Comparison of an Individual Congener Standard and a Technical Mixture for the Quantification of Toxaphene in Environmental Matrices by HRGC/ECNI-HRMS ERIC BRAEKEVELT, GREGG T. TOMY, AND GARY A. STERN* Freshwater Institute, Department of Fisheries and Oceans, Winnipeg, Manitoba R3T 2N6, Canada Both a technical standard and a recently commercially available standard containing 25 congeners were used to quantify toxaphene in a variety of environmental matrices, using high-resolution gas chromatography/electron capture negative ion high-resolution mass spectrometry (HRGC/ ECNI-HRMS). The purpose was to examine the differences between the two standards and to assess how well the congener standard describes the total toxaphene profile. At a resolving power of ∼11 000 no interferences from other organochlorines were observed. Biotic matrices were enriched in octa- and nonachlorobornanes relative to the technical mixture, whereas abiotic matrices were enriched in hexa- and heptachlorobornanes. The hexa- and heptachlorobornanes were generally overestimated by the weighted response of the technical mixture, whereas the nonachlorobornanes were consistently underestimated. The extent to which the technical mixture over- or underestimates total toxaphene concentrations depends on the distribution of congeners among homologue groups and the abundance of particular congeners. The current 25-congener mixture described only ∼35-75% of the total toxaphene response: more congeners are needed to adequately describe some matrices. Correction factors were developed that will allow laboratories to report reliable concentrations of individual congeners in samples that were quantified using the technical mixture, but they should be applied with caution, as they may be highly instrument dependent. Introduction Toxaphene (camphechlor) was first introduced as a broad- spectrum insecticide in 1945.It was used primarilyon cotton, soybeans, and peanuts and by fishery managers to rid lakes of undesirable fish. Toxaphene has been one of the most heavily used chlorinated pesticides in the world, with total globalproduction since 1950estimated at >1 000 000 tonnes (1).Despite beingbanned in much ofthe industrialized world in the mid-1980s, toxaphene residues are readily detectable in a variety of environmental matrices. Toxaphene can be transported atmospherically and is now a widespread contaminant in the Arctic (2). It is a continued concern because ofitspersistence and high bioaccumulation potential (3). Technical toxaphene is produced by the chlorination of camphene and is a complex mixture of ∼200 compounds, consisting primarily of hexa- to nonachlorinated bornanes as well as small quantities ofunsaturated components such as chlorinated camphenes and bornenes (4). The technical toxaphene mixture isnot completelyresolvable even byhigh- resolution GC columns, and many toxaphene peaks coelute with other chlorinated contaminants, including polychlo- rinated biphenyls (PCBs) and chlordane compounds. Early quantitative methods relied extensively on gas chromatographywith electron capture detection (GC-ECD), which required extensive extract cleanup to reduce interfer- ences from other organochlorine compounds. Increased selectivity was achieved by use of mass spectrometry (MS) in the electron ionization (EI) selective ion monitoring (SIM) mode but lacked sensitivity because of extensive ion frag- mentation (5). Currently, the most common method for toxaphene analysis is GC-MSin the SIM mode under electron capture negative ionization (ECNI) conditions. Totaltoxaphenecan bedetermined bysummingthetotal area of all peaks and subtracting known interferences such aschlordanes(6).Thismethod istime-consuming[although it can be automated (7)] and subject to interference by unknown compounds. The use of high-resolution mass spectrometry (HRMS) eliminates interferences from chlor- danes and PCB-oxygen adducts and the need for extensive mathematical corrections (8). Analysis can be greatly simpli- fied by selecting several “marker peaks” from the technical mixture, which are summed to determine total toxaphene (8, 9). However, many important toxaphene congeners are only minor components ofthe technical material or coelute *Corresponding author phone: (204) 984-6761; fax (204) 984- 2403; e-mail: sterng@dfo-mpo.gc.ca. TABLE 1. IUPAC Names, Andrews-Vetter (AV) Codes, and Other Common Names of Individual Toxaphene Congeners in the Congener Standard IUPAC name a AV code other names 2-exo,3-endo,6-exo,8,9,10-HxCB B6-923 Hx-sed 2-endo,3-exo,5-endo,6-exo,8,9,10-HpCB B7-1001 Hp-sed 2-exo,3-endo,5-exo,8,9,10,10-HpCB B7-1450 2,2,5,5,8,9,10-HpCB B7-495 2,2,5-endo,6-exo,8,9,10-HpCB B7-515 P32, Tox B 2-exo,3-endo,6-exo,8,9,10,10-HpCB B7-1474 2-exo,3-endo,5-exo,6-exo,8,9,10-HpCB B7-1440 2-exo,5-exo,6-endo,8,9,10,10-HpCB B7-1059 2-endo,3-exo,5-endo,6-exo,8,8,10,10-OCB B8-1413 P26, T2, Tox 8 2,2,5,5,9,9,10,10-OCB B8-789 P38 2,2,3-exo,5-endo,6-exo,8,9,10-OCB B8-531 P39, TS2 2-endo,3-exo,5-endo,6-exo,8,9,10,10-OCB B8-1414 P40, TS3 2-exo,3-endo,5-exo,8,9,9,10,10-OCB B8-1945 P41 2,2,5-endo,6-exo,8,8,9,10-OCB B8-806 P42a, Tox A 2-exo,5,5,8,9,9,10,10-OCB B8-2229 P44 2,2,5-endo,6-exo,8,9,10,10-OCB B8-810 P49a 2-endo,3-exo,6-exo,8,8,9,10,10-OCB B8-1471 2-endo,3-exo,5-endo,6-exo,8,8,9,10,10- NCB B9-1679 P50, T12, Tox Ac, Tox 9 2,2,3-exo,5,5,9,9,10,10-NCB B9-718 2,2,3-exo,5-endo,6-exo,8,9,10,10-NCB B9-743 2-exo,3,3,5-exo,6-endo,8,9,10,10-NCB B9-2006 2,2,5-endo,6-exo,8,8,9,10,10-NCB B9-1046 P56 2,2,3-exo,5,5,8,9,10,10-NCB B9-715 P58 2,2,5,5,8,9,9,10,10-NCB B9-1025 P62 a HxCB, hexachlorobornane; HpCB, heptachlorobornane; OCB, octachlorobornane; and NCB, nonachlorobornane. Environ. Sci. Technol. 2001, 35, 3513-3518 10.1021/es0018567 CCC: $20.00 Published 2001 by the Am. Chem. Soc. VOL. 35, NO. 17, 2001 / ENVIRONMENTAL SCIENCE & TECHNOLOGY 9 3513 Published on Web 08/08/2001