## 4 Conclusions  
The main goal of the work described above was to provide a simple, fast, inexpensive, sensitive, reliable and non-time-consuming method for the determination of essential and non-essential trace elements in urine using a micro volume of sample. To assess this, a suite of sixteen (Al, V, Cr, Mn, Fe, Co, Cu, Zn, As, Se, Mo, Cd, Sn, Ba, TI and Pb) trace elements--which play an important role in the context of chelation therapy and heavy metal discharge--were selected. After all conditions had been established, measurements became very efficient. After the subsequent participation in an external quality assessment, we can conclude that our method is suitable for detecting a lack or an overload of the \begin{table}
\begin{tabular}{c c c c c c c c c c} \hline \hline \multirow{2}{*}{**Analyte**} & \multirow{2}{*}{**Sample**} & \multirow{2}{*}{**Unit**} & \multicolumn{2}{c}{**Measured**} & \multicolumn{2}{c}{**Theoretical**} & \multicolumn{2}{c}{**Lower**} & \multicolumn{2}{c}{**Upper**} & \multicolumn{2}{c}{**Deviation**} \\  & & & **Value** & **Value** & **Limit** & **Limit** & **(\%)** & **Z-Score** & **Fulified** \\ \hline Al & 61 & 26.90 & 32.00 & 20.5 & 43.50 & -16.10 & -1.03 & + \\  & 62 & \(\mathrm{\SIUnitSymbolMicro L}^{-1}\) & 49.60 & 63.60 & 40.70 & 86.50 & -22.00 & -1.31 & + \\ Cr & 61 & \(\mathrm{\SIUnitSymbolMicro L}^{-1}\) & 4.75 & 5.09 & 3.26 & 6.92 & -6.70 & -0.80 & + \\  & 62 & \(\mathrm{\SIUnitSymbolMicro L}^{-1}\) & 2.37 & 2.68 & 1.72 & 3.65 & -11.60 & -0.94 & + \\ Mn & 61 & \(\mathrm{\SIUnitSymbolMicro L}^{-1}\) & 10.30 & 9.89 & 6.33 & 13.50 & 4.00 & 0.41 & + \\  & 62 & \(\mathrm{\SIUnitSymbolMicro L}^{-1}\) & 2.48 & 2.73 & 1.75 & 3.71 & -9.20 & -0.59 & + \\ Fe & 61 & \(\mathrm{\SIUnitSymbolMicro L}^{-1}\) & 0.20 & - & - & -\(\mathrm{\SIUnitSymbolMicro L}^{3}\)0.0 & - & -0.86 & + \\  & 62 & \(\mathrm{\SIUnitSymbolMicro L}^{-1}\) & 750 & 749 & 47.00 & 1019.00 & 0.011 & 0.01 & + \\ Co & 61 & \(\mathrm{\SIUnitSymbolMicro L}^{-1}\) & 1.29 & 1.47 & 0.94 & 2.00 & -12.20 & -1.57 & + \\  & 62 & \(\mathrm{\SIUnitSymbolMicro L}^{-1}\) & 2.54 & 2.85 & 1.82 & 3.88 & -10.90 & -1.35 & + \\ Cu & 61 & \(\mathrm{\SIUnitSymbolMicro L}^{-1}\) & 67.50 & 67.60 & 43.30 & 91.90 & -0.10 & -0.01 & + \\  & 62 & \(\mathrm{\SIUnitSymbolMicro L}^{-1}\) & 5.70 & 6.36 & 4.07 & 8.65 & -10.40 & -0.34 & + \\ Zn & 62 & \(\mathrm{\SIUnitSymbolMicro L}^{-1}\) & 0.42 & 0.43 & 0.27 & 0.58 & -11.10 & -0.11 & + \\ Zn & 62 & \(\mathrm{\SIUnitSymbolMicro L}^{-1}\) & 0.12 & 0.12 & 0.07 & 0.16 & 0.30 & 0.02 & + \\ As & 61 & \(\mathrm{\SIUnitSymbolMicro L}^{-1}\) & 75.60 & 79.30 & 50.80 & 108.00 & -4.60 & -0.79 & + \\ As & 62 & \(\mathrm{\SIUnitSymbolMicro L}^{-1}\) & 21.90 & 23.30 & 149.30 & 31.70 & -6.00 & -0.86 & + \\ Cd & 61 & \(\mathrm{\SIUnitSymbolMicro L}^{-1}\) & 3.38 & 4.95 & 3.17 & 6.73 & -3.90 & -3.90 & + \\ Cd & 62 & \(\mathrm{\SIUnitSymbolMicro L}^{-1}\) & 0.68 & 1.02 & 0.65 & 1.39 & -2.60 & -2.60 & + \\ Pb & 61 & \(\mathrm{\SIUnitSymbolMicro L}^{-1}\) & 43.50 & 48.60 & 31.10 & 66.10 & -10.50 & -1.02 & + \\  & 62 & \(\mathrm{\SIUnitSymbolMicro L}^{-1}\) & 139.00 & 149.00 & 95.40 & 203.00 & -6.80 & -0.72 & + \\ \hline \hline \end{tabular}
\end{table} 
Table 8: Results of the external quality assessment. mentioned trace elements. Moreover, its advantage to other reported methods lies in the speed, robustness and simplicity of the former. This method is also suitable for routine analysis and diagnosis in infants and newborns since it uses only micro amounts of urine. Conceptualization, H.-P.D. and R.K.; methodology, N.L. ; software, N.L. ; validation, N.L. ; formal analysis, N.L. ; investigation, N.L. ; resources, H.-P.D. and R.K.; data curation, N.L. and L.K. ; writing--original draft preparation, N.L. and H.-P.D. ; writing--review and editing, L.K. and H.-P.D. ; visualization, N.L. ; supervision, H.-P.D. and R.K.; project administration, H.-P.D. ; funding acquisition, N.L. All authors have read and agreed to the published version of the manuscript.