PERFORMANCE OF TXRF and GI-XRF ANALYSES - Total-Reflection X-Ray Fluorescence Analysis and Related Methods - page 209

Figure4.2. A special support of carriers used in the cleaning process. The support is made of
Teflon  and is designed for 24 carriers. Figure from Ref. [4], reproduced with permission.
Copyright1996, John Wiley and Sons.
A simple cleaning process can be recommended that works even without a
time-consuming steaming step. This process is preferably carried out for a set of
several carriers. Figure 4.2 shows a special support made of PTFE and designed
to take 24 different carriers with a diameter of 30 mm. This support is immersed
in a large beaker of 800 ml, half filled with a cleaning agent (e.g., RBS 50 in a
10% dilution; Carl Roth GmbH & Co., Karlsruhe, Germany), which is brought
to a boil and cooled down. The support with the carriers is rinsed with distilled
water and put into a second beaker with Milli-Q water (Millipore Corp.,
Bedford, Massachusetts). This water is boiled and then cooled down to about
40 ° C, after which all carriers and the support are dried with fluff-free precision
wipers (Kimwipes, Kimberly-Clark Corp., Northop, UK). Thereafter, the
support with the carriers is placed in a third beaker with concentrated nitric
acid (p.a. grade, E. Merck, Darmstadt, Germany), boiled for 1 h, cooled down,
and again placed in the second beaker with fresh ultrapure water. It is warmed
up to about 60 ° C for 1 h. Each bath has to be prepared freshly, and the beakers
must be covered appropriately. The boiling must take place in a clean fume
cupboard only used for such a purpose in order to preclude any source of
contamination. The support and carriers must not be touched by hand.
After a last cooling to 40 ° C in a clean bench, the support with the carriers is
lifted out and remaining droplets are wiped down. The dried carriers are put
into clean Petri dishes. Covered by the top, they are kept in a drawer until
needed for analysis. The total procedure takes about 4 h. The clean carriers can
be used for deposition of solid samples without restrictions. For deposition of
liquid samples they must be hydrophobic, otherwise the deposited droplets run
out. Silicon, glassy carbon, boron nitride, and Plexiglas are hydrophobic by