Development and validation of a liquid chromatography—tandem mass spectrometric method for the determination of the major metabolites of duloxetine in human plasma

A glassy carbon electrode modified with a multiwalled carbon nanotube@reduced graphene oxide nanoribbon core-shell structure for electrochemical sensing of p-dihydroxybenzene

“…It is noted that the fitted charge transfer resistance (R ct ) value of the MWCNT/GCE is much lower than that of the bare GCE, suggesting that the MWCNT has high conductivity. For the MWCNT@GONR/GCE, the R ct increases obviously, this indicates that the electron transfer of the electrochemical probe Fe(CN) 6 3-/4-on the MWCNT@GONR/GCE is obstructed by GONR due to the poor electronic conductivity of GONR. However, the R ct for MWCNT@rGONR/GCE i s d r a m a t i c a l l y d e c r e a s e d , i m p l y i n g t h a t t h e MWCNT@rGONR has excellent conductivity after the reduction of MWCNT@GONR.…”

“…Figure 3 shows the electrochemical impedance analysis (EIS) results of different electrodes recorded in 5 mM Fe(CN) 6 3-/4-and 0.1 M KCl aqueous solution. It is noted that the fitted charge transfer resistance (R ct ) value of the MWCNT/GCE is much lower than that of the bare GCE, suggesting that the MWCNT has high conductivity.…”

“…However, it is very toxic to humans and difficult to degrade in the ecological environment as a kind of environmental pollutant, thus the determination of DHB is of great interest [1][2][3]. Up to now, several methods have been developed for the determination of DHB, including gas chromatography [4], gas chromatography-mass spectrometry [5], liquid chromatographymass spectrometry [6], high performance liquid chromatography (HPLC) [7], room-temperature phosphorescence [1] and electrochemical techniques [8]. However, most of the above methods usually need complex and expensive instruments, take a long time to make previous separation to the obtained analytical signals, which make them less convenient in practice.…”

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“…By literature survey, several analytical techniques have been stated for DLX determination in its pure form, pharmaceuticals and bio-fluids, where DLX is not specifically assigned to any pharmaceutical constitution. These techniques include highperformance liquid chromatography, [2,3] liquid chromatography joined with mass spectrometry, [4][5][6] high-performance thinlayer chromatography, [7] spectrofluorimetry, [8] spectrophotometry, [9] and capillary zone electrophoresis. [10] Although these techniques are very sensitive, and not adapted for in situ, and DLX real-time detection also takes a long time, involve expensive devices and skilled technicians are required.…”

Determination of duloxetine in human plasma by capillary electrophoresis with laser-induced fluorescence detection

“…After oral administration, the drug is well absorbed, protein binding is relevant (96%) and the mean elimination half-life is 12 h [5]. DLX is metabolised in the liver by the cytocrome P450 system (in particular the CYP1A2 and CYP2D6 isoforms) to inactive metabolites (4-hydroxy duloxetine glucuronide and 5-hydroxy-6-methoxy duloxetine sulphate are the most abundant), which are excreted in the urine [7,8].…”