Acute and chronic effects from pulse exposure of D. magna to silver and copper oxide nanoparticles.

Aquatic toxicity testing of nanoparticles (NPs) is challenged by their dynamic behavior in test suspensions. The resulting difficulties in controlling and characterizing exposure concentrations are detrimental to the generation of concentration-response data needed for hazard identification of NPs. This study explores the applicability of short-term (1, 2 and 3h) pulse exposures as means to keep the exposure stable and at the same time disclose acute and chronic effects of AgNPs and CuONPs in D. magna. Dissolution, agglomeration and sedimentation were found to have less influence on exposure concentrations during 1-3h pulses than for 24-48h continuous exposures. For AgNPs, preparation of test suspensions in medium 24h before toxicity testing (aging) increased stability during the short-term pulses. In pulse tests, organisms were exposed to the test materials, AgNPs and CuONPs for 1, 2 and 3h, and afterwards transferred to clean medium and observed for 48h (post-exposure period) for acute effects and for 21 d for chronic effects. AgNO3 and CuCl2 were used as reference materials for dissolved silver and copper, respectively. For all test materials, a 3h pulse caused comparable immobility in D. magna (observed after 48h post-exposure) as 24h continuous exposure, as evidenced by overlapping 95% confidence intervals of EC50-values. In the 21 d post-exposure period, no trends in mortality or body length were identified. AgNP and AgNO3 pulses had no effect on the number of moltings, days to first live offspring or cumulated number of offspring, but the number of offspring increased for AgNPs (3h pulse only). In contrast, CuONP and CuCl2 pulses decreased the number of moltings and offspring, and for CuONPs the time to first live offspring was prolonged. After CuONP exposures, the offspring production decreased more with increasing concentrations than for CuCl2 exposures when taking the measured dissolved copper into account. This indicates a nanoparticle-specific effect for CuONPs, possibly related to the CuONPs accumulated in the gut of D. magna during the pulse exposure. Pulse exposure is an environmentally relevant exposure scenario for NPs, which for AgNPs and CuONPs enables more stable exposures and cause acute immobility of D. magna comparable to continuous 24h exposures. Pulse exposure is likely relevant and applicable for other toxic and dissolving metal NPs, but this requires further research.

Ultrasonic extraction of veterinary antibiotics from soils and pig slurry with SPE clean-up and LC-UV and fluorescence detection.

A simple and rapid analytical method is presented in which the three veterinary antibiotics oxytetracycline (OTC), sulfachloropyridazine (SCP) and tylosin (TYL) are simultaneously extracted and determined in four different soils. Extractions were carried out by a combination of ultrasonic agitation and vortex mixing using a mixture of methanol, EDTA and McIlvaine buffer at pH 7 as the extractant solution. The extracts were then cleaned-up by a tandem solid phase extraction (SPE) method using an Isolute SAX anion exchange cartridge to remove natural organic matter and an Oasis HLB polymeric cartridge to retain the study compounds. Analysis was by HPLC-UV with additional fluorescence detection for SCP. Recoveries were in the range 68-85% for SCP in all soil types, 58-75% for OTC in sandy soils, 27-51% for OTC in clay containing soils, 74-105% for TYL and 47-61% in a clay soil. OTC and SCP were also extracted from liquid pig manure using a mixture of EDTA and McIlvaine buffer at pH 7 with ultrasonic agitation and vortex mixing with SPE clean-up and HPLC-UV analysis. Recoveries were greater than 77% and 58% for OTC and SCP, respectively. Limits of detection were 18mugkg(-1) for OTC and SCP and 40mugkg(-1) for TYL in soils and 70mugL(-1) for OTC and 140mugL(-1) for SCP in pig slurry.