Yet-to-emerge contaminants in the Great Lakes region: Analytical method development and measurement of concentrations in a Great Lakes fish

Persistent, bioaccumulative, and toxic (PBT) substances are a continuing cause of concern because of their effects on environmental and human health. The objectives of this pilot study were (1) to develop a screening method that could be used for the extraction and analysis of a group of 10 PBT compounds selected from the priority lists of Muir and Howard (2007) and (2) to apply those methods to measure the concentrations of these analytes in lake trout collected from Lake Michigan. These compounds included 1,2,3,4,5-pentabromo-6-chlorocyclohexane(PBCCH);1,2,5,6,9,10-hexabromocyclododecane (HBCDD);1,2,3,4,5,5-hexachloro-1,3-cyclopentadiene (HCCPD); 3,4,4'-trichlorocarbanilide (TCCBA); 3,4-dichlorobenzotrifluoride (DCBTF);4-chloro-3,5-dinitrobenzotrifluoride (CDNBTF); triphenylphosphine (TPPine); 2,4,6-tri-tert-butylphenol(TTBP); dodecamethylpentasiloxane (DDMPS); and dodecamethylcyclohexasiloxane (DDMHS). Difficulty was encountered in obtaining reference materials for TTBP and DDMHS. Thus, triphenylphosphite (TPPite) was substituted for TTBP, and DDMHS was omitted from the list. Standard solvent extraction, gel permeation chromatography (GPC),and silica gel chromatography (SGC) methods were applied and modified as necessary for the clean-up preparation of fish samples. This included a serial evaluation of GPC elutants, which indicated the 150 to 350 mL fraction yielded the best results. Subsequently, an evaluation of SGC elutants revealed that the first two fractions combined yielded the best results. After solvent extraction, the quality control and fish samples were analyzed via gas chromatography/mass spectrometry (GC/MS) along with a set of calibration standards. DCBTF, DDMPS, and HCCPD produced symmetrical, well-shaped peaks and well-defined spectra. HBCDD performed acceptably well and was detectable at 10to 50 pg/μL. PBCCH chromatographed well, but it produced two peaks, both of which were detectable at approximately 50 pg/μL. The spectra of the two peaks suggested that the compounds were very similar in structure; the reference material was a technical grade product that could have consisted of a mixture of isomers. CDNTFMB(2-chloro-1,3-dinitro-5-[trifluoromethyl]-benzene)did not chromatograph well and results were quite variable. Both TPPine and TPPite exhibited some degradation during the instrumental analysis. TPPine produced only onepeak, identified as triphenylphosphine oxide (TPPineO); the chromatography was acceptable and the compound was detectable at 50 pg/μL. Triphenylphosphine was detected at 10 ng/μL, although the peak shape was poor and the major component in the chromatogram was TPPineO. Injection of TPPite yielded two peaks, one identified as TPPite, and the second identified as Triphenylphosphate (TPPate). TCCBA was not detected at ppb levels. When injected at ppm levels, several peaks were present in the chromatogram. It was speculated, based on their spectra, that they were fragments of TCCBA. The surrogates indicated that the method was functioning as expected for all of the quality control and fish samples. In the analyses of reagent blanks, DDMPS, HCCPD, TPPate, and TPPineO were present even though they had not been added to the samples. This may indicate contamination in one or more of the reagents, or that some component of the reagents was interfering with the analytes. Although reagent spike recoveries were low or nonexistent, this was expected as several of the compounds were not detected at the spiking level. Similarly, spiked samples recovered low, if at all. Conversely, TPPate recovered up to 700 times higher than the theoretical spike level. In general, spiked sample duplicate recoveries were low or nonexistent. DDMPS recovered well in three of four samples, whereas TPPate recovered extremely high in those same samples. Six of the compounds were detected in one or more tissues from the six lake trout samples. 3,4-DCBTFwas detected, albeit at very low levels in the tissues of two fish, and HBCCD was detected in the muscle of one fish. DDMPS was detected in all tissue samples from all of the fish examined. HCCPD, TPPate, and TPPineO were observed in one or more tissues of all six fish. Given the ostensible PBT nature of these chemicals, further refinement of the analytical methods and examination of these compounds in the Great Lakes environment appear warranted