The use of the 14‐d earthworm toxicity test to aid in the evaluation of the ecological impact of contaminated soils is becoming increasingly widespread. However, the method is in need of further standardization. As part of this continuing process, the choice of reference toxicants was evaluated. Reference toxicants were rated in relation to the following criteria: (a) reproducibility, (b) low human health hazard, (c) feasibility of measurement, and (d) chemical stability. Potassium chloride (KCl) and ammonium chloride (NH4Cl) were evaluated as possible alternatives to the one currently in common use, 2‐chloroacetamide. Potassium chloride rated the best for the combination of the four criteria, followed by NH4Cl and 2‐chloroacetamide. Coefficients of variation (C.V.s) from control charts of six definitive tests were used to measure reproducibility. The best reproducibility (lowest C.V.) was shown by KCl, followed by NH4Cl and 2‐chloroacetamide. Toxicants ranked KCl < NH4Cl ≪ 2‐chloroacetamide in terms of health hazard; and KCl = NH4Cl > 2‐chloroacetamide in terms of measurement feasibility. Both 2‐chloroacetamide and NH4Cl changed in concentration during testing. Evidence is also presented that 2‐chloroacetamide degrades rapidly during testing, and that, as dead worms decay, ammonification may be adding another toxicant, ammonia, to tests.

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The toxicity of a range of surfactant and surfactant‐related compounds was investigated in the 2‐d whole life cycle bioassay with the rotifer, Brachionus calyciflorus. Compounds were selected to gain an understanding of how structural components, especially the polar head groups, contribute to toxicity. Rotifers were exposed under static test conditions to the 22 compounds for 2d. Exposure concentrations were verified analytically in the test system. Results demonstrate a relationship between alkyl chain length and toxicity within a surfactant class. Between classes, N‐containing amines and quaternary ammonium compounds had greatest toxicity, in general, followed by the nonionic compounds. Anionic compounds were typically least toxic. A good quality (R2 = 0.86), three‐variable, parametric QSAR model was developed using the ADAPT software package. The model contains one variable to account for the contribution of the hydrophobic tail group to observed toxicity (the number of sp3‐hybridized carbons bonded to two other carbons [2SP3]) and two descriptors, the valence‐corrected, fourth‐order cluster index (4XvC) and a count of the number of nitrogens in the molecule (NN), to account for the contribution of the polar head group.

Characterizing the decomposition of electrogenerated species in solution is essential for applications involving electrosynthesis, homogeneous electrocatalysis, and energy storage with redox flow batteries. In this work, we present an automated, multiplexed, and highly robust platform for determining the rate constant of chemical reaction steps following electron transfer, known as the EC mechanism. We developed a generation-collection methodology based on microfabricated interdigitated electrode arrays (IDAs) with variable gap widths on a single device. Using a combination of finite-element simulations and statistical analysis of experimental data, our results show that the natural logarithm of collection efficiency is linear with respect to gap width, and this quantitative analysis is used to determine the decomposition rate constant of the electrogenerated species (k c). The integrated IDA method is used in a series of experiments to measure k c values between ∼0.01 and 100 s–1 in aqueous and nonaqueous solvents and at concentrations as high as 0.5 M of the redox-active species, conditions that are challenging to address using standard methods based on conventional macroelectrodes. The versatility of our approach allows for characterization of a wide range of reactions including intermolecular cyclization, hydrolysis, and the decomposition of candidate molecules for redox flow batteries at variable concentration and water content. Overall, this new experimental platform presents a straightforward automated method to assess the degradation of redox species in solution with sufficient flexibility to enable high-throughput workflows.