No abstract

Twenty-nine derivatives of fluorene were tested for mutagenic potency in four strains of Salmonella typhimurium with and/or without S9 microsomal activation. The effects of a second functional group on the mutagenic activity of an amino-, nitroso-, and nitrofluorene were correlated with its physical and chemical properties. When the functional group is conjugated by resonance, both inductive and resonance effects are determinants of mutagenic potency. Electron-withdrawing groups such as the halogens (F, C1, Br, and I), nitro, nitroso, and cyano at C-7 increased the mutagenic potency of 2-nitrofluorene. Electron-donating substituents such as hydroxy and amino groups at C-7 decreased the mutagenic potency of 2-amino, 2-nitroso-, and 2-nitrofluorene. Acetylation of a hydroxy or an amino group at C-7 increased the mutagenic potency of 2-nitrofluorene, presumably by decreasing the electron-donating properties of these groups. In contrast, acetylation of a nonresonance-conjugated amino group decreased mutagenic activity. The physical properties of a second functional group are expected to exert their effect(s) at three points in the metabolic activation of 2,7-disubstituted fluorene derivatives: initial reduction of the nitro group (redox effect), stabilization of the hydroxylamine (inductive effect), and stabilization/destabilization of the nitrenium ion (resonance and inductive effects). The relationships between the physical properties of a second functional group and their effects on biological activities of nitro- and aminofluorenes in the Ames Salmonella assay may be of predictive value in a first approximation of both the mutagenic and carcinogenic potency of chemicals with comparable structures such as fluoranthene and biphenyl.

Ion chromatography with suppressed conductivity was used to develop the California Department of Health Services trace concentration method for perchlorate analysis. This article describes an ion chromatography method to analyze trace concentrations of perchlorate in drinking water. Perchlorate was separated from anions commonly found in groundwater and surface water by elution through an AS5 anion exchange column with 120 mmol/L sodium hydroxide + 2 mmol/L ρ‐cyanophenol. Analytes were measured by conductometric detection using signals enhanced by chemical suppression of the conductance from the eluent. A 740‐μL sample injection provided the sample mass necessary to achieve a perchlorate method detection limit of ≤ 1 μg/L and a working range of 2.5–100 μg/L, without sample preconcentration. Interference studies showed that 5.0 μg/L of perchlorate could be measured in the presence of 1,000 mg/L of bicarbonate, chloride, or sulfate. The method was successfully used to survey drinking water wells in California considered vulnerable to perchlorate contamination.