MEPS 287:251-253 (2005)  -  doi:10.3354/meps287251

ABSTRACT: Enrichment of the stable isotopes ¹³C and ¹⁵N across trophic levels is a commonly used tool in studies on organic matter flow and food webs. However, there is still no accepted standard for pre-analysis sample preparation. Thus, potential methodological bias in single studies may hamper comparability and scalability of data from different sources. Sample CaCO₃ content introduces a positive bias in δ¹³C measurements and a negative bias in δ¹⁵N measurements. The acidification of samples to remove inorganic carbonate significantly reduces both δ¹³C and δ¹⁵N. As a standard procedure we recommend (1) acidifying samples with as little hydrochloric acid (HCl) as possible using the drop-by-drop technique, and (2) restraining from rinsing after HCl application.

KEY WORDS: Isotope signatures · Carbonates · Sample acidification