Low-density Solvent Dispersive Liquid-liquid Microextraction Research Articles

Simultaneous determination of 10 new psychoactive piperazine derivatives in urine using ultrasound-assisted low-density solvent dispersive liquid-liquid microextraction combined with gas chromatography-tandem mass spectrometry.

With the rapid development of synthetic drugs, novel piperazine derivatives, as an increasingly important class of new psychoactive substances (NPS), have attracted global attention owing to their increasing demand in the illicit drug market. In this study, ten piperazine derivatives were analyzed in urine samples after pre-treatment with ultrasound-assisted low-density solvent dispersive liquid-liquid microextraction (UA-LDS-DLLME) combined with gas chromatography-tandem mass spectrometry (GC-MS/MS). This simple approach involved the use of urine samples (1mL) adjusted to pH 12, which was added to 100 µL of n-hexane and subjected to ultrasonication for 3min to completely disperse the sample in the n-hexane solution. The resulting turbid suspension was centrifuged at 10,000rpm for 3min, and the supernatant was extracted and analyzed using GC-MS/MS. Under the optimized conditions presented in this study, the linear relationship between the analytes was good within 10-1500ng/mL, and the correlation coefficient (r) was between .9914 and .9983. The limit of detection (LOD) was 0.3-2ng/mL (S/N=3), and the lower limit of quantification (LLOQ) was 10ng/mL (S/N=10) with the recovery of the analytes of interest from the spiked samples being 76.3%-93.3%. This method has been used to analyze real-world samples; our study shows that the UA-LDS-DLLME approach can be used for rapid analysis while consuming minimal solvent for the simultaneous determination of a range of analytes. This method has the potential for use in clinical analyses and forensic toxicology.

Simultaneous determination of nine anticoagulant rodenticides by ultra-performance liquid chromatography–tandem mass spectrometry with ultrasound-assisted low–density solvent dispersive liquid–liquid microextraction

A sensitive determination method is developed for nine anticoagulant rodenticides (ARs) in urine samples by ultra-performance liquid chromatography–tandem mass spectrometry (UPLC–MS/MS) with ultrasound-assisted low–density solvent dispersive liquid-liquid microextraction (UA–LDS–DLLME) pretreatment. The target analytes are brodifacoum, bromadiolone, warfarin, coumachlor, coumatetralyl, difenacoum, pindone, diphacinone and chlorophacinone. The parameters that influence the extraction recovery in the UA–LDS–DLLME were systematically investigated and optimized. With the optimized extraction parameters, recoveries ranging from 64.6%–124.2% were obtained for the target analytes. The linear range for all analytes was 0.1–100 ng/mL with correlation coefficients higher than 0.99. Very low LODs ranging in 0.003–0.03 ng/mL were obtained. LOQs were in the range of 0.01–0.1 ng/mL for the nine target analytes. The accuracy that was expressed as mean relative error was within ±5.8% while the precision expressed as relative standard error was less than 5.9%. The combination of UA–LDS–DLLME with UPLC–MS/MS is a feasible, sensitive and rapid analytical approach for the determination of ARs in urine matrix, which is particularly suitable for clinical and forensic purposes.

Gas chromatography–mass spectrometry determination of polycyclic aromatic hydrocarbons in baby food using QuEChERS combined with low-density solvent dispersive liquid–liquid microextraction

A sensitive GC–MS method is reported for the determination of twelve polycyclic aromatic hydrocarbons (PAHs) in baby food. The sample preparation involves QuEChERS extraction combined with low-density solvent dispersive liquid–liquid microextraction (LDS-DLLME) and ultra-low temperature (−80 °C). Plackett–Burman screening design was employed to identify the main sample preparation variables that affect the extraction efficiency, such as the volume of toluene used in LDS-DLLME. The suitability of proposed method was verified by analytical selectivity, linearity in solvent and matrix-matched calibration curves and adequate recoveries (72–112%) and precision (RSD values ≤11%), under repeatability and within-laboratory reproducibility conditions. High analytical sensitivity was achieved for the monitoring of PAHs at the strict limit of 1 µg kg−1 fixed by the European Commission for baby foods. The validated method was applied to thirty-two commercial baby food samples, and the investigated PAHs were not detected in any sample.

Ultrasound-assisted low-density solvent dispersive liquid-liquid microextraction for the determination of 4 designer benzodiazepines in urine samples by gas chromatography-triple quadrupole mass spectrometry.

A novel microextraction technique based on ultrasound-assisted low-density solvent dispersive liquid-liquid microextraction (UA-LDS-DLLME) had been applied for the determination of 4 designer benzodiazepines (phenazepam, diclazepam, flubromazepam and etizolam) in urine samples by gas chromatography- triple quadrupole mass spectrometry (GC-QQQ-MS). Ethyl acetate (168μL) was added into the urine samples after adjusting pH to 11.3. The samples were sonicated in an ultrasonic bath for 5.5min to form a cloudy suspension. After centrifugation at 10000rpm for 3min, the supernatant extractant was withdrawn and injected into the GC-QQQ-MS for analysis. Parameters affecting the extraction efficiency have been investigated and optimized by means of single factor experiment and response surface methodology (Box-Behnken design). Under the optimum extraction conditions, a recovery of 73.8-85.5% were obtained for all analytes. The analytical method was linear for all analytes in the range from 0.003 to 10μg/mL with the correlation coefficient ranging from 0.9978 to 0.9990. The LODs were estimated to be 1-3ng/mL. The accuracy (expressed as mean relative error MRE) was within ±5.8% and the precision (expressed as relative standard error RSD) was less than 5.9%. UA-LDS-DLLME technique has the advantages of shorter extraction time and is suitable for simultaneous pretreatment of samples in batches. The combination of UA-LDS-DLLME with GC-QQQ-MS offers an alternative analytical approach for the sensitive detection of these designer benzodiazepines in urine matrix for clinical and medico-legal purposes.

Evaluation of the Effects of Hofmeister Series on Salting Out in the Determination of Organophosphorous Pesticides and Pyrethroids by LDS/DLLME

Various greener microextraction procedures have been proposed with low limits of detection to control of pesticides present in the environment, including the low-density solvent dispersive liquid‑liquid microextraction (LDS/DLLME) technique. The addition of electrolytes is important in order to induce the salting-out effect. Thus, it is possible to use the Hofmeister series and the Voet lyotropic number to study the effect of different ions on pesticide extraction in LDS/DLLME technique. Different anions were tested and a strong correlation was observed between the lyotropic number of the anion and the recovered volume of extraction solvent. The lyotropic numbers of the anions were successfully compared with the chromatographic peak areas normalized by the recovered solvent volumes, and similar empirical cubic relationships were obtained for all the pyrethroids evaluated. In the extraction of the organophosphorous pesticides, chlorpyrifos presented similarity with the pyrethroids, while correlation was observed between methyl parathion and profenofos.

Ultrasound-assisted low-density solvent dispersive liquid-liquid microextraction for the determination of eight drugs in biological samples by gas chromatography-triple quadrupole mass spectrometry

A novel microextraction technique based on ultrasound-assisted low-density solvent dispersive liquid-liquid microextraction (UA-LDS-DLLME) has been developed for the determination of multiple drugs of abuse in biological samples by gas chromatography-triple quadrupole mass spectrometry (GC-QQQ-MS). A total of 100 µL of toluene as extraction solvent was dropped into the sample solution. Then the mixture was sonicated drastically in an ultrasonic bath for 3 min with occasional manual shaking to form a cloudy suspension. After centrifugation at 10,000 r/min for 3 min, the upper layer of low-density extractant was withdrawn and injected into the GC-QQQ-MS for analysis. The parameters affecting extraction efficiency have been investigated and optimized. Under the optimum conditions, good linearities were observed for all analytes with the correlation coefficients ranging from 0. 998 4 to 0. 999 4. The recoveries of 79.3%-100.3% with RSDs < 5.7% were obtained. The LODs (S/N = 3) were in the range from 0.05 to 0.40 µg/L. UA-LDS-DLLME technique has the advantages of less extraction time, suitable for batches of sample pretreatment simultaneously, and higher extraction efficiency. It was successfully applied to the analysis of amphetamines in real human urine samples.

Ultrasound-Assisted Low-Density Solvent Dispersive Liquid-Liquid Extraction for the Determination of Amphetamines in Biological Samples Using Gas Chromatography-Mass Spectrometry

In order to control drug crime effectively, it is necessary to develop selective analytical methods suitable for unambiguous identification and determination of drugs in illicit samples and biological matrices. A novel microextraction technique based on ultrasound-assisted low-density solvent dispersive liquid-liquid microextraction, (UA-LDS-DLLME) has been applied to the determination of four amphetamines (methamphetamine, amphetamine, 3,4-methylenedioxymethamphetamine, and 3,4-methylenedioxyamphetamine) in urine samples by gas chromatography-mass spectrometry. The parameters affecting extraction efficiency have been investigated and optimized. UA-LDS-DLLME used ultrasound energy to assist in the emulsification process without any disperser solvent. Under the optimized conditions, linearity was observed for all analytes in the 0.15–10 μg/mL range with correlation coefficients (R) ranging from 0.9886 to 0.9894. The recoveries of 75.6–91.4% with relative standard deviations of 2.5–4.0% were obtained. The limits of detection (S/N = 3) were estimated to be in the 5–10 ng/mL range. The UA-LDS-DLLME technique had the advantages of shorter extraction time, suitability for simultaneous pretreatments of batches of samples, and the higher extraction efficiency. It was successfully applied to the analysis of amphetamines in real human urine samples.

Low density solvent based dispersive liquid–liquid microextraction with gas chromatography–electron capture detection for the determination of cypermethrin in tissues and blood of cypermethrin treated rats

A simple and rapid method to determine the cypermethrin (CYP) insecticide in rat tissues (kidney, liver and brain) and blood has been developed for the first time using low density solvent-dispersive liquid–liquid microextraction (LDS-DLLME) followed by gas chromatography–electron capture detector (GC–ECD) analysis. Initially, tissue samples containing CYP were homoginized in acetone. Subsequently, homogenate was mixed with n-hexane (extraction solvent) and the mixture was rapidly injected into water. The upper n-hexane layer was collected in a separate microtube and injected into GC–ECD for analysis. Blood samples were diluted with ultrapure water and subjected to DLLME through similar procedure. Parameters such as type and volume of disperser and extraction solvent, salting out effect and extraction time, which can affect the extraction efficiency of DLLME, were optimized. Method was validated by investigating linearity, precision, recovery, limit of detection (LOD) and quantification (LOQ). LODs in tissue were in the range of 0.043–0.314ngmg−1 and for blood it was 8.6ngmL−1 with a signal to noise ratio of 3:1. LOQs in tissue were in the range of 0.143–1.03ngmg−1 and for blood it was 28.3ngmL−1 with a signal to noise ratio of 10:1. Mean recoveries of CYP at three different concentation levels in all the matrices were found to be in the range of 81.6–103.67%. The results show that, LDS-DLLME coupled with GC–ECD offers a simple, rapid and efficient technique for extraction and determination of CYP in rat tissues and blood samples, which in turn would be useful for toxicological studies of CYP.