Before use, tubes were first left in tap water for 3–4 h then 0.3% sodium sulphite solution at 80 °C for 1 min, followed by rinsing in pure water (60 °C – 2 min)
Before use, tubes were first left in tap water for 3–4 h then 0.3% sodium sulphite solution at 80 °C for 1 min, followed byrinsing in pure water (60 °C – 2 min)