Liu Jian-ben

The action of Cu2+ on Bacillus thuringiensis growth investigated by microcalorimetry.

By using an LKB-2277 Bioactivity Monitor, ampoule mode, the heat output of Bacillus thuringiensis growth metabolism is determined at 28°C and the effect of Cu2+ on B. thuringiensis growth is studied. Copper is regarded as an essential trace element for life. Its deficiency may be the cause of diseases. Cu2+ at different concentrations has different effects on B. thuringiensis growth metabolism: a low concentration (0–30 μg/ml) of Cu2+ can promote the growth of B. thuringiensis, a high concentration (40–120 μg/ml) can inhibit growth of the bacteria, and a concentration of Cu2+ of up to 130 μg/ml completely inhibits B. thuringiensis growth.

Determination of trace selenium in electrolytic manganese by graphite furnace atomic absorption spectrometry

The effects of four types of graphite tube and five matrix modifiers on the determination of selenium by graphite furnace atomic absorption spectrometry were compared. The results show that platform thernolysis coat graphite tube and magnesium nitrate and cobaltco as matrix modifer can get a high sensitivity and a good recovery. The optimized working conditions and interference in the determination were invesigated. This result is consistent with that of XRF. The recovery is from 100.8% to 102.2%, the relative standard deviation is from 3. 47% to 5.56% (n=9), and the detection limit of selenium is 378 pg (C=44.5 μ/g to 97.3μg/g.). The proposed method can be applied to the rapid determination of selenium in electrolytic manganese.