Patent ID: 8501498

Claim:
A method comprising: a) reacting two or more samples, each sample comprising one or more analytes, with a different labeling reagent, the labeling reagents being isotopic and/or isobaric to one another, to thereby produce two or more differently labeled samples each comprising one or more labeled analytes, wherein the labeling reagents are represented by the formula: or a salt form and/or hydrate form thereof, wherein independently for each labeling reagent: RP is a reporter group represented by either formula: wherein ring A is aromatic; each Z can be independently CH, CR 2 or N provided that no more than two Z groups are N; and n can be 1 or 2, or wherein ring B is non-aromatic; n is 1 or 2, each W is independently O, S, or NR 4 ; each W′ is independently CH 2 , CHR 2 , C(R 2 ) 2 , C(O), S(O), S(O) 2 , or C═N—R 4 ; and Q is CH or CR 2 ; and each R 2 is independently hydrogen, deuterium, —OH, halogen, —CN, —NO 2 , alkyl, alkenyl, alkynyl, aryl, heteroaryl, arylalkyl, heteroarylalkyl, heteroalkyl, heterocycloalkyl, —R 3 or -T-R 3 , each R 3 can be independently hydrogen, deuterium, alkyl, alkenyl, alkynyl, aryl, arylalkyl, heteroalkyl, heterocycloalkyl, heteroaryl, or heteroaralkyl; T can be —O—, —NR 4 , —S—, —C(O)—, —S(O)—, —SO 2 —, —NR 4 C(O)—, —C(O)NR 4 —, —NR 4 SO 2 —, —SO 2 NR 4 —, —C(O)O—, —OC(O)—, —NR 4 C(O)O—, or —OC(O)NR 4 —; and each R 4 is independently hydrogen, deuterium, alkyl, heteroalkyl, aryl, or aralkyl; and RP has a unique gross mass for each labeled analyte, and the remainder of the labeling reagent structure has a unique gross mass for each labeled analyte that compensates for the difference in unique gross mass between the RP for each labeled analyte such that the aggregate gross mass of the labeling reagent for each labeled analyte is the same; and b) producing a mixture by mixing together the two or more differently labeled samples, and optionally one or more calibration standards.