In RP HPLC, one of the most common separation methods used to measure purity, strength, dosage, etc, a protein would be put into 0.1% (1000 ppm) TFA (Trifluoroacetic acid), what do you suppose this does to the protein in many cases? (Pick the BEST answer).    somewhat denaturing to very denaturing   oxidizes cysteine   ionizes acid and base groups

  High Performance Liquid Chromatography (HPLC) is biochemical separation method for organic molecules or solutes of a compound solution depending on the period of their respective interaction with the solid matrix. There are two separate phases in the matrix, one is mobile phase, which is liquid, another one is solid stationary phase. The mixture, whose compounds are to be separated are called analytes. Analyte compounds are carried by the fluid phase through the solid stationary matrix. The separation of the molecules depend on their affinity to the stationary matrix, for example if they are strongly bonded by covalent interaction to the solid phase, due to higher affinity, the velocity of the analyte's movement is slower than the analyte which do not bond or fix on the solid matrix, and flow with the mobile phase due to its higher affinity for the mobile phase. The velocity of the movement of the analyte compounds depend on their polarity, hence their interaction with the non-polar mobile phase. If the organic molecules are non-polar they move faster through the solid stationary phase. Proteins are organic molecules which are often separated by chromatographic technique as they have different side chains which are acidic and or basic in nature.