## 4 Conclusions  
The novel and greener WB-MAD method was successfully developed for complete digestion of toothpaste samples containing sodium monofluorophosphate prior to F- determination using a fluoride-ion-selective electrode (F-ISE). The newly developed acid-free digestion method resulted in water-based digests that were also compatible with ion chromatographicalysis. The proposed WB-MAD method was accurate (96.0-100.1%) and precise (\(\leq\)0.7), with a low method detection limit of 0.0159 \(\mathrm{\SIUnitSymbolMicro g}/\mathrm{kg}\). The F- concentration levels in all the investigated samples (A-L) were within the regulation limits (500 to 1500 mg/kg) specified by the World Health Organization (WHO) and thereby safe for consumption by both toddlers and adults. The proposed WB-MAD method showed  
Figure 8: Chromatograms of digested toothpaste samples A (Blue), B (Red) and I (Black) showing different anionic peaks using a mixture of 5 \(\times\) 10\({}^{-3}\) M Na\({}_{2}\)CO\({}_{3}\) and 0.2 \(\times\) 10\({}^{-3}\) M NaHCO\({}_{3}\) as an eluent, at a flow rate of 1.200 mL/min. The peak assignments are as follows: 1 is fluoride, 2 is chloride and 3 is carbonate. \begin{table}
\begin{tabular}{l c c c c c} \hline
**Toothpaste** & **F– Content Determined Using ISE** & **F– Content Determined Using IC** &
\begin{tabular}{c} **Declared F–** \\ **Concentration** \\ \end{tabular} \\ \hline \multicolumn{5}{c}{**(mg/kg \(\pm\) SD), \(n\) = 3**} & **(\%R)** & **(mg/kg \(\pm\) SD), \(n\) = 3** & **(\%R)** & **(mg/kg)** \\ \hline A & 1448.36 \(\pm\) 1.74 & 99.9 & 1443.34 \(\pm\) 0.34 & 99.5 & 1450 \\ B & 970.21 \(\pm\) 1.90 & 97.0 & 997.31 \(\pm\) 0.36 & 99.7 & 1000 \\ C & 1452.13 \(\pm\) 3.99 & 100.1 & 1447.17 \(\pm\) 1.07 & 99.8 & 1450 \\ D & 1437.72 \(\pm\) 4.34 & 99.2 & 1460.61 \(\pm\) 2.17 & 100.7 & 1450 \\ E & 989.41 \(\pm\) 3.78 & 98.9 & 908.01 \(\pm\) 0.24 & 90.9 & 1000 \\ F & 1449.17 \(\pm\) 2.86 & 99.9 & 1454.83 \(\pm\) 3.53 & 100.3 & 1450 \\ G & 1353.31 \(\pm\) 4.85 & 93.3 & 1445.76 \(\pm\) 1.56 & 99.7 & 1450 \\ H & 1456.85 \(\pm\) 4.76 & 100.5 & 1452.31 \(\pm\) 0.84 & 100.2 & 1450 \\ I & 482.81 \(\pm\) 0.103 & 96.6 & 508.22 \(\pm\) 0.98 & 101.6 & 500 \\ J & 499.33 \(\pm\) 1.70 & 99.9 & 495.65 \(\pm\) 1.05 & 99.1 & 500 \\ K & 496.71 \(\pm\) 1.25 & 99.2 & 518.44 \(\pm\) 1.11 & 103.7 & 500 \\ L & 500.12 \(\pm\) 1.05 & 100 & 497.01 \(\pm\) 0.78 & 99.4 & 500 \\ \hline \end{tabular}
\end{table} 
Table 3: Concentration levels of F determined in 12 toothpaste digests using ISE and IC. better accuracy (96.6 to 99.9%) compared to the classical microwave-assisted acid digestion method (MAAD) (71.3 to 92.1%). Moreover, Table 3 shows that the F\({}^{-}\) concentration levels obtained from both F-ISE and IC were statistically insignificant. In view of the validation results and the figures of merit discussed, the WB-MAD method can be considered as an alternative to substitute the conventional acid digestion methods for decomposition of sodium monofluurophosphate (Na\({}_{2}\)PO\({}_{3}\)F) in any dental or oral hygiene products. Conceptualization, N.M.; methodology, M.D.M. ; software, N.M.; validation, M.D.M. ; formal analysis, M.D.M. ; investigation, N.M. and M.D.M. ; resources, N.M.; data curation, M.D.M. ; writing--original draft preparation, M.D.M. ; writing--review and editing, N.M.; visualization, N.M.; supervision, N.M.; project administration, N.M.; funding acquisition, N.M. All authors have read and agreed to the published version of the manuscript. This research was funded by South African National Research Foundation-THUTHUKA (113951) and the APC was funded by College of Science, Engineering and Technology, UNISA. Not applicable. Data Availability Statement: Data is contained within the article.