Comparison of solid phase extraction combined with vortex assisted liquid liquid micro extraction and vortex thesis title assisted liquid liquid micro extraction with increased

1 THAI NGUYEN UNIVERSITY UNIVERSITY OF AGRICULTURE AND FORESTRY NGO QUI TRUNG COMPARISON OF SPE VALLME AND VALLME WITH INCREASED SAMPLE VOLUME FOR SENSITIVITY ENHANCEMENT IN DETERMINATION OF STRONTIUM[.]

THAI NGUYEN UNIVERSITY

UNIVERSITY OF AGRICULTURE AND FORESTRY

NGO QUI TRUNG

BACHELOR THESIS Study Mode : Full-Time

Major : Environmental Science and Management

Faculty : International Programs Office

Batch : 2013 – 2017

Thai Nguyen, 20/07/2017

DOCUMENTATION PAGE WITH ABSTRACT

Thai Nguyen University Of Agriculture And Forestry

Thesis Title:

Comparison of solid phase extraction combined with vortex-assisted liquid-liquid micro-extraction and vortex-assisted liquid-liquid micro-extraction with increased sample volume for sensitivity enhancement in the determination of strontium by ion chromatography

Abstract: Strontium compound that is considered a danger to human health If

it absorb to much in the body, it will make some disease such as: lung cancer

or bone cancer Many methods was found by difference scientists but the

sensitivity quite low Therefore, in this research, we compared solid phase

extraction and large sample volume (50 mL) combined with vortex-assisted

liquid–liquid micro-extraction to test the sensitivity enhancement in the

determination of strontium by ion chromatography According to VALLME,

dispersion of micro-volumes of a low density extraction organic solvent into

the water sample is achieved by using for the first time vortex mixing

Strontium from the organic phase was stripped with nitric acid back to aqueous

solution and determined by ion chromatography The optimum

micro-extraction conditions were as follows: 50 mL aqueous samples with 3 mL 50

DtBuCH18C6 followed by sequential vortex 20s and manual shaking 10s The

strontium-rich organic solvent was recovered by centrifugation at 3200 rcf for

4 min The calibration curve showed good linearity over the range between

when we combined vortex-assisted liquid–liquid micro-extraction with solid

phase extraction at the same linearity range, the detector sensitivity was 1.0671

methodology more effective than other methods (with highest detector

sensitivity) when we increased sample volume

chromatography, vortex-assisted liquid–liquid extraction (VALLME)

Supervisor’s

Foremost, I would like to express my sincere gratitude and deep regards to my

supervisor: Assoc Prof Dr Wu, Chien-Hou of National Tsing Hua University

(Taiwan), who guidance, encouragement, suggestion and very constructive criticism have contributed immensely to the evolution of my ideas during the project Without his guidance, I may not have this thesis

My special thanks go to Mr.Bill (Wang Chin Yi) Ph.D student-second

supervisor - who offered me a warm welcome and provided the information and data necessary for my implementation process and helped me finish this thesis

I sincerely thanks to Assoc Prof Dr Nguyen The Hung for his advices,

assistance, sharing experiences before and after I went to Taiwan, helping me to understand and complete proposal and thesis

finish the study

Special thanks to Lam, Tar Mivongsack, members in Chien’s laboratory who hearty

help me a lot of when I work in there and all the people who helped me when I stayed

Hsinchu, April 2017

Student

Ngo Qui Trung

TABLE OF CONTENT

LIST OF FIGURES 8

LIST OF TABLES 9

LIST OF ABBREVIATIONS 10

PART I INTRODUCTION 11

1.1 Research rationale 11

1.2 Objectives of this research 12

1.3 Research questions and hypothesis 13

1.4 Limitation of this research 13

PART II LITERATURE REVIEW 14

2.1 The characteristics and health effects of strontium(Sr) 14

2.1.1 Characteristics of strontium 14

2.1.2 Applications 16

2.1.3 Origins of strontium in the environment 16

2.1.4 Health effects of strontium 16

2.1.5 Effects of strontium on the environment 18

2.2 Methods to determine strontium in the environmental sample 19

2.2.1 Solid-phase extraction (SPE) 19

2.2.2 Vortex-assisted liquid-liquid microextraction (VALLME) 23

2.2.3 Combination two methods: solid-phase extraction and vortex-assisted liquid-liquid microextraction (SPE-VALLME) 26

2.3 Crown ether 28

2.4 NaTPB (Sodium tetraphenylboron) 31

PART III.METHOD 32

3.1 Material 32

3.1.1 Chemical materials 32

3.1.2 Instrumentation 32

3.2 Method 34

3.2.1 Determine the optimum concentration 34

3.2.2 Solid-phase extraction (SPE) 36

3.2.3 Vortex-assisted liquid-liquid microextraction (VALLME) 37

4.1 Analysis 38

PART IV: RESULTS 39

PART V: DISCUSSION AND CONCLUSION 47

4.2 Discussion 47

4.3 Conclusion 48

REFERENCES 49

LIST OF FIGURES

Figure 2.1 Solid phase extraction steps 22 Figure 2.2 Structures of common crown ether: 12-crown-4, 15-crown-5, 18-crown-6, dibenzo-18-crown-6 and diaza-18-crown-6 29 Figure 3.1 Ion chromatography system diagram 34

chromatography graph of 4 samples 39

chromatography graph of 4 samples 40 Figure 4.3 Calibration curve of concentration Sr (II) at low volume sample (2ml)415 Figure 4.4 Comparison 1-octanol recovery between solution sample with crown ether, TPB and without crown ether,TPB 37 Figure 4.5 Effect of volume of extraction solvent on the extraction efficiency of

strontium Extraction condition: volume 50ml, Sr (II) concentration 50µg/L, 3ml TPB 38 Figure 4.6 Calibration curve of concentration Sr (II) at high volume sample (50ml) 39 Figure 4.7 Comparison solid phase extraction combined with vortex-assisted liquid-liquid microextraction and vortex-assisted liquid-liquid microextraction at low and high volume 40

LIST OF TABLES

Table 2.1 Physical and chemical properties of strontium (A.crawford 1790) 15 Table 2.2 Properties of 4’,4”(5”)-di-tert-butyldicyclohexano 18-crown-6 30 Table 2.3 Properties of sodium tetraphenylboron (NaTPB) 31 Table 4.1 Comparison recoveries 1-octanol with and without crown ether and TPB 36

PART I INTRODUCTION

1.1 Research rationale

Strontium is an alkaline-earth metal that occurs commonly in the environment Typical concentrations range from tens of ppb in fresh water to several ppm in seawater and mineral water (Bruland, Middag, & Lohan, 2013) In seawater, strontium

is the fifth most abundant cation behind sodium, magnesium, calcium, and potassium Strontium is a sensitive indicator in natural clayey formations and the incorporation of strontium into coral exoskeletons is highly related to its concentration in seawater, which may vary with depth, salinity, temperature, and over timescales greater than a million years (Lerouge et al., 2010) Strontium compounds that are water-insoluble can become water-soluble as a result of chemical reactions The water-soluble compounds are a greater threat to human health than the water-insoluble ones Therefore, water-soluble forms of strontium have the opportunity to pollute drinking water For most people, strontium uptake will be moderate The only strontium compound that is considered a danger to human health, even in small quantities is strontium chromate Strontium chromate is known to cause lung cancer, but the risks of exposure have been greatly reduced by safety procedures in companies so that it is no longer an important health risk Moreover, for children exceeded strontium uptake may be a health risk because it can cause problems with bone growth When strontium uptake is extremely high, it can cause disruption of bone development But this effect can only occur when strontium uptake is in thousands of ppm range Radioactive strontium is much more of

a health risk than stable strontium When the uptakes is very high, it may cause anemia

genetic material in cells when uptake at extremely high concentrations So the development of a sensitive and selective analytical method for strontium is crucial for marine studies and safety control of natural waters

In recent years, different methods and techniques have been developed for the analysis of strontium ion by ion chromatography such as: solid phase extraction (SPE), vortex-assisted liquid-liquid micro-extraction (VALLME) Especially, vortex-assisted liquid-liquid micro-extraction method has been in use by physical chemists in general and analytical chemistry in particular for many years by advantage of the intrinsically high sensitivity and help scientist save time in research In this method, dispersion of micro-volumes of a low density extraction organic solvent into the aqueous sample is achieved by using vortex mixing This method is relatively successful when performed

at low volume sample (2mL) Therefore, our next goal is to test the sensitivity when increasing sample volume Moreover, we need to test the sensitivity when combined two methods SPE-VALLME at high sample volume and then comparison the results when using each method (solid phase extraction and vortex-assisted liquid-liquid micro-extraction) Thus, this project conducted “Comparison of solid phase extraction combined with vortex-assisted liquid-liquid micro-extraction and vortex-assisted liquid-liquid micro-extraction with increased sample volume for sensitivity enhancement in the determination of strontium by ion chromatography”

1.2 Objectives of this research

The aim of this work was to evaluate the sensitivity enhancement of strontium

by solid phase extraction and large sample volume combined with vortex assisted liquid–liquid micro-extraction

The specific objectives of this study are:

1.3 Research questions and hypothesis

Is SPE-VALLME methodology more effective than other methods?

When increased sample volume, does the sensitivity of strontium determine by ion chromatography increased or decreased?

1.4 Limitation of this research

Because the thesis training time was too short, this research project is incomplete

PART II LITERATURE REVIEW

2.1 The characteristics and health effects of strontium (Sr)

2.1.1 Characteristics of strontium

In Scotland during the 1790s, Adair Crawford and William Cruickshank first

When they mixed witherite with Hydrochloric acid they did not get the results they expected They assumed that their sample of witherite was contaminated with an

Davy, a British chemist, first isolated strontium in 1808 through the electrolysis of a

chloride, usually mixed with potassium chloride (KCl), is then melted and

chemically similar to calcium, strontium can replace calcium in the mineral of the growing bones and thus may lead to bone growth problems in children (De Rosa, El-Masri, Pohl, Cibulas, & Mumtaz, 2004) Release of radio-strontium isotopes is also an important issue due to atmospheric nuclear explosions, nuclear waste discharges, and

most hazardous radionuclides, has been released into the environment after the Fukushima Daiichi Nuclear Power Plant Disaster (Ding, Yang, Huang, Liu, & Hou, 2015) This isotope, formed by nuclear explosions, is considered the most dangerous constituent of fallout Because of its chemical resemblance to calcium, it is assimilated

in bones and teeth, where it continues ejecting electrons that cause radiation injury by damaging bone marrow, impairing the process of forming new blood cells, and possibly inducing cancer

Table 2.1 Physical and chemical properties of strontium (A.crawford 1790)

2.1.2 Applications

Strontium has uses similar to those of calcium and barium, but it is rarely employed because of its more expensive cost Strontium compounds usually use in pyrotechnics for the brilliant reds in fireworks and warning flares and in greases A litter is used as a getter in vacuum tubes to remove the last traces of air Most strontium is used as the carbonate in special glass for television screens and visual display units Although strontium-90 is a dangerously radioactive isotope, it is a useful

by product of nuclear reactors from whose spent fuel is extracted Its high-energy radiation can be used to generate an electric current and for this reason it can be used

in space vehicles, remote weather stations and navigation buoys

2.1.3 Origins of strontium in the environment

Strontium is commonly occurs in nature, forming about 0.0034% of all igneous rock and in the form of the sulfate mineral celestine (SrSO4) and the carbonate strontianite (SrCO3) Celestine occurs frequently in sedimentary deposits of sufficient size, thus the development of mining facilities attractive The main mining areas are United Kingdom, Mexico, Turkey and Spain World production of strontium ores is about 140.000 tones per years from an unassessed total of reserves Foods containing strontium range from very low e.g in corn 0.4 ppm and in orange 0.5 ppm to high, e.g

in cabbage 45 ppm, onions 50 ppm and lettuce 74 ppm

2.1.4 Health effects of strontium

Strontium compounds that are water-insoluble as a result of chemical reactions The water-soluble compounds are a greater threat to human health than the water-

insoluble ones Therefore, water-soluble forms of strontium have the opportunity to pollute drinking water Fortunately the concentrations in drinking water are usually quite low People can be exposed to small levels of (radioactive) strontium by breathing air or dust, eating food, drinking water or by contact with soil that contains strontium We are most likely to come in contact with strontium by eating or drinking

Strontium concentrations in food contribute to the strontium concentrations in the human body Foodstuffs that contain significantly high concentrations of strontium are grains, leafy vegetables and dairy products For most people, strontium uptake will

be moderate The only strontium compound that is considered a danger to human health, even in small quantities is strontium chromate The toxic chromium that is contains mainly causes Strontium chromates is known to cause lung cancer, but the risks of exposure have been greatly reduced by safety procedures in companies, so that

it is no longer an important health risk

The uptake of high strontium concentrations is generally not known to be a great danger to human health In one case someone experienced an allergic reaction to strontium but there have been no similar cases For children exceeded strontium uptake may be a health risk because it can cause problems with bone growth Strontium salts are not known to cause skin rashes or other skin problems of any kind When strontium uptake is extremely high, it can cause disruption of bone development But this effect can only occur when strontium uptake is in the thousands

of ppm range Strontium levels in food and drinking water are not high enough to be able to cause these effects

Radioactive strontium is much more of a health risk than stable strontium When the uptake is very high, it may cause anemia and oxygen shortages and at extremely high concentrations it is even known to cause cancer as a result of damage

to the genetic materials in cells

2.1.5 Effects of strontium on the environment

Strontium in its elemental form occurs naturally in many compartments of the environment including rocks, soil, water and air Strontium compounds can move through the environment fairly easily because many of the compounds are water-soluble

Strontium is always present in air as dust, up to a certain level Strontium concentrations in air are increased by human activities such as coal and oil combustion Dust particles that contain strontium will settle to surface water, soils or plant surfaces at some point When the particles do not settle they will fall back onto Earth when rain or snow falls All strontium will eventually end up in soil or bottoms

of surface waters, where they mix with strontium that is already present

Strontium can end up in water through soils and through weathering of rocks Only a small part of the strontium in water comes from dust particles from the air Most of the strontium in water is dissolved but some of it is suspended, causing muddy water at some locations Not much strontium ends up in drinking water When strontium concentrations in water exceed regular concentrations, this is usually caused

by human activities, mainly by dumping waste directly in the water Exceeded strontium concentrations can also be caused by settling of dust particles from air that have reacted with strontium particles from industrial processes

Strontium concentrations in soil may also be increased by human activities such

as the disposal of coal ash and incinerator ash or industrial wastes Strontium in soil dissolves in water, so that it is likely to move deeper into the ground and enter the groundwater A part of the strontium that is introduced by humans will not move into groundwater and can stay within the soil for a long time Because of the nature of strontium, some of it can end up in fish, vegetables, livestock and other animals

One of the isotopes of strontium is radioactive This isotope is not likely to occur naturally in the environment It ends up in the environment as a result of human activities such as nuclear bomb testing and radioactive storage leaking The only way

to decrease concentrations of this isotope is through radioactive decay to stable zirconium

The concentrations of radioactive strontium in the environment are relatively low and the particles will always end up in soils or water-bottoms eventually, where they mix with other strontium particles It is not likely to end up in drinking water

2.2 Methods to determine strontium in the environmental sample

Nowadays several methods have been developed to determine strontium In this part, first I will review some methods used in determine analytical strontium in general Next, the advantages and disadvantages of these methods will be compared with method we use in this study to see which methods are more suitable

2.2.1 Solid-phase extraction (SPE)

Sample preparation in ion chromatography (IC) is often required to eliminate

disturbances, rendering analysis impossible The column life can be reduced owing to sample components irreversibly binding to the packing While many approaches

to sample preparation exist, not all will solve the interference problems unique to IC Two of the simplest and easiest to use sample preparation methods, dilution and filtration, differ greatly in concentration or the interfering compound and the analysis are both soluble, neither method is satisfactory Hydrophobic components in samples may be irreversibly retained on the column, thus shortening the column lifetime Injection of samples with either a high or a low pH will often produce unacceptable chromatograms due to baseline disturbances Naturally occurring anions such as: chloride and sulfate can interfere with the determination of other ions in samples such

as sea water and oil-field brine These samples require selective removal of interfering matrix components

Solid phase extraction (SPE) is introduced in 1970s It is one of the fastest growing sample preparation techniques used in chromatography SPE is frequently used to solve interference problems in high performance liquid chromatography (HPLC) and thin-layer chromatography Solid phase extraction cartridges can also be used to eliminate matrix interferences from samples prior to analysis by IC Not all SPE devices are appropriate for IC applications Conventional sample preparation devices were plagued with contaminants released from the cartridge or filter Bagchi and Haddad (Bagchi & Haddad, 1986) studied SPE devices packed with octadecylsilyl silica and discovered considerable amounts of extractable anions and cations New SPE cartridges have been developed to alleviate the interference problem unique to IC without contaminating or altering the sample Each cartridge consists of polystyrene

based packing material cleaned with ion free aqueous and molded into medical-grade polypropylene housing These cartridges are available in five different chemistries to address a variety of IC sample pretreatment problems

There can be no doubt that solid-phase extraction is today most popular sample preparation method to analyze chemical compound It is a very active area in the field

of separation science But one should remind that this trend is rather recent Disposable cartridges for solid-phase extraction have been introduced for more than 20 years (first cartridges in 1978, syringe-format types in 1979, pre-columns for the on-line coupling with liquid chromatography (LC) in the early 1980s) yet, SPE development has been slow for many years Liquid-liquid extraction (LLE) has remained the preferred technique for the preparation of liquid samples for several years, especially in the environmental field The rapid developed of SPE has occurred during the past five or six years with many improvements in formats, automation and introduction of new phases One reason was the pressure to decrease organic solvent usage in laboratories which has encouraged the requirement for solvent free procedures and has greatly contributed to the growth of SPE at the expense of liquid-liquid extraction procedures (Hennion, Cau-Dit-Coumes, & Pichon, 1998) The introduction of servey lists containing polar analysis such as some degradation products of organic micro-pollutants has also pointed out the need for alternative methods to LLE because of many polar analysis are often partly soluble in water and cannot be extracted with good recoveries whatever the organic solvent selected (Barceló, 1997) & (Chiron, Fernandez Alba, & Barcelo, 1993) At the same time, the

its increasing acceptance by regulatory agencies The other reasons for the growing interest in SPE techniques are the large choice or sorbents with the capability for new ones of trapping polar analysis SPE is also an active area of research as shown by the increasing number of publications describing new and more selective sorbents or procedures

SPE can be performed off-line, the sample preparation being separated from the subsequent chromatographic analysis, or on-line by direct connection to the chromatographic system(Font, Manes, Molto, & Pico, 1993); (Fritz, Dumont, & Schmidt, 1995); (Brouwer, Kofman, & Brinkman, 1995) & (Berrueta, Gallo, & Vicente, 1995) On-line techniques do not require further handling of the samples between the trace-enrichment and the separation step and therefore are highly suitable for fully automated techniques, which can be used on-site (Barceló & Hennion, 1995); (Geerdink, Niessen, & Brinkman, 2002) & (Brinkman, 1994)

Figure 2.1 Solid phase extraction steps

Optimizing steps for the “Blind-elute” SPE experiment (non-polar example):

1 Conditioning: solvent is passed through the SPE material to wet the bonded functional groups => ensures consistent interaction

2 Sample loading: introduction of the sample = analysis of interest are bound/extracted onto the phase/sorbent Must be an aqueous solvent (no organic)

3 Washing: use the “strongest” aqueous solution that will NOT elute the target compounds Increasing the percentage organic, increasing or decreasing the pH, changing the ionic strength are all tips for increasing clean-up Dry the cartridge

to remove all the water

4 Elution: use the smallest volume of organic solvent that will elute all of the target analysis Use the “weakest” organic solvent that will remove all of the target analysis As a general rule the “strength” of the solvent is directly related

to the target compound Polar target compounds elute best in polar solvents so

in order of polarity try: methanol > acetonitrile > ethylacetate > acetone > THF Modify the pH, increase the ionic strength

2.2.2 Vortex-assisted liquid-liquid micro-extraction (VALLME)

In the last two decades, miniatuzied solvent extraction procedures also called liquid phase micro-extraction (LPME) have attracted much attention by many researchers in the world The principle of LPME is based on the traditional liquid-liquid extraction whereby the organic phase is substantially reduced The general

in the sample solution Up to now, different methodologies evolved from this approach including amongst others immersion and headspace single-drop micro-extraction, static and dynamic LPME or even hollow fiber LPME A historical overview of the LPME techniques has been recently published by Pena-Pereira et al (Pena-Pereira, Lavilla, & Bendicho, 2010) The LPME techniques have become popular since they generally offer simplicity, high enrichment factors, low cost and they are environment friendly

In 2006, a new LPME method termed dispersive liquid-liquid micro-extraction (DLLME) has been developed by Assadi and co-workers(Rezaee et al., 2006) DLMME is based on a ternary component solvent scheme whereby cloudy micro-droplets are formed when a mixture of an extraction (typical non-miscible organic solvent or ionic liquid (Chen, Chen, Ying, Huang, & Liao, 2009).) and disperser solvent (miscible organic solvents, e.g methanol, acetone, acetonitrile, etc.) is rapidly injected into an aqueous sample Perpose analysis were extracted into these fine droplets which could be subsequently separated by centrifugation and used for analysis However, one main disadvantages associated with DLLME were the difficulty to automate and the necessity of using a third component (dispersive solvent) that usually reduces the partition coefficient of the hydrophobic analysis into the extraction solvent (Regueiro, Llompart, Garcia-Jares, Garcia-Monteagudo, & Cela, 2008)

In addition, ultrasound energy has been employed in LPME techniques to create

or accelerate the emulsification process (Du, Yan, She, Liu, & Yang, 2010) Submicron size droplets of extraction solvent are formed during this process resulting into fast and efficient analysis transfer due to the large surface contact between the two

immiscible phases However, this problem was lack of uniformity in the transmission

of ultrasound energy throughout the sample or even in some cases analysis degradation may occur during this process (De Castro & Priego-Capote, 2007),(Sanchez-Prado et al., 2008)

In order to overcome the drawbacks, the research group of Psillakis introduced

a new type of LPME namely vortex-assisted liquid-liquid micro-extraction (VALLME) (Yiantzi, Psillakis, Tyrovola, & Kalogerakis, 2010) In this technique a mild emulsification process can be achieved by dispersion of a low-density extraction organic solvent directly into the aqueous phase (without the need of disperser solvent), enhanced by vortex agitation The fine droplets formed could extract analysis toward equilibrium faster because of the shorter diffusion distance and larger specific surface area After a certain period of extraction time, centrifugation is typically performed for phase separation The VALLME approach has been adopted by Jia et al for the determination of organochlorine pesticides in water sample (Jia et al., 2010) Moreover, Yang et al extended Psillakis methodology by developing the vortex-assisted surfactant-enhanced emulsification liquid-liquid micro-extraction, in which a surfactant is used as “disperser” to improve the mass transfer of analysis from the aqueous to the organic phase (Yang et al., 2011) However, this approach is more complicated than former VALLME

In method vortex-assisted liquid-liquid micro-extraction to determine the strontium in the water sample we use: crown ether with name: 4’,4”(5”)-di-tert-

2.2.3 Combination of two methods: Solid-phase extraction and vortex-assisted liquid-liquid micro-extraction (SPE-VALLME)

Solid-phase extraction (SPE) is a widely used sample-preparation technique for isolation of selected analysis, usually from a gas, fluid or liquid phases The advantages of SPE are trace enrichment (pre-concentration), matrix simplification (sample clean-up) and medium exchange However, VALLME is not suitable for complex matrixes (namely highly saline solution) Assadi and co-workers (Fattahi, Samadi, Assadi, & Hosseini, 2007) introduced combination of SPE and VALLME for extraction and determine chlorophenols (CPs) with various matrixes (such as highly caline solution) using GC-MS This combination leads to a very high PF (up to about

18000 ultra-pre-concentration) In SPE-DLLME, CPs were adsorbed from a large volume of the liquid samples (100ml) into 100 mg functionalized styrence-devinelybenzene polymer sorbent After elution of the desired compounds from the sorbent by acetone, the DLLME technique was performed on the obtained solution

from 0.0005 to 0.1 µg L-1 In 2009, Liu et al (Liu et al., 2009) developed DLLME-GC-MS for determination of polybrominated dephenyl ethers (PBDEs) in water and plant samples After pre-concentration and purification of the samples in C18 cartridge, 1mL of the elution sample containing 22 µL 1,1,2,2-tetrachloroethane, was injected rapidly into 5 mL of pure water After centrifugation the sediment phase was injected in to the GC-ECD Under the optimum conditions, the PFs obtained were

SPE-in the range of 6838-9405 for liquid samples The calibration curves were lSPE-inear SPE-in the