
\begin{tikzpicture}[line cap=round,line join=round,>=triangle 45,x=1.2cm,y=0.12cm]
\begin{axis}[
x=1.2cm,y=0.12cm,
axis lines=middle,
ymajorgrids=true,
xmajorgrids=true,
minor tick num =4,
yminorgrids=true,
xminorgrids=true,
major grid style=black,
xmin=-0.4,
xmax=7,
ymin=-10,
ymax=30,
xtick={-1,0,...,7.0},
ytick={-10.0,0.0,...,30.0},]
\clip(-1,-10) rectangle (7,30);

\draw [samples=50,rotate around={0.:(0.,0.)},xshift=0.cm,yshift=0.cm,line width=0.5pt,domain=0.0:0.4)] plot (\x,{(13.5625*(\x)^3+-1.0*(\x)^2+23.23*(\x)+0.0)/1.0}););\draw [samples=50,rotate around={0.:(0.,0.)},xshift=0.cm,yshift=0.cm,line width=0.5pt,domain=0.4:1.4)] plot (\x,{(0.94*(\x)^3+-17.008*(\x)^2+42.0952*(\x)+-4.17696)/1.0}););\draw [samples=50,rotate around={0.:(0.,0.)},xshift=0.cm,yshift=0.cm,line width=0.5pt,domain=1.4:4.0)] plot (\x,{(0.43628*(\x)^3+-5.03769*(\x)^2+11.54022*(\x)+16.52042)/1.0}););\draw [samples=50,rotate around={0.:(0.,0.)},xshift=0.cm,yshift=0.cm,line width=0.5pt,domain=4.0:5.5)] plot (\x,{(2.45037*(\x)^3+-32.31111*(\x)^2+133.05111*(\x)+-162.05037)/1.0}););

%\draw (0.10776703510728024,30.286243184198444) node[anchor=north west] {$\text{Concentration} ( mg.L^{-1})$};
%\draw (4.855105766470641,-3) node[anchor=north west] {$\text{ Temps} (h)$};
%\draw (4.136074535260497,14.504055164362875) node[anchor=north west] {$y=C(t)$};
\end{axis}
\end{tikzpicture}