Simultaneous determination of free methamphetamine, pethidine, ketamine and tramadol in urine by dispersive liquid–liquid microextraction combined with GC–MS

Figures & data

Figure 1. Efficiency of different extraction solvent and disperser solvent evaluated for extraction of the four drugs by DLLME. Extraction conditions: sample volume, 5.00 mL; extraction solvent volume, 20 μL; disperser solvent volume, 0.5 mL; room temperature; concentration of each drug, 0.1 μg/mL.

Figure 2. Efficiency of the volume of C₂Cl₄ evaluated for extraction of the four drugs by DLLME. Extraction conditions: sample volume, 5.00 mL; extraction solvent volume, 5.0, 10.0, 15.0, 20.0, 25.0, 30.0 and 40.0 µL; disperser solvent volume, 0.5 mL; room temperature; concentration of each drug, 0.1 μg/mL.

Figure 3. Efficiency of the volume of C₂Cl₄ on the volume of sediment phase in DLLME. Extraction conditions: sample volume, 5.00 mL; extraction solvent volume, 5, 10.0, 15.0, 20.0, 25.0, 30.0 and 40.0 µL; disperser solvent volume,0.5 mL; room temperature; concentration of each drug, 0.1 μg/mL.

Figure 4. Efficiency of the volume of C₂H₆O evaluated for extraction of the four drugs by DLLME. Extraction conditions: sample volume, 5.00 mL; extraction solvent volume, 30.0 µL; disperser solvent volume, 0.25, 0.50, 1.00, 1.50 and 2.00 mL; room temperature; concentration of each drug, 0.1 μg/mL.

Figure 5. Efficiency of the extraction time evaluated for extraction of the four drugs by DLLME. Extraction conditions: sample volume, 5.00 mL; extraction solvent volume, 30.0 µL; disperser solvent volume, 0.5 mL; room temperature; concentration of each drug, 0.1 μg/mL.

Figure 6. Efficiency of the sample pH value evaluated for extraction of the four drugs by DLLME. Extraction conditions: sample volume, 5.00 mL; extraction solvent volume, 30.0 µL; disperser solvent volume, 0.5 mL; room temperature; concentration of each drug, 0.1 μg/mL.

Figure 7. Efficiency of salt evaluated for extraction of the four drugs by DLLME. Extraction conditions: sample volume, 5.00 mL, extraction solvent volume, 30.0 µL; disperser solvent volume, 0.5 mL; room temperature; concentration of each drug, 0.1 μg/mL.

Figure 8. Total ion chromatogram of the four drugs. Extraction conditions: sample volume, 5.00 mL; extraction solvent volume, 30.0 µL; disperser solvent volume, 0.5 mL; room temperature; concentration of each drug, 0.1 μg/mL.

Table 1. Quantification and diagnostic ions used in GC–MS analysis.

Analyte	Retention time (min)	Molecular mass	Quantification ions (base ions, m/z)	Diagnostic ion (m/z)
MA	4.708	149.2	58	91 (17%)
PD	8.397	247.3	71	172 (70%), 70 (50%)
KT	9.072	237.7	180	182 (35%), 209 (25%)
TD	9.492	263.4	58	263 (10%), 135 (7%)

Inside brackets refer to the relative abundance of ions (m/z) for each analyte.

Table 2. Quantitative features of the method for the four drugs.

Analyte	Linear range (µg/L)	r^2	RSDs (n = 7, %)	LOQs (µg/L)	LODs (µg/L)	EF	Recovery (%)
MA	10.0–1000.0	0.998	3.90	6.53	1.96	226	95.55
PD	10.0–1000.0	0.991	3.78	1.44	0.43	190	82.85
KT	10.0–1000.0	0.996	3.40	3.03	0.91	204	90.63
TD	10.0–1000.0	0.994	1.98	2.57	0.77	185	80.45

Table 3. Comparison of the method with other studies.

Method	Analyte	Linear range	Concentration (μg/mL)	Recovery (%)	LOD	Reference
LLE–GC/MS	MA, PD, TD, etc.	10–5000 ng/mL	2.5	63.3–81.1	2 ng/mL	[18]
SPE–GC/MS	MA, PD, TD, etc.	10–5000 ng/mL	2.5	66.8–98.5	2 ng/mL	[18]
SPE–GC/MS	MA, KT, etc.	5–200 ng/mL	0.1	95.4–96.8	2.5 ng/mL	[19]
SPE–GC/MS	MA, KT, TD, etc.	0.2–50 μg/mL	10	30–82	0.06–2 μg/mL	[20]
LLE–GC/MS	MA, PD, TD, KT	–	0.5	63–104	25–50 ng/mL	[21]
SPE–GC/MS	PD	1.25–40 ng/mL	0.02	109 ± 10.9	0.5 ng/mL	[22]
DLLME–GC/MS	MA, PD, TD, KT	10–1000 ng/mL	0.1	80.45–95.55	0.43–1.96 ng/mL	Present work

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