Perhaps you should try some spelling variations:
ppm decrease » _ decrease (Expand Search), a decrease (Expand Search), pa decreased (Expand Search)
nn decrease » _ decrease (Expand Search), a decrease (Expand Search), mean decrease (Expand Search)
ng decrease » _ decrease (Expand Search), a decrease (Expand Search), we decrease (Expand Search)
50 ppm » 5 ppm (Expand Search)
50 nn » 50 ns (Expand Search), 50 n (Expand Search), 59 nn (Expand Search)
50 ng » 50 mg (Expand Search), 10 ng (Expand Search), 5 ng (Expand Search)

You may be able to get more results by adjusting your search query.

• The words AND, OR and NOT may confuse the search; try adding quotes: "(((( 50 ppm decrease ) OR ( 50 nn decrease ))) OR ( 50 ng decrease ))~".
• Adding a wildcard symbol may retrieve word variants: (((( 50 ppm decrease ) OR ( 50 nn decrease ))) OR ( 50 ng decrease ))*.