Fluorine MR Spectroscopy (19F MRS) allows in vivo quantification of fluorine-containing antipsychotic and antidepressant drug concentrations in the brain. To detect the low concentration of the drugs (~ 5-30 µM) in the brain, it requires multiple repeated acquisitions to increase SNR and the scan time is relatively long. Therefore, it is important to ensure consistent frequency alignment across the repeated acquisitions. However, MR system instability induces drifts of the scanner frequency, particularly following MR scans with a high gradient duty cycle. Previous frequency correction methods for 1H MRS require internal reference signals, such as under- or un-suppressed water, and cannot be applied to 19F MRS, where the SNR of 19F signals is low at each repeated acquisition. The purpose of this study is to investigate the feasibility of using an external reference for retrospective frequency correction in 19F MRS.