Directly Suspended Droplet Microextraction Research Articles

Green Sample Preparation Based on Directly Suspended Droplet Microextraction using Deep Eutectic Solvent for Ultra-Trace Quantification of Nitroaromatic Explosives by High Performance Liquid Chromatography

Green Sample Preparation Based on Directly Suspended Droplet Microextraction using Deep Eutectic Solvent for Ultra-Trace Quantification of Nitroaromatic Explosives by High Performance Liquid Chromatography

Investigation of directly suspended droplet micro extraction method for extraction of trihalomethane and halomethane in water samples

Simple and efficient directly suspended droplet micro extraction (DSDME) in conjunction with gas chromatography-electron capture detector (GC-ECD) has been developed for extraction and determination of Halomethane and Trihalomethane from water samples. In this technique a micro drop of n-hexane is delivered to the surface of an aqueous sample while being agitated by a stirring bar in the bulk of solution. Factors relevant to the extraction efficiency were studied and optimized. The optimized extraction conditions were extraction solvent: n- hexane; NaCl concentration: 1M; solvent extraction volume: 50μL; stirring rate: 720rpm and the extraction time: 5min. The detection limits of the method were in the range of 0.059–0.137µgL−1, relative standard deviation (n=3) range were 0.019–0.048%. A good linearity (r2≥0.997) and a relatively broad dynamic linear range (10–200µgL−1) were obtained and recoveries of method were in the range of 97.69–99.51%. Finally, the proposed method was successfully utilized for pre concentration and determination of halo methane in different real samples. Successfully DSDME technique combined with capillary GC-ECD for the analysis of THMs and HMs in the water investigated samples.

Fast agitated directly suspended droplet microextraction technique for the rapid analysis of eighteen organophosphorus pesticides in human blood

A new sample preparation technique named as fast agitated directly suspended droplet microextraction (FA-DSDME) was proposed as an improved version of directly suspended droplet microextraction (DSDME) for the extraction and pre-concentration of wide-range organophosphorus pesticides (OPPs) from human blood prior to liquid chromatography tandem mass spectrometric (LC–MS/MS) analysis. In this method, instead of protecting the unwanted rupturing of extraction droplet (organic solvent), it was deliberately splintered into fine droplets by providing automated high-speed agitation to the biphasic extraction system (extraction solvent and sample solution). Fine organic droplets were then recollected into one, not by using a centrifuge machine but just by giving a very slow stirring to the bottom of the extraction system. The present method has surmounted the problem of prolonged extraction time associated with old DSDME. Under optimum extraction conditions, the method showed good sensitivity with low detection limits ranging from 0.0009 to 0.122μgL−1. Mean recoveries were achieved in the range of 86–109% at three levels of spiking concentration (low, middle and high) from linearity range of individual analyte. Intra-day and inter-day precisions were ≤4.68 and ≤9.57 (%RSD) respectively. Enrichment factor (EF) for each analyte varied from 30 to 132 which prove the ability of this technique to pre-concentrate the extracted analytes up to a good extent. The sample matrices have shown an insignificant influence on method's sensitivity. The proposed method may find immense use in epidemiological, toxicological, regulatory and forensic laboratories.

Indirectly suspended droplet microextraction of water-miscible organic solvents by salting-out effect for the determination of polycyclic aromatic hydrocarbons.

A simple and low-cost method that indirectly suspended droplet microextraction of water-miscible organic solvents (ISDME) by salting-out effect before high-performance liquid chromatography and ultraviolet (HPLC-UV) detection was used for the determination of polycyclic aromatic hydrocarbons (PAHs) in different samples. The ISDME is a combination of salting-out extraction of water-miscible organic solvent and directly suspended droplet microextraction (DSDME). Ninety-five microliters water-miscible organic solvent (1-propanol) was added to a 500-µL sample. A homogeneous solution was formed immediately. To produce a steady vortex at the top of the solution, the sample was agitated at 700 rpm using a magnetic stirrer. By the addition of ammonium sulfate (saturated solution) to the homogeneous solution, 1-propanol was separated and collected at the bottom of the steady vortex. Finally, 20 µL 1-propanol was injected into HPLC-UV. The effects of important parameters such as water-miscible organic solvent (type and volume), type of salt, and extraction time were evaluated. Under optimum conditions, the method has a good linear calibration range (0.1 µg/L-300 µg/L), coefficients of determination (R(2) > 0.998), low limits of detection (between 0.02 µg/L and 0.27 µg/L), and acceptable recovery (>85.0%).

Determination of Organochlorine Pesticides in Tea Beverage by Directly Suspended Droplet Microextraction Combined with GC-ECD

In this paper, a simple and efficient directly suspended droplet microextraction (DSDME) method has been developed and optimized, which can be applied on extracting organochlorine pesticides (OCPs) in beverage for gas chromatography–electron capture detector (GC-ECD) analysis. The optimal DSDME was adding 100 μL of isooctane into 5 mL of the beverage sample and stirred for 10 min at 1,000 rpm. The relative recoveries of the DSDME method were ranged from 81 to 117 % (relative standard deviations were 2–20 %, n = 5). The limits of detections were 0.8–5.0 ng/L. Furthermore, DSDME was applied to rapidly determine the OCPs in tea beverage and the results suggested that the method can be used as rapid determination of OCPs in the tea beverage.

Determination of organochlorine pesticide residues in rice by gas chromatography-mass spectrometry following directly suspended droplet microextraction

A simple and efficient approach as directly suspended droplet microextraction (DSDME) was applied to the determination of organochlorine pesticides in rice prior to analysis by gas chromatography-mass spectrometry (GC-MS). The extraction parameters such as organic solvent type and volume, extraction time, and ion strength were systemically optimized. Furthermore, method linearity, recovery, limits of detections (LODs), and precision were also investigated. The proposed method provided good linearity (R2 = 0.9900–0.9996). LODs determined by GC-MS in selected-ion monitoring (SIM) mode were between 0.0005–0.033 mg/kg. The relative standard deviations (RSDs) varied from 2.0–14.0%, while the enrichment factors were between 221–550. The experimental results suggest that DSDME followed by GC-MS is a simple, sensitive, low-cost and little solvent consumption for the determination of organochlorine pesticides in rice, and has high enrichment factors suitable to trace analysis.

Combination of Directly Suspended Droplet Microextraction and Flame Atomic Absorption Spectrometry for Determination of Trace Amounts of Iron and Copper

A miniaturized liquid-phase extraction procedure based on directly suspended droplet microextraction combined with flame atomic absorption spectrometry was developed for determination of trace amounts of iron and copper, without any need for the centrifugation step for phase separation. The method was based on the extraction of the iron and copper complexes with 2-mercaptopyridine-N-oxide onto a microdrop of methyl isobutyl ketone (MIBK) as extractant solvent. The factors influencing the extraction were optimized. Under optimum conditions, an enrichment factor of ~25 was obtained for both iron and copper from only 6.5 mL of aqueous phase. The analytical curves were linear between 40-800 μg L-1 and 25-1200 μg L-1 for iron and copper, respectively. The limits of detection were 3.76 μg L-1and 1.84 μg L-1 for iron and copper, respectively. The developed method has been successfully applied for the determination of iron and copper ions in environmental waters, fruits, vegetables and also certified reference materials, with high efficiency.

Determination of Aroma Components in Chinese Southwest Tobacco by Directly Suspended Droplet Microextraction Combined with GC–MS

In this paper, a simple and efficient approach, directly suspended droplet microextraction (DSDME), has been applied to extract aroma components in Chinese southwest tobacco prior to analysis by gas chromatography-mass spectrometry (GC-MS). The extraction parameters such as organic solvent type, extraction time, temperature, stirring speed and volume were systemically optimized. A single drop of cyclohexane was placed on the top of the aqueous sample which was used as solvent. Under the optimal conditions of DSDME, 62 aroma components of tobacco were analyzed and identified by GC-MS. The approach was used to determine some important aromas in tobacco with the relative recoveries ranged from 75.92 to 102.88%, relative standard deviations in the range of 3.40-7.14% (n = 5) and the limits of detection of 0.0002-0.002 μg/mL. Moreover, the DSDME was applied to identify the aromatic components in Chinese southwest tobacco in this research for the first time and the results suggested that the method can be used as rapid determination of the tobacco. This method can enhance the extracting rate of tobacco aromatic components and meet the need of qualitative analysis of large amount samples.

Rapid analysis of organochlorine and pyrethroid pesticides in tea samples by directly suspended droplet microextraction using a gas chromatography–electron capture detector

A simple and efficient directly suspended droplet microextraction (DSDME) has been developed to extract and pre-concentrate organochlorine and pyrethrin pesticides from tea samples prior to analysis by a gas chromatography–electron capture detector (GC–ECD). The optimal experimental conditions of DSDME were: 100μL isooctane exposed for 15min to 5mL of the tea aqueous sample stirred at 1100rpm. For most of the target analytes, the optimal pretreatment of DSDME processes led to no significant interference of tea matrices. The approach was applied to the determination of organochlorine and pyrethroid pesticides in tea samples, with a linearity range of 0.0005–2μg/mL. The relative recoveries of all the pesticides ranged between 80.0% and 120.8% with relative standard deviations (RSDs) in the range of 0.8–19.9% (n=5). The limits of detections (LODs) ranged between 0.04 and 1μg/L for all the target pesticides.

Directly suspended droplet microextraction combined with energy-dispersive X-ray fluorescence spectrometry to determine nano levels of phosphate in surface water

Directly suspended droplet microextraction (DSDME) for determination of phosphate by energy-dispersive X-ray fluorescence spectrometry (EDXRF) is proposed. The method is based on the determination of phosphate, through molybdenum in the phosphomolybdenum blue complex. Because phosphorus is determined indirectly via molybdenum fluorescent radiation the difficulties of low fluorescent yield and low energy of phosphorus radiation are successfully overcome. A good ratio of phosphorus to molybdenum (1 to 37) and a sensitive Kα line of molybdenum give the possibility to determine a low concentration of phosphorus. Under the optimized conditions, good linearity, up to 20 μg of phosphorus (r = 0.9995), and the detection limit (2.8 ng mL−1) for the sample of 1.5 mL were achieved. The total RSD for the EDXRF determination of phosphorus followed by DSDME was 2.6% and taking into account all steps preceding the determination and the uncertainty of EDXRF measurements, the proposed method can be recognized as highly precise. The enrichment factor was equal to 56.8. The developed method was used to determine the total phosphorus content in surface waters. The accuracy and repeatability of the proposed procedure were checked by the standard addition method. The recovery in the range 93.5–97% was satisfactory and indicated the usefulness of the developed procedure.

Rapid screening of polycyclic aromatic hydrocarbons (PAHs) in waters by directly suspended droplet microextraction-microvolume fluorospectrometry

A rapid and simple screening method for polycyclic aromatic hydrocarbons (PAHs) in water samples is proposed. The method is based on the combination of a miniaturized sample preparation approach, namely, directly suspended droplet microextraction (DSDME), and microvolume fluorospectrometry. Benzo[a]pyrene (BaP) was used as the model compound for screening purposes. Under optimal conditions, a detection limit of 0.024μgL−1 and an enrichment factor of 159 were obtained for BaP in 5min. The repeatability, expressed as relative standard deviation (RSD), was 4.9% (n=8). The unreliability region of the screening method was 0.54–0.67μgL−1, by using a cut-off value of 0.6μgL−1 of BaP. Finally, the proposed method was applied to the in situ achievement of the binary “yes/no” response for PAHs in different water samples and recovery studies were performed at three different levels, with BaP recoveries in the range of 93–104%.

Directly suspended droplet microextraction in combination with microvolume UV–vis spectrophotometry for determination of phosphate

A miniaturized methodology for the determination of phosphate in waters has been developed by combining directly suspended droplet microextraction (DSDME) with microvolume spectrophotometry. The method is based on the extraction of the ion pair formed between 12-molybdophosphate and malachite green onto a microdrop of methyl isobutyl ketone and subsequent spectrophotometric determination with no dilution. An enrichment factor of 325 was obtained after 7.5 min of microextraction. The detection limit was 6.1 nM phosphate and the repeatability, expressed as relative standard deviation, was 2.7% ( n = 6). The method was successfully applied to the determination of dissolved reactive phosphorus in different freshwater samples.

Directly suspended droplet microextraction combined with single drop back-extraction as a new approach for sample preparation compatible with capillary electrophoresis

A simple and novel method of directly suspended droplet microextraction (DSDME) combined with single drop back-extraction prior to capillary electrophoresis (CE) measurement is developed. In this technique, DSDME was firstly carried out under the maximum stirring rate for a desired time. Then, an aqueous droplet as back-extractive phase suspended at the needle tip was immersed in droplet of organic phase for back-extracted. After extraction, the aqueous droplet was transferred into a suitable vial and injected into CE for analysis. Three alkaloids were selected as model compounds for developing and evaluating the method performance. Under the optimum conditions, the enrichment factors ranged from 231 to 524. The relative standard deviations for five replicates were in the range of 4.8–8.1%. The calibration graph was linear in the range of 20–1000ngmL−1 yielding correlation coefficients higher than 0.9983. The limit of detections varied from 8.1 to 14.1ngmL−1. Human urine samples were spiked with three alkaloids standard to assess the matrix effects and satisfactory results were obtained. The advantages of this method are simplicity of operation, rapid detection, low cost, high enrichment factor and little solvent consumption.

Separation and determination of benzene, toluene, ethylbenzene and o-xylene compounds in water using directly suspended droplet microextraction coupled with gas chromatography-flame ionization detector

The directly suspended droplet microextraction (DSDME) technique coupled with the capillary gas chromatography-flame ionization detector (GC-FID) was used to determine BTEX compounds in aqueous samples. The effective parameters such as organic solvent, extraction time, microdroplet volume, salt effect and stirring speed were optimized. The performance of the proposed technique was evaluated for the determination of BTEX compounds in natural water samples. Under the optimal conditions the enrichment factors ranged from 142.68 to 312.13, linear range; 0.01–20 μg mL −1, limits of detection; 0.8–7 ng mL −1 for most analytes. Relative standard deviations for 0.2 μg mL −1 of BTEX in water were in the range 1.81–2.47% ( n = 5). The relative recoveries of BTEX from surface water at spiking level of 0.2 μg mL −1 were in the range of 89.87–98.62%.

Directly Suspended Droplet Microextraction and Analysis of Amitriptyline and Nortriptyline by GC

Directly Suspended Droplet Microextraction (DSDME) was used for the determination of two tricyclic antidepressant drugs (TCAs), amitriptyline and nortriptyline. In this technique, an aqueous sample is agitated with a stirring bar, creating a mild vortex at the center of the vial. A droplet of an immiscible organic solvent is placed at the bottom of the vortex. After 20 min a portion of the organic droplet is withdrawn with a syringe and injected into the GC. Experimental conditions, such as the extraction solvent, extraction time, solvent volume, stirring rate, pH and salt addition were optimized. In order to evaluate the practical application of the method, relative standard deviations, linearity range and limits of detection were calculated. Typical enrichment factors were 167 and 179 for amitriptyline and nortriptyline, respectively. The method was applied to the determination of these drugs in urine samples.

Directly suspended droplet microextraction

This work describes a new sampling method termed directly suspended droplet microextraction (DSDME) was developed. In this technique a free microdroplet of solvent is delivered to the surface of an immiscible aqueous sample while being agitated by a stirring bar placed on the bottom of the sample cell. After some time, the microdroplet of solvent is withdrawn by a syringe and analyzed. Under the proper stirring conditions, the suspended droplet can remain in a top-center position of the aqueous sample. The droplet can become partly engulfed within the sample while maintaining a stable shape with mechanical equilibrium and the mass transfer could be effectively intensified. Using 1,8-dioxyanthraquinone as a model compound and 1-octanol as the solvent, the extraction performance was investigated using HPLC. Since DSDME is based on a self-stable single microdroplet system, there are no requirements for special equipment or other supporting material like hollow fibers. Other advantages include ease of operation, free from cross contamination, quick to reach extraction equilibrium, and the ability to be combined with various analysis instruments. In our experiments, good linearity ( r 2 = 0.9992) and precision (R.S.D. < 1%, n = 5) were achieved. DSDME is a promising pre-treatment method for the fast analysis of trace components in complicated matrices.