Determination of Cu, Zn, Cd and Pb in fish samples by slurry sampling electrothermal vaporization inductively coupled plasma mass spectrometry

Ultrasonic slurry sampling electrothermal vaporization isotope dilution inductively coupled plasma mass spectrometry (USS-ETV-ID-ICP-MS) has been applied to the determination of Cu, Zn, Cd and Pb in several fish reference samples. NH4NO3 was added to the sample solution to work as a modifier. Since the sensitivity of the elements studied in fish slurry and aqueous solution was quite different, isotope dilution was used for the determination of Cu, Zn, Cd and Pb in reference samples. The influences of instrument operating conditions, slurry preparation, non-spectroscopic and spectroscopic interferences on the ion signals and accuracy and precision of isotope ratio determination were reported. The isotope ratios of each element were calculated from the peak areas of each injection peak. Precision of isotope ratio determination was better than 6%. This method has been applied to the determination of Cu, Zn, Cd and Pb in dogfish muscle reference material (DORM-2), dogfish liver reference material (DOLT-1) and oyster tissue (NIST SRM 1566a). Accuracy was better than 19% and precision was better than 14% with ultrasonic slurry sampling and electrothermal vaporization isotope dilution inductively coupled plasma mass spectrometry. Detection limits estimated from standard addition curves were in the range of 5–50, 200–500, 8–20 and 20–50 ng g−1 for Cu, Zn, Cd and Pb, respectively, in different samples.