YMC-Pack TMS columns are bonded with trimethylmonochlorosilane to create a phase with intermediate polarity for analysis of extremely hydrophobic compounds using conventional reversed-phase solvents and highly polar compounds using highly aqueous solvents. The unique chemistry of TMS is also well-suited for the analysis of multifunctional compounds. Selectivity characteristics of a C1 bonded phase can be unique and samples must be tested to determine the applicability of the phase.