documentclass[12pt,a4paper]{article}
usepackage{multirow}
usepackage{multicol}
usepackage{booktabs}
usepackage[
    font=footnotesize,
    justification=centering,
    figurewithin=section,
    tablewithin=section
]{caption}
usepackage{siunitx}
usepackage{chemformula}

begin{document}

begin{table}[h]
centering
footnotesize
caption{My caption}
label{my-label}
begin{tabular}{cccccc}
toprule
multicolumn{2}{c}{textbf{Time (si{min})}} &%
multicolumn{2}{c}{textbf{Water + ch{CH3COOH} SI[inter-unit-product=~]{0,15}{%~v/v}}} &%
multicolumn{2}{c}{textbf{Oil}} \
midrule
textbf{Point 1} & textbf{Point 2} &%
textbf{Point 1} & textbf{Point 2} &%
textbf{Point 1} & textbf{Point 2} \
midrule
0,00    & 0,00  & 100   & 90    & 0     & 10 \
0,50    & 0,50  & 90    & 70    & 10    & 30 \
8,50    & 8,00  & 100   & 0     & 0     & 100 \
13,50   & 8,10  & 100   & 90    & 0     & 10 \
bottomrule
end{tabular}
end{table}

end{document}