High sensitivity Fourier transform ion cyclotron resonance mass spectrometry for biological analysis with nano-LC and microelectrospray ionization

Modifications to a 7 T nano-LC micro-ESI FT-ICR mass spectrometer, includin g a shorter octopole, similar to 100% duty cycle, improved nano-U3 micro-ES I emitter tips, and reverse-phase HPLC resins that require no ion-pairing a gent, combine to achieve attomole detection limit. Three peptides in a mixt ure totaling 500 attomoles (amol) each in water (10 muL, 50 anol/muL) are s eparated and detected, demonstrating detection from a mixture at low endoge nous biological concentration. Two peptides in a mixture totaling 500 amol each in artificial cerebrospinal fluid (1 muL, 500 amol/muL) are separated and detected, demonstrating detection from a mixture at a biological concen tration in a biological solvent. The highest sensitivity is attained with a rg(8)-vasotocin, in which a total of 300 amol is detected in artificial cer ebrospinal fluid (1 muL, 300 amol/muL) and a total of 100 amol in water (1 muL, 100 amol/muL). Arg(8)-vasotocin isolated from the pineal gland of rain bow trout is detected, demonstrating the ability of FT-ICR to detect and id entify a true endogenous biological analyte.