Contamination and blank problems are usually negligible. Samples ground in tungsten carbide, however, are usually seriously contaminated with W, Co, and Ta. Small sample can be analyzed. For our lunar work, we routinely analyze 1-50 mg samples. We have analyzed individual glass spheres as small as 50 g.
Matrix effects are minimal.
Most samples are effectively transparent to both neutrons and gamma rays, thus certain types of matrix effects are negligible. The technique is mostly nondestructive. After analysis, the sample is moderately radioactive. Isotope ratios are noticeably altered for some elements. However, we routinely make thin sections of analyzed rock chips for petrographic study and subsequent analysis by electron and ion microprobe.