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The Determination of Dexamethasone in Human Plasma with Solid Supported Liquid-liquid Extraction

Application Introduction

In DMPK research, there is a universal problem to develop a treatment of plasma samples with high efficiency and satisfying purification.



In DMPK research, there is a universal problem to develop a treatment of plasma samples with high efficiency and satisfying purification. We develop a method named solid supported liquid-liquid extraction (SLE) by taking advantage of diatomite which has a porous structure. The aqueous sample such as plasma will spread as a thin film on the hydrophilic surface of diatomite’s pore, then when a water immisicible organic solvent elutes the diatomite, the target compound will be extracted by the organic solvent while protein and phospholipids will be adsorbed by the hydrophilic diatomite’s surface.

A plasma sample containing Dexamethasone was treated by SLE. By contrast, we compared SLE with SPE and found SLE method has a better recovery for its better ability of impurities removal.


LC-MS/MS Conditions

Instrument: Agilent 1200 HPLC system with API 4000+ MS detector

Column:Venusil® ASB C18 (2.1×150 mm, 3μm)

Mobile phase:38% ACN: 62% 0.01 mol/L ammonium acetate

Flow rate:0.25 mL/min

Injection volume: 5 µL

Temperature:25 °C

ESI(+),MRM: m/z 496/184 (phospholipids), m/z 393.4/373.3(Dexamethasone)

Table 1 the parameter of  API4000+ MS detector












63 V

20 V

25 V

10 V

5 500 V


50 Pa

50 Pa

13 Pa


50 V

14 V

9 V

10 V

5 500 V


60 Pa

60 Pa

12 Pa

Sample treatment

Sample treatment with Oasis HLB SPE column ( 30mg/1mL)

1). Activated HLB column with 1 mL MeOH, then 1 mL Water;

2). Loaded 50 µL sample diluted by 50 µL water;

3). Washed columns with 1mL Water-Methanol (8:2);

4). Elute sample with 1 mL ACN-Methanol (9:1).

Sample treatment with Cleanert® SLE column (200 mg/3 mL)

1). 50 µL plasma diluted by 50 µL water;

2). Load sample solution, stands for 10min;

3). 1.5 mL MTBE elution in 2 times.

All the elution were dried by Nitrogen blowing and reconstituted with 1mL mobile phase of LC/MS.

Results and Discussion

Figure 3 the chromatogram of Dexamethasone in the sample treated with HLB

Figure 4 the chromatogram of Dexamethasone in the sample treated with SLE

Table 2  Comparison of response of Dexamethasone between SPE and SLE

Concentration   of


Peak   area






Figure 5 Chromatogram of phospholipids in the sample treated by SPE

Figure 6 Chromatogram of phospholipids in the sample treated by SLE

The SLE can remove phospholipids better than SPE with Oasis HLB, which lead to ion suppression of Dexamethasone in LC/MS analysis. So the response of Dexamethasone in the sample from SLE is higher than that from SPE.


When Cleanert® SLE applies Diatomite to achieve solid supported liquid-liquid extraction, the hydroxyl on the surface of Diatomite provides an adsorption of phospholipids so that the matrix effect is reduced remarkably. Also, the SLE is a liquid-liquid extraction actually, so the feasibility of operation is predicted to transfer traditional LLE method to SLE method in DMPK sample treatment.

  • Cleanert SLE Products

    Cleanert SLE (Supported Liquid Extraction) plates and cartridges contain a high quality modified diatomaceous earth with an ideal surface with large specific area and low activity. Cleanert SLE plates and cartridges are used to extract analytes from bio-analytical, clinical, forensic, environmental and agrochemical samples, it even can replace most of the Liquid/Liquid extraction (LLE).

  • UHP ASB C18

    Chromatography separation technology has been revolutionized by Ultra-Performance Liquid Chromatography (UHPLC) System. Sub-2 μm particles make UPLC analysis more quickly, and more sensitive than traditional liquid chromatography. Since 2014, Bonna-Agela has launched our UHPLC series columns and provided different kinds of bonding chemistry on several modified silica particles surface. Bonna-Agle

  • Venusil ASB Series Columns (C1, C8, C18 and phenyl)

    The Venusil ASB series columns are specially designed for the separation of polar compounds under low (extremely stable at pH=0.8) to medium pH condition. The stationary phase is bonded with unique bulky silanes that sterically protect the siloxane bond. We offer a line of bonding chemistry of C1, C8, C18 or Phenyl groups presenting a broad selection of different polarity for various applications.

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