Versatile and fast gas chromatographic determination of frequently used brominated flame retardants in styrenic polymers.

Two versatile and fast methods to identify and quantify brominated flame retardants (BrFRs) in styrenic polymers were developed. Gas chromatography/mass spectrometry (GC/MS) as well as gas chromatography with electron-capture detection (GC/ECD), both following ultrasonic-supported dissolution and precipitation (USDP), were applied. The substance range includes poly-brominated biphenyls (PBBs) and diphenyl ethers (PBDEs), as well as other commonly used flame retardants (FRs), including two phosphate-based flame retardants. The methods were verified using congener standards and flame-retardant polymer samples. Good recoveries were found. Overall run time for the analysis, including sample preparation, is less than 60 min.

Polybrominated diphenyl ethers and polybrominated biphenyls in sediment and floodplain soils of the Saginaw River watershed, Michigan, USA.

Despite known historical release of polybrominated biphenyls (PBBs; brominated flame retardants) into the Pine River (St. Louis, MI, USA), a tributary of the Tittabawassee River which subsequently forms the Saginaw River and flows into Saginaw Bay-Lake Huron, little is known about spatial patterns of sediment contamination by PBBs in this watershed. In this study, concentrations of two groups of brominated flame retardants, polybrominated diphenyl ethers (summation PBDE; BDE-28, -47, -66, -100, -99, -85, -154, -153, -138, and -209) and PBBs were measured in more than 120 floodplain soil samples, surface sediment samples, and sediment cores collected in 2004 from the Shiawassee River, the Saginaw River, and Saginaw Bay, Michigan. In addition, sediment samples collected in 2002 from the Pine River and the Tittabawassee River were analyzed, to elucidate riverine transport and attenuation of PBBs and PBDEs in this watershed. The mean concentration of summation PBDE decreased from upstream to downstream, from the Shiawassee River and the Tittabawassee River to Saginaw Bay. BDE-209 was the predominant congener, accounting for 79% of the total PBDE concentration in the Shiawassee River and 90% in the Saginaw River. BDE-209 was followed, in order of decreasing abundance, by BDE-47, -99, and -100. The proportions of BDE congeners varied by water body, and by sample type, whether floodplain soil or sediment. High summation PBDE concentrations were found in floodplain soil collected from the Shiawassee River near Chase Lake (55 ng/g, dry weight) and in sediment from the Saginaw River near Middleground Island (49 ng/g, dry weight). There was a significant positive correlation between summation (9)PBDE (tri- to hexa-BDE) and BDE-209 in samples collected from the Shiawassee River and Saginaw Bay, but not in samples from the Saginaw River. Among PBBs, bromobiphenyl congener 153 (BB-153) was found in sediments from the Saginaw River but not in sediments from the Shiawassee River. An elevated concentration of BB-153 (13.5 ng/g, dry weight) was found in floodplain soil collected from the Pine River. The BB-153 concentration in sediment decreased by two to three orders of magnitude, from the Pine River downstream to Saginaw Bay. An elevated concentration of BB-153 (4.7 ng/g) was found in sediment collected from the mouth of the Saginaw River. Surface sediments collected near the mouth of the Saginaw River contained higher concentrations of both PBDEs and PBBs than did the subsurface sediments at these locations.

On-site polymer-coated hollow fiber membrane microextraction and gas chromatography--mass spectrometry of polychlorinated biphenyls and polybrominated diphenyl ethers.

Porous polypropylene hollow fiber membrane coated with a conjugated polymer was used as an on-site sampling device for the extraction of polychlorinated biphenyls and polybrominated biphenyl ethers from coastal sea water samples. The coated hollow fiber membrane was placed in a vial containing the sample, and the target compounds extracted via manual shaking of the vials at the site of sample collection. For each extraction, two fibers were used. After extraction, the fibers with the adsorbed analytes were brought back to the laboratory for further processing. Care was taken to preserve the integrity of the analytes and to avoid contamination during transport; after extraction, the fibers were carefully removed and placed in air-tight crimper vials which were stored in an ice-box. The analytes were desorbed by solvent in the laboratory and analyses were carried out using gas chromatography/mass spectrometry. This method was highly reproducible with relative standard deviations in the range of 1-9%. Recoveries from spiked water samples ranged from 83% to 98%. Low limits of detections between 0.04 and 0.21ngl(-1) were achieved. The extraction efficiency was compared with solid-phase microextraction.

Quantitation of crystalline material within a liquid vehicle using 1H/19F CP/MAS NMR.

A method to detect and quantify a small amount crystalline material within a liquid solution of solubilized material is described. 19F CP-MAS ssNMR was investigated as a technique to detect low levels (0.2 mg/g) of crystalline sodium (2R)-7-{3-[2-chloro-4-(2,2,2-trifluoroethoxy)phenoxy]propoxy}-2-methyl-3,4-dihydro-2H-chromane-2-carboxylate (I) within a solid mixture (with microcrystalline cellulose) and a slurry with a liquid vehicle (capric and caprylic acid triglycerides). The results demonstrate that the area of the 19F CP/MAS signal obtained in 25 min at 25 degrees C is linearly dependent (R2=0.997) on the mass of I within the ssNMR rotor. Slopes of CP-MAS peak area versus mass of I in the rotor were nearly identical for the solid mixture and slurry suspension. Signal-to-noise ratio for the low potency slurry suggest detection and quantitation of 0.1 mg of crystalline I in the rotor, corresponding to 2 mg/g of crystalline material within the slurry suspension.

Accumulation, tissue-specific distribution and debromination of decabromodiphenyl ether (BDE 209) in European starlings (Sturnus vulgaris).

In this study we investigated the accumulation, tissue-specific distribution and possible debromination of BDE 209 in a terrestrial songbird species, the European starling, using silastic implants as a method of exposure. BDE 209 accumulated in the blood of the exposed starlings to a mean peak concentration of 16+/-4.1 ng/ml on day 10. After this peak, there was a decline to 3.3+/-0.4 ng/ml blood at the end of the exposure period of 76 days, which suggests elimination of BDE 209. In the exposed group, the muscle concentrations (461 ng/g lipid weight [lw], 430 ng/g lw) were about twofold those in liver (269 ng/g lw, 237 ng/g lw). In addition to BDE 209, other PBDE congeners, particularly octa- and nonaBDEs, were also present in the muscle and liver, suggesting bioformation from BDE 209. To our knowledge, these results are the first indications for the debromination of BDE 209 in birds.

Effect of Tween 80 and beta-cyclodextrin on degradation of decabromodiphenyl ether (BDE-209) by White rot fungi.

The environmental safety of decabromodiphenyl ether (BDE-209), a widely used flame retardant, has been the topic of controversial discussions during the past several years. Degradation of BDE-209 into lower brominated diphenyl ether congeners, exhibiting a higher bioaccumulation potential, has been a critical issue. White rot fungi are known to degrade a wide variety of recalcitrant pollutants. In this work, white rot fungi were used to degrade BDE-209 in liquid culture medium, and the effects of Tween 80 and beta-cyclodextrin on BDE-209 degradation by white rot fungi were evaluated. On the basis of these results, it appears that BDE-209 could be degraded by white rot fungi, and Tween 80 and beta-cyclodextrin can both increase the biodegradation. The best result in Tween 80 experiments was obtained at a Tween 80 concentration of 500mgl(-1) within 10d, which showed 96.5% (w/w) BDE-209 transformed. Tween 80 at a high concentration will restrain the fungal growth and the degradation of BDE-209. However, beta-cyclodextrin had positive effects both on the BDE-209 degradation and the fungal growth.

Calibration of polyurethane foam (PUF) disk passive air samplers for quantitative measurement of polychlorinated biphenyls (PCBs) and polybrominated diphenyl ethers (PBDEs): factors influencing sampling rates.

PUF disk passive air samplers are increasingly employed for monitoring of POPs in ambient air. In order to utilize them as quantitative sampling devices, a calibration experiment was conducted. Time integrated indoor air concentrations of PCBs and PBDEs were obtained from a low volume air sampler operated over a 50 d period alongside the PUF disk samplers in the same office microenvironment. Passive sampling rates for the fully-sheltered sampler design employed in our research were determined for the 51 PCB and 7 PBDE congeners detected in all calibration samples. These values varied from 0.57 to 1.55 m3 d(-1) for individual PCBs and from 1.1 to 1.9 m3 d(-1) for PBDEs. These values are appreciably lower than those reported elsewhere for different PUF disk sampler designs (e.g. partially sheltered) employed under different conditions (e.g. in outdoor air), and derived using different calibration experiment configurations. This suggests that sampling rates derived for a specific sampler configuration deployed under specific environmental conditions, should not be extrapolated to different sampler configurations. Furthermore, our observation of variable congener-specific sampling rates (consistent with other studies), implies that more research is required in order to understand fully the factors that influence sampling rates. Analysis of wipe samples taken from the inside of the sampler housing, revealed evidence that the housing surface scavenges particle bound PBDEs.

Temporal trends in polychlorinated dibenzo-p-dioxins and dibenzofurans, dioxin-like PCBs, and polybrominated diphenyl ethers in Niagara river suspended sediments.

Archived suspended sediment samples collected over the period 1980-2002 at Niagara-on-the-Lake in the Niagara river were analyzed to assess temporal trends in contaminants associated with historical industrial activities in the watershed (PCDDs/PCDFs, DLPCBs), compared to more modern industrial chemicals (PBDEs). The temporal trends for PCDDs/PCDFs and DLPCBs were generally similar, and showed a general trend toward decreasing concentrations, which was presumably due to implementation of control measures in the Niagara river watershed, including the remediation of hazardous waste facilities. The temporal trend in PBDEs contrasted with those of PCDDs/PCDFs and DLPCBs. Prior to 1988, PBDEs (sum of 16 congeners including deca-BDE) were generally detected at low-ppb concentrations, but showed a trend toward increasing concentrations over the period 1980-1988. After 1988, PBDE concentrations in the Niagara river showed a more rapidly increasing trend to a maximum of approximately 35 ng/g in 1995, with deca-BDE as the predominant congener detected. Samples collected over the period February 2003 to March 2004 at the head and mouth of the Niagara river were also analyzed for PBDEs; in all cases PBDE concentrations were higher at the mouth of the river at the outflow to Lake Ontario, indicating the Niagara river watershed is a source of PBDE contamination to Lake Ontario. However, PBDE concentrations in suspended sediments of the Niagara river were comparable to, or lower than, concentrations in bottom sediments in other industrialized/urbanized areas of the world. Based on these comparisons of global PBDE bottom sediment concentrations, the Niagara river watershed does not appear to be a significant local source of PBDEs to Lake Ontario, and concentrations in suspended sediments appear to be indicative of general PBDE contamination from a contamination of local, regional, and continental sources.

PCBs, PCNs and PBDEs in sediments and mussels from Qingdao coastal sea in the frame of current circulations and influence of sewage sludge.

Influence of current circulation and sewage sludge on spatial distributions of polychlorinated biphenyls (PCBs), polychlorinated naphthalenes (PCNs), and polybrominated diphenyl ethers (PBDEs) in sediments and mussels from the Qingdao coastal sea were investigated. Total concentrations of PCBs, PCNs and PBDEs in sediments ranged 6.5-32.9, 0.2-1.2, and 0.1-5.5 ngg(-1) dry wt, respectively. The maximum concentrations were all found near the Haibo River mouth, affected by sewage sludge input from the river. Under the current system in Jiaozhou Bay the organic pollutants were subject to deposit on the east side of the bay and trapped inside the bay. Sewage sludge was an important source of PCBs, PCNs and PBDEs in the bay and exponentially magnified the enrichment of PCBs. On the other hand, the congener profiles of PCBs in sediments outside the bay may signify an atmospheric source of PCBs. Total Concentrations of PCBs, PCNs and PBDEs in mussels were 61.4-88.6, 9.0, and 13.8 ngg(-1)lipid, respectively. Mussels enriched significantly PCBs, PCNs and PBDEs relative to the sediments. The total toxicity equivalent quantities (TEQs) of PCNs in mussels were generally lower than that of PCBs. The fluxes of the total PCBs and their TEQs have been decreased steadily since 1950s. The lower chlorinated/brominated congeners of PCNs and PBDEs may exhibit a greater tendency due to less lipophilic and thus a greater probability of being affected by the current circulation in the bay.

Characterisation of polymer fractions from waste electrical and electronic equipment (WEEE) and implications for waste management.

There is an increasing interest in the end-of-life management of polymers present in waste electrical and electronic equipment (WEEE). This is mainly due to high recycling and recovery quotas set by the European WEEE directive, which can only be fulfilled by including the plastic fraction in recycling and recovery approaches. Previous studies identified a high material diversity and various contaminants in WEEE plastics, including heavy metals, polybrominated biphenyls (PBB), diphenyl ethers (PBDE), as well as polybrominated dibenzodioxins and dibenzofurans (PBDD/F). These substances are regulated by European directives that limit their levels in marketable products. Consequently, both material diversity and contaminants are strong arguments against material recycling and point to hazardous waste treatment. However, recent developments in the production of flame retardants and electrical and electronic goods aimed to reduce contaminants and material diversity. Thus, the present study summarises updated contaminant levels of plastic fractions of European WEEE, as well as data on materials in waste housing polymers. Material characterisation revealed housing fractions to be interesting sources for polymer recycling, which however has to implement potent material separation and/or bromine elimination techniques. With respect to contaminants, our data indicate an effective phase-out of PBB, but still high levels of PBDE and PBDD/F are found. Sources and implications for the material recycling and thermal recovery approaches are discussed in detail.

[Synthesis and characterization of citric acid mono-polyethyleneoxide nonyl phenyl ether amber diehylene glycoldinitrate diglycollic amide].

In the present paper, citric anhydride was made using citric acid. The citric acid mono-polyethyleneoxide nonyl phenyl ether was synthesized by using citric anhydride and polyethyleneoxide nonyl phenyl ether. Finally, the citric acid mono-polyethyleneoxide nonyl phenyl ether amber diehylene glycol dinitrate diglycollic amide was synthesized by using diethanolamine. The raw material, intermediate and product were characterized by IR. The two absorption peaks at 1866.90 cm(-1) and 1781.08 cm(-1) respectively are both strong, with the latter stronger than the former. It was indicated that citric acid had changed into citric anhydride. The absorption peak at 1736.14 cm(-1) is attributable to the stretching vibration of C==O in ester, and that at 1642.39 cm(-1) is attributable to the stretching vibration of C==O in acidamide. It was indicated that the product was citric acid mono-polyethyleneoxide nonyl phenyl ether amber diehylene glycol dinitrate diglycollic amide. So, the synthesis process conditions were right according to the IR data.

Potentiometric perchlorate determination at nanomolar concentrations in vegetables.

In this work, an expeditious method based on the multi-commutated flow-analysis concept with potentiometric detection is proposed to perform determinations of the emergent contaminant perchlorate in vegetable matrices down to nanomolar concentration. To accomplish the task, a tubular shaped potentiometric sensor selective to perchlorate ion was constructed with a PVC membrane containing 12mmol/kg of the polyamine bisnaphthalimidopropyl-4,4'-diaminodiphenylmethane and 2-nitrophenyl phenyl ether 68% (w/w) as plasticizer casted on a conductive epoxy resin. Under optimal flow conditions, the sensor responded linearly in the concentration range of 6.3×10-7-1.0×10-3mol/L perchlorate. In order to extend the determinations to lower concentrations (4.6(±1.3)×10-10mol/L perchlorate), a column packed with 70mg of sodium 2,5,8,11,14-pentaoxa-1-silacyclotetradecane-polymer was coupled to the flow-system thus enabling prior pre-concentration of the perchlorate. The proposed procedure provides a simpler alternative for the determination of perchlorate in foods, nowadays only allowed by sophisticated and expensive equipment and laborious methods.

Leaching characteristics of polybrominated diphenyl ethers (PBDEs) from flame-retardant plastics.

To investigate the effect of leachant on the leachability of polybrominated diphenyl ethers (PBDEs), we determined the leaching concentrations of PBDEs from flame-retardant plastic samples (TV housings and raw materials before molding processing) that are regarded as a source of PBDEs in landfill sites. The leachants used were distilled water, 20% methanol solution, and dissolved humic solution (DHS) of 1000 mg/l based on organic carbon. The leaching test conditions were a liquid-to-solid ratio of 100:1, and a contact period of five days, with twice-daily agitation in a temperature-controlled room of 30 degrees C without pH or ionic strength control. The leaching concentrations of PBDEs increased with increased content, and were found to be remarkably enhanced when methanol and DHS were used instead of distilled water. The enhancement of leachability in the presence of the latter was attributed to the cosolvency effect, and complex formations between the PBDEs and dissolved humic matter (DHM). PBDE concentrations in the leachate obtained from the leaching test and an actual landfill site revealed a significant presence of congeners below heptabromodiphenyl ethers (H7BDEs), detected in the leachate of the actual landfill, while significant amounts of nonabromodiphenyl ethers (N9BDEs) and decabromodiphenyl ether (D10BDE) were detected in the leachate of the leaching test.

Polybrominated diphenyl ethers (PBDEs) in mussels from selected French coastal sites: 1981-2003.

The present study focused on the retrospective analysis of PBDEs in archived blue mussel (Mytilus edulis or Mytilus galloprovincialis) samples collected over the past 22 years (1981-2003) from coastal areas of France. We have found that PBDE levels in mussels from the English Channel increased markedly from 1981 to 1991-1995, doubling approximately every 5-6 years followed by a levelling off and a possible beginning of a decrease. The rate of the decline of hexa- and hepta-BDE congeners was more rapid than the decline of tetra- and penta-BDEs in these mussel samples. The difference in the course of time of lower and higher brominated PBDE concentrations suggests that the congener profile in the mussel samples changes over time. The increase in PBDE concentrations in the mussel samples contrasts with a concomitant constant decrease of chlorobiphenyls (CBs) in the same set of samples. However, pulse inputs of both groups of organohalogen compounds were determined for the mussel samples collected at the mouth of the Seine estuary and were probably related to riverine inundations and a flushing out of the deposited sediments from the internal estuary into the bay of the River Seine, as well as considerable dredging activities taking place during same years. In France, the highest PBDE concentrations were determined in the mussels from the English Channel, more precisely in the bay of the Seine, and the regional differences in PBDE levels were mainly connected to the difference in anthropogenic urban and industrial environmental pressures. Published data comparing PBDE levels in mussels have shown significant differences in concentrations between North/South America and Europe. This observation further confirms that the PBDE levels in the North American environment are higher than in Europe. However, the data used for this comparison of mussel contamination by PBDEs is still relatively sparse.

Rapid identification of RoHS-relevant flame retardants from polymer housings by ultrasonic extraction and RP-HPLC/UV.

A rapid method was developed for the extraction and identification of RoHS-relevant organic flame retardants in polymer material. Extraction was carried out using ultrasonic supported solvent extraction (USSE) and isopropanol. HPLC separation was achieved using a reversed-phase phenylhexyl-modified column and methanol, containing 2-aminoethanol-buffered, alkaline water. Identification was carried out by scanning UV detection and comparison with a library assembled from spectra of reference substances. The method was used to extract and identify polymer additives in TV and PC monitor housings. The overall runtime required for extraction and chromatographic analysis is less than 10 min. The limits of detection comply with the recommendations set by the German draft law.

Rapid determination of decabromodiphenyl ether in polystyrene by thermal desorption-GC/MS.

A rapid determination of decabromodiphenyl ether (DeBDE) in polystyrene (PS) by thermal desorption (TD)-GC/MS was studied. The TD-GC/MS method using a pyrolysis-GC/MS system allowed the quick quantification of DeBDE in a waste TV back plate composing of a PS flame-retarded with polybrominated diphenyl ethers on the basis of the resulting chromatogram with a ca. 4% relative standard deviation without using any tedious sample pretreatment, such as solvent extraction.

Methodology and determination of tetradecabromo-1, 4-diphenoxybenzene flame retardant and breakdown by-products in sediments from the Laurentian Great Lakes.

Tetradecabromo-1,4-diphenoxybenzene (TeDB-DiPhOBz) is a brominated polyphenyl ether flame retardant (FR) that is known to photolytically degrade to produce lower brominated polybrominated-diphenoxybenzenes (PB-DiPhOBzs), which may be precursors to MeO-PB-DiPhOBzs recently reported in the Great Lakes herring gulls eggs. To our knowledge, there are no reports on TeDB-DiPhOBz or other PB-DiPhOBz by-products in any environmental sample. The present study analyzed for the presence of PB-DiPhOBzs (including TeDB-DiPhOBz) and MeO-PB-DiPhOBzs in surficial sediment from sites in Saginaw Bay in western Lake Huron (n = 7), and in comparison to southern Lake Huron (open water) (n = 5) and Lake Erie (n = 3) sediment collected in the summers of 2012 or 2013. To analyze for possible PB-DiPhOBzs (Br14­Br0), the first known analytical method was developed for extraction and cleanup of sediment samples, and analysis by HPLC­atmospheric pressure photoionization (−)-quadrupole time-of-flight-mass spectrometry. The overall recovery efficiency was optimized to on average 33­104% progressing from Br14- to Br10-PB-DiPhOBzs. Br10- to Br14-PB-DiPhOBz detection and quantification limits ranged from 0.05 to 0.15 ng g(−1) dw and 0.17 to 0.49 ng g(−1) dw, respectively. Although this is the first report, PB-DiPhOBzs (Br14­Br10) and MeO-PB-DiPhOBzs were not detectable in any sediment sample. This included a site near the mouth of the highly FR-contaminated Saginaw River, near the confined disposal facility (CDF) located in Saginaw Bay at Channel-Shelter Island, which receives dredged sediment from the Saginaw River. Our findings suggest sediments from the presently studied sites in the Great Lakes ecosystem are not a sink for TeDB-DiPhOBz and PB-DiPhOBz by-product contaminants.

Spectra and concentration profiles throughout the reaction of curing epoxy resins from near-infrared spectroscopy and multivariate curve resolution methods.

When applied to near-infrared (NIR) data, multivariate curve resolution methods, in particular alternating least squares (ALS), make it possible to calculate the concentration profiles and the spectra of all species involved in the reaction of curing epoxy resins. In this paper, the model reaction between phenyl glicidyl ether and aniline (2:1) was studied at 95 degrees C. A NIR spectrum was recorded every five minutes throughout the eight-hour reaction process. The data display rank deficiency. This problem was overcome by supplying additional information to the system in the form of known spectra of some reactants. The recovered spectra and concentration profiles satisfactorily reproduced the experimental data. In this way, 99.99% of the variance associated with the experimental matrix was reproduced. A value of 0.87% was obtained for lack of fit while the similarity coefficient r between the spectra recovered and the spectra corresponding to the three pure species involved in the reaction were PGE (r = 0.994), aniline (r = 0.994), and tertiary amine (r = 0.999). The maximum and minimum limits associated with the ALS solutions were calculated, which made it possible to limit to a considerable extent the ambiguity that is characteristic of these curve resolution methods.

Reconstructing source polybrominated diphenyl ether congener patterns from semipermeable membrane devices in the Fraser River, British Columbia, Canada: comparison to commercial mixtures.

Semipermeable membrane devices (SPMDs) were placed in the Fraser River near Vancouver, British Columbia, Canada, between August 6 and September 30, 1996. This location is near a large urban and industrial region (population 2,000,000) and is expected to be representative of other large, modern cities. After exposure to the ambient water column, SPMD samples were analyzed for a suite of 36 polybrominated diphenyl ether (PBDE) congeners plus all homologue groups from mono- through hexa-brominated. Observed congener patterns differed significantly from that of the commercial penta- and octa-BDE mixtures. A reconstruction approach was developed based on an aquatic transport model and utilizing published octanol-water partition coefficients, calculated SPMD uptake rates, and predicted water concentrations by using the EcoFate multimedia mass balance aquatic simulation model for the 13 major PBDE congeners. In combination, composite technical mixtures were created by combining commercial penta-BDE mixtures (Bromkal 70-SDE and Great Lakes Chemicals DE-71) with commercial octa-BDE mixtures (Bromkal 79-8DE and Great Lakes Chemicals DE-79) in their relative 2000 North American production volumes. The reconstructed SPMD patterns more closely approximated the composite technical mixtures and suggest that PBDEs in such an industrial region arise primarily from penta- and octa-BDE source mixtures.

Salivary and plaque triclosan levels after brushing with a 0.3% triclosan/copolymer/NaF dentifrice.

The concentration and elimination rate of triclosan in saliva was assessed as part of a six week clinical study which evaluated the antiplaque efficacy of a 0.3% triclosan/PVM/MA copolymer/NaF dentifrice. On day one of the study the concentration of triclosan in whole saliva was determined at various times after dentifrice use for both the triclosan/PVM/MA copolymer/NaF and placebo dentifrice groups. The results indicated that the salivary triclosan levels ranged from 19.7 micrograms/ml at 5 minutes to 1 microgram/ml at 2 hours after use of the 0.3% triclosan dentifrice. The triclosan elimination curve for saliva exhibited a mono-exponential decline with a half-life of 26 minutes. The plaque content of triclosan, one hour after dentifrice use, which was determined at the end of the study, was found to be relatively high (25 micrograms/g) compared to that seen in saliva at the same time (6.2 micrograms/ml). It was concluded that the 0.3% triclosan/PVM/MA copolymer/NaF test dentifrice provided effective delivery and bioavailability of the antiplaque agent, triclosan. This was based on the relatively high salivary and plaque triclosan levels observed and the concomitant reduction in plaque formation seen at the end of the study.