For monitoring purposes, broad range analytical methods areneeded to reduce analytical costs and allow for a more frequentmonitoring of phthalates in milk and milk products. For the detec-tion and quantification of phthalates, chromatographic techniqueslike high performance liquid chromatography (HPLC) with diodearray detector (DAD) [14], gas chromatography (GC) and liquidchromatography (LC) coupled to mass spectrometry (MS) havebeen used [15–17]. Under GC–MS (electron ionization, EI) con-ditions, the fragment at m/z 149 is the common ion for mostphthalates. This is a major limitation in using GC–MS for the deter-mination of phthalates isomeric mixtures, primarily because ofthe occurrence of coeluting isomers with varying composition ofalkyl substitution [18,19]. LC–MS is a suitable technique for theanalysis of phthalates because no derivatization step is requiredas in GC–MS. Tandem quadrupole MS has been widely accepted