The primary means of cleaning your boats should be by heat treatment.
Carry out the heat treatment of a sample boat according to (1) or (2) described below.
(1) Repeatedly run empty boats using the MA-3 analyzer until the blank value has been stabilized.
(2) Put a boat in a heat-resistant ceramic container such as a crucible, and heat it at 750C for three hours or more using an electric furnace.
Clean boats should be stored in an air tight container to prevent mercury absorption onto the boat surface
If possible, use different boats for high concentrations and for low concentrations.
Occassionally heat treating is not enough. To clean a dirty sample boat that can not be cleaned by heat treatment use the following steps:
(1) First, soak the boat(s) in a neutral detergent, like 1% Alconox, for immersion cleaning, and carry out ultrasonic cleaning for at least 30 minutes.
(2) Then, remove sticking dirt or other foreign material using a swab or a brush
(3) Next, soak and/or sonicate the boat in a 1% nitric acid solution for 30 minutes
Do not use a stronger Nitric Acid Solution greater than 1%
(4) Rinse it sufficiently with pure water and allow it to dry completely