Analytical chemistry in monitoring the effects of aquaculture: one laboratory's perspective

Abstract

Many pesticides, antibiotics, and therapeutants can be used in aquaculture operations and the selection of these compounds changes frequently. Engineering materials used contain additional chemicals. The large number of chemicals and frequent changes of pesticides make it difficult to develop and implement comprehensive analytical methods validated by interlaboratory tests, as well as to undertake the search for chemicals of potential concern. Consequently, reports are often based on methods of questionable reliability. In some instances it is difficult even to obtain calibration standards of certified purity and even the most trivial quality control procedures, such as duplicate analyses, are frequently not performed. There are no established and validated protocols for collecting and processing samples, particularly of sediment samples. Sediments may be very heterogeneous in the vicinity of aquaculture sites and improper sampling can lead to misleading conclusions. Storage conditions of samples can also affect analytical results. Total organic carbon, loss on ignition, sulphide concentration, and redox potential are general indicators of the concentration of organic compounds in sediments. There are no routine chemical methods for a more detailed characterization of the organic loading. Ultraviolet and visible spectra of dichloromethane and methanol extracts of freeze-dried sediments may contribute to a rapid characterization of major organic compounds in the vicinity of aquaculture sites. The inclusion of ‘‘latent’’ duplicates and spiked samples is a simple quality control measure.