http://www.altcancerweb.com/fluoride/fluoridation-book-1954/determination-f-water.pdf (zirconium and alizarin)

This is a colorimetric method that I've used, it can detect fluoride in drinking water.

Graphite AA may be the best bet if ICP doesn't work. If you need quant.

I had experience with Ion Chramatography (IC) and I got sharp peak of F. I would like to suggest to dilute the sample 1000/100/10 times and measure again.

My first thoughts were to consider ICP/MS. However I just read in Spectroscopy Online that only five elements cannot be directly measured by ICP-MS: hydrogen, helium, fluorine, neon, and argon. The first four are not ionized because their first ionization potentials are higher than that of argon, and the last argon is not measurable in an argon plasma. Sorry I cannot be more helpful but at least you know that this technique will not work.

Neutralize the pH to around pH 7 with NaOH and then use a fluoride selective electrode. Ion-selective potentiometry is probably the most economical method to quantify fluoride at those levels. (see my monograph “Working with Ion-Selective Electrodes”, Springer Publishing Corporation) or the SOP’s from the electrode manufacturers. The failure in Ion Chromatography is because at this pH the fluoride is not present as free fluoride anion, instead complexes of HF, HF and HF2 etc. are present.

feel you should try to precipitate entire chloride using Ag/ Hg salt, centrifuge it ,then u can use supernatant for Ion chromatographic determination, . DIlution of sample beyond 100 times may bring F to below detection limit. so direct dilution of sample may not give desired result. Directestimation of F in concentrated Cl media will overload the column Avoid it for integrity of the IC column

The fluoride selective electrode is a viable option as Karl mentions. Keep in mind that the NaOH could introduce additonal fluoride which would have to be accounted for. It's possibe too that the large amount of NaCl could also interfere. Be sure to include appropriate spikes to determine recoveries. A preliminary distillation step might be needed. Refer to one of the latest editions of Standard Methods for the Examination of Water and Waste Water. Since you are starting with HCl though some modifications might be needed. I am curious to learn of what works.

Thomas might be right: the used NaOH may contain traces of fluoride; either you use supra-pure reagents or better use standard addition technique. When the pH of your solution is 7 the hydroxyl anions do not interfere (selectivity coefficient around 0,001); the build NaCl does not interfere: by the standard addition method the variations of the activity coefficient will be compensated. To correct for the fluoride impurities in your NaOH you should run a blank: use the typical amount of NaOH you needed for neutralizing the HCL and neutralize this amount of NaOH with fluoride-free HCl. Then perform also a standard addition technique with this blank to get the amount of fluoride present in the blank. For the every right blank correction always subtract calculated amount of analytes from each other. Never subtract only blank signals from sample signals since the calibration slope might be different due to sample matrix effects normally absent in blanks.

The fluoride selective electrode might be helpful. You must use standard additions method due to the high matrix interference. You also have to pay attention at pH value. A TISAB buffer might be helpful.

the method is depending on the concentration of F in HCL, if it is low value, you can not dilute and inject as it is in a Ion chromatographic method, if F content is high (20ppm - 100ppm) you can dilute and use colorimetric method (APHA method) or electrode method after adjusting the pH.

F-ISE should work quite well. The two main limitations are interference from the presence of hydroxide—which will not be the case in 33% HCl—and that it detects only soluble fluorides—again, not an issue unless a divalent cation is used to provide the fluoride.