Bioanalytical Reviews

, 1:35

Analysis of biological samples using solid-phase microextraction

Authors

  • Ashwini Kumar
    • Department of ChemistryPunjabi University
  • Gaurav
    • Department of ChemistryPunjabi University
    • Department of ChemistryPunjabi University
  • Frank-Michael Matysik
    • Universität Regensburg, Institut für Analytische Chemie, Chemo- und Biosensorik
Article

DOI: 10.1007/s12566-009-0004-z

Cite this article as:
Kumar, A., Gaurav, Malik, A.K. et al. Bioanal Rev (2009) 1: 35. doi:10.1007/s12566-009-0004-z

Abstract

Solid-phase microextraction (SPME) has gained widespread acceptance for analyte-matrix separation and preconcentration. SPME is a simple, effective adsorption/desorption technique that eliminates the need for solvents or complicated apparatus for concentrating volatile or non-volatile compounds in liquid samples or headspace. SPME is compatible with analyte separation/detection by gas chromatography and high performance liquid chromatography and provides linear results for a wide range of concentrations of analytes. By controlling the polarity and thickness of the coating on the fiber, maintaining consistent sampling time, and adjusting several other extraction parameters, an analyst can ensure highly reliable results for low concentrations of analytes. This review provides updated information on SPME with chromatographic separation for the extraction and measurement of different analytes in biological fluids and materials. Firstly the background to the technique is given in terms of apparatus, fibers used, extraction conditions and derivatisation procedures. Then the different matrices, urine, blood, breast milk, hair and saliva are considered separately. Finally, the future potential of SPME for the analysis of biological samples in terms of the development of new devices and fiber chemistries as well as applications for in vivo studies are discussed.

Keywords

Solid phase microextractionUrineHairBloodSalivaBreast milkIn vivo analysis

Introduction

Analytical capability for the extraction and preconcentration of the trace organic contaminants from aqueous, gaseous and solid samples has become extremely important with increasing environmental and health awareness. Various forms of Soxhlet extraction, liquid-liquid extraction, accelerated solvent extraction, microwave-assisted solvent extraction, solid-phase extraction, supercritical fluid extraction, purge and trap, and other methods are traditionally used for this purpose. Some of these methods are time consuming and/or expensive while others, employ a large volume of hazardous organic solvents. SPME as developed by Pawliszyn and co-workers in 1989 effectively overcomes these difficulties [13]. SPME was developed to address the need for fast, solvent free and field compatible sample preparation methods [35]. It has been used routinely, in combination with gas chromatography (GC), and successfully applied to a wide variety of compounds, especially for the extraction of volatile and semivolatile organic compounds from environmental, biological and food samples [37]. SPME was also introduced for direct coupling with HPLC and LC-MS in order to analyze weakly volatile or thermally labile compounds not amenable to GC or GC–MS [5, 7] and with supercritical fluid extraction [8]. SPME has successfully been coupled to capillary electrophoresis (CE) [9, 10] and packed column supercritical fluid chromatography (PCSFC) [11].

SPME is a microextraction technique meaning that the amount of extraction solvent is very small compared to the sample volume. As a result exhaustive removal of the analyte to the extracting phase does not occur, rather equilibrium is reached between the sample matrix and extracting phase. The design of SPME extraction phase must take into consideration the stability, polarity and thickness of coating. Coating thickness determines the volume and surface area of the stationary phase and consequently, the amount and rate of accumulation of the target species, depending on the partitioning of the analytes between sample matrix and extraction phase for required sensitivity. Therefore, the solid phase technology for SPME fibers presents a more complex problem than in conventional extraction techniques. Among the different approaches to stationary phase development for SPME fibers, sol–gel approach represents a promising direction in this important research area with applicability in preparation of surface coatings for the SPME fibers. To make this approach practical the extracting phase, which is a cross-linked polymeric organic phase is permanently attached to the fiber. When the coated fiber is placed into an aqueous matrix, the analyte is transferred from the matrix into the coating. The amount of analyte extracted is described by Nernst’s partition law [2]. SPME has several important advantages compared to the traditional sample preparation techniques:
  • It is a rapid, simple, solvent free and sensitive method for the extraction of analytes.

  • It is a simple and effective adsorption/desorption technique.

  • It is compatible with analyte separation and detection by HPLC-UV, GC-MS, and capillary electrophoresis (CE).

  • It provides linear results for a wide range of concentrations of analytes.

  • It has small size, which is convenient for designing portable devices for field sampling.

  • It gives highly consistent, quantifiable results for very low concentration of analytes.

SPME has been applied to a range of applications including environmental, industrial hygiene, process monitoring, clinical, forensic, drugs and food analysis. The details of SPME and its application are also summarized in corresponding monographs [5, 7], and well-documented reviews [26, 1218].

The scope of the present review is to survey the literature regarding the use of SPME for the determination of pharmaceuticals, drugs of abuse, biologically active compounds and compounds of general biological or toxicological interest in biological samples. The major criteria are the type of the analyte and the type of sample. First a short and general description of the method and its main features is given. In the applications part, the paper is divided into five major paragraphs with regard to the groups of different biological matrices. Finally recent trends of in vivo SPME are discussed.

Solid-phase microextraction

SPME is a technique whereby an analyte is sorbed onto the surface of a coated silica fiber. This is followed by desorption of the analytes into a suitable instrument such as GC or HPLC for the separation which is combined with a suitable detector for quantification. Sorption of analyte onto a suitably coated silica fiber or stationary phase is the most important stage. SPME is performed with GC in most of the applications. In case of SPME-GC, the analytes are thermally desorbed or vaporized (in dependence on the kind of fiber coating) into the injector of the chromatograph. It is however, generally limited to volatile and thermally stable compounds. Some of the applications involve the derivatization within the sample matrix or the injection port. Derivatization on the fiber after and/or during SPME can be applied to overcome the problem of its limited use. More recently, SPME is applied to nonvolatile and thermally unstable compounds by interfacing with HPLC. In SPME-GC, the fiber is introduced into the injector port and analytes are thermally desorbed from the coating. But in SPME-HPLC, desorption is carried out in an appropriate interface. It consists of a six port injector with a special fiber desorption chamber, installed in place of the sample loop. Desorption is carried out by the use of organic solvent or mobile phase because the thermal desorption at high temperature leads to degradation of the polymer and incomplete desorption of many nonvolatile compounds from the fiber.

Design of SPME

There are two different techniques for the SPME method; fiber SPME and in-tube SPME. Fiber SPME is a modified syringe like instrument which consists of fiber holder and fiber assembly with built-in fiber inside the needle. The fiber is coated with a relatively thin film of several polymeric phases. Due to its small physical diameter, cylindrical geometry and stability at higher temperatures, it can be incorporated into a syringe like holder. The SPME holder provides protection to fiber and allows piercing of rubber septum of the GC injector. The fiber is retracted within the needle of the SPME holder when it is not in use. During operation, the silica fiber is exposed to the sample in its matrix. In-tube solid-phase microextraction (SPME) [19] is an automated version of SPME that can be easily coupled to a conventional HPLC autosampler for on-line sample preparation, separation and quantitation. It has been termed “in-tube” SPME because the extraction phase is coated inside a section of tubing rather than coated on the surface of a fiber rod as in the conventional syringe-like SPME device. The new in-tube SPME technique has been demonstrated as a very efficient extraction method for the analysis of polar and thermally labile analytes.

Operation of SPME in conjunction with HPLC

As SPME-HPLC is less common than SPME-GC the operation of the former technique is shortly described in the following.

The fiber should be cleaned before analyzing any sample as the contaminants are responsible for the background in the chromatogram. It is done in the desorption chamber within the HPLC system by running solvent. During the process, the fiber is lowered into the vial which is sealed with a septum type cap. The fiber is extended into the sample through the needle. It results in the adsorption of analyte on the fiber. After sampling, the fiber is retracted within its holder for protection. The analytes are desorbed from the fiber using the mobile phase, i.e., solvent desorption. This requires a special interface which consists of a six port injection valve and a desorption chamber. The desorption chamber is placed in the position of the injection loop. When sample is extracted, the fiber is inserted into the desorption chamber at the ‘load’ position. After changing the injector to ‘inject’ position, the mobile phase comes in contact with the fiber. Desorption of analytes occurs and the mobile phase delivers them to the HPLC column where they get separated and detected by a suitable detector.

Selection of the fiber

The properties (physical and chemical) of the coating are crucial for the partition process. Selection of the coating is mainly based on the principle ‘like dissolves like’. Non-polar analytes have relatively high affinity for the apolar polydimethylsiloxane phases which are often first choice, since they also offer long life time. Polyacrylate is more polar and can be used for the extraction of polar compounds, such as phenols. The technique has found limited use in high performance liquid chromatographic applications because of the unavailability of fibers that are stable and durable in strong organic solvents. Proper fiber selection is important for the efficient extraction of the analyte from the sample. It is based on the nature of the analyte. There are seven different types of fibers available from Supelco, namely polydimethylsiloxane (PDMS) [20], polydimethylsiloxane/divinylbenzene (PDMS/DVB) [21, 22], stableflex polydimethylsiloxane/divinylbenzene (PDMS/DVB), polyacrylate (PA) [2326], carboxen/polydimethyl-siloxane(CAR/PDMS), carbowax/divinylbenzene (CW/TPR) [2730], stableflex divinylbenzene/carboxen/polydimethylsiloxane (DVB/CAR/ PDMS). But the modifications of fibers and preparation of new fibers increases the interest towards SPME-HPLC methods.

Some methods for the modifications of the fiber are reported using sol gel processes [17, 3133], these fibers are stable in strong organic solvents (xylene and methylene chloride) as well as acidic and basic solutions. The method of preparation involves four steps. In the first step, the fiber is pretreated by burning the tip to remove the polyimide coating, then it is washed with methanol and air-dried. The sol–gel solutions prepared and stirred for 4 h at room temperature. The fiber is coated by exposing to the sol–gel solution for 20 min and end capped. The fiber is conditioned by placing it in the GC injector port at a temperature of 130°C. Before use the fiber is conditioned in the mobile phase for 30 min and dried at room temperature. The hydrolytic stability of these sol–gel prepared SPME fibers towards organic solvents and high and low pH solutions can be attributed to the fact that the coating is chemically bonded to the surface of the fused silica substrate. A thermal stability shows that the PDMS fiber could be used up to 320°C whereas commercial PDMS fibers typically start to bleed at lower temperatures (200°C). The high degree of porosity of sol–gel fiber resulted in higher sensitivity and faster extraction times relative to commercial fibers.

Selection of extraction mode

There are two types of extraction modes [34, 35] in fiber SPME; head space SPME (HS-SPME) and direct immersion SPME (DI-SPME). HS is used when GC is employed for final analysis. In case of HS-SPME two equilibria exist: sample—gas phase and gas phase—fiber coating which differs in their temperature dependence. It involves the exposure of fiber in the vapour phase above the gaseous, liquid or solid sample. In this the fiber is not in contact with the sample. The analytes need to be transported through a layer of air before they can reach the coating. In DI-SPME the coated fiber is inserted into liquid sample and the analytes are transported directly to the extraction phase. For volatile compounds, fiber HS-SPME is preferred over the DI-SPME as the former has longer lifetime. The fiber coating can be damaged by high molecular weight species and other non-volatile contaminants present in the liquid sample matrix in case of DI-SPME as the fiber is directly immersed into it. It is also found that HS is more selective than DI [4].

Optimization of extraction

Extraction temperature

Analyte equilibrium concentration in the HS can be increased by heating the sample and by cooling the fiber. It is applied to the analysis of very volatile components in heavily contaminated liquid and solid samples [3639].

Sample agitation

Agitation speeds up the transfer of analytes from matrix to coating of the fiber [40]. It is done by magnetic stirring, sonication and intrusive stirring [4042]. Another way to speed up the extraction is fiber vibration [43] and rotation [44] which increases precision also.

Salting out effect [2, 41, 4553]

Addition of an electrolyte can reduce the extraction time by increasing the ionic strength and reducing analyte solubility. The electrolytes generally used for this purpose are NaCl, NaHCO3, K2SO4 and (NH4)2SO4. The salting out effect makes HS-SPME more effective.

pH of the solution [41, 50, 5256]

The dissociation equilibria in the aqueous phase are strongly affected by the pH adjustment. The adjustment of the pH in the aqueous sample can improve the sensitivity for acidic and basic analytes. The decrease of the pH results in concentration increase of basic species present in the sample. In practice, it is very difficult to implement large pH change with the direct extraction approach since high and low pH damages the coating. A typical range for varying the pH is 2 to 10. Appropriate buffer should be used to ensure high reproducibility if basic and acidic compounds are present in the sample.

The relation between the pH and extraction yield is, as expected, described by the dissociation of protonated analyte (AH+) by means of the Henderson-Hasselbalch equation:
$$ {{pH}} = {{pK}}_a + \log \frac{{ \left[ {{A}} \right]}}{{\left[ {{{AH}}^{ + } } \right]}} $$

The amount of neutral analyte (A) can be calculated and, therefore, also the extraction yield of this deprotonated form. The ionic compounds can be converted to a non-ionic form and are extracted by nonpolar and weakly polar stationary phases.

Extraction time

When developing the conditions for SPME sampling, one should plot detector response versus sampling time for each analyte in the sample. After the resulting curves are examined, the data will show that highly volatile analytes will reach a plateau in 15 min or less, indicating the equilibrium. Compounds of lower volatility will show a steadily increasing response with time.

Derivatization

It is based on analyte conversion to another compound by reacting with a specially selected reagent. An analyte derivative should be characterized by better and/or more selective SPME extraction. There are two derivatization approaches; in matrix derivatization and on fiber derivatization [56]. In matrix derivatization is based upon the addition of a derivatization reagent to a container with a sample and extraction of a derivative from HS. On fiber derivatization is conducted directly on the SPME fiber. The fiber is immersed in reagent solution and then in the sample. The analyte is extracted and converted to a derivative within the coating.

Optimization of analyte desorption

Dynamic desorption involves the removal of analytes by a moving stream of mobile phase and static desorption involves the soaking of fiber in the mobile phase for a specified time for desorption of strongly sorbed analytes. The rapid and complete desorption of analytes using a minimal quantity of solvent is important for optimizing SPME-HPLC.

SPME in bioanalysis

Since its invention there has been a rapid growth in the number of applications of SPME as evidenced by the growing number of published papers. Originally, it was confined to analysis of pollutants in environmental matrices (e.g. pesticide and aromatic hydrocarbon contamination of water) [5, 57]. The potential of the technique was soon recognised for measuring volatile and semivolatile components in beverages, flavourings, foodstuffs, forensic specimens and pharmaceutical products and a tool for determining physicochemical properties of organic compounds. Many of these applications are summarized in ref. [7]. The aim of this review is to provide an updated information on the use of SPME for the analysis of biological fluids and materials. The majority of reports is concerned with HS-SPME coupled to GC. However, it should be recognised that direct immersion SPME interfaced with either GC or HPLC can also be used to measure a range of biologically relevant compounds. The method selected depends on the extraction properties (primarily volatility and polarity) of the analyte and the type of material being handled. HS-SPME is ideal for the analysis of biological specimens as interference from high-molecular-mass components (e.g., proteins), in the matrix is reduced yielding cleaner extracts. Although HS-SPME is an equilibrium rather than an exhaustive (e.g., LLE) extraction method, by careful adjustment of the extraction conditions (agitation, pH, salting out, temperature, time) significant enhancements in sensitivity can be achieved to enable the detection of even semivolatile analytes. Derivatisation of target compounds by acylating, alkylating and silylating reagents can also improve sensitivity. As only the HS gas is sampled, more aggressive (e.g., strong acid or alkaline media) sample preparation and derivatisation regimes can be used compared to direct immersion where fibre damage might occur. However, high levels of non-polar organic solvents in, or added to, the matrix can cause the fibre to swell. As complex interactions occur between the different phases in HS sampling, appropriate internal standards (preferably isotopically labelled), are essential for quantitative analysis.

Hair samples

The analysis of hair can be used for forensic purposes and to monitor drug compliance and abuse. As with biological fluids, drugs and their metabolites are expressed in hair. Measurements along a strand of hair can provide a record of drug usage. Before analysis the hair matrix must be either digested enzymatically (e.g. with a protease) or more commonly with a strong alkaline solution (e.g. 1 M NaOH). SPME has been used to detect ethanol, cannabinoids, cocaine, methadone and its metabolites [5866] by direct immersion of the fibre in the solution remaining after digestion. However, with highly basic conditions damage to the polymer coating of the fibre can occur leading to variable results. Nishida et.al performed single hair analysis of methamphetamine and amphetamine by solid phase microextraction coupled with in-matrix derivatization [59]. Yahata et.al. developed in-matrix derivatization and automated headspace solid-phase microextraction for GC-MS determination of amphetamine-related drugs in human hair [60]. Gentili et.al. developed a rapid screening procedure based on headspace solid-phase microextraction and gas chromatography-mass spectrometry for the determination of many recreational drugs in hair [61]. Wu et.al. performed the determination of stimulants in human urine and hair samples by polypyrrole coated capillary in-tube solid phase microextraction coupled with liquid chromatography-electrospray mass spectrometry [66]. Details of the determination of different organic compounds in the hair samples by different research groups are given in Table 1. Sporkert et al. developed a headspace solid-phase microextraction (HS-SPME) in hyphenation with GC-MS in hair analysis for many lipophilic basic drugs such as nicotine, amphetamine derivatives, local anaesthetics, phencyclidine, ketamine, methadone, diphenhydramine, tramadol, tricyclic antidepressants and phenothiazines (Fig. 1) [72].
Table 1

Applications of SPME for the analysis of hair, saliva and human milk samples

Sr. no.

Analyte

Matrix

Extraction

Analytical instrument

Detector

LOD

Ref

1.

Ethanol, ethylesters and fatty acid ethylesters

Hair

HS-SPME

GC

MS

17–135 ng/mg

[58]

2.

Methamphetamine and amphetamine

Hair

HS-SPME

GC

 

0.02 and 0.05 ng /0.08 mg/vial

[59]

3.

Amphetamine related drugs

Human hair

HS-SPME

GC

MS

0.01 to 0.5 ng/mg

[60]

4.

Cocaine, amphetamine, methamphetamine, methylenedioxyamphetamine, methylene dioxymethamphetamine, methylenedioxyethamphetamine, N-methyl-1-(1,3-benzodioxol-5-yl)-2-butanamine, ketamine, and methadone

Human hair

HS-SPME

GC

MS

0.7 ng/mg of hair for the majority of substances

[61]

5.

Methadone, the trimethylsilyl derivatives of cannabinoids and the trifluoroacetyl derivatives of amphetamines and designer drugs

Hair

HS-SPME

GC

MS/MS

Between 6 and 52 pg/mg

[62]

6.

Methylenedioxyamphetamine, methylenedioxymethamphetamine, methylenedioxyethamphetamine and N-methyl-1-(1,3-benzodioxol-5-yl)-2-butanamine

Hair, saliva, urine and blood

HS-SPME

GC

MS/MS

Less than 0.7 ng/mg For each substance

[63]

7.

Amphetamines and synthetic designer drugs

Human hair

HS-SPME

GC

MS

Between 0.01 and 0.17 ng/mg

[64]

8.

Methamphetamine and amphetamine

Hair

HS-SPME

GC

MS

-

[65]

9.

Amphetamine, methamphetamine and their methylenedioxy derivatives

Urine and hair

In-tube SPME

LC

MS

8–56 ng/L

[66]

10

Thiopental and pentobarbital

Head and pubic hair

SPME

GC

MS/MS

-

[67]

11.

Ethyl myristate, ethyl palmitate, ethyl oleate and ethyl stearate

Human hair

HS-SPME

GC

MS

0.01 and 0.04 ng/mg

[68]

12.

Cannabidiol, cannabinol, and A-9-tetrahydrocannabinol

Human head hair

HS-SPME

GC

MS

0.12 ng/mg

[69]

13.

Cannabinoids

Hair

HS-SPME

GC

MS

0.09-0.14 ng/mg

[70]

14.

Cannabinoids

Hair

HS-SPME

GC

MS

0.05–0.14 ng/mg

[71]

15.

Lipophilic basic drugs

Hair

HS-SPME

GC

MS

0.05-1.0 ng/mg

[72]

16.

Cannabinoids

Hair

SPME

GC

MS

0.1–0.7 ng/mg

[73]

17.

Cocaine

Hair

SPME, SFE

GC

MS

0.1 ng/mg

[74]

18.

Cocaine and cocaethylene

Hair

SPME

GC

MS

-

[75]

19

Cocaine, benzoylecgonine and cocaethylene

Hair

SPME

GC

MS

0.1–0.5 ng/mg

[76]

20.

Fatty acid ethyl esters

Hair care products

HS-SPME

GC

MS

-

[77]

21.

Methadone and its main metabolite

Hair

SPME

GC

MS

0.15–2.48 ng/mg

[78]

22.

Volatile organic compounds

Canine hair

HS-SPME

GC

MS

-

[79]

23.

Methadone and its metabolites

Human hair

HS-SPME

GC

MS

0.03–0.05 ng/mg

[80]

24.

Methadone and 2-ethylidine-1,5-dimethyl-3,3-diphenyl-1-pyrrolidine (EDDP)

Hair of patients

HS-SPME

GC

MS

-

[81]

25.

Amphetamines

Saliva

SPME, LLE

GC, LC

MS

-

[82]

26.

Methadone, 2-ethyl-1,5-dimethyl-3,3-diphenylpyrrolinium perchlorate, cocaine, cocaethylene, amphetamine, methamphetamine, 3,4-methylenedioxymethamphetamine, 3,4-methylenedioxyethyl amphetamine, N-methyl-1-(3,4-methylenedioxyphenyl)-2-butanamine, cannabidiol, Δ9-tetrahydrocannabinol, cannabinol

Saliva

HS-SPME, DI-SPME

GC

MS

1–100 ng/mL

[83]

27.

Tetrahydrocannabinol (THC), amphetamine, methamphetamine, cocaine and ethanol

Saliva

SPME

GC

MS, Flame ionisation detector (FID)

0.5–10 ng/mL

[84]

28.

Cannabinoids

Saliva

SPME

GC

MS

-

[85]

29.

Cannabidiol, Δ8-tetrahydrocannabinol, Δ9-tetrahydrocannabinol

Saliva

SPME

GC

MS

1.0 ng/mL

[86]

30.

Methyl ethyl ketone, isopropyl alcohol, and N,N-dimethyl formamide, acetone and N-methyl formamide

Saliva

HS-SPME

GC

MS

0.003–0.10 μg/mL

[87]

31.

Methadone and 2-ethyl-1,5-dimethyl-3,3-diphenyl-pyrrolinium perchlorate

Oral fluid

SPME

GC

MS

-

[88]

32.

Methadone and 2-ethylidine- 3,3-diphenylpyrrolidine

Saliva

SPME, LLE

GC

MS

0.04 and 0.008 μg/mL

[89]

33.

Cortisol

Saliva

SPME

LC

MS

5 pg/mL

[90]

34.

Chlorhexidine

Saliva

SPME

LC

MS

0.01 and 0.02 μg/mL

[91]

35.

Acetone, ethyl hexanoate and heptan-2-one

Saliva, Breath, Chewing

SPME

GC

MS, API-MS

-

[92]

36.

Methadone

Saliva and urine

SPME

GC

MS

-

[93]

37.

Dibenzylamine

Saliva leachates

SPME, SPE

GC

MS

-

[94]

38.

Tetracyclines

Chicken feed, chicken muscle and milk samples

SPME

HPLC

FD

1.0–2.3 μg/L

[95]

39.

Polycyclic musk compounds

Serum and breast milk

SPME, SPE

GC

MS

0.03–0.3 ng/mL

[96]

40.

Polychlorinated biphenyls

Human milk

HS-SPME

GC

ECD

0.45–2.24 μg/L

[97]

https://static-content.springer.com/image/art%3A10.1007%2Fs12566-009-0004-z/MediaObjects/12566_2009_4_Fig1_HTML.gif
Fig. 1

GC/MS-SIM chromatogram of a 10-mg hair sample (non-smoker) spiked with 16 drugs after HS-SPME sample preparation. Concentrations: 1 ng/mg, ethylbenzhydramine (peak 11, internal standard) 10 ng/mg, nicotine not added. Fiber: PA 85 µm. Adsorption: 15 min at 70°C (reproduced with the permission from reference [72])

Saliva samples

Personal air monitoring is a routine method used by industrial hygienists to investigate external exposure to hazardous volatile organic compounds. Total internal exposure, including topical absorption of organic solvents, can be elucidated by biological monitoring of blood and/or urinary metabolites. Many authors have produced remarkable advances in sensitive techniques which have encouraged the analysis of chemicals in conventional biological samples, particularly in urine. Wang et al. applied solid-phase microextraction and gas chromatography–mass spectrometry for measuring chemicals in saliva of synthetic leather workers (Fig. 2) [87]. In comparison to blood and urine matrices, saliva has the advantages of being non-invasively collected, being readily accessible with fewer confidentiality concerns, having a much lower protein content than other physiological fluids, and being relatively free of interfering substances [86]. A good correlation between saliva and plasma levels for health investigation parameters makes saliva an attractive health diagnostic tool for systemic diseases [98]. There is a wide variety of applications in saliva investigation that are pursued by dental and medical researchers for therapeutic drug monitoring and illicit drug abuse detection. A few studies have also explored saliva from a comprehensive health perspective, considering the role of this fluid in reflecting the health, comfort, and well-being of the human organism [99]. Some studies have investigated saliva in terms of evaluating the chemical exposure and consequent health effects. For example, Ernstgård et al. investigated biological samples of exhaled air, blood, saliva, and urine in an inhalation toxicokinetics study on isopropyl alcohol and m-xylene exposure. The headspace of isopropyl alcohol, its metabolite acetone, and m-xylene were monitored in biological matrices, and the authors proposed that the compounds measured in saliva might be a useful indication of internal exposure [100, 101]. Rose et al. studied concentrations of acetone in both blood and saliva during isopropyl alcohol exposure and concluded that a high correlation was found between these two biological matrices for either individual subjects or the entire study group [102]. Saliva is a complex and dynamic biological fluid. A properly established method of collection, storage, and analysis is essential to obtaining meaningful results for saliva monitoring and consequent health effect evaluation [103]. Details of the determination of different organic compounds in the saliva samples by various research groups are given in Table 1.
https://static-content.springer.com/image/art%3A10.1007%2Fs12566-009-0004-z/MediaObjects/12566_2009_4_Fig2_HTML.gif
Fig. 2

SPME chromatograms of saliva samples: a blank; b standards in blank saliva matrix; c real saliva sample. Peak identifications: 1, acetone; 2, methyl ethyl ketone; 3, isopropyl alcohol; 4, N,N-dimethyl formamide; 5, N-methyl formamide (reproduced with the permission from reference [87])

Urine samples

Due to the widespread use and presence of different organic compounds in environmental samples and drugs, humans are exposed to these compounds via different pathways, i.e. inhalation, consumption, ingestion of contaminated food and dermal contact. In this complex context, biological monitoring of exposure, that is the identification and quantification of toxic substances and/or of their metabolites in biological fluids, is a useful tool to estimate the total uptake of the chemicals by the human body. Thus, their determination in human body fluids could be very useful for toxicological, pharmaceutical and forensic purposes. Chia et al. developed a sensitive and solvent-free procedure for the determination of amphetamine-like drugs, amphetamine (AM), methamphetamine (MeAM), methylenedioxyamphetamine (MDA), methylenedioxymethamphetamine (MDMA) and methylenedioxyethylamphetamine (MDEA) in urine samples was developed using SPME with an on-fiber derivatization device (Fig. 3) [104]. Details of the determination of different organic compounds in the urine samples by different research groups are presented in Table 2.
https://static-content.springer.com/image/art%3A10.1007%2Fs12566-009-0004-z/MediaObjects/12566_2009_4_Fig3_HTML.gif
Fig. 3

SPME chromatograms of urine samples. a U1 sample from a drugs abuser. b Spiked blank urine which is at a concentration of 50 ng/ml of amphetamine (AM) methamphetamine (MeAM), methylenedioxyamphetamine (MDA), methylene-dioxymethamphetamine (MDMA) and methylenedioxyethylamphetamine (MDEA) (reproduced with the permission from reference [104])

Table 2

Applications of SPME for the analysis of urine, blood, serum and plasma samples

Sr. no.

Analyte

Matrix

Extraction mode

Analytical

Detector

LOD

Ref

1.

Amphetamine, methamphetamine and their methylenedioxy derivatives

Urine

In tube SPME

HPLC

UV

1.4–4.0 ng/mL

[104]

2.

Amphetamine, norephedrine and 3,4-methylenedioxyamphetamine

Urine

SPME

LC

-

≤10 μg/mL

[105]

3.

Ephedrine and methamphetamine

Human urine

HS- SPME

-

-

0.33 ng/mL, 0.60 ng/mL

[106]

4.

l-Amphetamine-d 3 and l-methamphetamine-d 6

Urine

HS- SPME

GC

MS

-

[107]

5.

Selegiline and desmethylselegiline

Urine and Blood

HS- SPME

GC

MS

0.01–0.05 ng/mL

[108]

6.

Amphetamine, methamphetamine, methylenedioxyamphetamine, methylenedioxymethamphetamine and methylenedioxyethylamphetamine

Urine

HS- SPME

GC

MS

0.016–0.193 ng/mL

[109]

7.

Stimulants and narcotics

Urine

SPME

GC

MS

50 ng/mL

[110]

8.

Amphetamine, methamphetamine, 3,4 - methylene— dioxyamphetamine and 3,4-methylenedioxymethamphetamine

Urine

SPME

GC

MS

0.4 ng/mL to 9.5 ng/mL

[111]

9.

Amphetamines

Urine

SPME

LC

-

-

[112]

10.

Methamphetamine and amphetamine

Urine

HS- SPME

GC

MS

0.3 and 1.0 ng/mL, respectively

[113]

11.

Amphetamine, methamphetamine, and their methylenedioxy derivatives

Human urine

SPME

GC

MS

200 pg/mL and 7.5 ng/mL

[114]

12.

Amphetamine

Human urine

SPME

GC

MS

250 pg/mL and 100 pg/ mL

[115]

13.

Amphetamine, lidocaine, procaine, and mepivacaine

Human urine

SPME

GC

-

-

[116]

14.

Methamphetamine and amphetamine

Human urine

SPME

GC

MS

-

[117]

15.

Methamphetamine, fenfluramine, and methylenedioxymethamphetamine, amphetamine and phentermine, methylenedioxyamphetamine, phenethylamine, 4-bromo-2,5-dimethoxyphenethylamine

Urine

HS- SPME

GC

MS

-

[118]

16.

Amphetamine

Urine

DI-SPME

GC

-

-

[119]

17.

Amphetamines and their 3,4-methylenedioxy derivatives

Urine

Intube SPME

LC

MS

0.4–0.8 ng/mL

[120]

18.

Barbiturates

Urine and human blood

DI-SPME

GC

MS

For blood 0.05–1 μg/mL, For urine 0.01-0.6 μg/mL

[121]

19.

Amphetamines, barbiturates, benzodiazepines, benzoylecgonine, methadone and opiates

Urine and serum

HS-SPME

GC

MS

-

[122]

20.

Delorazepam

Human urine

SPME

HPLC–

UV

-

[123]

21.

Clonazepam, oxazepam, temazepam, nordazepam, and diazepam

Urine

SPME

HPLC

UV

600, 750, 333, 100, and 46 ng/mL

[124]

22.

Diazepam, nordiazepam, temazepam, oxazepam, 7-aminoflunitrazepam, N-desmethylflunitrazepam, and clonazepam

Urine and serum

Intube SPME

LC

MS

0.02 ng/mL to 2 ng/mL

[125]

23.

5α-Androst-2-en-17β-ol and -17-one

Urine

HS-SPME

GC

MS

-

[126]

24.

Cocaine and cocaethylene

Urine

SPME

GC

MS

LOQ 5.0 ng/mL

[127]

25.

gamma-Hydroxybutyrate, ketamine, methamphetamine, methylenedioxymethamphetamine

Urine

SPME

GC

MS

-

[128]

26.

Ephedrine

Urine

SPME

IMS

-

50 ng/mL

[129]

27.

Ketamine

Urine

Intube SPME

HPLC

-

6.4 ng/mL-1

[130]

28.

Amphetamine, methamphetamine, and their 3,4-methylenedioxy

Urine

Intube SPME

LC

MS

0.38–0.82 ng/mL

[131]

29.

Amphetamine, methamphetamine, 3,4-methylenedioxyamphetamine 3,4-methylenedioxymethamphetamine

Urine

SPME

GC

MS

10 ng/mL for amphetamine and methamphetamine and 20 ng/mL for others

[132]

30.

Citalopram, fluoxetine and its main metabolites demethylcitalopram, didemethylcitalopram, norfluoxetine

Human urine

SPME

HPLC

MS

0.01 mg/L

[133]

31.

Ethylbenzene, xylene and mesitylene

Urine and Blood

HS-SPME

GC

-

-

[134]

32.

Phenol, hydroquinone and catechol

Urine

SPME

GC

MS

0.3 μg/mL, 0.15 μg/mL and 0.02 μg/mL

[135]

33.

N-Hydroxymethyl-N-methylformamide and N-methylformamide

Urine

HS-SPME

GC

nitrogen-phosphorus detector

-

[136]

34.

Venlafaxine, fluvoxamine, mirtazapine, fluoxetine, citalopram, and sertraline

Urine

SPME

GC

MS

<0.4 ng/mL-1

[137]

35.

Ochratoxin A

Human urine

SPME

LC

MS

0.3 ng/mL

[138]

36.

Clenbuterol

Human urine and serum

SPME

LC

UV

9 ng/mL (urine) 5 ng/mL (serum)

[139]

37.

(S)-Propranolol and (R)-propranolol

Human urine

Intube SPME

pressure-assisted CEC

-

4 and 7 ng/mL, respectively

[140]

38.

Tetramethylenedisulfotetramine (tetramine)

Human urine

DI-SPME

GC

Flame thermionic detection (FTD)

LOQ: 0.082 ng/mL

[141]

39.

Candesartan, losartan, irbesartan, valsartan, telmisartan

Urine and human plasma

in-tube SPME

HPLC

Fluorescence detection

0.1–15.3 ng/mL and 0.1–15.2 ng/mL in human plasma and urine, respectively

[142]

40.

Propranolol

Human urine

Sol gel SPME

GC

FID

0.275 μg/L for HS-SPME and 0.193 μg/L for DI-SPME

[143]

41.

Clenbuterol

Urine

HS-SPME

GC

MS

0.23 ng/mL

[144]

42.

Naproxen

Human urine

SPME

LC

UV

0.03 μg/mL

[145]

43.

Ibuprofen

Urine

SPME

HPLC

UV

-

[146]

44.

Barbital

Urine and blood

DI-SPME

GC

MS

60 and 3 ng/mL, respectively

[147]

45.

Ketoprofen, fenbufen and ibuprofen

Urine

in-tube SPME

HPLC

-

38, 18 and 28 ng/mL, respectively

[148]

46.

Lidocaine

Urine

SPME

Ion trap MS

-

below 1 ng/mL

[149]

47.

Methylamine, dimethylamine, ethylamine, propylamine, butylamine, pentylamine, and hexylamine

Human Urine

SPME

GC

FID

below 0.05 μg/L

[150]

48.

Verapamil, gallopamil, norverapamil and PR22

Urine, Plasma, and cell culture media

in-tube SPME

LC

MS

5, 6, 6 and 8 ng/mL

[151]

49.

2–Chlorovinylarsonous acid

Human Urine

SPME

GC

MS

7.4 pg/mL

[152]

50.

Lidocaine

Urine

SPME

ion-trap mass MS

-

0.4 ng/mL

[153]

51.

Daidzein, genistein

Urine

SPME

HPLC

MS

25.4 pg/mL, 2.70 pg/mL respectively

[154]

52.

gamma-Hydroxybutyrate

Urine

SPME

GC

MS

2 μg/mL

[155]

53.

Organochlorine and organophosphorus pesticides

Urine samples and human serum

DI- SPME

GC

ECD/FPD

1-10 ng/mL for serum, 0.1–0.4 ng/mL in urine

[156]

54.

Alprenolol, atenolol, oxprenolol, pindolol, β-propranolol, and timolol

Urine and plasma

SPME

-

PD and EFD

2 to 25 μg/mL

[157]

55.

γ-Hydroxybutyric acid

Urine and plasma

HS-SPME

GC

MS

-

[158]

56.

Amitriptyline, imipramine, nortriptyline, and desipramine

Human urine

SPME

micro LC

-

3 ng/mL-1

[159]

57.

Stimulants and β-blockers

Human urine and serum

in-tube SPME

LC

MS

0.1–1.2 ng/mL

[160]

58.

Amphetamine

Urine

HS-SPME

GC

MS

0.25 mg/L

[161]

59.

Nicotine and cotinine

Urine

HS-SPME

GC

MS

1.1 μg/L and 0.9 μg/L

[162]

60.

Verapamil

Urine

SPME

Ion mobility spectrometry (IMS)

-

-

[163]

61.

Quinine, naproxen, haloperidol, ciprofloxacin and paclitaxel

Urine

SPME

HPLC

[164]

62.

Norfloxacin and enrofloxacin

Urine

SPME

HPLC

UV

0.17 and 0.12 ng/mL

[165]

63.

Eugenol

Serum

HS- SPME

GC

MS

3.2 ng/mL

[166]

64.

Amphetamine, methamphetamine, methylenedioxyamphetamine and methylenedioxymethamphetamine

Blood

HS- SPME

GC

MS

10 ng/mL

[167]

65.

Amphetamine and methamphetamine

Serum

SPME

LC

MS

0.3 μg/L and 0.04 μg/L, respectively

[168]

66.

Methamphetamine and amphetamine

Blood

HS-SPME

GC

MS

-

[169]

67.

Diazepam, lorazepam, nordiazepam, and oxazepam

Human blood

SPME

LC

MS

LOQ : 4 ng/mL

[170]

68.

Diazepam, nordiazepam, temazepam, and oxazepam

Blood

SPME

LC

MS

20, 20, 30, and 35 ng/mL

[171]

69.

Benzodiazepines

Dog blood and dog plasma

SPME

LC

MS

-

[172]

70.

Oxazepam, temazepam, nordazepam and diazepam

Human serum

Intube SPME

HPLC

-

26, 29, 22 and 24 ng/mL

[173]

71.

Camptothecin and 10-hydroxycamptothecin

Human plasma

Intube SPME

HPLC

UV

2.62 and 1.79 ng/mL, respectively

[174]

72.

Pentane and isoprene, acetone, isoflurane, dimethyl sulfide

Blood of humans and animals

SPME

GC

MS

0.02– 0.10 nmol/L

[175]

73.

Cocaine and cocaethylene

Plasma

SPME

GC

MS

-

[176]

74.

Cocaine (COC) and cocaethylene

Sweat

SPME

GC

MS

5 ng/mL

[177]

75.

Methadone and its metabolite

Plasma

SPME

GC

MS

-

[178]

76.

Drug Compounds

Human plasma

SPME

HPLC

MS

1 ng/mL

[179]

77.

Fluoxetine and norfluoxetine

Plasma

SPME

HPLC

-

-

[180]

78.

Dextromethorphan and dextrorphan

Human plasma

Sol-gel SPME

GC

MS

0.010 and 0.015 ng/mL

[181]

79.

Model drug

Human plasma

in-tip SPME

LC

MS

5 ng/mL

[182]

80.

Tamoxifen, cis- and trans-clomiphene

Rabbit liver solutions

SPME

GC

MS

LOQ: 0.02–0.16 ng/mL-1

[183]

81.

Toluene and styrene

Blood, serum, and perilymph

HS-SPME

GC

Flame-ionization

0.13 and 0.08 ng/10 μL

[184]

82.

Caffeine, paracetamol and acetylsalicylic acid

Bovine plasma

SPME

Capillary zone electropho-resis (CZE)

-

0.3, 0.8 and 1.9 ng/mL, respectively

[185]

83.

Nitromethane

Human blood

HS-SPME

GC

MS

0.01 μg/L

[186]

84.

3,4-Methylenedioxy, methamphetamine Methamphetamine

Human serum

HS-SPME

IMS

-

5 and 8 ng/mL, respectively

[187]

85.

Trichloroethylene

Blood and tissues

HS-SPME

GC

MS

0.25 ng/mL and 0.75 ng/g respectively

[188]

86.

Mirtazapine, citalopram, paroxetine, duloxetine, fluoxetine, and sertraline

Human plasma

in-tube SPME

LC

UV

LOQ between 20 and 50 ng/mL

[189]

87.

Desipramine, imipramine, nortriptyline, amitriptyline, and clomipramine

Plasma

SPME

LC

MS

0.1 ng/mL

[190]

88.

Mirtazapine, citalopram, paroxetine, fluoxetine, and sertraline

Human plasma

SPME

LC

-

LOQ:25 to 50 ng/mL

[191]

89.

Fentanyl

Human plasma

HS-SPME

GC

MS

0.03 ng/mL

[192]

90.

Clozapine

Human plasma

SPME

GC

MS

0.1 ng/mL

[193]

91.

Paeonol

Rabbit plasma

HS-SPME

GC

MS

2.0 ng/mL-1

[194]

92.

Organochlorine pesticides and polychlorinated biphenyls

Human serum

HS-SPME

GC

ECD

1 pg/mL to 52 pg/mL

[195]

93.

α-Asarone and β-asarone

Rabbit plasma

HS-SPME

GC

MS

<2.0 ng/mL

[196]

94.

Volatile organic compounds

Human blood

SPME

GC

MS

0.005 to 0.12 μg/L

[197]

95.

Diazepam

Human plasma

SPME

GC

MS

LOQ: 10.0 ng/mL-1,

[198]

96.

Tramadol

Human plasma

HS-SPME

GC

MS

0.2 ng/mL-1

[199]

97.

Hexanal and heptanal

Human blood

HS-SPME

GC

MS

0.006 nM, 0.005 nM, respetively

[200]

98.

Amino acids

Blood

SPME

GC

MS

-

[201]

99.

Theobromine, theophylline and caffeine

Human serum

Intube-SPME

HPLC

UV

12, 8 and 6.5 ng/mL, resp

[202]

100.

Rivastigmine

Canine plasma

SPME

GC

MS

0.2 ng/mL

[203]

101.

Mycophenolic acid

Human serum

SPME

HPLC

UV

0.05 μg/mL

[204]

102.

Acetone

human plasma

SPME

GC

MS

0.017 mM

[205]

103.

Acetaminophen

Human plasma

SPME

GC

-

0.5 μg/mL

[206]

104.

Busulphan

Human plasma

SPME

GC

MS

LOQ = 20 ng/mL

[207]

105.

Sufentanil

Human plasma

SPME

GC

MS

LOQ = 6 ng/mL

[208]

106.

Lamotrigine with primidone, carbamazepine, carbamazepine epoxide, phenobarbital, and phenytoin

Human plasma

SPME

GC

Thermionic specific detection (TSD)

0.05 to 0.20 pg/mL

[209]

107.

Carbamazepine and carbamazepine 10,11-epoxide

Human plasma

Off-line SPME

LC

-

LOQ: 0.05 to 1.0 μg/mL

[210]

108.

Thymol

Human plasma

HS-SPME

GC

Flame ionization detector (FID)

LOQ:8.1 ng/mL

[211]

109.

Organophosphorous pesticides

Human blood

SPME

GC

MS

0.01 and 0.3 pg/g

[212]

110.

Midazolam

Human plasma

SPME

GC

MS

1 ng/mL

[213]

111.

Propranolol

Serum

in-tube SPME

-

UV

0.32 μg/mL

[214]

112.

Levomepromazine

Human plasma

SPME

GC

-

5 ng/mL

[215]

113.

Amphetamine and methamphetamine

Serum

HS-SPME

GC

MS

6.0 μg/L to 77 μg/L

[216]

114.

Halothane

Blood

HS-SPME

GC

MS

0.004 mg/kg

[217]

115.

Fenfluramine, methamphetamine and amphetamine

Blood

HS-SPME

GC

MS

5.0 ng/g for fenfluramine and methamphetamine, and 10 ng/g for amphetamine

[218]

116.

Lidocaine

Human plasma

DI-SPME

GC

-

5 ng/mL

[219]

117.

Tetramethylenedisulfotetramine

Human blood

SPME

GC

Nitrogen/phosphorus detector (NPD

0.001 μg/mL–1

[220]

118.

Malathion and Diazinon

Blank blood

SPME

GC

MS/NPD

-

[221]

119.

Polynuclear aromatic hydrocarbons

Blood

SPME

GC

FID

2.7 to 30.4 ng/mL

[222]

120.

Diazepam

Rat blood

SPME

LC

MS/MS

-

[223]

121.

Cyanide

Blood

HS-SPME

GC

MS

0.006 μg/mL

[224]

122.

Anticonvulsants and tricyclic antidepressants

Plasma

SPME

LC

-

LOQ 0.5–5.0 μg/mL-1

[225]

Blood, plasma and serum samples

There are several problems involved in the measurement of toxic compounds in biological samples, the most important being the low concentration levels involved and the complexity of sample matrices (plasma, serum or blood). Therefore, biological monitoring requires reliable analytical methods for the accurate determination of organic compounds and/or metabolites at the low levels found in these types of samples. SPME represents a gentle extraction technique. That means that in case of strong analyte-matrix interactions only the free part of analytes can be extracted by SPME which can be an advantage or a disadvantage. Liu et al. developed a simple, rapid and sensitive method for the determination of trichloroethylene in rat blood, liver, lung, kidney and brain, using headspace solid phase microextraction (HS-SPME) and gas chromatography/mass spectrometry (GC/MS) (Fig. 4) [188]. Details of the determination of different organic compounds in the blood, plasma and serum samples by different research groups are summarized in Table 2.
https://static-content.springer.com/image/art%3A10.1007%2Fs12566-009-0004-z/MediaObjects/12566_2009_4_Fig4_HTML.gif
Fig. 4

Representative chromatograms using selected-ion monitoring (SIM) mode by monitoring m/z 130 obtained from (a) blank blood, liver, lung, kidney, brain; (b) blood, liver, lung, kidney, brain spiked with the lower limit of quantitation (0.25 ng/mL in blood or 0.75 ng/g in tissues) concentration of trichloroethylene (TCE) (reproduced with the permission from reference [188])

Breast milk samples

Polychlorinated biphenyls (PCB) can eventually contaminate breast milk, which is a serious issue to the newborn due to their high vulnerability. Kowalski et al. developed a neuro-genetic multioptimization of the determination of polychlorinated biphenyl congeners in human milk (Fig. 5) by headspace solid phase microextraction coupled to gas chromatography with electron capture detection [97]. Kuklenyik et al. combined solid phase extraction (SPE) and SPME coupled to detection by gas chromatography mass spectrometry for measuring four polycyclic musk compounds in serum and breast milk [96].
https://static-content.springer.com/image/art%3A10.1007%2Fs12566-009-0004-z/MediaObjects/12566_2009_4_Fig5_HTML.gif
Fig. 5

HS-SPME-GCh-ECD chromatogram of an unspiked breast milk sample for the detection of a mixture of polychlorinated biphenyls in isooctane (IUPAC 28, 52, 74, 101, 118, 128, 138, 153, 156, 170, 180 and 198) (reproduced with the permission from reference [97])

Recent trends of in vivo SPME

A new field of application with particular relevance for bioanalytical studies has been opened in the context of in vivo SPME. This approach allows for monitoring of analytical data from a living system without the need to withdraw a sample solution from the organism. In this way an integration of sampling and sample preparation can be managed under in vivo conditions. Consequently, in vivo SPME has the potential to contribute to a deeper understanding of complex biological processes in living species. SPME probes are well suited for in vivo application owing to their small physical dimensions. However, a greater challenge is the development of biocompatible coatings. The first demonstration of SPME application for in vivo studies in the circulating blood of a living animal was reported by Pawliszyn and co-workers [226]. A SPME probe based on polypyrrole was used for in vivo monitoring of blood concentrations of benzodiazepines. An attractive field of application is the in vivo study of pharmacokinetics of drugs and their corresponding metabolites in circulating blood of animals [223, 227]. Examples of recently reported studies include in vivo SPME applied to semisolid fish tissue for the determination of pharmaceuticals [228], investigations of allelochemical uptake by tomato plants [229] and pesticide determination by direct insertion of a SPME fiber in plant leaves [230]. The latter report addressed the methodically interesting comparison of microdialysis and SPME. It was concluded that in vivo SPME has the potential to replace in vivo microdialysis in the future. However, regarding time resolution of analytical data and applicability to a wide range of analytes microdialysis still has some advantages over SPME. An important issue for further development of in vivo SPME is the development of SPME probes with biocompatible coatings. Advances in this direction have been reported for poly(ethylene glycol)-based coatings [231] and metal fibers coated with a mixture of proprietary biocompatible binder and various types of coated silica (octadecyl, polar embedded and cyano) particles [232]. Figure 6 shows a photograph of the in vivo application of a biocompatible SPME probe used for pharmacokinetic studies in dogs.
https://static-content.springer.com/image/art%3A10.1007%2Fs12566-009-0004-z/MediaObjects/12566_2009_4_Fig6_HTML.jpg
Fig. 6

Photograph of an in vivo experiment with a dog showing the implanted SPME probe (reproduced with the permission from [233])

Conclusion

SPME has evolved rapidly as a major sample pretreatment technique with a wide application area. There is a continuously growing interest in this technique from various fields. SPME was originally introduced for the GC analysis of volatiles in environmental samples. Since then, SPME has also proven useful and beneficial to the analysis of biological fluids and materials. It affords a number of advantages in simplifying sample preparation, increasing reliability, selectivity and sensitivity. The physicochemical principles and parameters underlying the SPME process are being described and these allow for improvements in calibration and quantitation under different sampling conditions. SPME itself may be used to measure physicochemical constants and coefficients in complex biological systems. Its versatility is enhanced by the possibility of using direct insertion into the sample matrix for less volatile components and there are significant benefits to be gained through careful manipulation of the extraction conditions. Novel derivatisation procedures may extend further the utility of SPME. Besides the great advantages, SPME also has some disadvantages as low extraction yields due to the small amount of extraction medium and matrix interferences. Possibilities to overcome these disadvantages are modifications of SPME like in-tube SPME or stir bar sorptive extractions (Twister). The unique, solvent-free, and easy sample preparation method of SPME has been successfully applied to many organic target analytes in environmental, bioanalytical and industrial hygiene studies. Recent developments in the field of in vivo SPME are very promising and will stimulate further research in this area.

Acknowledgement

The authors are thankful to the CSIR, New Delhi (No.80 (0063)/07/EMR-I) and DST-DAAD (DST/INT/DAAD/P-180/2008) for supporting this research work.

Copyright information

© Springer-Verlag 2009