A method for detecting and quantitatively analysing hexose-monophosphates in a biological sample comprising: (a) obtaining an extract of the biological sample in a form suitable for ionization, wherein the hexose-monophosphate extract of the biological sample suitable for ionization is obtained by extracting the sample with a solvent selected from the group consisting of acetonitrile in water, ethyl acetate in water, tetrahydrofuran in water, methanol in water, and isopropanol in water; (b) ionizing the extract to form a stream of gas phase ions; (c) selecting precursor molecular ions having a mass to charge ratio of hexose-monophosphate; (d) fragmenting the precursor molecular ions to obtain product ions of hexose-monophosphate; (e) selecting product ions of interest from other product ions by their mass to charge ratio; (f) detecting the product ions of interest and obtaining their ion intensities; and (g) using the ion intensities of the product ions to: (i) determine by spectrum analysis the quantitative abundance of hexose-monophosphates in the biological sample; and/or (ii) determine the concentration of hexose-monophosphates or a particular species thereof by comparing the ion intensities of a control sample or samples having a known concentration of hexose-monophosphates and/or the particular species thereof; and/or (iii) determine ion abundance ratios indicating the relative amount of a hexose-monophosphate species present within the biological sample. (a) obtaining an extract of the biological sample in a form suitable for ionization, wherein the hexose-monophosphate extract of the biological sample suitable for ionization is obtained by extracting the sample with a solvent selected from the group consisting of acetonitrile in water, ethyl acetate in water, tetrahydrofuran in water, methanol in water, and isopropanol in water; (b) ionizing the extract to form a stream of gas phase ions; (c) selecting precursor molecular ions having a mass to charge ratio of hexose-monophosphate; (d) fragmenting the precursor molecular ions to obtain product ions of hexose-monophosphate; (e) selecting product ions of interest from other product ions by their mass to charge ratio; (f) detecting the product ions of interest and obtaining their ion intensities; and (g) using the ion intensities of the product ions to: (i) determine by spectrum analysis the quantitative abundance of hexose-monophosphates in the biological sample; and/or (ii) determine the concentration of hexose-monophosphates or a particular species thereof by comparing the ion intensities of a control sample or samples having a known concentration of hexose-monophosphates and/or the particular species thereof; and/or (iii) determine ion abundance ratios indicating the relative amount of a hexose-monophosphate species present within the biological sample. (i) determine by spectrum analysis the quantitative abundance of hexose-monophosphates in the biological sample; and/or (ii) determine the concentration of hexose-monophosphates or a particular species thereof by comparing the ion intensities of a control sample or samples having a known concentration of hexose-monophosphates and/or the particular species thereof; and/or (iii) determine ion abundance ratios indicating the relative amount of a hexose-monophosphate species present within the biological sample.