Two types of automated solid phase extraction (SPE) were assessed for the determination of human exposure to fentanyls in urine. High sensitivity is required to detect these compounds following exposure because of the low dose required for therapeutic effect and the rapid clearance from the body for these compounds. To achieve this sensitivity, two acceptable methods for the detection of human exposure to seven fentanyl analogs and three metabolites were developed using either off-line 96-well plate SPE or on-line SPE. Each system offers different advantages: off-line 96-well plate SPE allows for high throughput analysis of many samples, which is needed for large sample numbers, while on-line SPE removes almost all analyst manipulation of the samples, minimizing the analyst time needed for sample preparation. Both sample preparations were coupled with reversed phase liquid chromatography and isotope dilution tandem mass spectrometry (LC-MS/MS) for analyte detection. For both methods, the resulting precision was within 15%, the accuracy within 25%, and the sensitivity was comparable with the limits of detection ranging from 0.002-0.041ng/mL. Additionally, matrix effects were substantially decreased from previous reports for both extraction protocols. The results of this comparison showed that both methods were acceptable for the detection of exposures to fentanyl analogs and metabolites in urine.
The Vibrio fischeri bioluminescence
inhibition assay (Microtox) was slightly modified to use an in-house
diluent containing 2% DMSO and was successfully applied to perform
a rapid toxicity screening of 24 compounds including commercial plasticizers
and chemicals currently studied as potential “green”
plasticizers. Comparison of the EC50 values obtained indicated
that 1,3-propanediol dibenzoate (PrDDB), 1,4-butanediol dibenzoate
(BDDB), and dihexyl maleate (DHM) might not be good candidates as
“green” plasticizers because of their higher toxicity
(EC50 < 1 mg L–1). Results also indicated
that Microtox is a useful technique to better understand the effect
of key structural features on the toxicity of plasticizers. Comparison
of EC50 values of similar compounds having a different
alkyl chain lengths indicated a decrease in toxicity of dibenzoate
plasticizers with respect to increasing alkyl chain size. The Microtox
technique that we adapted to test compounds having low solubility
was proven to be useful to evaluate the toxicity of potential “green”
plasticizers relative to commercial products. However, these results
cannot be used alone to select the best candidates. The Microtox technique
is complementary to biodegradation experiments and plasticizing properties
tests and allows, at the development stage, the screening of a large
number of potential “green” plasticizers on the basis
of their relative toxicity.
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