A NEW MICROWAVE ACID DIGESTION BOMB METHOD FOR THE DETERMINATION OF TOTAL FLUORINE

A new microwave acid digestion method for total fluorine analysis was compared to the reliable reverse-extraction technique. The commerciall y available Parr bombs which are compatible with microwave heating wer e modified for this purpose. The Mann-Whitney statistical test did not show any significant differences (p>0.05) in the determinations of to tal fluorine in various samples between the two above-mentioned method s. The microwave method also gave high fluorine recoveries (> 97%) whe n fluoride was added to different samples. The great advantage of the microwave acid digestion bomb method is that the digestion under press ure is so aggressive that only a few minutes is needed for complete di gestion (also of covalently bonded fluorine), which reduces the time f or fluorine analysis dramatically, while no loss of fluorine or contam ination from extraneous sources could take place during the ashing pro cedure. The digestion solution was made up of 300 mu l of concentrated nitric acid plus 537 mu l of water. After digestion 675 mu l of simil ar to 8.5 M sodium hydroxide plus 643 mu l of citrate/TISAB buffer was added resulting in an alkaline solution (pH similar to 12) which was finally adjusted to a pH of similar to 5.3 for fluoride determination.