detection of environmentally important polychlorinated aromatics by ion mobility
spectrometry (IMS) was investigated. Single polychlorinated biphenyl (PCB) isomers
(congeners) having five or more chlorine atoms were reliably detected in isooctane solution at
levels of 35 ng with a Barringer IONSCAN ion mobility spectrometer operating in negative
mode; limits of detection CLOD) were extrapolated to be in the low ng region. Mixtures of up to
four PCB congeners, showing characteristic multiple peaks, and complex commercial mixtures
of PCBs (Aroclors) were also detected. Detection of Aroclors in transformer oil was suppressed
by the presence of the antioxidant BHT (2,6-di-t-butyl-4-methylphenol) in the oil. The wood
preservative pentachlorophenol (PCP) was easily detected in recycled wood shavings at levels of
52 ppm with the IONSCAN; the LOD was extrapolated to be in the low ppm region.
INTRODUCTION
The Barringer IONSCAN ion mobility spectrometer is a proven instrument for the
detection of trace amounts of explosives and illicit drugs. Current research efforts at Barringer
are aimed at new IONSCAN applications, including the analysis of environmentally important
compounds. IONSCAN systems require minimal or no sample preparation, are easy to use, and
are very selective towards high electron affinity compounds such as polychlorinated aromatics.
This presentation describes initial research to develop the IONSCAN into a rapid and on-site
PCB and PCP detector.
Polychlorinated Biphenyls
PCBs are non-flammable, non-conductive, chemically quite inert, and have high boiling
points; these properties make the commercial Aroclor mixtures desirable for use as insulator
fluids or oil additives in electrical utility equipment such as transformers and capacitors.
Unfortunately they have also been identified as major environmental pollutants, because high
application temperatures can generate dangerous levels of dioxins and chlorinated dibenzofurans
in the insulating fluids. Programs to remove PCBs from service usually either replace the whole
transformer assembly (in case of high PCB content), or exchange the PCB containing oil with
clean fluids (in case of lower PCB content). The present cutoff level for transformer replacement
vs. oil exchange in Ontario is 50 ppm PCB in the oil. Analysis methods able to detect PCBs at
levels below 50 ppm are needed to select the appropriate PCB removal action. 1
PCB analysis is usually carried out by expensive and time consuming GC or GC/MS
techniques. Recently, immunoassay 2 and colorimetric techniques aimed at on-site analysis have
been developed; however, these require several handling and analysis steps, and are prone to
interferences from other chlorinated organics or inorganic chlorides.
193
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Wood Preservatives
Growing environmental awareness has led to a different attitude towards preservative-
treated wood. It constitutes hazardous waste at the end of its life cycle, and it cannot be burned
or landfilled due to release of the potentially dangerous preservatives. Manufacturers and users
of this wood, faced with "cradle-to-grave" responsibility for these products, are looking for
disposal alternatives. 3 Recycling is one important possibility, and in the case of wooden utility
poles can result in almost complete recovery of the preservative (mostly creosote or PCP).
The patented TWT Technologies recycling process first removes the outer preservative-
containing layer from the pole, and the somewhat smaller pole can then be reused, possibly for
less demanding applications. The outer layer is subjected to a precisely defined heat treatment,
dependent on the preservative used, which reclaims the preservative by distillation, and also
produces a clean wood shaving product. 4
Operational requirements are that the preservatives be identified before processing, and
that the clean wood shaving product be declared non-hazardous (<40 ppm PCP, possibly
reducing to 5 ppm). Fast, low-cost altemative methods to GC/MS are required, and again IMS
appears to be a promising technique. 5
EXPERIMENTAL METHODS
Table 1 details the analysis conditions that were employed on a Barringer IONSCAN
Model 350 for the analyses of PCBs and PCP.
Table 1
PCB Analysis PCP Analysis
Negative" Negative"
No Yes
115°C 120°C
300°C 300°C
300°C 300°C
Ion Mode
Chloride Reactant Addition
Drift Tube Temperature
Inlet Temperature
Desorber Temperature
• explosives mode
PCB standard solutions (35 Ixg/ml in isooctane) were obtained from AccuStandard. Of
the 209 different congeners, the following were chosen for analysis: 2-Chlorobiphenyl (#1),
3,3'-Dichlorobiphenyl (#11), 2,4,5-Trichiorobiphenyl (#29), 2,2'4,4'-Tetrachlorobiphenyl (#47),
2,3',4,5',6-Pentachlorobiphenyl (#121), 2,2',3,3',6,6'-Hexachlorobiphenyl (#136),
2,2',3,4,5,5',6-Heptachlorobiphenyl (#185), 2,2',3,3',4,4',5,5'-Octachlorobiphenyl (#194),
2,2',3,3',4,4',5,5',6-Nonachiorobiphenyl (#206), and Decachlorobiphenyl (#209). The numbers in
parentheses represent the Ballschmiter-Zell numbering method.
Aroclor standard solutions in Volt-Esso 35 (a hydrocarbon transformer oil) and in
isooctane were provided by Ontario Hydro and Barringer Laboratories, respectively. The
following Aroclors were investigated: Aroclor 1254 (54% chlorine by weight, 75 ppm in Volt-
Esso 35, and 35 ktg/ml in isooctane) and Aroclor 1260 (60% chlorine by weight, 50 ppm in Volt-
Esso 35, and 5 mg/ml in isooctane). BHT was available in-house.
1 Ixl aliquots of the PCB or Aroclor solutions in isooctane were applied to a standard
194
IONSCANTeflonfilter,andthesolventwasallowedtoevaporate(ca.30s)before IMS analysis.
Aroclor analysis from transformer oil was carried out by applying ca. 10 IJ.l of the oil solutions
onto a standard Teflon filter, followed by desorption.
PCP samples supplied by TWT Technologies included a 5% solution in oil (a typical
solution used in applying PCP to utility poles), and wood shavings containing 52 ppm PCP.
Barringer Ionscan System Manager Software Version 2.209 was used to acquire and
handle the data.
RESULTS AND DISCUSSIONS
Polychlorinated Biphenyls
PCBs have been investigated by IMS by Karasek et al. as early as 1971. _'7 He identified
the species giving rise to the observed peaks as (C12H_o.,Cl_)(H20)H + for the positive ions and as
(C12Hto.,C1,)- for the negative ions. He also noted that the response of his instrument to the PCBs
increased with degree of chlorine substitution in the negative mode and decreased in the positive
mode, both due to increasing electron affinity with higher degree of chlorine substitution.
Under our analysis conditions, the PCBs with less than five chlorine atoms did not lead
to an IONSCAN response, but the PCBs containing five or more chlorine atoms gave strong
signal responses for 35 ng PCB. Typical plasmagrams and growth curves (the signal response
plotted vs. desorption time) are shown in Figures 1 - 4. (Note: Since the negative mode in the
IONSCAN is the explosives mode, all figures illustrations are titled Explosives Plasmagrams)
The results are summarized in Table 2.
Table 2
PCB Ko Drift Time Peak Area" Max. Peak Estimated
(ms) Height b LOD (ng)
Penta-C1 1.1813 15.265 288 320 <5 ng
Hexa-C1 1.1572 15.566 49 70 #
Hepta-C1 1.1004 16.373 396 371 <5 ng
Octa-C1 1.0443 17.267 274 238 <5 ng
Nona-C1 1.0182 17.734 389 244 <5 ng
Deca-C1 0.9964 18.127 221 193 <5 ng
# see text " in digital units * ms b in digital units
(1 digital unit corresponds to ca. 1.4 x 10 9 ions)
Unlike Karasek, we did not observe an increase of response with higher chlorine
substitution. All PCBs investigated gave rise to single peak plasmagrams with a reasonable
correlation between inverse reduced mobility (1/K_) and molecular mass as shown in Figure 5.
The growth curves show that the PCBs desorb relatively quickly under the conditions used,
despite their high boiling points. The relatively poor response to the hexachlorobiphenyl is likely
to be due to an impurity in this standard suppressing the ionization of the biphenyl. From Table
2 data, limits of detection (LOD) for the single PCB isomers are estimated to be in the low ng
region.
195
Figures6- 8depictplasmagramsof examplesof binary, temary, and quatemary mixtures
of PCBs (35 ng for each individual compound) and show the expected multiple peaks. Unless
not available due to partial peak overlap, the integrated and maximum peak heights of each
component in the mixtures were calculated and compared to the equivalent data from the single
isomer analysis; the data are listed in Table 3. There is not an appreciable degree of suppression
of the responses if mixtures are analyzed except in mixtures containing the hexachlorobiphenyl
where the impurity in that solution seems to suppress responses of the other isomers as well. The
comparisons are also less reliable if there is peak overlap.
Figures 9 and 10 show Aroclor 1254 and Aroclor 1260, respectively, analyzed from
isooctane solutions. Aroclors are highly complex mixtures of PCBs, and the plasmagrams show
peaks that can be interpreted as sums of the individual responses. Based on the results of the
single PCB isomer analyses, the observed peaks in the plasmagram of Aroclor 1254 can be
assigned to pentachlorobiphenyls (peak 110), and hexachlorobiphenyls or possibly a mixture of
hexa- and heptachlorobiphenyls (peak 111). In the analysis of Aroclor 1260, the peaks 120 - 123
are most likely derived from penta-, hexa-, hepta-, and octachlorobiphenyls, respectively. The
distribution of the peaks reflect the different components in these Aroclors, with 1260 having a
higher proportion of more substituted PCB isomers. It is thus possible to distinguish different
Aroclors with an IONSCAN, without the need for a lengthy GC proftling analysis.
IMS analysis of blank (unspiked) Volt-Esso 35 transformer oil, shown in Figure 11,
reveals the presence of a large peak (peak 100). Such a large peak must be due to an additive,
since Volt-Esso 35 is a hydrocarbon oil, and hydrocarbons do not give good responses in IMS.
Further investigation confirmed that the oil contains 0.03% of 2,6-di-t-butyl-4-methylphenol
(BHT), a common antioxidant. The plasmagram of BHT is shown in Figure 12, confirming that
this additive to Volt-Esso 35 is responsible for the large peak. Unfortunately presence of this
compound in PCB containing oil suppresses the ionization of PCBs by an order of magnitude, as
demonstrated in the plasmagram of Volt-Esso 35 spiked with 350 ng of heptachlorobiphenyl
(Figure 13). IMS data on transformer oil samples are summarized in Table 4.
Figures 14 and 15 show plasmagrams of Aroclors 1254 and 1260, respectively, dissolved
in Volt-Esso 35. Again it can easily be seen by comparison with Figures 9 and 10 that the
presence of BHT suppresses any PCB response. Further research will be conducted into ways to
eliminate the interference and suppression from BHT, e.g. possibly a quick sample filtration to
selectively adsorb BHT on basic media.
196
Mixtureof
PCBs
(#of C1)
CompoundsInt.Peak
Area"
Table 3
Max. Peak
Height b
Individual
Int. Peak
Area"
Individual
Max. Peak
Height b
5+6
5+7
5+8
5+9
5+10
6+7
7+8
8+9
9+10
5+7+9
7+8+10
8+9+10
5+7+8+10
Penta-C1 n.a.
Hexa-C1 n.a.
Penta-C1 187
Hepta-C1 273
Penta-C1 193
Octa-C1 331
Penta-C1 176
Nona-C1 326
Penta-C1 232
Deca-C1 284
Hexa-C1 90
Hepta-C1 152
Hepta-C1 211
Octa-C1 248
Octa-C1 n.a.
Nona-C1 n.a.
Nona-C1 n.a.
Deca-Cl n.a.
Penta-C1 141
Hepta-C1 147
Nona-C1 204
Hepta-C1 223
Octa-C1 252
Deca-C1 168
Octa-C1 n.a.
Nona-C1 n.a.
Deca-C1 n.a.
Penta-C1 119
Hepta-C1 166
Octa-C1 190
Deca-C1 136
83 288 320
59 49 70
209 288 320
244 396 371
304 288 320
204 274 238
278 288 320
243 389 244
305 288 320
202 221 193
89 49 70
149 396 371
284 396 371
172 274 238
111 274 238
133 389 244
148 389 244
98 221 193
232 288 320
185 396 371
165 389 244
256 396 371
139 274 238
122 221 193
103 274 238
70 389 244
53 221 193
208 288 320
166 396 371
117 274 238
107 221 193
• in digital units * ms b in digital units
n.a. not available due to partial peak overlap
197
Table4
35 ng in isooctane 35 ng in Volt-Esso
Compound Peak Max. Peak Peak Max. Peak Peak Max. Peak
Area * Height b Area" Height b Area" Height b
Penta-C1 288 320 # # # #
Hexa-C1 49 70 # # # #
Hepta-C1 396 371 39 62 382 645
Octa-C1 274 238 & & & &
Nona-C1 389 244 & & & &
Deca-C1 221 193 27 49 166 233
350 ng in Volt-Esso
* in digital units * ms b in digital units
# no detection due to direct overlap with BHT & not carried out
Wood Preservatives
Figure 16 shows a plasmagram for the IMS analysis of a 5% PCP solution in oil, and
Figure 17 depicts a plasmagram from wood chips containing 52 ppm PCP. Both demonstrate
that PCP gives rise to strong single peak plasmagrams in the IONSCAN. The weaker adjacent
peak 130 in Figure 17 is most likely a tetrachlorophenol, and a previously conducted GC/MS
analysis of this sample had shown the presence of ca. 3 ppm of this substance.
Figure 17 shows that the LOD for PCP is much lower than 52 ppm; it is extrapolated to
be in the neighbourhood of 1 ppm, making IMS ideally suited for the wood recycling application
for which the PCP levels of product shavings should be less than 40 ppm, or possibly less than 5
ppm.
Further experiments with more samples will be conducted to enable calibration of the
IONSCAN for PCP in the region between 0 and 50 ppm; also, tetrachlorophenols will be
analyzed to confirm the identity of the extra peak in Figure 17.
CONCLUSIONS
It was shown that Barringer's IONSCAN is in principle useful in environmental analysis
since it is able to detect PCBs and PCP at low levels; however, in the case of PCB analysis the
presence of BHT in transformer oil presents a major problem that has to be solved before this
application can be developed any further. On the other hand PCP analysis in wood recycling
applications presents no problems, and the development of this application is continuing.
ACKNOWLEDGMENTS
The authors wish to thank Ron Massey of Ontario Hydro for providing the transformer
oil standards, Andy Murray of Barringer Laboratories for samples of Aroclors in isooctane, and
198
PeterFranshamof TWTTechnologiesfor thePCPandwoodsamples.
REFERENCES
1. Massey, R. Personal communication.
. Harrison, R.O., Carlson, R.E., Weiss, A.J. Analysis of PCBs in Soil, Sediments, and
Other Matrices by Enzyme Immunoassay. Proceedings: 1993 U.S. EPA/A&WMA
Intemational Symposium on Field Screening Methods for Hazardous Wastes and Toxic
Chemicals, Las Vegas, Nevada, pp. 462-471.
. Meil, J. Exploring the Resource - Timber Supplies & Life Cycle Analysis. Canadian
Institute of Treated Wood: Treated Wood Life Cycle Workshop, Toronto, ON, June
1994.
. Fransham, P. Chemical Extraction Processes. Canadian Institute of Treated Wood:
Treated Wood Life Cycle Workshop, Toronto, ON, June 1994.
. Lawrence, A.H. Rapid Characterization of Wood Species by Ion Mobility Spectrometry.
J. Pulp Pap. Sci. 15, J196-J199 (1989).
. Karasek, F.W. Plasma Chromatography of the Polychlorinated Biphenyls. Anal. Chem.
43, 1982-1986 (1971).
. Karasek, F.W., Tatone, O.S., and Kane, D.M. Study of Electron Capture Behaviour of
Substituted Aromatics by Plasma Chromatography. Anal. Chem. 45, 12t0-1214 (1973).
199
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Environment applications for ion mobility spectrometry

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