Analytical method for determining concentration of decomposition products in solvent used for solvent extraction

A method for determining the concentration of an undeuterated compound in a sample of a solution by gas chromatography/mass spectrometry using an internal standard, said undeuterated compound having a first chemical formula, said internal standard being a deuterated compound having a second chemical formula, the only difference between said first and second chemical formulas being that a predetermined number of hydrogen atoms in said undeuterated compound are replaced by an equal number of deuterium atoms to form said deuterated compound, wherein said undeuterated compound is a phosphoric acid taken from the group consisting of dibutyl phosphoric acid and monobutylphosphoric acid, comprising the steps of:

• forming a calibration curve showing the standard correlation between the mass spectra of said undeuterated and deuterated compounds for known concentrations of said undeuterated compound;
• forming a predetermined volume of a solution comprising an unknown weight of said undeuterated compound, a known weight of said deuterated compound, and a silylating agent;
• producing a graph of the mass spectra corresponding to said solution using gas chromatography/mass spectrometry;
• determining the ratio of the area under a first peak on said graph corresponding to said undeuterated compound to the area under a second peak on said graph corresponding to said deuterated compound;
• and
• determining the concentration of said undeuterated compound in said predetermined volume of said solution using said determined ratio and said calibration curve,
• wherein said step of forming a predetermined volume of a solution comprising an unknown weight of said undeuterated compound, a known weight of said deuterated compound, and a silylating agent comprises the steps of:
• placing a predetermined volume of an internal standard solution having a predetermined concentration of said deuterated compound dissolved in a first solvent into a first vial;
• evaporating said first solvent to form a residue;
• mixing said residue with water to form an aqueous mixture;
• adding a predetermined weight of a sample of a solution comprising said undeuterated compound to said aqueous mixture to form a first two-phase solution and then agitating said first two-phase solution;
• placing said aqueous bottom layer of said first two-phase solution in a second vial;
• adding a predetermined volume of a second solvent to said sample of said aqueous layer to form a second two-phase solution and then agitating said second two-phase solution;
• placing the aqueous bottom layer of said second two-phase solution in a third vial;
• evaporating the water from said third vial to form a dry residue;
• and
• adding a predetermined volume of a silylating agent to said dry residue.