Determination of heavy metals in sea water and in marine organisms by flameless atomic absorption spectrophotometry

Summary In natural waters, heavy metals such as Cd may be present in bound form. It is, therefore, important to consider chemical speciation, especially at low concentrations of the metal where a significant part can be bound by other trace constituents so tightly that it escapes several forms of its determination. It has been demonstrated that even the very strong complexant APDC is unable to leach out all of the heavy metal present in several coastal water samples from the German Bight.This paper describes a new micro method for the determination of total Cd in natural waters. First a small sample is dried in a polypropylene vial. Then the salt residue is heated to 90° C with a mixture of sulphuric and nitric acid for digestion of organic trace constituents (and oxidation of sulphides if present). After dilution subsamples are neutralized using an excess of NaHCO₃ buffer solution. Extraction results are then independent from the possible slight variations of pH. The extractant, a solution of APDC in CCl₄ is stable for weeks, and even the extract is stable for at least 16h. Precision is in the range of 7% at a concentration of 0.066 g Cd l^–1; the detection limit is below 0.002 g l^–1 and can be lowered, if necessary, by enlargement of the original sample. According to the sensitivity of the method the typical blank of 0.022 g Cd l^–1 is high, but it is rather constant (mean variation from the mean: 0.0024 g l^–1).Teil XI: Fresenius Z. Anal. Chem. 299, 206–207 (1979)