Suppression of analyte signal in inductively-coupled plasma/mass spectrometry and the use of an internal standard

The signal suppression of ⁹Be, ²⁷Al, ⁶⁴Zn, ⁸⁵Rb, ¹¹⁵In and ²⁰⁸Pb in the presence of increasing amounts of sodium chloride is studied. The suppression does not depend significantly on the analyte element considered. The use of ¹¹⁵In as internal standard thus allows correction for the matrix effect. It is shown that the suppressive effect decreases in the order CsCl>NaCl>NH₄Cl. The use of the internal standard also significantly improves the precision. The signal suppression is probably due largely to an increasing number of extracted ions resulting in a more pronounced space-charge effect.