6386
The enhancement of 350 - and 50 - fold in the sensitivity of Pb and Ni were achieved by combination of the slotted tube atom trap - atomic absorption spectrometry with the optimised preconcentration method , respectively .
 Chemical: Pb; Chemical: Ni
Please list all entity words in the text that fit the category.Output format is "type1: word1; type2: word2". 
Option: Chemical 
Text: {0} 
Answer:
 Chemical: Pb; Chemical: Ni