Development of gaseous trimethylamine trap tube using activated carbon for sampling of fish derived malodorous gases

VIETNAM NATIONAL UNIVERSITY, HANOI VIETNAM JAPAN UNIVERSITY NGUYEN TUAN KHANG DEVELOPMENT OF GASEOUS TRIMETHYLAMINE TRAP TUBE USING ACTIVATED CARBON FOR SAMPLING OF FISH-DERIVED MALO

VIETNAM NATIONAL UNIVERSITY, HANOI

VIETNAM JAPAN UNIVERSITY

NGUYEN TUAN KHANG

DEVELOPMENT OF GASEOUS TRIMETHYLAMINE TRAP TUBE USING ACTIVATED CARBON FOR SAMPLING OF FISH-DERIVED MALODOROUS GASES

MASTER'S THESIS

Hanoi, 2018

VIETNAM NATIONAL UNIVERSITY, HANOI

VIETNAM JAPAN UNIVERSITY

NGUYEN TUAN KHANG

RESEARCH SUPERVISOR:

PROF TAKASHI HIGUCHI ASSOC PROF TRAN HONG CON ASSOCIATE PROF TU BINH MINH

Hanoi, 2018

ACKNOWLEDGEMENTS

First of all, I would like to express my greatest thank to my supervisor, Professor Takashi Higuchi and Associate Professor Tran Hong Con for supporting me all the time It is my honor to be able to study and work with them They always willing to help me at any time a need throughout my study

I gratefully acknowledge the financial support from Associate Professor Tran Hong Con With his support and good relationship, I am able to do my thesis smoothly In addition, special thanks to Associate Professor Cao The Ha, Professor Jun Nakajima for the valuable working experiences and useful advices Thank Dr Nguyen Thi An Hang for being such a great mentor, a great friend that share me a lot

of valuable advices

Besides, It is a pleasure for me to show my gratitude to all members in Environmental Chemistry Laboratory, who instructed, supported, encouraged me during the completion of the thesis

I would like to thank teachers in Environmental Engineering Program from Vietnam Japan University who gave me essential knowledge of environmental major Last but not least, I would like to thank my family, my classmate and my friends for encourage and support me throughout this process to complete my master degree

Hanoi, June 15th 2018 Nguyen Tuan Khang

TABLE OF CONTENTS

ACKNOWLEDGEMENTS i

LIST OF FIGURES iv

LIST OF TABLES v

LIST OF ABBREVIATIONS vi

INTRODUCTION 1

CHAPTER 1 LITERATURE REVIEW 4

1.1 Trimethylamine Gas 4

1.1.1 Physical and Chemical properties 4

1.1.2 Human odor threshold of trimethylamine 5

1.1.3 Toxicity of trimethylamine 7

1.2 Overview of fish-derived malodorous gases 8

1.2.1 Fish processing activities 8

1.2.2 Fish-derived gases emissions 10

1.2.3 Vietnamese Regulation for organic malodorous gases 11

1.3 Review on Trimethylamine gas sampling and measurement methods 13

1.3.1 Colormetric Determination of TMA as the picrate salt 13

1.3.2 Thermal desorption with GC and time of flight mass spectroscopy 15

1.3.3 TMA adsorption of Activated Carbon 16

CHAPTER 2 EXPERIMENT 18

2.1 Assessment of Activated Carbon material 19

2.2 Preparation of Activated Carbon tube 20

2.3 Generation of Odorless gas 22

2.4 Preparation of Trimethylamine operating gas samples 23

2.5 TMA gas sampling using Activated Carbon Tubes 26

2.6 In-situ sampling at fish-processing sites 28

2.7 TMA extraction from the AC adsorbent tube 29

2.8 Instrument analysis 31

CHAPTER 3 RESULTS AND DISCUSSION 32

3.1 TMA calibration curve 32

3.2 Study of the TMA adsorption efficiency 33

3.3 Study of the TMA extraction efficiency 35

3.3.1 Effect of different initial TMA concentration on the TMA extraction

efficiency 35

3.3.2 Ethanol as an alternate solvents on the TMA extraction efficiency 37

3.3.3 Microwave as an alternate method for extraction techniques 37

3.4 In-situ sampling 38

CHAPTER 4 CONCLUSION AND RECOMMENDATION 40

REFERENCES 41

LIST OF FIGURES

Figure 1.1 An overlay of aromagram and chromatogram represent panelist’s

perception on Trimethylamine and Dimethylsulfide with hedonic tone and qualifier

(Caraway, 2007) 6

Figure 1.2 Conventional fish sauce making process 9

Figure 1.3 Breakthrough curve of Methyl mercaptan, Demethyl sulfide and Trimethylamine on Activated Carbon (Lee, 2010) 17

Figure 2.1 Experimental procedure 18

Figure 2.2 Scanning electron microscope (SEM) pictures of Tra Bac activated carbon 20

Figure 2.3 Activated Carbon adsorbent tube 22

Figure 2.4 Odorless gas generation procedure 22

Figure 2.5 Kitagawa detector tube’s structure 24

Figure 2.6 Kitagawa gas detector system procedure 25

Figure 2.7 Scheme of TMA sampling 27

Figure 2.8 Odor sampling at fish sauce incubation area 29

Figure 2.9 Diagram of TMA extraction experiments 30

Figure 3.1 Calibration curve of TMA 32

Figure 3.2 Comparison between estimated TMA and analyzed TMA results of T0.02A, T0.02B, T0.02C samples respectively 35

Figure 3.3 Comparison between estimated TMA and analyzed TMA results of T20A, T20B, T20C samples 36

Figure 3.4 TMA adsorption analyzed from 6 samples Tm20A, Tm20B, Tm20C, T20A, T20B, T20C at 20ppmv initial adsorping concentration respectively 38

LIST OF TABLES

Table 1.1 Chemical and physical properties of Trimethylamine(EPA, 2008) 4 Table 1.2 Maximum allowed concentration of some harzardous gases in the

ambient air (ENVIRONMENT, 2009) 11

Table 3.1 Standard solutions procedure 32 Table 3.2 TMA Adsorption rate measured by the inlet and outlet amount of 6

samples 34

LIST OF ABBREVIATIONS

INTRODUCTION

Research’s purpose and significance

In the recent years, air pollution has been considered as an emerging problem that can directly cause adverse effects on both environmental and human health The sources of air pollution mostly come from anthropogenic activities: energy generation

by burning fossil fuels, industrial producing/manufacturing and commercial activities, etc They all emit a tremendous amount of various chemical gases into the atmosphere Among different issues related to air pollution, the odor problems raise

up as the top of air pollution complaints to governments around the world, especially

in Vietnam

An odor can be understood as a mixture of gases contained light and small chemical molecular, which can trigger human sense of smell if it is inhaled at a certain concentration(Brattoli, 2011) There are many chemical gases which have the odor properties to human sense, most of them are volatile organic compounds (VOCs) such

as sulfurous compounds and amine compounds These gases may interfere with people normal behavior due to its annoying smell at low concentration, e.g feeling uncomfortable and losing attention to work At higher level, the health risks appear when a person get to inhale large amount of chemical gases or be exposed to them during a long period

In Vietnam, there are many activities that can causes nuisance odor Recently, one of the most complaint issues related to smell comes from the fish-processing manufacturer, especially in the central areas of the country Miller et al (1993) used the liquid chromatography to determine several VOCs gases related to decayed fish including hydrogen sulfide, methylmercaptan, trimethylamine oxide, ammonia, etc Among those gases, trimethylamine (TMA) has been considered as a specific indicator of fish-processing emission, since its formation comes from the reduction

of trimethylamine oxide (TMAO) through aerobic bacteria activities such as

Alteromonaces and A putrefaciens (Caraway, 2007) Besides TMAO exists inside

the tissues of almost any sea fish but not present in other animal Therefore, an appropriate procedure for TMA gas sampling and measurement is necessary in order

to control the air quality at the fish-processing sites

In the ambient environment, TMA gas usually exists at low concentration due

to the diffusion of TMA into the air, plus the slow rate of TMA emission from fish muscles under the activities of bacteria On the other hand, TMA is known as the gas with very low odor threshold - 0.00026 ppmv for detection threshold or 0.0034 ppmv for recognition threshold(Caraway, 2007) As a result, people around the emission source can easily feel the malodor and suffer from it even though the TMA concentration at that time is still low The conventional method for TMA sampling is

to pump the TMA sample into diluted sulfuric acid for absorption and then desorb it with base solution such as potassium hydroxide For in situ sampling, that method requires many chemical and equipment which is costly and inconvenient To overcome this difficulty, the activated carbon tubes or cartridges can be applied as a device for quick concentrating and sampling The activated carbon is well known for its ability to adsorb a wide range of chemical, including VOCs Besides it is also a cheap non-chemical material that can be made or purchased easily Moreover, the adsorption tube has a small size, no longer than 10cm, make it comfortable to carry

to multiple areas Therefore, these activated carbon tube is a good approach for a more convenient, flexible and less costly sampling procedure

Objective and scope

This research is mainly focus on the sampling method for TMA gas using the Activated Carbon trap tube as a portable device In previous researches, the carbons have been chosen to be the effective material to isolate the VOCs gas in the air(Brewer, 2004) This trapping techniques were firstly employed for detection and analysis of VOCs released from swine finishing chamber and swine manure, now will

be studied on TMA gas adsorption in laboratory experiment, followed by processing in situ malodor sampling

fish-Liquid chromatography tandem-mass spectrometry (LC-MS/MS) is introduced for the quantification of TMA of samples The objective of this research is to be able

to determine the TMA adsorption rate of the AC adsorbent tube Besides, every adsorption process always come along with the adsorbate extraction from the sorbent material, therefore the choice of extract solvents and different extraction techniques are also examined to determine the extraction efficiency of the completed sampling method Last but not least is the in-situ sampling to directly evaluate the applicability

of this method

CHAPTER 1 LITERATURE REVIEW

1.1 Trimethylamine Gas

1.1.1 Physical and Chemical properties

Trimethylamine is also known as TMA, or N,N-Dimethylmethanamine, is a volatile organic compound, with a structure of aliphatic tertiary amine At normal room temperature, TMA exists as gas phase with a very fishy, pungent smell at low concentration, which will turn into ammonia-like odor when it reaches to high concentration in the air(EPA, 2008) TMA can solube very easily in water and several organic solvents such as acetonitrile or ethanol

Due to the distinct fishy smell, TMA can be used as signal agent for natural gas leakage In the industry, people synthesizes trimethylamine by dry heating the exceed amount of paraformaldehyde with ammonium chloride through the reaction of dimethylamine with formaldehyde Basic chemical and physical properties of TMA are shown in the table below

Table 1.1 Chemical and physical properties of Trimethylamine(EPA, 2008)

Conversion factors 1ppm = 2.42 mg/m3

1mg/m3 = 0.4136ppm

1.1.2 Human odor threshold of trimethylamine

In the past, there were many researches aim at determining the human odor threshold of trimethylamine through several different methods and conditions One

of the oldest research by Leonardos (1969), when the researchers conducted a series

of experiments to determine the odor threshold of 53 commercial odorous compounds The threshold determination method was focusing on human nose detection of each chemical A group of four trained panel members was used in this test, by staying inside test room filled with one odorant chemical The test room had the volume of approximately 13.2 m3 The odorants were introduced to the test room through various ways, depended on their chemical properties The liquid odorous chemicals were injected into the test room using the micro syringes, while the gas odorants were diluted with odorless air outside the test room using the dilution apparatus, and then swept into the test room Each chemical odorant was tested at 5 concentrations at least, and different compounds were test in different day The odor threshold reported is the concentration that all four panel members could recognize the gas in the test room In this research, the TMA threshold was record as the lowest threshold, at 0.00021 ppmv (Leonardos, 1969)

In the other article named “Identification of malodorous compounds from a Fish meal plant”, Caraway (2007) introduced an integrated methods using gas liquid chromatography – Mass Spectroscopy system with olfactometry (GC/MS-O) to identify fish-derived Volatile organic compounds (VOCs) Since the olfactometry test alone was not good enough for further research on odor control and abatement, the GC/MS system was also applied to accurately measure the odorant chemical concentration in amost any given samples The samples were collected at 2 positions: 1km downwind of the fish meal facility, and directly at the emission source Adsorption tubes were packed with Tenax TA, then sealed in zip top bags for further sampling events After that the samples were analyzed by thermal desorption

technique using GC/MS system modified with two olfactometry ports The panelists were asked to sniff the gas coming out from the GC system and give their perception

on what they can sense, including hedonic tone and relative qualifier Odor panelist data (aromagram) and GC/MS data (chromatogram) were then overlaid to each other

to make a chart with illustrations of relative odorous compound quantities and panelist perceptions of respective compounds This graph below shows the panelist’s perception on TMA and Dimethyl sulfide (DMS):

Figure 1.1 An overlay of aromagram and chromatogram represent panelist’s perception on Trimethylamine and Dimethylsulfide with hedonic tone and qualifier

(Caraway, 2007)

The results point out that TMA and DMS have the highest perception of odor

in ambient air at the fish-meal plant Although offensiveness and compounds concentration may be not necessarily correlated, any change of odor concentration could lead to an increase or decrease in offensive perception The data also show that TMA has the lowest threshold, which is 0.00026 ppmv for detection threshold, and 0.0034 ppmv for recognition threshold, while DMS has 33.2 ppmv and 730 ppmv respectively

1.1.3 Toxicity of trimethylamine

According to Castleman (1994), Trimethylamine is considered to be corrosive

to human skin and eyes A human skin contact with concentrated solution of TMA can cause severe burning & hyperemia Petechial hemorrhages appear on the skin even when the chemical was washed away with soap and water within minutes of contact The exposed skin stayed tender for 1 to 2 hours and slight desquamation was observed 2 to 3 hours later On the other hand, accidental human eye contact with TMA caused corneal epithelial sloughing In this case, eventhough the concentration

of TMA involved was not measured, it was suspected to be minimal exposure.(Castleman, 1994)

So far, there is no report on human acute lethality case, no data related to lethal concentration of TMA in human were found In term of carcinogenicity, since the carcinogen N-nitrosodimethylamine can be formed from Trimethylamine and Trimethylamine oxide with the presence of nitrosatinf agents, there are anxieties of the carcinogenic potentiial of TMA However, no report or studies on human carcinogenic from TMA were found(EPA, 2008)

On the other hand, several studies of TMA toxicity to animal had been conducted, especially on mice and rats Generally TMA was toxic to the nervous and respiratory system in all of the conducted researches Koch et al (1980) used female Wistar rats that exposed to high concentration of TMA to determine the lethal concentration (LC) The results of 4-hour LC50 values are approximately 4300 ppm

at 22°C and approximately 3300 ppm at 29°C The animals had severe central nervous system (CNS) effects and respiratory system toxicity, and microscopic evaluation made by Johannsen (1980)(Johannsen, 1986) showed pathological shifts

of the liver, spleen, and kidneys, lung, and brain In the IRDC (1992) LC50 study, rats were exposed for 6, 10, 20, or 60 minutes, these animals appeared to be gasping, labored breathing, rales, increased salivation, corneal opacity, and lung lesions Kinney et al (1990) figured out that male rats that inhaled 2000 or 3500 ppm TMA for 4 hours were immobile, did not react to sound, had difficult in breathing, nasal

and oral discharge, and 3/6 died at 3500 ppm(Kinney, 1990) White mice had intact with TMA for 2 hours were initially agitated but then this symptom gradually progressed to slower movement, loss of motor coordination, and clonic spasms that led to lethality (LC16 = 5910 ppm, LC50 = 7850 ppm, and LC84 = 10,250 ppm)(Rotenberg, 1967)

Animals non-lethal toxicity of TMA studies were also available Rats exposed

to 74, 240, or 760 ppm of TMA for 6 hours per day, 5 days per week for 2 weeks had decreased response to auditory stimuli alterations in the nose, trachea and lungs with dose-related severity that persisted through a 14-day recovery period

Rotenberg and Mashbits (1967) stated that, in a 7-month chronic experiment, rats exposed 5 hours per day to 10.4 ppm or 31.0 ppm TMA were excited, aggressive, and had diarrhea in the first month of exposure, and had a significant reduction in the threshold for nervous and muscular excitability After 7 months, extensive lung lesions were found that were more pronounced in the 31 ppm group, which also had increased relative adrenal gland weight Gagnaire et al (1989) exposed male mice to ranges of TMA concentration from 17 to 70 ppm for 15 minutes, and pointed out that

61 ppm inhibited the animals’ respiratory rate by 50% (RD50)

In term of cell’s interaction, trimethylamine is cabable of causing liquefaction necrosis It can lead to saponification of fats in the cell membrane, destroying the cell and allowing deep penetration into mucosal tissue In gastrointestinal tissue, an initial inflammatory phase may appear, followed by tissue necrosis (sometimes resulting in perforation), then granulation and finally stricture formation

1.2 Overview of fish-derived malodorous gases

1.2.1 Fish processing activities

Vietnam is a country with a long coastal line, which is conterminous to the East Sea with enormous amount of high economic value fishes Therefore, fishery and seafood processing take important roles in Vietnamese economic development The fishes and seafood after being caught or harvested, they are not only sold to people at

the market, but a large amount of fishes also been transport to many manufacturers for processing into variety of products such as: fish-meal, fish sauce, frozen fish, fish ingredient, etc

The chart below shows one specific tecnique of making fish sauce that exists in Vietnam:

Figure 1.2 Conventional fish sauce making process

The fishes are categorized directly after purchasing Type 1,2,3 fishes, which are fresh and in sufficient size are sold directly to the market Fish type 4,5,6 are smaller, not appeal in appearance are utilized for making fish sauce

Procedure

The collected fishes are placed into open tanks Then water and salt are added with specific ratio and mixed very well The tank are left for sun dry and covered by bamboo grates or wooden boards to prevent flies and partly inhibit microorganism activities These processes take 12-15 month in total Sun drying heat the yeast and bacteria, facilitate the microorganism’ cooking of the fishes The mixing let the yeast and bacteria contact to the fish meat Because the right temperature for the microorganism to make the sauce is from 27 to 45°C, combining mixing process with sun drying increase the efficiency of protein degradation and produce a signature flavor for the fish sauce

The Filtration step is only conducted to type 4 and type 5 fishes The fish sauce from the tank is filted through layers of fish bone and one layer of ash husk The filtration circulated 6-7 times Products collected after that is high quality fish sauce

Condensed cooking

The residues from the filtration stage are mixed together with type 6 fish, then put into cooking pot with addtional salt and water The cook lasts for 7 to 10 hours, followed by secondary filtration The lower quality of fish sauce and discharge residues are made after this stage

1.2.2 Fish-derived gases emissions

During storage the compounds responsible for the very fresh fish flavors deteriorate through autolytic and microbial reactions The fresh and metallic flavors disappear and are replaced with a neutral, flat flavor When microbes start growing rapidly sulfur compounds, phenols, and certain fatty acids give spoiled and putrid aromas and flavors Through microbial breakdown of trimethylamine oxide (TMAO) trimethylamine (TMA) is formed and the result is fishy odor, remind of old, stale fish

or dried fish Freshwater fish generally do not contain TMAO and TMA is not present

in freshly harvested marine fish When high concentrations of TMA have been created, the fish is in a very bad condition undesirable for consumption TMAO

seems to serve an osmoregulatory function in saltwater fish and is normally not found

in freshwater fish above trace amounts Dimethylamine, which has an ammoniac aroma, is formed along with formaldehyde from enzymatic activity in fish muscle It

is formed in frozen fish rather than TMA, which is dominantly formed in storage above freezing temperatures The enzymatic activity is also associated with toughening of fish muscle It appears that the formaldehyde crosslinks with proteins, thus changing the texture (Högnadóttir, 2000) Dimethyl sulfide and methylmercaptan have both been reported to contribute offensive odors and flavors

in fish and are usually formed microbially

1.2.3 Vietnamese Regulation for organic malodorous gases

In Vietnam, there are several regulations related to ambient air quality and industrial emission of organic compounds Among all regulations, the National technical regulation on hazardous substances in ambient air (QCVN 06:2009/BTNMT) and the National technical regulation on Industrial emission of Organic Substances (QCVN 20:2009/BTNMT) stand out as the clearest control and management method of hazard and odorous compounds

Table 1.2 Maximum allowed concentration of some harzardous gases in the

ambient air (M.O.N.R.E, 2009)

No Sustances Formula Average

exposure

Allowed concentration

(g/m 3 ) Organic

No Sustances Formula Average

exposure

Allowed concentration

Offensive odor compounds

No Sustances Formula Average

exposure

Allowed concentration

(g/m 3 )

16 Acid propionic CH3CH2COOH 8 hours 300

1.3 Review on Trimethylamine gas sampling and measurement methods

1.3.1 Colormetric Determination of TMA as the picrate salt

In 1945, Dyer developed a sensitive colorimetric method for TMA determination A sample contain nitrogen as trimethylamine is made alkaline with

potassium carbonate with the presence of formaldehyde The TMA was extracted with toluene solvent, then the solvent was dried out Dried samples were colorized

by mixing with a mixing solution of toluene and picric acid The yellow color of trimethylamine picrate was measure in colorimeter

An aliquot of a sample solution containing 0.002 to 0.02 mg nitrogen as trimethylamine was made to 4 ml in a test tube 1 ml formaldehyde, 10 ml toluene, and 3 ml potassium carbonate solution are added into the tube Then it was stoppered with a cellophane-covered cork and is shaken vigorously, approximately 40 times After that, 5ml of the toluene layer in the tube was pipetted off into a small test tube and added 0.3 to 0.4 g granular anhydrous sodium sulfate This was shaken a few times to dry the toluene, which was then poured off into a dry colorimeter tube containing 5 ml of the 0.02 per cent picric acid reagent After mixing, the yellow color was read in a photoelectric colorimeter using a filter with maximum trans- mission at

4200 Angstrom units The blank being made similarly except that water is used instead of trimethylamine or test solution The color was stable and obey Beer’s law over a given range of concentration (Dyer, 1945)

The aim of this method was to evaluate the spoilage of the fish through trimethylamine measurement by colormetric analysis There were many researchers used Dyer’s method as a comparison when they encountered any trimethylamine determination’s relevant issues However the data results might be interfered by a lot

of compounds existed in the samples because those compounds gave the similar color with trimethylamine So that this method required many different chemical to pretreat and eliminate all interference’s effects Therefore the colormetric approach was not appropriate in recent time when many sophisticate analysis systems have been developed which used less chemicals and still be able to give such an reliable quantification data

1.3.2 Thermal desorption with GC and time of flight mass spectroscopy

In 2013, a technique for the quantitative analysis of gas phase TMA was developed by Kim using thermal desorption (TD)-gas chromatography (GC)-time of flight mass spectrometry (TOF-MS) This new approach yielded good linearity (R2 = 0.9930), precision (RSE = 1.59%), and high sensitivity with the method detection limit (MDL) of 51 pg, i.e., detection of 0.021 ppb of TMA at 1 L sample (limit of detection (LOD): 5.32 pg (0.002 ppb)

In term of laboratory’s sample preparation, the calibration and quality assurance/quality control (QA/QC) for TMA analysis were investigated using gaseous TMA working standards (WS) As for the environmental samples to determine TMA concentration, two different samples of (1) rotten thornback fish and (2) cat urine-soaked clays were prepared for the analysis method TMA emitted from these environmental samples was collected into the bag at a flowrate of 100 mL/min for 100 min To obtain the enough sample volume (10 L), a long sampling time of

100 min was applied because the TMA concentration in environmental sample was unknown

The sorbent tube (ST) prepared was a three bed type, which contained 100mg

of Tenax TA, Carbopack B and Carbopack X The purpose of the multi bed type sorbent tube was to collect not only TMA but also other VOCs at wide range of sorption capacity The inlet and outlet of the ST were connected with 10L PEA bag filled with TMA samples and a vacuum pump respectively Then the TMA was pump through the ST at constant flow rate (50mL/min) The samples after preconcentrating using the ST were analyzed using two different MS system, which were Quadrupole

MS (Q-MS) and Time of flight MS (TOF-MS)

The gaseous TMA emitted from two different samples of (1) rotten thornback fish and (2) cat urine-soaked clay with varying sample volumes (10–100 mL) were analyzed The experimental results for each yielded the mean TMA values of 293 ± 29.7 ppm and 74.1 ± 5.78 ppb, respectively

The results of this study showed that the TD-GC-TOF-MS approach was appropriate for acquiring the reliable data for the measurement of TMA in environmental air The ST approach also demonstrated high precision for TMA analysis, at a stable relative standard error (RSE) value of 1.59% The method detection limit (MDL) of this approach was very low, at 0.00051 ng This implies that real samples present above the threshold concentration (0.032–0.58 ppb) can be quantified if one collects an air sampling volume of 1 L (the MDL should be equal to 0.021 ppb) However this method required such an very expensive and unique sorbent tube, and the author only investigate the application of this method on laboratory-made sample Therefore a cheaper sorbent tube should be developed, which is compatible with instrument analysis and also is applicable to take in-situ samples (Kim, 2013)

1.3.3 TMA adsorption of Activated Carbon

In 2010, Lee and Daud carried out an investigation related to the adsorption properties of trimethylamine and other sulfurous compounds on activated carbon (Lee, 2010) The AC with BET specific surface area of 1067 m2/g and total pore volume of 0.552cm2/g was used in their experiment Under the adsorption conditions such as inlet concentration of gas was 300ppmv, temperature at 20°C and flow rate equal to 100ml/min, the authors was able to determine the breakthrough curve of each compound including TMA vapor on 0.1g of activated carbon, which is shown in this figure below:

Figure 1.3 Breakthrough curve of Methyl mercaptan, Demethyl sulfide and

Trimethylamine on Activated Carbon (Lee, 2010)

By measuring the area under the breakthrough curve, the equilibrium adsorption

capacity of AC was calculated for TMA, and this value reach nearly 100 mg TMA

per 1g AC In my study, the aim is to completely adsorb the TMA gas into the AC

bed inside the tube Therfore when design the AC tube, the adsorption capacity of the

tube can be determine based on the amount of activated carbon used in each tube