Nova Biotechnol Chim (2018) 17(1): 1-15 

                         DOI: 10.2478/nbec-2018-0001 
 

 

 Corresponding author: svetlana.hrouzkova@stuba.sk 

Nova Biotechnologica et Chimica 

Review 

Present state and applications of single drop microextraction for the 

determination of harmful organic compounds and pollutants 

Silvia Zichová, Adriana Brisudová and Svetlana Hrouzková 

Institute of Analytical Chemistry, Faculty of Chemical and Food Technology, Slovak University of Technology in Bratislava, 

Radlinského 9, Bratislava, SK-812 37, Slovak Republic 

 

 

Article info 
 

Article history: 

Received: 29th March 2018 

Accepted: 20th June 2018 

 

Keywords: 

Harmful organic compounds 

Microextraction 

Pollutants 

Single drop microextraction 

 

 

 

 

 

 

 

 

 

 

Abstract 
 

Single drop microextraction (SDME) nowadays earns an increasing attention  

by scientists due to its simplicity, low cost and the need for only common laboratory 

equipment. This microextraction technique combines sample cleanup  

and pre-concentration of analytes in one step. Furthermore, a significant reduction  

in the amount of organic solvents needed comparing to standard LLE techniques 

places SDME into the position of environmental friendly extraction techniques. 

SDME is a straightforward technique in which a micro-drop of solvent is suspended 

from the tip of a conventional micro-syringe and then it is in a direct contact  

with a sample solution in which it is immiscible or it could be suspended  

in the headspace above the sample. The paper overviews developments of the state-

of-the-art SDME techniques for the extraction of harmful organic compound  

and pollutants from environmental, food and biological matrices. Key extraction 

parameters essential for SDME performance were described and discussed. 

 
 University of SS. Cyril and Methodius in Trnava

 

 

 

Introduction 
 

The toxicity of pesticides and pollutants and their 

harmful environmental effects are attracting  

the attention of the society and interest  

in the identification and quantification of such 

compounds in various matrices have aroused.  

Thus, the importance is put on the development  

of the faster and selective analytical methodology, 

suitable for the determination of the low levels  

of these compounds. The limits of quantitation 

(LOQs) of pesticides and pollutants are usually  

in mg/L or below. Therefore, in order  

to accomplish the quantitation of these compounds 

in various samples, a pre-treatment step,  

extraction  and pre-concentration  step are required. 

Generally, when conventional liquid phase 

extraction is used, the preconcentration  

of the analytes is very small or not even obtained.  

A lot of research efforts have been focused  

on the development of combined sample 

preparation techniques, when conventional liquid 

phase extraction is in the combination with a proper 

liquid phase microextraction technique or sorptive 

based microextraction technique, in order  

to achieve additional preconcentration  

of the analytes. Contrary to this, in the case of  

the single drop microextraction (SDME) these two 

processes are performed in a single step (De Souza 

Pinheiro et al. 2011; Andraščíková et al. 2016). 

Currently SDME has been increasingly used in the 

analysis of pesticides and other environmental

Bereitgestellt von  Slovenská poľnohospodárska knižnica | Heruntergeladen  28.02.20 08:24   UTC



Nova Biotechnol Chim (2018) 17(1): 1-15  

2 

pollutants in various matrices because it is simple, 

cheap, fast, effective and consuming only 

microliters of organic solvents per analysis. SDME 

technique is based on the principle of a distribution 

of analytes between a microdrop of the organic 

solvent and an aqueous phase or headspace phase 

above the solid/liquid sample. Using volume  

of sample in a milliliter scale and microliters  

of organic solvent leads to a high enrichment factor 

obtained. The SDME procedure using conventional 

microsyringe has the advantage of combining 

manipulation and injection of the sample  

into a single-step extraction and thus simplify  

the extraction process. However, some problems 

such as microdrop instability leading to  

the dislodgement of the drop or dislocation of the 

drop from the needle tip, and partial solvent loss 

caused by the high temperature and high solubility 

of the drop in the sample during extraction may 

reduce the repeatability of the method (Jeannot et 

al. 2010; Ramos 2012). Sampling repeatability 

requires the use of the proper syringe needle for  

the extraction. The use of the microdrop  

as a collector phase of analytes from the gaseous 

samples (Liu and Dasgupta 1995) and liquid 

samples (Liu and Dasgupta 1996) was described 

for the first time in the nineties of the 20th century. 

By the time, SDME has undergone many technical 

changes, and it is known in various modes. 

Seven different modes of solvent microextraction 

that belong to the category of single drop 

microextraction are currently in use for various 

applications. The base classification of SDME 

modes is dividing into two sub-categories, two  

and three-phase techniques, which exist  

in equilibrium (Table 1). All modes are based  

on the principle of passing the analytes from  

the sample directly, or through the other phase  

(e.g. headspace) or mediator to the final extraction 

solvent having a volume in microliters (Ramos 

2012). There are more advances to classify SDME, 

e.g. according to hydrodynamic features, static  

and dynamic modes of operation are distinguished 

(Alexovič et al. 2016). 

Use of the extraction solvent, which is volatile,  

e.g. hexane or toluene, makes the application 

directly compatible with gas chromatography 

(Jeannot et al. 2010). Moreover, combinations  

of SDME with high performance liquid 

chromatography (HPLC) and capillary 

electrophoresis were reported (Amde et al. 2015; 

García-Vázquez et al. 2016; Yohannes et al. 2016). 

 
Table 1. Overview of the SDME modes. 

SDME mode Acronym 

Two-phases techniques 

 direct immersion DI-SDME 

continuous flow microextraction CFME 

drop-to-drop microextraction DDME 

directly suspended droplet 

microextraction 
DSDME 

Three-phases techniques 

 headspace HS-SDME 

liquid-liquid-liquid microextraction LLLME 

solvent-supported microextraction SSME 

 

SDME has become frequently used for  

the extraction of a broad scope of compounds  

for numerous analytical application due  

to the advantages as reviewed by more papers 

(Lamboropoulou et al. 2007; Jeannot et al. 2010; 

Jain and Verma 2011). In this review, the focus 

was given to the three main application areas  

of SDME for the extraction of the harmful organic 

compounds and pollutants in environmental, food 

and biological samples in the recent years.  

 
Environmental samples 
 
SDME has been used to extract a wide range  

of organic compounds from the environmental 

samples, mostly several types of water and soil. 

Overview of the applicability of SDME  

for environmental sample analysis is shown  

in the Table 2. SDME was an appropriate 

extraction technique for liquid samples such as tap 

water (Kaykhaii et al. 2005; Lamboropoulou et al. 

2007; Yohannes et al. 2016), river water (Kaykhaii 

et al. 2005; Saraji and Bankhshi 2005; Ahmadi et 

al. 2006; De Souza Pinheiro et al. 2009; De Souza 

Pinheiro et al. 2011; Soares et al. 2014; Amde et 

al. 2015; Yohannes et al. 2016), lake water (Wu et 

al. 2008; Xie et al. 2014; Amde et al. 2015; 

Yohannes et al. 2016), surface water (Lopez-

Blanco et al. 2003; Lamboropoulou et al. 2007; 

Santos et al. 2017), drinking water (Lopez-Blanco 

et al. 2003; Ahmadi et al. 2006; Carlos et al. 2013), 

effluent and influent water (Amde et al. 2015), 

ground water (Yohannes et al. 2016; Santos et al. 

2017), water from the farm (Ahmadi et al. 2006), 

Bereitgestellt von  Slovenská poľnohospodárska knižnica | Heruntergeladen  28.02.20 08:24   UTC



Nova Biotechnol Chim (2018) 17(1): 1-15 

3 

sea water (Tian et al. 2014) and other water 

samples (Przyjazny and Kokosa 2002). 

Furthermore, SDME was applied for the extraction 

of the pesticides from the soil samples (Salemi et 

al. 2013; Williams et al. 2014; Soares et al. 2015).  

Organic pollutants, such as pesticides 

(organochlorine pesticides (OCPs), 

organophosphorus pesticides (OPPs)), fungicides, 

aliphatic amines, volatile organic compounds, 

phenols, polyaromatic hydrocarbons (PAHs), nitro-

PAHs and quinones extracted by SDME were 

mostly reported. Generally, two SDME modes 

were employed, DI and HS, nevertheless DI was 

preferably used due to the chemical properties  

of analyte and the type of the sample. 

Special pre-treatment was not necessary for  

the majority of selected applications, except 

addition of NaCl to the sample for increasing  

the ionic strength by Lamboropoulou et al. (2007),  

Wu et al. (2007) and Yohannes et al. (2016), 

adjustment of pH to 2 – 6 reported by Saraji and 

Bankhshi (2005), and filtration in the case  

of surface and ground water (Santos et al. 2017). 

The volume of a sample varied in the range  

of 1 mL – 30 mL, the most commonly selected 

volume of the sample was 5 mL. 

The pre-treatment of the solid samples was more 

difficult in comparison with water samples. Drying, 

sieving, ultrasonic extraction, sonication, 

centrifugation and final dilution with an appropriate 

solvent were used due to the matrix of the sample. 

The amount of sample was ranging from 2 g to 5 g 

(Salemi et al. 2013; Williams et al. 2014; Soares et 

al. 2015).  

The selection of a suitable extraction solvent is  

a crucial step for SDME performance. According  

to the extracted analytes, mostly organic solvents 

differing in Kow compatible with GC and HPLC 

were chosen, in order to obtain the highest 

extraction efficiency. Toluene, provided stable drop 

and avoided bubble formation during extraction 

according to vapour pressure lower than other 

solvents, was mostly used in direct immersion (DI) 

mode (Lamboropoulou et al. 2007; De Souza 

Pinheiro et al. 2009; De Souza Pinheiro et al. 2011; 

Tian et al. 2014; Santos et al. 2017). However,  

the bubble formation in the drop was required for 

the extraction of pesticides from lake water by Xie 

et al. (2014) by exposing the liquid-gas pendant 

drop (CPD) to the sample. The stability of the CPD 

was investigated by monitoring the formation  

of 1 μL organic droplets (toluene, chlorobenzene) 

containing different volumes of air bubble  

in a sample solution resulting in the better stability 

of the drop using chlorobenzene. A formation  

of a liquid-gas CPD was performed using a novel 

extraction assembly consisting of a 10 mm long 

quartz capillary, a funnel-like PMMA cap and  

a 5 mL microsyringe. The limitation of droplet 

instability in comparison with DI-SDME was 

overcome, larger microdrop size and higher stirring 

rates could be employed, as well as liquid-gas CPD 

has a potential to be fully automated by using  

a syringe pump (Xie et al. 2014). A 70- to 135-fold 

enrichment of pesticides was obtained.  

In comparison to a conventional SDME, 

improvement of the extraction efficiency could be 

ascribed by the increased surface area of the 

microdrop. The bubble in drop (BID) was studied 

by Williams et al. (2014) when chloroform was 

used as the extraction solvent. For the extraction  

of OCPs from tap and surface water, toluene and 

isooctane gave similar results for the majority  

of target analytes, but toluene was selected due to 

the selectivity and no significant loss  

of solvent during extraction (Lamboropoulou  

et al. 2007). The similar observation was reported 

for n-hexane that was selected due to its lower 

solubility in water, which increases the stability  

of the microdrop in comparison to the use  

of toluene. The analyte extraction was not 

significantly affected by the type of extraction 

solvent (n-hexane or toluene) (Soares et al. 2014). 

n-Hexane was suitable for the extraction of OCPs 

and pyrethroids from drinking water (Carlos et al. 

2013), multiclass pesticides from water and soil 

(Soares et al. 2014; Soares et al. 2015).  

For the extraction of the atrazine, desethyl-atrazine, 

desisopropyl-atrazine from the water samples, 

toluene, n-hexane, and cyclohexane were 

investigated, however, due to their low viscosity 

and density, the microdrop was not stable. 

Formation of the stable drop under the vigorous 

stirring and higher extraction efficiency was 

reached using 1-octanol as the extraction solvent 

(Yohannes et al. 2016). Solubility of the extraction 

solvent in water had a great effect for the extraction 

of 2 pesticides, α-endosulphane and β-endo-

sulphane from water. n-Hexane didn’t exhibit  

a good extractability of these compounds, because

Bereitgestellt von  Slovenská poľnohospodárska knižnica | Heruntergeladen  28.02.20 08:24   UTC



Nova Biotechnol Chim (2018) 17(1): 1-15 

4 

S
o
a
re

s 
e
t 

a
l.

 

(2
0

1
4
) 

  A
m

d
e
 e

t 
a
l.

 

(2
0

1
5
) 

        T
ia

n
 e

t 
a
l.

 (
2
0
1
4
) 

    X
ie

 e
t 

a
l.

 (
2
0
1
4

) 

    C
a
rl

o
s 

e
t 

a
l.

 

(2
0

1
3

) 

 Y
o
h

a
n
n
e
s 

e
t 

a
l.

 

(2
0

1
6

) 

 

Bereitgestellt von  Slovenská poľnohospodárska knižnica | Heruntergeladen  28.02.20 08:24   UTC



Nova Biotechnol Chim (2018) 17(1): 1-15 

5 

 

D
e
 S

o
u

z
a
 

P
in

h
e
ir

o
 e

t 
a
l.

 

(2
0

1
1

) 

 D
e
 S

o
u

z
a
 

P
in

h
e
ir

o
 e

t 
a
l.

 

(2
0

1
1

) 

  P
rz

y
ja

z
n
y
 a

n
d
 

K
o
k

o
sa

 (
2
0
0
2

) 

  K
a
y
k

h
a
ii

 e
t 

a
l.

 

(2
0

0
5

) 

  A
h
m

a
d

i 
e
t 

a
l.

 

(2
0

0
6

) 

  L
o

p
e
z
-B

la
n
k
o
 e

t 

a
l.

 (
2
0
0
3

) 

 S
a
ra

ji
 a

n
d
 

B
a
n
k
h
sh

i 
(2

0
0
5

) 

   L
a
m

b
o
ro

p
o
u

lo
u

 

e
t 

a
l.

 (
2
0
0
7

) 

 S
a
n
to

s 
e
t 

a
l.

 

(2
0

1
7

) 

 

Bereitgestellt von  Slovenská poľnohospodárska knižnica | Heruntergeladen  28.02.20 08:24   UTC



Nova Biotechnol Chim (2018) 17(1): 1-15 

6 

W
u
 e

t 
a
l.

 (
2
0
0
7

) 

     S
a
le

m
i 

e
t 

a
l.

 

(2
0

1
3

) 

  W
il

li
a
m

s 
e
t 

a
l.

 

(2
0

1
4

) 

      S
o
a
re

s 
e
t 

a
l.

 

(2
0

1
5

) 

 

Bereitgestellt von  Slovenská poľnohospodárska knižnica | Heruntergeladen  28.02.20 08:24   UTC



Nova Biotechnol Chim (2018) 17(1): 1-15  

7 

it is more soluble in water in comparison to 

isooctane. Isooctane, being solvent of low polarity, 

provided higher extractive efficiency  

and reproducibility for both analytes (Lopez-

Blanco et al. 2003). Extraction of the phenols from 

the river water by DI-SDME followed by in- 

syringe derivatization was investigated by Saraji 

and Bankhshi (2004). Several organic solvents  

in the broad range of polarity were investigated, 

resulted hexyl acetate being the most suitable for 

the extraction. Hexyl acetate provided the selective 

extraction of the phenols, in comparison to other 

solvent, when 4­nitrophenol was not extracted. 

Furthermore, the manipulation with hexyl acetate 

microdrop was acceptable without any stability 

problems during the extraction, however, 

chromatographic peak overlaps were observed 

(Saraji and Bankhshi 2004). 

The volatile compounds were preferably extracted 

by using HS mode. Octanol, benzylalkohol  

and β-cyclodextrine were investigated as potential 

extraction solvents (Przyjazny and Kokosa 2002; 

Kaykhaii et al. 2005; Salemi et al. 2013).  

HS- SDME was found as an efficient technique for 

the extraction of the organic compounds such  

as benzene, toluene, ethylbenzene and xylenes from 

the water samples. Gas chromatography with flame 

ionization detector (GC-FID) was employed.  

For the highest extraction efficiency under  

the experimental conditions, solvents with a high 

boiling point and low vapour pressure were 

investigated, so as to minimize the evaporation  

of the microdrop during the extraction. 1-Octanol 

and n-hexadecane provided satisfactory extraction 

of the analytes. However, less impurities using  

n-hexadecane were interfering the analyte signal 

(Przyjazny and Kokosa 2002). The specific 

application of HS-SDME which was free  

of organic solvent was provided by Wu et al. 

(2007), when β-cyclodextrine was used  

as extraction solvent for PAHs from the lake water. 

Nanofluid (NF) prepared by dispersion of ZnO 

nanoparticles in 1-hexyl-3-methylimidazolium-

hexafluorophosphate was reported as an extraction 

solvent for three fungicides in water. A syringe tip 

cap (obtained from 5 mL disposable syringe) was 

used as a holder of the microdrop instead  

of the syringe needle. The microdrop was 

immersed on the syringe tip cap by microsyringe 

and after the extraction, the microdrop was placed  

in an Eppendorf vial containing 100 μL methanol 

with the aim to remove nanoparticles. Nowadays, 

NFs earn an attention due to the frequent 

applications in many research directions. Replacing 

conventional solvent in liquid–liquid system  

by NPs can cause an increase of mass transfer 

coefficient and increase the efficiency of extraction 

as the main goal (Amde et al. 2015).  

Volume of the drop is the next important factor for 

the efficient extraction. In general, increasing the 

drop volume results in the significant improvement 

of the extraction efficiency. However, when  

the microdrop volume increases further, the drop 

became unstable due to the gravity. The volume  

of the drop was in the range of 0.9 μL (Ahmadi et 

al. 2006) and 10 μL (Wu et al. 2007; Amde et al. 

2015). Drop volume 1 μL was the most frequently 

applied, what can be explain by the found 

consensus between the volume, stability  

and extraction capacity of the drop (Kaykhaii et al. 

2005; De Souza Pinheiro et al. 2009; De Souza 

Pinheiro et al. 2011; Williams et al. 2014; Xie et 

al. 2014; Santos et al. 2017). Sampling 

repeatability of the microdrop requires the use  

of the proper syringe needle for the extraction. 

Generally, 10 μL Hamilton syringe routinely used 

for GC was frequently used as a holder  

of the microdrop during the extraction process.  

The needle should have a minimum dead volume, 

for instance using a 1 μL microsyringe, no dead 

volume is occurred. The modification of needle tip, 

e.g. cones tip, or modified microsyringe causes 

increasing adhesion force between needle tip  

and drop, thereby increasing drop stability  

and achieving a high stirrer speed (up to 700 rpm 

for the cones tip and up to 1,700 rpm for  

the modified microsyringe) (Ahmadi et al. 2006).  

Furthermore, improved holding of the microdrop 

and larger extraction solvent volumes used for  

the extraction were reached by attaching a 2-mm 

long cone that was cut off from a 200 μL pipette tip 

onto the needle tip of a GC microsyringe (Tian et 

al. 2014). The similar approach was used for  

the modification of the HPLC syringe, which was 

supported by a part of the pipette tip, thus the larger 

microdrop was obtained (Wu et al. 2007). To avoid 

impurities, a rinse of the microsyringe before 

extraction was presented, mostly by the extraction 

solvent (Przyjazny and Kokosa 2002; Kaykhaii et 

al. 2005; Ahmadi et al. 2006; Wu et al. 2007;

Bereitgestellt von  Slovenská poľnohospodárska knižnica | Heruntergeladen  28.02.20 08:24   UTC



Nova Biotechnol Chim (2018) 17(1): 1-15 

8 

Salemi et al. 2013; Tian et al. 2014; Yohannes et 

al. 2016; Santos et al. 2017).  

Sample agitation is an important factor for  

the reduction of the extraction time. From the film 

theory of convective-diffusive mass transfer,  

the agitation of the sample solution enhances  

the extraction efficiency and reduce the extraction 

time, since the thickness of the stagnant film 

around the extracting phase (i.e. Nernst diffusion 

film) decreases with increasing stirring rate, and it 

results in faster extraction rate (Pena-Pereira et al. 

2010). Magnetic stirring, mechanical vibration, 

continuous flow and syringe plunger motion are 

usually used for the sample agitation to increase the 

amount of convective mixing or interfacial contact 

area for the dynamic modes of SDME. The time 

required to reach equilibrium in SDME dependent 

on the type and degree of agitation, phase volumes, 

interfacial contact area and equilibrium distribution 

constant (Jeannot and Cantwell 1996; Jeannot et al. 

2010). Magnetic stirring was applied for the 

majority of the applications, with the velocity range 

from 155 rpm (Soares et al. 2014) to 1,300 rpm 

(Ahmadi et al. 2006). High velocity of agitation 

was used for the HS mode, when the drop is not  

in the direct interaction with a sample. For the 

extraction of the atrazine and metachlor from soil, 

no stirring was used and the extraction was 

performed under static conditions (Williams et al. 

2014). The positive effect of the ultrasound waves 

has been used in SDME for the OPPs extraction 

from the soil sample (Salemi et al. 2013). 

For HS-SDME, the temperature is a key parameter 

to speed-up the rate of mass transfer  

of compounds from the sample to the headspace 

increasing the number and the amount  

of compounds of interest moved to the gas phase. 

Increased temperatures lead to the decrease  

of the extractant-headspace phase distribution 

constant and this results in the decrease of 

sensitivity of the method. Cooling of the extraction 

solvent, while the sample could be heated, is the 

promising solution of this problem. However, such  

an arrangement of experiment brings apparatus 

design complications, therefore, it is useful for 

ultra-trace analyses or for very volatile analytes 

with a low possibility to transfer to the headspace 

at ambient conditions (Jeannot et al. 2010). 

Extraction temperature was in the range from 17 °C 

(Soares et al. 2014) to 60 °C (Salemi et al. 2013). 

The increase of the ionic strength of the water-

based sample can affect the analyte transfer  

by the increase of the amount of salt to the aqueous 

phase (Wang et al. 2017). The majority  

of the publications were reported to be without salt 

addition.  

 
Food samples 
 

SDME extraction of the organic compounds from 

food samples is an important application field  

of SDME technique, it earns nowadays great 

interest proved by the published papers in recent 

years. Overview of papers reporting the analysis  

of various samples, such as tea (Liu et al. 2012; Wu 

et al. 2015), wine (Garbi et al. 2010; Perreira Dos 

Anjos et al. 2015), vegetables (Amrvrazi and 

Tsiropoulos 2009; Kin et al. 2009; Wu et al. 2016) 

and fruits (Perreira Dos Anjos et al. 2014; Pano-

Farias et al. 2017) are summarized in the Table 3. 

All of them were targeted on the determination  

of the pesticides. No special pre-treatment was 

reported for liquid samples such as wine or coconut 

water, mainly conventional sonication, 

acidification, pH adjustment and centrifugation 

were used (Garbi et al. 2010; Perreira Dos Anjos et 

al. 2014; Perreira Dos Anjos et al. 2015).  

On the other hand, more difficult pre-treatment was 

required for solid samples prior to the extraction 

step (Amrvrazi and Tsiropoulos 2009; Kin et al. 

2009; Liu et al. 2012; Wu et al. 2015; Wu et al. 

2016; Pano-Farias et al. 2017). DI was the most 

occurred mode of SDME (Amrvrazi and 

Tsiropoulos 2009; Garbi et al. 2010; Perreira Dos 

Anjos et al. 2014; Perreira Dos Anjos et al. 2015; 

Pano-Farias et al. 2017). For the extraction  

of 8 pesticides from cucumber and strawberries,  

the HS mode was selected and its application was 

compared to headspace solid phase microextraction 

(HS-SPME) and solid phase extraction (SPE) (Kin 

et al. 2009). More complex apparatus was 

employed by Wu et al. (2015, 2016) for the 

dynamic microwave assisted extraction (DMAE) 

and dynamic microwave assisted extraction in 

combination with continuous flow microextraction 

(DMAE-CFME) of pesticides from tea (Wu et al. 

2015) and cabbage, cauliflower, red cabbage and 

cucumber (Wu et al. 2016). Furthermore, DSDME 

using 100 μL isooctane for isolation of OCPs was 

used to analyze samples of tea by Liu et al. (2012).

Bereitgestellt von  Slovenská poľnohospodárska knižnica | Heruntergeladen  28.02.20 08:24   UTC



Nova Biotechnol Chim (2018) 17(1): 1-15 

9 

  

W
u
 e

t 
a
l.

  

(2
0

1
5

) 

  L
iu

 e
t 

a
l.

  

(2
0

1
2

) 

     Pe
rr

e
ir

a
 D

o
s 

 

A
n
jo

s 
e
t 

a
l.

  

(2
0

1
5

) 

  G
a
rb

i 
e
t 

a
l.

  

(2
0

1
0

) 

  W
u
 e

t 
a
l.

  

(2
0

1
6

) 

  Pe
rr

e
ir

a
 D

o
s 

 

A
n
jo

s 
e
t 

a
l.

  

(2
0

1
4

) 

K
in

 e
t 

a
l.

  

(2
0

0
9

) 

 

Bereitgestellt von  Slovenská poľnohospodárska knižnica | Heruntergeladen  28.02.20 08:24   UTC



Nova Biotechnol Chim (2018) 17(1): 1-15  

10 

A
m

rv
ra

z
i 

a
n
d

 

T
si

ro
p
o
u
lo

s 

(2
0

0
9

) 

   P
a
n
o

-F
a
ri

a
s 

 

e
t 

a
l.

 (
2
0
1
7

) 

 

 

K
u
m

a
ri

 e
t 

a
l.

 

(2
0

1
6

) 

       P
e
li

t 
a
n
d
 

Y
e
n
g

in
  

(2
0

1
4

) 

 

T
a
b

le
 2

. 

 

Bereitgestellt von  Slovenská poľnohospodárska knižnica | Heruntergeladen  28.02.20 08:24   UTC



Nova Biotechnol Chim (2018) 17(1): 1-15 

11 

For effective extraction of the pesticides from the 

vegetable samples and stable drop in the 

continuous flow by DMAE-CFME, a variety  

of water-immiscible extraction solvents (n-hexane, 

cyclohexane, dichloromethane, chloroform, carbon 

tetrachloride, ethyl acetate, and toluene) were 

investigated, resulting dichloromethane and ethyl 

acetate as inappropriate for this mode. The major 

loose of these solvents was presented in the 

continuous sample flow arrangement. Toluene 

exhibited the most promising results of extraction 

efficiency for the majority of studied compounds 

(Wu et al. 2016). The wide scale of solvents, such 

as dichloromethane, chloroform, carbon 

tetrachloride, and chlorobenzene were examined 

for the extraction of the pesticides from the tea.  

An improved extraction chamber using as a holder 

of the microdrop was employed. The microdrop 

provided a sufficient stability in the flowing system 

and the microdrop transfer to analytical instruments 

by microsyringe after extraction was without loose 

of the extraction solvent. Carbon tetrachloride 

exhibited the highest extraction efficiency for most 

of the analytes, also the carbon tetrachloride extract 

was proved to be cleaner in comparison to other 

solvents. Chlorobenzene was not stable enough  

in the flow (Wu et al. 2015). Analyzing tea 

samples, cyclohexane drop immersed to the tea 

sample solution was not reproducible with low 

stability. Toluene was problematic as it extracted 

tea pigments and further cleaning was necessary. 

Isooctane showing the highest viscosity among 

studied solvents was selected as the final solvent 

for real-samples extraction, in addition, it formed 

stable microdrop (Liu et al. 2012). Microsyringe  

of the volume 10 μL was used in all of the 

mentioned applications and the drop of the sample 

was in the range of 1 μL and 10 μL. Especially,  

the volume 100 μL was used for the DSDME mode  

to measure the volume of the sample. Presence  

of the steady vortex was important for the 

formation of the microdrop (Liu et al. 2012).  

To avoid carry over effect, the rinse  

of the microsyringe was used mostly  

by the extraction solvent or polar organic solvents 

(Amrvrazi and Tsiropoulos 2009; Kin et al. 2009; 

Garbi et al. 2010; Perreira Dos Anjos et al. 2015; 

Pano-Farias et al. 2017).  

The highest speed of the magnetic stirrer was used 

for the DSDME extraction, the stirring speed above

1,100 rpm causes instability and dissolution  

of the solvent microdrop (Liu et al. 2012).  

Low speed of magnetic stirrer was mostly used for 

the DI-SDME in the range of 180 – 700 rpm 

(Amrvrazi and Tsiropoulos 2009; Garbi et al. 2010; 

Perreira Dos Anjos et al. 2014; Perreira Dos Anjos 

et al. 2015; Pano-Farias et al. 2017) and microwave 

irradiation was employed for the DMAE (Wu et al. 

2015) and DMAE-CFME (Wu et al. 2016).  

The influence of microwave energy (100 – 350 W) 

on the extraction was studied. Implementation  

of the microwave-assisted extraction (MAE) prior 

to SDME simplify the pre-treatment process  

by the acceleration of the disruption  

of the vegetable cells under the high temperature. 

The high temperature improves the diffusion  

and mass transfer during extraction,  

and the dissolving capacity of extraction solvent  

at the same time, as well as, the target compounds 

dissolves faster. However, when high microwave 

power is used, it may cause the analyte degradation 

(Wu et al. 2016). No salt addition was reported  

in the published papers for food samples analysis. 

Satisfactory recovery values in the acceptable limit 

(between 70 % and 120 %) were mostly reposted. 

Difficulties to extract some compounds were 

mostly explained by chemical properties of the 

analytes and by the interaction of the analytes with 

other compounds presented in the sample.  

Low values of recovery were reported for dursban  

(the pesticide) with recoveries in the interval  

of 13.2 % – 52.4 % (Perreira Dos Anjos et al. 

2015), and for the pyrethroid insecticide  

λ-cyhalothrin (1.4 for grape and 1.5 for apple) 

(Amrvrazi and Tsiropoulos 2009). Permethrin I  

and permethrin II are compounds exhibiting higher 

affinity toward water phase, which is demonstrated 

by low partition coefficient, therefore, as a result, 

insufficient recovery rates were reported (39.4 % 

and 45.0 %, respectively). Thus, it is possible to 

notice a difficulty of the migration of these analytes 

from the aqueous sample to the organic solvent. 

Although a relatively high partition coefficient 

belonging to the pesticide endosulfane, a low 

recovery rate was reported (29.0 %), what was 

explained by the interaction with other matrix 

components comprising the coconut water.  

In general, extraction of the compounds with higher 

polarity such as OCPs, compared to other classes  

of compounds such as OPPs, is more difficult

Bereitgestellt von  Slovenská poľnohospodárska knižnica | Heruntergeladen  28.02.20 08:24   UTC



Nova Biotechnol Chim (2018) 17(1): 1-15 

12 

hence they promote a higher affinity for water-

based sample than for organic extractant (Perreira 

Dos Anjos et al. 2014). 

 
Biological samples 

 

Sample preparation step is essential for the 

isolation of analytes from complex biological 

matrices and has a great influence on their reliable 

and accurate determination. Suitable extraction 

technique is usually necessary because almost all 

biological samples are incompatible with  

the following chromatographic instrumentation, 

these samples exhibit complicated matrix for direct 

analysis, and components in the sample may 

interfere the signal acquisition. In addition,  

the analytes are present at concentration levels 

below the limit of detection of regular analytical 

methods (Ocaña-González et al. 2016). Biological 

samples contain proteins, salts, acids, bases,  

and various organic components with properties 

close to those of searched analytes. 

In the recent years, applications of the SDME were 

aimed mostly to extraction of the several organic 

compounds in the biological samples such as fish 

(Botrel et al. 2017), urine and blood of the rats 

(Agrawal et al. 2007), human urine (Gao et al. 

2011; García-Vasquéz et al. 2015), saliva 

(Timofeeva et al. 2016) and human blood serum 

(Shrivas and Patel 2009) (Table 4). The 

solidification of the extraction solvent in microliter 

scale after dispersive liquid-liquid microextraction 

for the extraction of drugs (Ebrahimzadeh et al. 

2011; Ahmadi-Jouibari et al. 2014; Tehrani et al. 

2014), medicaments (Ebrahimzadeh et al. 2013;  

Jia et al. 2013; Suh et al. 2014) was also reported.  

A few papers were devoted to the extraction  

of pesticides, namely maneb (fungicide)  

and paraque (herbicide) in albine mice by Kumari 

et al. (2016) and chlorpyrifos and chlorpyrifos-

oxon by Pelit and Yengin (2014).  

1-Undecanol, 1-dodecanol, 2-dodecanol and  

n-hexadecane were investigated for the extraction 

of maneb and paraque from albine mice. Except  

n-hexadecane, all other solvents were found  

to recover comparably the same amount of targeted 

analytes. This maybe because all these solvents 

possess nearly similar affinity toward the targeted 

analytes. In this case, the solidification of the 

solvent drop was used, which offered manipulation

with a microdrop without significant losing  

of extract. This approach was reported to be semi-

automated and could be fully automated without 

varying from the original concept by the further 

modifications. Finally, 1-dodecanol was chosen  

to be used for further experiments, due to its 

peculiar characteristic of being easily solidified 

near room temperature. (Kumari et al. 2016).  

In the case of urine, this matrix offers several 

advantages as it is very easy to obtain and 

specimen volume is not a limitation. Biomonitoring 

of the chlorpyrifos exposure in human urine was 

reported and 2-dodecanol as extraction solvent was 

selected due to the absence of the solvent peak 

presented in the same time as the analytes  

in the chromatogram in comparison with the other 

studied solvents. The extraction was performed 

using increased temperature, and no addition  

of the salt was presented. In this case, it was 

difficult to collect the organic phase due to 

the formation of smaller droplets of the solvent  

in the solution after addition of 0.5 g NaCl to  

10.0 mL of the solution (Pelit and Yengin 2014).  

 

Conclusions 
 

SDME showed its suitability for the extraction  

of various type of analytes, which belongs to the 

wide group of harmful organic compounds  

and environmental pollutants from numerous types  

of samples. Applications of SDME for real samples 

analysis were sorted into 3 groups according  

to sample nature and summarized into the form  

of overview tables. As it was shown by the largest 

group of applications, SDME has the major 

utilization in the area of environmental samples 

analysis, then followed by food samples analysis. 

Nowadays, there is an increasing frequency  

of publication devoted to the SDME for biological 

samples analysis. SDME offered the reach of high 

pre-concentration, clean final extract directly 

suitable for analysis, fast extraction and the 

simplicity of the process. It was shown, that the 

two most common SDME modes DI and HS have 

slightly different general fields of applicability, but 

they show their wide applicability for various 

matrices. DI-SDME was approved to be suitable 

mostly for the extraction of the nonpolar  

or moderately polar volatile and semivolatile 

analytes from relatively clean matrices, such as 

Bereitgestellt von  Slovenská poľnohospodárska knižnica | Heruntergeladen  28.02.20 08:24   UTC



Nova Biotechnol Chim (2018) 17(1): 1-15 

13 

water, using appropriate water immiscible solvents, 

due to the direct contact of the solvent with a water 

sample. Since volatile compounds are best pre-

concentrated by headspace SDME. The selection  

of the working parameter was also established  

to be critical for the reaching satisfactory 

recoveries of the analytes and explained  

by numerous examples. In conclusion, miniaturized 

extraction methods such as SDME represent a new 

approach that is currently receiving a great deal  

of interest of researchers in the area of sample 

preparation methods for analytical purposes. 

 

Acknowledgements 
 
This work was supported by the Slovak Research  

and Development Agency under the contract No. SK-SRB-

2016-0006. SZ would like to thank for financial contribution 

from the STU Grant scheme for Support of Young 

Researchers. 

 

References 
 
Agrawal K, Wu FH (2007) Drop-to-drop solvent 

microextraction coupled with gas chromatography/mass 

spectrometry for rapid determination of trimeprazine  

in urine and blood of rats: application  

to pharmacokinetic studies. Rapid Commun. Mass 

Spectrom. 21: 3352-3356. 

Ahmadi F, Assadi Y, Hosseini SM, Rezaee M (2006) 

Determination of organophosphorus pesticides in water 

samples by single drop microextraction and gas 

chromatography-flame photometric detector.  

J. Chromatogr. A 1101: 307-312. 

Ahmadi-Jouibari T, Fattahi N, Shamsipur M (2014) Rapid 

extraction and determination of amphetamines in human 

urine samples using dispersive liquid-liquid 

microextraction and solidification of floating organic 

drop followed by high performance liquid 

chromatography. J. Pharm. Biomed. Anal. 94: 145-151. 

Alexovič M, Horstkotte B, Solich P, Sabo J (2016) 

Automation of static and dynamic non-dispersive liquid 

phase microextraction. Part 1: Approaches based  

on extractant drop-, plug-, film- and microflow-

formation. Anal. Chim. Acta 906: 22-40. 

Amde M, Tan ZQ, Liu R, Liu JF (2015) Nanofluid of zinc 

oxide nanoparticles in ionic liquid for single drop liquid 

microextraction of fungicides in environmental waters 

prior to high performance liquid chromatographic 

analysis. J. Chromatogr. A 1395: 7-15. 

Amvrazi EG, Tsiropoulos NG (2009) Application of single-

drop microextraction coupled with gas chromatography 

for the determination of multiclass pesticides  

in vegetables with nitrogen phosphorus and electron 

capture detection. J. Chromatogr. A 1216: 789-2797. 

Andraščíková M, Hrouzková S (2016) Fast preconcentration  

of pesticide residues in oilseeds by combination  

of QuEChERS with dispersive liquid–liquid 

microextraction followed by gas chromatography-mass 

spectrometry. Food Anal. Meth. 9: 2182-2193. 

Botrel BMC, Abreu DCP, Saczk AA, Bazana MJF, Coelho 

SM, El Rosa PV, De Lima RMF (2017) Residual 

determination of anesthetic menthol in fishes  

by SDME/GC-MS. Food Chem. 229: 674-679. 

Carlos EA, Alves RD, De Queiroz MEL, Neves A (2013) 

Simultaneous determination of the organochlorine and 

pyrethroid pesticides in drinking water by single drop 

microextraction and gas chromatography. J. Braz. 

Chem. Soc. 24: 1217-1227. 

De Souza Pinheiro A, De Andrade JB (2009) Development, 

validation and application of a SDME/GC-FID 

methodology for the multiresidue determination  

of organophosphate and pyrethroid pesticides in water. 

Talanta 79: 1354-1359. 

De Souza Pinheiro A, Da Rocha GO, De Andrade JB (2011) 

A SDME/GC–MS methodology for determination  

of organophosphate and pyrethroid pesticides in water.  

Microchem. J. 99: 303-308. 

Ebrahimzadeh H, Dehghani Z, Asgharinezhad AA, Shekari 

N, Molaei K (2013) Determination of haloperidol  

in biological samples with the aid of ultrasound‐assisted 

emulsification microextraction followed  

by HPLC‐DAD. J. Sep. Sci. 36: 1597-1603. 

Ebrahimzadeh H, Saharkhiz Z, Tavassoli M, Kamarei F, 

Asgharinezhad AA (2011) Ultrasound‐assisted 

emulsification microextraction based on solidification  

of floating organic droplet combined with HPLC‐UV for 

the analysis of antidepressant drugs in biological 

samples. J. Sep. Sci. 34: 1275-1282. 

Gao W, Chen G, Chen Y, Zhang X, Yin Y, Hu Z (2011) 

Application of single drop liquid–liquid–liquid 

microextraction for the determination  

of fluoroquinolones in human urine by capillary 

electrophoresis. J. Chromatogr. B 879: 291-295. 

Garbi A, Sakkas V, Fiamegos YC, Stalikas CD, Albanis T 

(2010) Sensitive determination of pesticides residues  

in wine samples with the aid of single-drop 

microextraction and response surface methodology. 

Talanta 82: 1286-1291. 

García‐Vázquez A, Borrull F, Calull M, Aguilar C (2016) 

Single‐drop microextraction combined in‐line with 

capillary electrophoresis for the determination  

of nonsteroidal anti‐inflammatory drugs in urine 

samples. Electrophoresis 37: 274-281. 

Jain A, Verma KK (2011) Recent advances in applications  

of single-drop microextraction: a review. Anal. Chim. 

Acta 706: 37-65.  

Jeannot MA, Cantwell FF (1996) Solvent microextraction 

into a single drop. Anal. Chem. 68: 2236-2240.  

Jeannot MA, Przyjazny A, Kokosa JM (2010) Single drop 

microextraction-development, applications and future         

trends. J. Chromatogr. A 1217: 2326-2336. 

Jia S, Li J, Park SR, Ryu Y, Park IH, Park JH, Lee J (2013) 

Combined application of dispersive liquid–liquid 

microextraction based on the solidification of floating 

Bereitgestellt von  Slovenská poľnohospodárska knižnica | Heruntergeladen  28.02.20 08:24   UTC



Nova Biotechnol Chim (2018) 17(1): 1-15 

14 

         organic droplets and charged aerosol detection for the 

simple and sensitive quantification of macrolide 

antibiotics in human urine. J. Pharm. Biomed. Anal. 86: 

204-213. 

Kaykhaii M, Saeed N, Chamsaz M (2005) Determination  

of aliphatic amines in water by gas chromatography 

using headspace solvent microextraction. Talanta 65: 

223-228. 

Kin ChM, Tan GH (2009) Comparison of HS-SDME with 

SPME and SPE for the determination of eight 

organochlorine and organophosphorus pesticide residues 

in food matrices. J. Chromatogr. Sci. 47: 694-699. 

Kumari R, Jha RR, Singh MP, Patel DK (2016) Whirling 

agitated single drop microextraction technique for the 

simultaneous analysis of Paraquat and Maneb in tissue 

samples of treated mice. J. Sep. Sci. 39: 1725-1733. 

Lamboropoulou DA, Albanis TA (2007) Liquid-phase micro-

extraction techniques in pesticide residue analysis.  

J. Biochem. Biophys. Methods 70: 195-228. 

Liu S, Dasgupta PK (1995) Liquid droplet. A renewable gas 

sampling interface. Anal. Chem. 7: 2042-2049. 

Liu S, Dasgupta PK (1996) Analytical chemistry in a drop. 

Solvent extraction in a microdrop. Anal. Chem. 68: 

1817-1821. 

Liu D, Min S (2012) Rapid analysis of organochlorine and 

pyrethroid pesticides in tea samples by directly 

suspended droplet microextraction using a gas 

chromatography–electron capture detector. 

J. Chromatogr. A 1235: 166-173. 

Lopez-Blanco MC, Blanco-Cid S, Cancho-Grande B, Simal-

Gandara J (2003) Application of single-drop 

microextraction and comparison with solid-phase 

microextraction and solid-phase extraction for the 

determination of α- and β-endosulfan in water samples 

by gas chromatography–electron-capture detection.  

J. Chromatogr. A 984: 245-252. 

Ocaña-González JA, Fernández-Torres R, Bello-López MÁ, 

Ramos-Payán M (2016) New developments  

in microextraction techniques in bioanalysis. A review. 

Anal. Chim. Acta 905: 8-23. 

Pano-Farias NS, Ceballos-Magana SG, Muniz-Valencia R, 

Jurado JM, Alcázar Á, Aguayo-Villarreal IA (2017) 

Direct immersion single drop micro-extraction method 

for multi-class pesticides analysis in mango using GC–

MS. Food Chem. 237: 30-38. 

Pelit FO, Yengin Ç (2014) Application of solidified floating 

organic drop microextraction method for biomonitoring 

of chlorpyrifos and its oxon metabolite in urine 

samples. J. Chromatogr. B 949: 109-114. 

Pena-Pereira F, Lavilla I, Bwndicho C (2010) Liquid-phase 

microextraction techniques within the framework  

of green chemistry. Trends Anal. Chem. 29: 617-628. 

Perreira Dos Anjos J, De Andrade JB (2014) Determination 

of nineteen pesticides residues (organophosphates, 

organochlorine, pyrethroids, carbamate, thiocarbamate 

and strobilurin) in coconut water by SDME/GC–MS. 

Microchem. J. 112: 119-126. 

Perreira Dos Anjos J, De Andrade JB (2015) Simultaneous 

determination of pesticide multiresidues in white wine 

and rosé wine by SDME/GC-MS. Microchem. J. 120: 

69-76. 

Przyjazny A, Kokosa JM (2002) Analytical characteristics  

of the determination of benzene, toluene, ethylbenzene 

and xylenes in water by headspace solvent 

microextraction. J. Chromatogr. A 977: 143-153. 

Ramos L (2012) Critical overview of selected contemporary 

sample preparation techniques. J. Chromatogr. A 1221: 

84-98. 

Salemi A, Rasoolzadeh R, Nejad MM, Vosough M (2013) 

Ultrasonic assisted headspace single drop micro-

extraction and gas chromatography with nitrogen-

phosphorus detector for determination  

of organophosphorus pesticides in soil. Anal. Chim. 

Acta 769: 121-126. 

Santos LO, Dos Anjos JP, Ferreira SL, De Andrade JB (2017) 

Simultaneous determination of PAHS, nitro-PAHS and 

quinones in surface and groundwater samples using 

SDME/GC-MS. Microchem. J. 133: 431-440. 

Saraji M, Bakhshi M (2005) Determination of phenols  

in water samples by single-drop microextraction 

followed by in-syringe derivatization and gas 

chromatography–mass spectrometric detection.  

J. Chromatogr. A 1098: 30-36. 

Shrivas K, Patel DK (2009) Matrix-assisted laser 

desorption/ionization mass spectrometry for quantitative 

determination of β-blocker drugs in one-drop of human 

serum sample. J. Chromatogr. B 879: 35-40. 

Soares CES, Neves AA, Quieroz ME, Oliveira AF, Costa AI, 

Assis RC, Andrade CEO (2014) Single drop 

microextraction: A sensitive multiresidue method for 

determination of pesticides in water using GC/ECD.  

J. Braz. Chem. Soc. 25: 2016-2025.  

Soares CE, Neves AA, Queiroz ME, Oliveira AF, Costa AI, 

Assis RC, Andrade CEO (2015) Determination  

of pesticides in soil using a hyphenated extraction 

technique. J. Braz. Chem. Soc. 26: 1790-1797. 

Suh JH, Lee YY, Lee HJ, Kang M, Hur Y, Lee SN, Han SB 

(2014) Dispersive liquid–liquid microextraction based 

on solidification of floating organic droplets followed  

by high performance liquid chromatography for the 

determination of duloxetine in human plasma. J. Pharm. 

Biomed. Anal. 75: 214-219. 

Tehrani MS, Givianrad MH, Mahoor N (2014) Surfactant-

assisted dispersive liquid–liquid microextraction 

followed by high-performance liquid chromatography 

for determination of amphetamine and 

methamphetamine in urine samples. Anal. Methods 4: 

1357-1364. 

Tian F, Liu W, Fang H, An M, Duan S (2014) Determination 

of six organophosphorus pesticides in water by single-

drop microextraction coupled with GC-NPD. 

Chromatographia 77: 487-492. 

Timofeeva I, Medinskaia K, Nikolaeva L, Kirsanov D, 

Bulatov A (2016) Stepwise injection potentiometric 

determination of caffeine in saliva using single-drop 

microextraction combined with solvent exchange. 

Talanta 150: 655-660. 

Yohannes A, Tolesa T, Merdassa Y, Megersa N (2016)

Bereitgestellt von  Slovenská poľnohospodárska knižnica | Heruntergeladen  28.02.20 08:24   UTC



Nova Biotechnol Chim (2018) 17(1): 1-15 

15 

        Single drop microextraction analytical technique for 

simultaneous separation and trace enrichment  

of atrazine and its major degradation products from 

environmental waters followed by liquid 

chromatographic determination. J. Anal. Bioanal. Tech. 

7: 1-8. 

Wang X, Li Y, Cai F, Qing Q, Juan K, Chen B, Luan T 

(2017) Fully automatic single-drop microextraction with 

one-setp extraction and derivatization and its application 

for rapid analysis of hydroxylated polycyclic aromatic 

hydrocarbons in seawaters. Talanta 164: 727-734. 

Williams DBG, George MJ, Marjanovič L (2014) Rapid 

detection of atrazine and metolachlor in farm soils: gas 

chromatography–mass spectrometry-based analysis 

using the bubble-in-drop single drop microextraction 

enrichment method. J. Agri. Food Chem. 62: 7676-7681. 

Wu Y, Hu B, Hu W, Jiang Z, Li B (2007) A novel capillary 

microextraction on ordered mesoporous titania coating 

combined with electrothermal vaporization inductively 

coupled plasma mass spectrometry for the determination 

of V, Cr and Cu in environmental and biological 

samples. J. Mass. Spectrom. 42: 467-475. 

Wu L, Hu M, Li Z, Song Y, Zhang H, Yu A, Wang Z (2015) 

Dynamic microwave-assisted extraction online coupled 

with single drop microextraction of organophosphorus 

pesticides in tea samples. J. Chromatogr. A 1407: 42-51.  

Wu L, Hu M, Li Z, Song Y, Yu C, Zhang H, Wang Z (2016) 

Dynamic microwave-assisted extraction combined with 

continuous-flow microextraction for determination  

of pesticides in vegetables. Food Chem. 192: 596-602. 

Wu Y, Xia L, Chen R, Hu B (2008) Headspace single drop 

microextraction combined with HPLC for the 

determination of trace polycyclic aromatic hydrocarbons 

in environmental samples. Talanta 74: 470-477. 

Xie HY, Yan J, Jahan S, Zhong R, Fan LY, Xiao H, Cao CX 

(2014) A new strategy for highly efficient single-drop 

microextraction with a liquid–gas compound pendant 

drop. Analyst 139: 2545-2550. 

 

Bereitgestellt von  Slovenská poľnohospodárska knižnica | Heruntergeladen  28.02.20 08:24   UTC