A new HILIC-MS/MS method for the simultaneous analysis of carbidopa, levodopa, and its metabolites in human plasma

Quantitative determination of dopamine in human plasma by a highly sensitive LC–MS/MS assay: Application in preterm neonates

“…The major limitations of these assays include insufficient sensitivity, laborious sample preparation and potential interferences from structurally similar endogenous and exogenous compounds [7][8]. Recently, hydrophilic interaction liquid chromatography (HILIC)-MS/MS has been reported as an alternative to the reverse phase liquid chromatography (RPLC)-based assays for the analysis of catechols [9]. However, the LLOQ of 20 ng/ml for dopamine, is insufficient to determine endogenous levels of dopamine in the pg/ml range.…”

Development and validation of a UPLC–MS/MS method for quantitation of droxidopa in human plasma: Application to a pharmacokinetic study

“…Compared with acetonitrile, the test results showed that methanol yielded about 1.5-fold higher recovery than acetonitrile. We added different proportions of formic acid [19,20] (0.5%, 1%, 3%, 10%) in methanol to improve the recovery of droxidopa. Methanol containing 3% formic acid was selected for its higher extraction efficiency.…”

Development and validation of an LC‐MS/MS method for simultaneous quantification of levodopa and MD01 in rat plasma and its application to a pharmacokinetic study of mucuna pruriens extract

“…Furthermore, matrix effect was not investigated in the above‐mentioned studies (Igarashi et al ., ). In 2014, a new HILIC‐MS/MS method was developed for the quantitation of levodopa in human plasma; the direct matrix factor data was, however, unavailable despite the fact that the relative standard deviation (RSD) between lots was <15% (Vilhena et al ., ). More recently, obvious matrix effects were observed when acetonitrile was used to precipitate plasma protein in an LC‐MS/MS assay for levodopa (Ribeiro et al ., ).…”

“…In addition, instability of levodopa and MD01 observed in the sample storage process and analysis led to assay inaccuracy owing to further oxidation of the phenol groups of levodopa and MD01. Previously, strong acids such as hydrochloric acid and perchloric acid, antioxidants like sodium metabisulfite and hydrazine dihydrochloride were used to maintain the stability of levodopa (Igarashi et al ., ; Jiang et al ., ; Cesar et al ., ; Venkatraman and Hermes, ; Vilhena et al ., ). However, both of these acids would seriously damage mass spectrometer detector after injecting a large number of samples and various stabilizers have not been comprehensively evaluated.…”

“…However, both of these acids would seriously damage mass spectrometer detector after injecting a large number of samples and various stabilizers have not been comprehensively evaluated. Moreover, working solutions were usually freshly prepared in each analytical batch in previous studies (Vilhena et al ., ; Ribeiro et al ., ). Thus, finding a proper stabilizer, which is compatible with LC‐MS/MS systems and capable of retarding the oxidation process, could make analysis of levodopa more robust and straightforward.…”