Advances in Liquid Phase Microextraction

84 Pages·2020·3.752 MB·English

by  Mazidatulakmam Miskam, Mohd Marsin Sanagi, Aemi Syazwani Abdul Keyon

Advances in
Liquid Phase Microextraction
Editors
Mazidatulakmam Miskam
Mohd Marsin Sanagi
Aemi Syazwani Abdul Keyon
Penerbit Universiti Sains Malaysia
Pulau Pinang
www.penerbit.usm.my
[email protected]
PenerbitUSM
PenerbitUSM
penerbit_usm
© Penerbit Universiti Sains Malaysia, 2020
EPUB, 2020
Perpustakaan Negara Malaysia Cataloguing-in-Publication Data
Advances in Liquid Phase Microextraction / Editors: Mazidatulakmam Miskam,
Mohd Marsin Sanagi, Aemi Syazwani Abdul Keyon.
Mode of access: Internet
e-ISBN 978-967-461-489-8
1. Solvent extraction.
2. Extraction (Chemistry).
3. Government publications Malaysia.
–
4. Electronic books.
I. Mazidatulalmam Miskam. II. Mohd Marsin Sanagi.
III. Aemi Syazwani Abdul Keyon.
660.284248
Copy Editor: Nur Naimah Jaafar
Cover Designer: Mohammad Ridhwan Jaapar
Proofreader: Rosni Habib
Typesetter: Nor Asnida Zubir
Published by Penerbit Universiti Sains Malaysia, 11800 USM Pulau Pinang, Malaysia.
A member of the Malaysian Scholarly Publishing Council (MAPIM).
This e-book is best viewed with iBooks. Penerbit USM shall not be liable for any loss or
damage caused by changes due to usage with other applications.
Contents
Preface vii
Introduction ix
Abbreviations xi
1 Liquid Phase Microextraction 1
Wan Nazihah Wan Ibrahim, Nor Suhaila Mohamad Hanapi,
Aemi Syazwani Abdul Keyon & Mohd Marsin Sanagi
2 Single-Drop Microextraction 14
Nurul Nabilah Zainal Abidin, Zetty Azalea Sutirman,
Aemi Syazwani Abdul Keyon & Mazidatulakmam Miskam
3 Hollow Fibre-Liquid Phase Microextraction 31
Mazidatulakmam Miskam, Aemi Syazwani Abdul Keyon & Mohd Marsin Sanagi
4 Dispersive Liquid-Liquid Microextraction 43
Noorfatimah Yahaya, Dyia Syaleyana Md Shukri & Mohd Marsin Sanagi
5 Electromembrane Extraction 61
Nor Suhaila Mohamad Hanapi, Siti Rosilah Arsad & Wan Aini Wan Ibrahim
Conclusion 76
Contributors 78
Index 79
PB v
1 Liquid Phase Microextraction
Wan Nazihah Wan Ibrahim, Nor Suhaila Mohamad Hanapi,
Aemi Syazwani Abdul Keyon & Mohd Marsin Sanagi
1.1 Introduction
Sample preparation is an essential step in chemical analysis; it influences
selectivity, sensitivity and accuracy of the analysis. Sample preparation
includes clean-up procedures for significantly complex or ‘dirty’ samples.
This step must also bring the analytes to a suitable concentration level for
analysis.
Traditional liquid-liquid extraction (LLE) is a versatile sample
preparation technique, utilised in many standard analytical methods.
Despite its widespread use, it is time-consuming, tedious and involving
a multistage operation, by problem of emulsion formation obstructs
automation. Ultimately, the use of substantial amount of toxic organic
solvents influences trace analysis, poses health hazard to laboratory
personnel and results in the production of hazardous laboratory waste,
thus adding extra operational cost for waste management.
Ideally, the characteristics of an ideal sample preparation technique are
listed as follows:
1. Minimum loss of the sample and maximum recovery of the
analyte.
2. Elimination of accompanying compounds with high yield.
3. Simple, fast and cheap method.
4. Compatible with analytical instruments.
5. In agreement with green chemistry.
PB 1
liquid phase microextraction
Considering these requirements, liquid phase microextraction (LPME)
has been developed towards simple, fast and miniaturised system. LPME
uses a small amount of a water-immiscible solvent (acceptor phase)
from an aqueous sample containing analytes (donor phase). LPME has
emerged as a green extraction method due to solvent-minimised sample
pre-treatment procedure (in μL volume) to pre-concentrate analytes
as compared to hundreds of mL volume needed in traditional LLE.
LPME is widely applied in analyses since it is compatible with various
instruments such as high-performance liquid chromatography (HPLC),
gas chromatography (GC) and capillary electrophoresis (CE).
Basically, LPME offers several advantages over LLE as listed below (More
& Mundhe, 2013):
1. It is a rapid, simple, solvent free and sensitive method for the
extraction of analytes.
2. It is a simple, effective adsorption/desorption technique.
3. It has small footprint, which is convenient for designing portable
devices for field sampling.
4. Consistent quantifiable results from very low concentrations of
analytes.
1.2 Basic Principles of Liquid Phase Microextraction
LPME is based on the distribution of analyte molecules between the
sample solution and the extraction solvent. The equilibrium distribution
coefficient, K is defined by the equation (1.1):
K = C /C (1.1)
o w
where C and C represent the concentrations of analyte in the organic
o w
extraction solvent and aqueous sample solution, respectively.
There are two sampling modes that can be used with LPME, namely two-
phase and three-phase sampling modes as shown in Figure 1.1.
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liquid phase microextraction
(1) Two-phase system (2) Three-phase system
Figure 1.1 Two-phase and three-phase sampling modes LPME
Source: Psillakis and Kalogerakis (2003)
In two-phase LPME sampling mode, analyte ‘i’ is extracted from an
aqueous sample (donor phase) through a water-immiscible solvent
immobilised in the pores of the hollow fibre (HF) into the same organic
solvent (acceptor phase) that presents inside the HF. The extraction
process of the two-phase LPME for analyte i can be respresented by
equation (1.2):
i ↔ i (1.2)
d org
It is characterised by the distribution ratio K , which is defined as the
org/d
ratio of the concentration of analyte i in the organic and donor phase at
the equilibrium conditions.
In the three-phase sampling mode, also known as supported liquid
membrane (SLM), analyte i is extracted from an aqueous solution (donor
phase) through the organic solvent immobilised in the pores of the HF
(organic phase) into another aqueous phase (acceptor phase) present
inside the lumen of the HF. The organic phase in this case serves as a
barrier between an acceptor and the donor aqueous solution to prevent
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liquid phase microextraction
mixing of these two phases. The three-phase sampling mode is usually
combined with HPLC or CE system, as the acceptor phase is aqueous.
Overall, the three-phase LPME extraction process for analyte i can be
represented by equation (1.3):
i ↔ i ↔ i (1.3)
d org a
The three-phase LPME process is characterised by K and K ,
org/d a/org
which are the distribution ratio equilibrium between the organic phase
and the donor phase, and the acceptor solution and the organic phase,
respectively (Liang et al., 2006; Rasmussen & Pedersen-Bjergaard, 2004).
1.3 Types of Liquid Phase Microextraction
In general, LPME can be divided into four main types (as shown in
Figure 1.2). These modes fulfilled the objectives of sample preparation,
such as to achieve better analyte pre-concentration, excellent of limit of
detection (LOD) and significantly high rate for elimination of matrix
interference.
Figure 1.2 Four types of modern sample preparation of LPME
4 5
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1.3.1 Single-drop microextraction
Among the earliest type of LPME is SDME in which the use of solvent
has been signifi cantly reduced (down to a droplet from few µL–nL)
as compared to the classical LLE. From what its name denotes, this
technique is based on suspended single microdrop of water-immiscible
organic solvent on the tip of a microsyringe needle immersed [direct
immersion (DI)-SDME] in the sample solution (Figure 1.3) or
performed from a headspace (HS) above the sample (HS-SDME). Th e
microdrop acts as a sampling interface to extract analytes from sample
solution. Aft er extraction, the microdrop is retracted into the syringe
and transferred for further analysis (e.g., HPLC or GC analysis). High
enrichment factors can be achieved because of great reduction of the
extractant phase-to-sample volume ratio. Proper selection of pH for
acceptor and donor phases, and consideration for the basic and acidic
properties of the extracted analytes can increase the enrichment factor as
well. For example, enrichment factors for aromatic amines using SDME-
GC could be up to 500 when 2 µL toluene was used as extractant for the
extraction of sample adjusted to pH 10 (Yu et al., 2014). SDME was made
fully automated in 2007 and became commercially available in the form
of an autosampler by coupling with commercially available sequential
injection system (Pena, Lavilla & Bendicho, 2008).
Figure 1.3 Schematic of SDME
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liquid phase microextraction
1.3.2 Hollow fibre-liquid phase microextraction
The application of SDME carries a risk of detachment of the drop during
the extraction process. One way to overcome this is to introduce the
organic liquid extractant inside a porous, semi-permeable polymeric
fibre, named as HF-LPME (Figure 1.4). In such a way, the liquid
extractant is not in direct contact with the sample solution; therefore,
sample can be stirred vigorously (to enhance extraction efficiency)
without any loss of the extractant because it is mechanically protected.
HF-LPME requires a few µL of liquid extractant trapped inside a porous
polypropylene tube that is attached to a syringe needle, and the tube is
subsequently immersed in the sample for extraction (HS option also
available). The analytes are then extracted from the aqueous sample
through the organic phase in the pores of the HF and further into an
acceptor solution inside its lumen.
Figure 1.4 Schematic of HF-LPME
After the extraction, this phase is drawn inside the syringe and
subsequently injected into analytical instruments. HF-LPME can be
used in a two-phase system, that is when organic solvent is used to fill
both wall pores and the HF lumen. In a three-phase system, the HF
lumen is filled with a different solvent that impregnating HF wall pores.
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