Hello.

I am doing selenium analysis by hydride generation and AA. The recovery is not as expected in the control sample (around 40%).

For the pretreatment, equal amounts of concentrated hydrochloric acid (37%) and sample (or standard) were combined and heated to 100°c for 20 min. After heating, allowed to cool to room temperature before being diluted to their final volume with deionized (DI) water. I made with two different volumes: 10 mL of sample + 10 mL HCl diluted to a final volume of 25 mL and 20 mL sample + 20 mL HCl diluted to 50 mL. Each preparation procedure results in a 2.5x dilution of the sample.

The hydride-forming solution consisted of 0.5% NaBH4 (w/v) + 0.05% NaOH (w/v) and HCl 20%.

Could you help me and tell me what I am doing wrong or give me another procedure?