Method for the direct detection and quantification of at least one compound with a molecular weight of at least 200, wherein the compound is a chemically complex molecule, wherein said chemically complex molecule is an inositol polyphosphate selected from the group containing from 2 to 6 phosphate groups, including ions or salts thereof, wherein the compound or compounds are within a biological matrix, wherein said biological matrix is a biological fluid selected from the list consisting of blood, plasma, serum, urine, saliva, lymphatic liquid, cerebrospinal fluid and mixtures thereof, wherein the method comprises at least the following steps: i) preparing at least one standard sample of the chemically complex molecule to be detected and quantified; ii) introducing the standard sample into the stream of a solvent system; wherein the solvent system consists of an aqueous solution of an amine; wherein the pH of the solvent has been buffered, between 8 and 13; iii) passing the sample and the solvent system through at least one column wherein the column is a reversed-phase stationary phase, being the particle size between 1.5-15 microns and the pore size between 60-500 Angstroms, while maintaining the pressure of the system between 5 and 1500 atm; iv) identifying the retention time and quantifying the intensity of the signal of when the chemically complex molecule is eluated, by means of a mass detector; v) preparing a sample of the chemically complex molecule from a biological matrix comprising the chemically complex molecule to be detected and quantified, wherein the process to prepare the sample comprises at least dissolving totally or partially the biological matrix to form a solution or a slurry, and, if necessary treating the solution or the slurry to remove particles in suspension; vi) repeating the steps (ii) and (iii) with the sample prepared in the step (v); together or sequentially with the standard; and vii) detecting and quantifying the presence of the chemically complex molecule by comparison of retention time and intensity of signal of the standard sample or the standard samples, or by comparison of retention time and intensity of signal obtained from previous studies or from literature, wherein the detector capable to detect the eluation of the chemically complex molecule is a mass spectrometer; a tandem mass spectrometer or a single quadrupole; working under any of the following operating modes: selected ion monitoring; multiple reaction monitoring; selected reaction monitoring and SCAN (negative/positive); or a combination of them. i) preparing at least one standard sample of the chemically complex molecule to be detected and quantified; ii) introducing the standard sample into the stream of a solvent system; wherein the solvent system consists of an aqueous solution of an amine; wherein the pH of the solvent has been buffered, between 8 and 13; iii) passing the sample and the solvent system through at least one column wherein the column is a reversed-phase stationary phase, being the particle size between 1.5-15 microns and the pore size between 60-500 Angstroms, while maintaining the pressure of the system between 5 and 1500 atm; iv) identifying the retention time and quantifying the intensity of the signal of when the chemically complex molecule is eluated, by means of a mass detector; v) preparing a sample of the chemically complex molecule from a biological matrix comprising the chemically complex molecule to be detected and quantified, wherein the process to prepare the sample comprises at least dissolving totally or partially the biological matrix to form a solution or a slurry, and, if necessary treating the solution or the slurry to remove particles in suspension; vi) repeating the steps (ii) and (iii) with the sample prepared in the step (v); together or sequentially with the standard; and vii) detecting and quantifying the presence of the chemically complex molecule by comparison of retention time and intensity of signal of the standard sample or the standard samples, or by comparison of retention time and intensity of signal obtained from previous studies or from literature,