Rapid and Robust Analysis Method for Quantifying Antidepressants and
Major Metabolites in Human Serum by UHPLC-MS/MS
Vincent Goudriaan1, Christ Pijnenburg2, Jacob Diepenbroek2, Jan Giesbertsen2, Annemieke Vermeulen Windsant-v.d. Tweel2
1 Shimadzu Benelux BV, ‘s-Hertogenbosch, Netherlands. 2 ZANOB BV, ‘s-Hertogenbosch, Netherlands.
Therapeutic drug monitoring (TDM) of antidepressants is one of the most widely utilized analysis in clinical labs in Dutch hospitals nowadays. Traditionally quantitation of antidepressants is performed by means
of HPLC with diode-array detection (DAD). Obvious disadvantages of the latter method are: sensitivity, selectivity and possibility of false positives as a result of co-elution with other administered drugs,
metabolites or endogenic compounds. UHPLC-MS/MS is much more sensitive, more selective, and if robust the perfect replacement of routine HPLC analysis. Due to simplified sample prep, faster analysis
and less solvent consumption UHPLC-MS/MS is much more cost effective. UHPLC-MS/MS methods will replace routine HPLC methods in clinical labs.
2. Methods and Materials
Human serum samples were extracted by means of off-line solid phase extraction. The extracts were analyzed with
3-1. Comparison of HPLC-DAD and UHPLC-MS/MS results
a Shimadzu Nexera UHPLC combined with a LCMS-8040 Tandem Mass Spectrometer. 5µL of sample was injected
with a SIL-30AC autosampler.
Several hundreds of serum extracts were analyzed with a LC-MS/MS method and three separate HPLC methods
with photo diode-array detection to compare results of both techniques.
2-1. Sample Preparation
Standards both for calibration and control are ready made serum standards. The standards are pretreated in the
same way as the samples.
1. Precondition SPE material1 with 1 mL 3% ammonia in acetonitrile
2. Equilibrate with 1 mL citrate buffer pH 3.0
Load 2 mL internal standard solution2
Load 1 mL homogenized serum
3. Wash with 3 mL water (extract A0)
4. Wash with 3 mL acetonitrile (extract A1)
5. Wash with 3 mL 3% ammonia in acetonitrile (extract A2)
1 : Bakerbond Speedisk C18 Polar Plus, 10 µm, 50mg/3mL (JT BAKER)
2 : 0.1 µg/mL triflupromazine in citrate buffer pH 3.0
The flow is in all steps adjusted to about 1 to 2 mL/min.
Antidepressants in sample extract A2 are analyzed with UHPLC and a triple quadrupole mass spectrometer using
the following conditions. Polar compounds are eluted in extract A0, neutral and acidic compounds are eluted in
Figure 2 Mass chromatograms of antidepressants and metabolites in calibration standard
（concentration of each compound : 90-100µg/L in serum, except clozapine: 600µg/L)
2-2. Analytical Conditions
UHPLC conditions (Nexera system)
: Phenomenex Kinetex XB-C18 100mm×2.1mm, 2.6 um
: A: 10mM Ammonium fomate
: B conc.10%(0 min) -50%(2.5-5min) - 75%(6min) – 10% (7-7.5min)
MS conditions (LCMS-8040)
Ion spray voltage
: 37 MRM transitions (2-3 MRMs / compound (see table 1)
Dwell time 10 or 20 msec. (compound dependent) / Pause time 3 msec
data dependent product ion scanning.
Table 1. MRM transitions
280.20 > 215.10
280.20 > 262.20 ; 280.20 > 231.10
Conc. (µg/L) in serum HPLC-DAD
313.10 > 192.10
313.10 > 270.05 ; 313.10 > 231.05
327.20 > 270.05
327.20 > 192.05 ; 327.20 > 227.05
Comparison of measured results with HPLC-DAD with UHPLC-MS/MS. N-desmethylclozapine shows
330.20 > 70.20
330.20 > 192.20
signs of ion-suppression.
319.20 > 71.15
319.20 > 41.15
267.15 > 208.10
267.15 > 193.10 ; 267.15 > 236.10
281.20 > 208.10
281.20 > 193.05
3-2. Automatic Synchronized Survey Scanning (DDA)
264.20 > 233.20
264.20 > 91.15 ; 264.20 > 117.10
296.20 > 30.30
296.20 > 134.10
The multi-component MRM method was extended with Synchronized Survey Events (DDA), to collect product ion
278.20 > 105.15
278.20 > 233.10 ; 278.20 > 91.10
scans for every positive peak above a certain level. The product ion spectra were identified by library search.
310.15 > 44.25
310.15 > 148.10
301.10 > 242.10
301.10 > 227.00 ; 301.10 > 270.10
315.15 > 242.10
315.15 > 227.05 ; 315.15 > 270.10
353.10 > 280.10
353.10 > 248.10 ; 353.10 > 308.05
High Speed Mass Spectrometer
Ultra Fast Mass Spectrometer
Ultra Fast Scan Speed
Ultra Fast Polarity Switching
Figure 4 N-desmethylclozapine (4A) and clozapine (4B) were both positively identified in the same patient serum
- Min. dwell time 0.8msec
(max. 555 MRM/sec)
Fig. 1 LCMS-8040 Triple Quadrupole Mass Spectrometer
• There is a good correlation between the results from HPLC-DAD and UHPLC-MS/MS. Correlation coefficient is between 0.965 and 0.995 for all compounds. Only N-desmethyl-clozapine deviates due to ion-
suppression. Generally can be concluded that the serum extracts obtained after off-line solid phase extraction are clean. There is no need for isotopically labeled internal standards.
• Combining MRM measurements with data dependent product ion scanning provides more reliable results since the identity of compounds can be confirmed by library search. Furthermore it is possible to
combine diode-array detection with LCMS/MS to offer even more assurance.
• Co-medication and medication adherence behavior of elderly patients is more easily traced by multi-target compound analysis by UHPLC-MS/MS, as with HPLC-DAD one needs the trained eye
• Reconstitution of the sample extract by solvent evaporation and subsequent dilution in another solvent is mandatory for HPLC-DAD to increase concentration and to eliminate peak broadening
of early eluting compounds, but is not necessary for UHPLC-MS/MS. Therefore sample pretreatment could be shortened, reducing the overall sample prep time from 40 to 15 minutes per batch
• UHPLC-MS/MS method for antidepressants will replace routine HPLC-DAD methods in clinical labs.
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