Vortex‐Assisted Surfactant‐Based Extraction

Surfactant‐Based Materials*

4.3 Surfactant‐Based Liquid‐Phase Extraction

4.3.4 Vortex‐Assisted Surfactant‐Based Extraction

In 2010, Yiantzi et al. proposed a new and fast LLME method whereby dispersion of the extractant into the aqueous phase was achieved using vortex mixing as a mild emulsifi- cation procedure [77]. The method was termed vortex‐assisted liquid–liquid microex- traction or VALLME, and was developed for trace analysis of octylphenol, nonylphenol, and bisphenol‐A in water and wastewater samples. By vortex agitation, equilibrium conditions could be achieved within only a few minutes under a mild emulsification procedure, avoiding problems associated with the application of ultrasound. Since its introduction, the method has been successfully applied in the determination of various compounds, both organic and inorganic analytes, as summarized in Table 4.4.

In 2011, Yang et al. introduced a novel extraction technique, named vortex‐assisted surfactant‐enhanced liquid–liquid microextraction (VSLLME), for the determination of organophosphorus in wine and honey samples [78]. In this microextraction process, the addition of surfactant as emulsifier combined with vortex agitation can greatly enhance the extraction efficiency and reduce the extraction time. Compared with ultra- sonic radiation, vortex mixing is a mild emulsification procedure that can avoid the degradation of some analytes under some special conditions. In the VSLLME method, chlorobenzene (as extraction solvent) was dispersed into the aqueous sample by the assistance of a vortex agitator. Addition of Triton X‐114 (as emulsifier) could enhance the speed of the mass transfer from the aqueous sample to the extraction solvent. The relatively high extraction efficiency was obtained using non‐ionic surfactant. This could be due to organophosphorus having no basic functional groups, so they cannot form an ion pair complex with any of surfactants. Therefore, the formation of non‐ionic inter- molecular forces between the analytes and the surfactants could be favored. A sur- factant concentration lower than its cmc was used. Dispersion of the extraction solvent into the aqueous sample depended on the rotational speed and vortex time. A positive effect on the extraction efficiency happened upon addition of salt (sodium chloride in this work). The proposed method has been applied to wine and honey samples.

Quantification could be performed without significant effect arising from sample matrices.

Analytes (Reference) Sample matrix Extraction conditions/Analytical technique Analytical performance Organophosphorus (ethoprophos,

malathion, chlorpyriphos, isocarbophos, methidathion, profenofos, triazophos) [78]

Wine, honey VSLLME/GC‐FPD Sample: 5.0 ml

Extractant: 15  μ l chlorobenzene Emulsifier: 5.0  μ l Triton X‐114 (200 mmol l ⁻¹ ) Vortex: 30 s (2800 rpm)

Centrifugation: 5 min (3800 rpm)

Linear range: 0.1–50.0  μ g l ⁻¹ RSDs: 2.3–8.9% ( n  = 6) EFs: 282–309 LODs: 0.01–0.05  μ g l ⁻¹ Recovery: 81.2–108.0%

Organophosphorus (ethoprophos, fenitrothion, malathion, chlorpyrifos, isocarbophos, methidathion, profenofos, triazophos) [79]

Water DA‐VSLLME/GC‐FPD

Sample: 5.0 ml Extractant: 35  μ l toluene

Emulsifier: 5.0  μ l Triton X‐100 (200 mmol l ⁻¹ ) Vortex: 3 min (2800 rpm)

Centrifugation: 5 min (3800 rpm)

Linear range: 0.1–50.0  μ g l ⁻¹ RSDs: 2.9–8.1% ( n  = 6) LODs: 0.01–0.05  μ g l ⁻¹ Recovery: 82.1–98.7% (RSDs 1.4–7.3%)

Organophosphorus (ethoprophos, fenitrothion, malathion, chlorpyrifos, isocarbophos, methidathion, profenofos, triazophos) [80]

Water, honey LDS‐VSLLME/GC‐FPD Sample: 5.0 ml Extractant: 30.0  μ l toluene

Emulsifier: 5.0  μ l Triton X‐100 (200 mmol l ⁻¹ ) Vortex: 1 min (2800 rpm)

Centrifugation: 5 min (3800 rpm)

Linear range: 0.1–50.0  μ g l ⁻¹ RSDs: 2.1–11.3% ( n  = 6) LODs: 0.005–0.05  μ g l ⁻¹ Recovery: 82.8–100.2% (RSDs 2.5–9.5%)

Triazine herbicides (simazine, atrazine, ametryn, prometryn, terbutryn) [81]

Water VSLLME/ MEEKC‐DAD

Sample: 5.0 ml

Extractant: 100  μ l chloroform

Emulsifier: 12.5  μ l Tween 20 (2.0 × 10 ⁻² mol l ⁻¹ ) Vortex: 3 min (2800 rpm)

Centrifugation: 5 min (2500 rpm)

Linear range: 2.0–200 ng ml ⁻¹ RSDs: 5.6% (intra‐day), 7.3%

(inter‐day) EFs: 265–318 LODs: 0.41–0.62 ng ml ⁻¹ Recovery: 80.6–107.3%

Analytes (Reference) Sample matrix Extraction conditions/Analytical technique Analytical performance Carbamates (25 carbamates) [82] Juices VSLLME/ MEKC‐MS/MS

Sample: 5 g

Extractant: 1300  μ l chloroform Emulsifier: 530  μ l APFO (100 mmol l ⁻¹ ) Vortex: 30 s

Centrifugation: 10 min (9509 rcf)

Linear range: 5–250  μ g kg ⁻¹ RSDs: <10% (intra‐day), <12%

(inter‐day) LODs: 0.7–1.4  μ g kg ⁻¹ Recovery: 91–104% (RSDs <15%)

Neonicotinoid pesticides (nitenpyram, thiamethoxam, clothianidin, imidacloprid, acetamiprid) [83]

Water, fruits VSLLME‐SFO/HPLC‐PDA Sample: 10.00 ml Extractant: 150  μ l octanol Emulsifier: 50  μ l SDS (0.050 mol l ⁻¹ ) Salt: 0.3% Na 2 SO 4

Vortex: 1 min

Centrifugation: 10 min (5000 rpm)

Linear range: 0.0005–5  μ g ml ⁻¹ RSDs: 0.75–1.45% ( t R , n  = 5), 1.54–3.45% (peak area, n  = 5) EFs: 20–100

LODs: 0.1–0.5  μ g l ⁻¹

Recovery: 85–105% (water), 87–105%

(fruits) 3,5,6‐Trichloro‐2‐pyridinol, phoxim,

chlorpyrifos‐methyl [84] Water LDS‐VSLLME‐SFO/HPLC‐UV

Sample: 15 ml Salt: 1.0 g NaCl

Extractant: 80  μ l 1‐undecanol

Emulsifier: 100.0  μ l Triton X‐114 (0.02 mol L ⁻¹ ) Vortex: 60 s (3000 rpm)

Centrifugation: 3 min (4000 rpm)

Linear range: 0.5–500  μ g l ⁻¹ RSDs: 0.26–2.62% ( n  = 6) EFs: 172–186 LODs: 0.05–0.12  μ g l ⁻¹ Recovery: 82–104% (RSDs <2.62%)

Herbicides (triazine, phenylurea) [85] Milk VASEME‐SFO/HPLC‐DAD Sample: 5.0 ml

Extractant: 30  μ l 1‐dodecanol Emulsifier: 0.04 mmol l ⁻¹ Tween 80 Vortex: 30 s

Centrifugation: 5 min (5000 rpm)

Linear range: 0.2–200  μ g l ⁻¹ (triazine),

2–400  μ g l ⁻¹ (phenylurea) RSDs: <10.6% ( n  = 6) LODs: 0.005–0.09  μ g L ⁻¹ Recovery: 80.5–105.6%

(Continued)

Analytes (Reference) Sample matrix Extraction conditions/Analytical technique Analytical performance Phthalate esters (dimethyl phthalate,

diethyl phthalate, di‐ n ‐butyl phthalate, benzyl butyl phthalate, di‐2‐ethyl hexyl phthalate, di‐ n ‐octyl phthalate) [86]

Bottled water LDS‐VSLLME/GC–MS Sample: 5 ml Extractant: 30  μ l toluene

Emulsifier: 50  μ l CTAB (2.0 × 10 ⁻² mol l ⁻¹ ) Vortex: 1 min (3200 rpm)

Centrifugation: 5 min (4000 rpm)

Linear range: 0.05–25  μ g l ⁻¹ RSDs: <11.9% ( n  = 5) EFs: 200–290 LODs: 8–25  μ g l ⁻¹ Recovery: 73.5–106.6% (RSDs

<11.7%) Phthalate esters (dibutyl phthalate,

butyl benzyl ester, di‐2‐ethyl hexyl phthalate, dioctyl phthalate) [87]

Liquor VSLLME/GC–MS

Sample: 5.0 ml Extractant: 250  μ l CCl 4

Emulsifier: 5.0  μ l Triton X‐100 (0.2 mmol l ⁻¹ ) Vortex: 30 s (2800 rpm)

Centrifugation: 5 min (6000 rpm, 2 °C)

Linear range: 0.05–50  μ g l ⁻¹ RSDs: 6.2–11.2%

LODs: 4.9–13 ng l ⁻¹ EFs: 140–184

Recovery: 75.2–92.9% (RSDs 4.3–4.7%)

Biogenic amines (tryptamine, histamine, cadaverine, tyramine, spermidine) [88]

Fermented

food VSLLME/HPLC‐UV

Sample: 200  μ l (with 4 ml borate buffer pH 9.0, 500  μ l 5000 mg l ⁻¹ FMOC)

Extractant: 165  μ l 1‐octanol Emulsifier: 100  μ l SDS (10 mmol l ⁻¹ ) Vortex: 1 min

Linear range: 0.002–1 mg l ⁻¹ RSDs: 3.64–6.86% (intra‐day), 5.90–7.76% (inter‐day) LODs: 0.0010–0.0026 mg l ⁻¹ EFs: 161–553

Recovery: 83.2–112.5%

Heterocyclic aromatic amines (2‐amino‐3,4‐dimethyl‐3 H ‐ imidazo[4,5‐f]quinolone, 2‐

amino‐3,4,8‐trimethyl‐3 H ‐ imidazo[4,5‐ f ]quinoxaline, 2‐amino‐1‐methyl‐6‐

phenylimidazo[4,5‐ b ]pyridine, 1‐methyl‐9 H ‐pyrido[3,4‐ b ]indole) [89]

Grilled pork IP‐SA‐DLLME/HPLC‐PDA Sample: 10 ml

Ion‐pair: 0.03 mmol l ⁻¹ SDS Extractant: 150  μ l 1‐octanol Vortex: 30 s

Centrifugation: 10 min (3000 rpm)

Linear range: 0.01–1000  μ g kg ⁻¹ RSDs: <0.79% ( t R ), <7.72% (peak area) EFs: 124–145

LOD: 0.01  μ g kg ⁻¹

Recovery: 90–106% (RSDs <7.6%)

Analytes (Reference) Sample matrix Extraction conditions/Analytical technique Analytical performance

Scutellarin [90] Urine VASEME/HPLC‐UV

Sample: 5 ml

Extractant: 300  μ l pentanol Emulsifier: 100  μ l Triton X‐100 Vortex: 1 min

Centrifugation: 5 min (3500 rpm)

Linear range: 0.04–24  μ g ml ⁻¹ RSD: 3.1% ( n  = 5) LOD: 1.3 ng ml ⁻¹ Recovery: 86.3–93.6%

Naproxen, nabumetone [91] Urine, water, wastewater, milk

VASEME‐SFO/HPLC‐FLD Sample: 13 ml (pH 3.0) Extractant: 20  μ l 1‐undecanol Emulsifier: 0.2 mmol l ⁻¹ Triton X‐100 Salt: 4.0% potassium chloride Vortex: 2 min

Centrifugation: 5 min (5000 rpm)

Linear range: 3.0–300.0 ng l ⁻¹ (naproxen),

7.0–300.0 ng l ⁻¹ (nabumetone) RSDs: 3.8–6.1% (intra‐day), 5.8–10.1% (inter‐day) EFs: 620 (naproxen), 621 (nabumetone)

LODs: 0.9 ng l ⁻¹ (naproxen), 2.1 ng l ⁻¹ (nabumetone)

Recovery: 94.80–102.46%

Nitrite [92] Urine VASEME/HPLC‐FLD

Sample: 5 ml (with 160  μ l 1 mol l ⁻¹ HCl + 200  μ l 0.025% o ‐phenylenediamine), adjusted pH with 164  μ l 1.09 mol l ⁻¹ NaOH, added 200  μ l 0.15 mol l ⁻¹ HP‐ β ‐CD

Extractant: 500  μ l n ‐octanol Emulsifier: 20  μ l Triton X‐114 Vortex: 1 min

Centrifugation: 5 min (3500 rpm)

Linear range: 4–80 ng ml ⁻¹ RSD: 3.7% ( n  = 5) LOD: 0.08 ng ml ⁻¹

Recovery: 85–92.6% (RSDs 4.3–5.5%)

(Continued)

Analytes (Reference) Sample matrix Extraction conditions/Analytical technique Analytical performance

Antimony (III,V) [93] Water VASEME‐SFO/ETAAS

Sample: 8 ml (with 3.2 × 10 ⁻⁴ mol l ⁻¹ dithizone) Extractant: 65  μ l 1‐undecanol

Emulsifier: 1.25 × 10 ⁻⁵ mol l ⁻¹ Triton X‐114 Vortex: 100 s (2800 rpm)

Centrifugation: 4 min (3600 rpm) Ice bath: 10 min

Linear range: 0.4–8  μ g l ⁻¹ RSDs: 4.3–5.4% ( n  = 6) EF: 53

LOD: 0.09  μ g l ⁻¹ Recovery: 94.6–105.0%

Lead [94] Water LT‐VSLLME/GFAAS

Sample: 10 ml

Chelating agent: 2.5 × 10 ⁻³ mol l ⁻¹ 5‐Br‐PADAP Extractant: 40  μ l 1‐bromo‐3‐methylbutane Emulsifier: 20  μ l Triton X‐100 (0.12 mol l ⁻¹ ) Vortex: 1 min (3000 rpm)

Centrifugation: 3 min (4000 rpm)

Linear range: 5–30 ng l ⁻¹ RSD: 5.6% ( n  = 7) EF: 320 LOD: 0.76 ng l ⁻¹ Recovery: 97.51–105.23%

AuNPs [95] Environmental

water SA‐DLLME/ ETV‐ICP‐MS

Sample: 5.0 ml

Extractant: 70  μ l 1,2‐dichloroethane Emulsifier: 50  μ l Triton X‐114 (10%) Vortex: 1 min

Centrifugation: 3 min (2500 rpm)

Linear range: 0.01–10  μ g l ⁻¹ RSD: 9.3% ( n  = 7) EF: 152 LOD: 2.2 ng l ⁻¹ Recovery: 89.6–102%

Cadmium [96] Water VALLME/FAAS

Sample: 10 ml (with 1 ml APDC, 0.2% w/v, adjusted pH to 6 with buffer solution) Extractant: 200  μ l [C 4 MIM][PF 6 ] Emulsifier: 500  μ l Triton X‐114 (0.1% w/v) Vortex: 10 s (2800 rpm)

Centrifugation: 10 min (3500 rpm)

Linear range: 10–200  μ g l ⁻¹ RSD: 4.2% ( n  = 10) EF: 20 LOD: 0.5  μ g l ⁻¹ Recovery: 98.1–101%

Analytes (Reference) Sample matrix Extraction conditions/Analytical technique Analytical performance Glucocorticoids (beclomethasone

dipropionate, hydrocortisone butylrate, nandrolone phenylpropionate) [97]

Water ILSVA‐SME/HPLC‐DAD

Sample: 5.0 ml

Extractant: 200  μ l [BMIM]PF 6 Emulsifier: 500  μ l Triton X‐100 (0.05% v/v) Vortex: 3 min

Ice bath: 5 min

Linear range: 0.6–300 ng ml ⁻¹ RSDs: 1.57–1.81% ( n  = 6) EF: 99.85

LODs: 4.11–9.19 ng ml ⁻¹ Recovery: 97.24–102.21% (RSDs

<1.81%) Benzimidazole anthelmintics

(thiabendazole, mebendazole, albendazole, fenbendazole) [98]

Tissues (liver,

kidney) VASEME‐SFO/HPLC‐PDA

Sample: 10 ml Extractant: 300  μ l octanol

Emulsifier: 0.01 mol l ⁻¹ SDS + 0.01 mol l ⁻¹ CTAB Salt: 5% w/v Na 2 SO 4

Vortex: 1 min (1500 rpm) Centrifugation: 10 min (3000 rpm)

Linear range: 5–1000  μ g kg ⁻¹ RSDs: <1.5% ( t R ), <8.0% (peak area) EFs: 33–60

LODs: 0.3–0.5  μ g kg ⁻¹

Recovery: 87–105% (RSDs 0.8–3.2%, n  = 3)

Synthetic antioxidants ( t ‐butyl hydroquinone, butylated hydroxyanisole) [99]

Edible oil WSVAME/HPLC‐UV

Sample: 5.0 ml

Extractant: 30  μ l Brij‐35 (0.10 mol l ⁻¹ ) Vortex: 1 min

Centrifugation: 1 min (3000 rpm)

Linear range: 0.200–200  μ g ml ⁻¹ RSDs: ≤3.0% (intra‐day, n  = 5),

≤3.80% (inter‐day, n  = 5) EFs: 164 ( t ‐butyl hydroquinone), 160 (butylated hydroxyanisole) LODs: 0.026  μ g ml ⁻¹ ( t ‐butyl hydroquinone), 0.020  μ g ml ⁻¹ (butylated hydroxyanisole) Recovery: >95% (RSDs <5%) VSLLME: vortex‐assisted surfactant‐enhanced liquid–liquid microextraction; GC‐FPD : gas chromatography‐flame photometric detector ; DA‐VSLLME : home‐made extraction device assisted vortex‐assisted surfactant‐enhanced‐emulsification liquid–liquidmicroextraction; LDS‐VSLLME : low‐density solvent‐based vortex‐assisted surfactant‐enhanced‐emulsification liquid–liquid microextraction ; MEEKC‐DAD : microemulsion electrokinetic chromatography‐diode array detector ; MEKC‐MS/MS:

micellar electrokinetic chromatography tandem mass spectrometry; VSLLME‐SFO: vortex‐assisted surfactant‐enhanced‐emulsification liquid–liquid microextraction with solidification of floating organic droplet; PDA: photodiode array detector; SDS: sodium dodecylsulfate; LDS‐VSLLME‐SFO : low‐density solvent‐based vortex‐assisted surfactant‐enhanced‐emulsification liquid–liquid microextraction with the solidification of floating organic droplet ; VASEME‐SFO : vortex‐assisted surfactant‐enhanced emulsification microextraction based on the solidification of a floating organic droplet ; GC‐MS: gas chromatography–mass spectrometry; IP‐SA‐DLLME: ion‐pair‐based surfactant‐assisted dispersive liquid–liquid microextraction; VASEME : vortex‐assisted surfactant‐enhanced emulsification microextraction ; FLD: fluorescence detector;

ETAAS: electrothermal atomic absorption spectrometry; LT‐VSLLME : low toxic solvent‐based vortex‐assisted surfactant‐enhanced emulsification liquid–liquid microextraction ; SA‐DLLME: surfactant‐assisted dispersive liquid–liquid microextraction; ETV‐ICP‐MS: electrothermal vaporization inductively coupled plasma mass spectrometry; VALLME: vortex‐assisted liquid–liquid microextraction; FAAS: flame atomic absorption spectrometry; APDC: ammonium pyrrolidine dithiocarbamate;

ILSVA‐SME: ionic liquid supported vortex‐assisted synergic microextraction; WSVAME: water‐contained surfactant‐based vortex‐assisted microextraction.

Other applications of VSLLME for organophosphorus have been proposed using two special home‐made extraction devices. The first device employed a 1.0 ml disposable sterilized syringe, whose needle section was cutt off and replaced with a 1.0 ml pipette tip [79]. The second was a disposable polyethylene pipette (bottom size is 40 mm × 12 mm i.d. and neck size is 120 mm × 6 mm i.d.) [80]. Toluene and Triton X‐100 were used as extractant and emulsifier, respectively, in both systems. The tube was shook on a vortex agitator. The equilibrium state could be achieved very quickly. Using a low density extractant, the upper extraction solvent was moved into the narrow pipette tip where it was easily collected efficiently for analysis.

Various VSLLME systems have been developed for preconcentration of different groups of pesticides. For trace herbicides, chloroform was used as extraction solvent, and Tween 20 was added as emulsifier [81]. The tube was vigorously shaken on a vortex agitator before collecting the organic droplets by centrifugation. Although Tween 20 at a concentration lower than the cmc was used, some aggregations like micelles could still be formed under vortex mixing, causing a decrease of extraction efficiency because a small fraction of analytes could probably incorporate into these micelles. The enrich- ment factors decreased on using a long vortex time because more chloroform dissolved in the aqueous solution. The applicability of the proposed method in the analysis of real water samples using microemulsion electrokinetic chromatography (MEEKC) was acceptable. For preconcentration of carbamates prior to analysis by micellar electroki- netic chromatography‐tandem mass spectrometry [82], the method allowed the satis- factory extraction of 25 carbamates from different fruit and vegetal juices by addition of ammonium perfluorooctanoate in an aqueous sample in combination with vortex agi- tation using chloroform as extractant.

Application of low‐density solvent in vortex‐assisted surfactant enhanced‐emulsification liquid–liquid microextraction with the solidification of floating organic droplet (VSLLME‐SFO) methods for preconcentration of pesticides have also been reported.

Five neonicotinoid pesticides in fruit juice and water samples were extracted using SDS as emulsifier [83]. The solution was subjected to vortex agitation and octanol (as extractant) was injected rapidly before centrifugation to complete the phase separation.

The reconstituted phase floated on the top of the tube as analyzed by HPLC. For extrac- tion of 3,5,6‐trichloro‐2‐pyridinol, phoxim, and chlorpyrifos‐methyl pesticides in water samples, a mixture of 1‐undecanol as an extraction solvent and Triton X‐114 as an emulsifier was added into the sample solution [84]. After adding acetic acid, the mixture was vigorously shaken on a vortex agitation to promote an emulsion containing fine droplets and facilitate mass transfer of the target analytes into the extractant. The emul- sion was disrupted by centrifugation and the organic phase was then analyzed. Triazine and phenylurea herbicides in milk could be preconcentrated using 1‐dodecanol as extraction solvent, dispersed into the aqueous sample by the assistance of vortex and surfactant addition [85]. Tween 80 non‐ionic surfactant was selected as emulsifier due to a suitable hydrophobicity for most of the target herbicides. The method has some advantages over other extraction techniques, such as short extraction time, easy to operate, low cost, and reduced exposure to dangerous organic toxic solvent.

Extraction of phthalate esters has been reported using low‐density solvent‐based vortex‐assisted surfactant‐enhanced‐emulsification liquid–liquid microextraction (LDS‐VSLLME) [86]. The method was developed using toluene and CTAB as extraction solvent and emulsifier, respectively. Toluene is much less toxic than the conventional

Surfactant-Based Materials 141

chlorinated solvents. The proposed method employed the surfactant as a substitute for the large amount of dispersive solvent that is often applied in DLLME. In addition, the combination of surfactant and vortex agitation was highly efficient for the dispersion of the organic extractant, and thus extraction equilibrium could be achieved in a short time. For application in samples with an alcohol content, a high‐density extraction sol- vent (carbon tetrachloride) was dispersed into the samples with the aid of Triton X‐100 surfactant and vortex agitation [87]. A short extraction equilibrium was achieved within 30 s. After centrifugation, a microdrop of extractant was collected for GC‐MS analysis.

For analysis of biogenic amine in high matrix samples, such as fermented food [88], biogenic amines were derivatized with 9‐fluorenylmethyl chloroformate, and then extracted using 1‐octanol and SDS as extraction solvent and emulsifier, respectively.

After vortex shaking, the floating phase was collected and injected into HPLC for analysis. The heterocyclic aromatic amines were determined based on ion‐pair forma- tion with SDS [89]. In the extraction process, SDS acted as both ion‐pairing and dis- perser agents. 1‐Octanol was selected as extraction solvent. A cloudy solution was quickly formed, within 30 s, under vortex agitation. After centrifugation, the floating phase was retained for HPLC analysis. The method was successfully applied to grilled pork samples.

Pentanol and Triton X‐100 have been used as extractant and emulsifier, respectively, for VASEME of scultellarin in urine samples prior to HPLC analysis [90]. Vortex agita- tion was applied for 1 min to form the cloudy solution before centrifugation for phase separation. A simple VASEME‐HPLC method provided a low detection limit in urine samples. Ultratrace amounts of naproxen and nabumetone were extracted using 1‐

undecanol and Triton X‐100 as extraction solvent and emulsifier, respectively [91].

Vortex mixing was applied for effective extraction of the target analytes. After centrifu- gation, the sample tube was immersed into an ice bath and the solidified organic solvent was collected for analysis. The findings of this research render the developed method as a green, inexpensive, and efficient method with high recoveries.

To demonstrate the application of VSLLME for inorganic anion and metal analyses, nitrite in urine was determined based on the selective reaction of nitrite with o‐phe- nylenediamine in acid media to form benzotriazole before extraction by non‐ionic surfactant Triton X‐114 and n‐octanol, as emulsifier and extractant, respectively [92].

Vortex mixing was applied to promote the emulsification. The fluorescence detection was enhanced by hydroxypropyl‐β‐cyclodextrin through complexation. Speciation of antimony(III,V) by ETAAS was proposed using VASEME‐SFO of Triton X‐114 and 1‐

undecanol as emulsifier and extraction solvent, respectively [93]. Complexation of Sb(III) and dithizone afforded a hydrophobic complex that was extracted into the extraction solvent under vortex agitation, whereas Sb(V) remained in solution. The extracted Sb(III) in the extraction solvent was analyzed directly by ETAAS, and Sb(V) was calculated by subtracting Sb(III) from the total antimony after reducing Sb(V) to Sb(III). The method is simple, rapid, and relatively free of organic hazardous solvent.

Before detection of lead in water samples using GFAAS, the low toxic solvent 1‐

bromo‐3‐methylbutane was used as extraction solvent for extraction of a chelate com- plex of Pb and 5‐Br‐PADAP, while Triton X‐100 was used as emulsifier [94]. The mixture was vigorously shaken on a vortex agitator, resulting in an emulsion contain- ing fine droplets. Simultaneous complex formation and extraction process were per- formed. The emulsion was disrupted by centrifugation and the organic phase

sedimented at the bottom of the tube was analyzed. The method offered low toxicity, short extraction time, high enrichment factor, and low LOD. Sodium thiosulfate was used as complexing agent for separation of AuNPs from ionic gold species [95]. 1,2‐

Dichloroethane and Triton X‐114 were added as extractant and emulsifier, respec- tively. The tube was vigorously shaken on a vortex agitator. The organic droplets were collected after centrifugation and sedimented phase was injected into the electrother- mal vaporization inductively coupled plasma mass spectrometer (ETV‐ICP‐MS) for determination of AuNPs. The proposed method was selective for trace AuNP determi- nation in environmental water samples. It can be extended to the analysis of other metal NPs such as AgNPs in water samples. The chelate of Cd with APDC was extracted into a droplet of IL 1‐butyl‐3‐methylimidazolium hexafluorophosphate, [C4MIM]

[PF6], which was used as extractant [96]. Triton X‐114 was added as dispersing medium under vortex mixing. The IL phase sedimented at the bottom of the tube after centrifu- gation was analyzed by FAAS. The proposed method employed a vortex mixer for the formation of a vortex stream and Triton X‐114 as dispersion medium accelerated Cd extraction into the IL extractant.

The IL 1‐butyl‐3‐methylimidazolium hexafluorophosphate ([BMIM]PF6) was also used as extractant for glucocorticoids [97]. Triton X‐100 was employed as synergic rea- gent in ionic liquid supported vortex‐assisted synergic microextraction (ILSVA‐SME).

Vortex apparatus was used to blend fluids quickly and thoroughly before cooling the solution in an ice‐water bath to promote the phase separation. The proposed method greatly improved the sensitivity of HPLC for determination of glucocorticoids.

A mixed anionic–cationic surfactant was reported as emulsifier for preconcentration of benzimidazole anthelmintics prior to HPLC analysis [98]. The binary mixture of anionic–cationic surfactants was formed by using SDS anionic surfactant and CTAB cationic surfactant, while 1‐octanol was used as extraction solvent. The solution was vortexed and the liquid organic droplet floated on the top layer was directly analyzed by HPLC. The mixed anionic–cationic surfactants act as pseudo‐non‐ionic surfactant and show great inherent synergism for the VASEME‐SFO procedure. The developed method has potential to be used as an alternative green extraction method with satisfactory recoveries for application in tissue samples.

A novel water‐contained surfactant‐based vortex‐assisted microextraction (WSVAME) method was developed for determination of synthetic antioxidants from edible oil [99]. The method was based on injection of an aqueous solution of non‐ionic surfactant Brij‐35 into an oil sample. Then, vortex mixing was applied to accelerate the dispersion process. After centrifugation, the lower sedimented phase was analyzed by HPLC. The experimental conditions were optimized using the central composite design and multiple linear regression methods. The proposed method is considered as a sim- ple, sensitive, and environmentally friendly method because of the biodegradability of the extractant and use of no organic solvents.

Magnetic stirring was also reported to accelerate the extraction equilibrium of a sur- factant‐assisted microextraction technique for the determination of benzimidazoles in eggs [100]. The microextraction was based on the rapid injection of emulsifier (Triton X‐114) and extraction solvent (1‐octanol) into a magnetically stirred aqueous solution to form a cloudy trinary component solvent (aqueous solution/extraction solvent/

emulsifier) system. No centrifugation step was necessary. A high enrichment factor and low detection limit were obtained.