Analysis of small samples of fish eggs, rat brain sections and aquatic macro-invertebrates for 78 PCB congeners, hexachlorobenzene, octachlorostyrene, p, p′-DDE and mirex is described. With a gas chromatograph equipped with an Apiezon L coated glass capillary and electron capture detector capable of determining 10 ng/ml of analyte in hexane, a 10 mg sample may be analyzed with a precision of better than ±5% relative standard deviation.