Determination of total fluoride in toothpaste by GC-FID

Abstract

       Determination of total fluoride in toothpaste was developed by using GC-FID technique under the condition i.e. HP-1 capillary column of 15 m × 0.53 mm × 1.5 μm. Carrier gas consist of helium together with hydrogen and air as make-up gas. Flowrate program starts from 3 ml/min and increase to 45 ml/min. Using flame ionization detector and inject volume is 3 μl. Temperature program of column is started at 80C and increase to 280C . The injector and detector temperature are 280C and 300C , respectively. Sodium monofluorophosphate is acid hydrolysed to be fluoride. Fluoride is converted to triethylfluorosilane (TEFS) by direct reaction with triethylchlorosilane (TECS) in acid solution and simultaneously extracted with xylene containing cyclohexane as an internal standard, then inject to GC. The method validation result show the retention time of internal standard and TEFS of 2.6 and 4.3 minutes, respectively. The linear relationship between concentration of fluoride and peak area ratio over the concentration range of 0.05 - 0.25 mg/ml with correlation coefficient (r) of 0.9993. The r of relationship between added concentration of fluoride and found concentration is 0.9868 and 0.9898 respectively, Repretability was tested by replicate analysis of fluoride in toothpastes containing sodium monofluorophosphate and sodium fluoride show %RSD of 0.56 and 0.68, respectively. There is no different of analytical results between five days which p-value is 0.93 and 0.36 respectively, show the precision of the method. Analysis of spiked sample showed percent recovery of 80.2 – 118.5% and 81.4 - 106.9%, respectively. Limit of detection (LOD) and limit of quantitation (LOQ) were 30 and 330 μg/g, respectively. Relative expanded uncertainty was 6.0 %.The developed method with acceptable validation results could be routinely used to analyse total fluoride in toothpaste.