APPARATUS

Eppendorfpipettes

Ionselective electrode for fluoride (Orion)

pH-meter with mV-display

Magnetic stirrer

REAGENTS:

TISAB-III-Buffer : 300g Na-Citrate * 2 H₂O

                     22g Titriplex IV (1,2-Cyclohexylendinitrilotetra-acetic-acid-Monohydrate)

                     60g NaCl

                     make up to 1000 dm³ with aqua bidest.                    

STANDARDS:

IAPSO-seawater standard (theoretical content of fluorid: 69,5 µM)

Stockstandard: NaF-Standard (52,636 mM) (Merck)

Work standards: Dilute the stock-standard with IAPSO in different relations to obtain standards with different concentrations for a calibration.

Calibration area: 69,5- 174,76 µM/l

PROCEDURE:

1000 µl sample or standard are mixed with 1000 µl TISAB-III-Buffer on the magnetic stirrer. After 5 minutes (value has to be constant!) the result can be read in mV.