Arsenic Contamination Source And Cycle Biology Essay

Harmonizing to Newman ( 2005 ) , arsenic is known as “ toxicant for king ” and “ male monarch for all toxicant ” . It is because arsenous anhydride has the all appropriate characteristics such as colourless and odourless to be utilize as toxicant ( Newman 2005 ) . In fact, centuries long, arsenous anhydride has been used as homicide toxicant ( Reilly 1980 ) . It is said that, there are possible that Napoleon Bonaparte, who died in twelvemonth 1821 was poisoned with arsenic. This hypothesis existed after a toxicologist analyses Napoleon ‘s hair sample ( Reilly 1980 ) .

In term of the use, arsenous anhydride was long introduced to medicate field. In the fifth centuries, arsenous anhydride was used to mend ulcer ( Newman 2005 ) . Arsenic was besides one of the ingredients in Fowler solution, which was produced in 1786 to handle all type of diseases from asthma to malignant neoplastic disease ( Newman 2005 ) . Fowler solution flourish in footings of use for more than 150 old ages ( Newman 2005 ) and in 1965, a publication shows that most of the patients treated with this solution for long term have developed skin malignant neoplastic disease ( Reilly 1980 ) . Until now, arsenous anhydride is used as an effectual chemotherapy agent. Besides its use in medical Fieldss, arsenous anhydride is besides being used as an ingredient on wood preservatives, agribusiness chemicals ( particularly in pesticides and drying agents, non-steel metal smelting, glass industry and other uses ( Codex 2007 ) .

Two chief chemical signifier of arsenous anhydride is inorganic arsenous anhydride which combines with elements such as O, Cl and sulfur ; and organic arsenic which combines with C and H ( Hymer & A ; Caruso 2004 ) . There are few differences in inorganic and organic arsenic signifier. Table 2.1 shows some of the signifiers of arsenous anhydride.

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Table 2.1 Forms of inorganic and organic arsenous anhydride

Name

Abbreviation

Chemical Form

Inorganic arsenous anhydride, trivalent

Arsenite

As III

As ( OH ) 3

Arsenic ( III ) oxide

As2O3

Inorganic arsenous anhydride, pentavalent

Arsenate

As V

AsO ( OH ) 3

Arsenic ( V ) oxide

As2O5

Organic arsenous anhydride

Monomethylarsinic acid

MMAIII

CH3As ( OH ) 2

Monomethylarsonic acid

MMAV

CH3AsO ( OH ) 2

Dimethlyarsinous acid

DMAIII

( CH3 ) 2AsOH

Dimethlyarsinic acid

DMAV

( CH3 ) 2AsO ( OH )

Arsenobetaine

AsB

( CH3 ) 3As+CH2COOA?

Arsenocholine

AsC

( CH3 ) 3As +CH2COOA?

Trimethylarsine oxide

TMAO

( CH3 ) 3AsO

Tetramethylarsonium

ion

Me4As+ or TETRA

( CH3 ) 4As+

Arsenic-containing ribosides

Arseno-sugar

Assorted sugar construction

Beginning: Hymer & A ; Caruso 2004

The most of import commercial signifier of arsenous anhydride is arsenic oxide. It is obtained as byproduct in Cu production. This is because oxide exists of course in arsenide metal and arsenic sulphite that is foamed and oxidised in smelting procedure ( Lao et al. 1974 ) . Important factor in distribution and transit of arsenous anhydride in the environment depends on the vapour force per unit area at ambient temperature produced in this procedure ( Lao et al. 1974 ) .

Harmonizing to ASTDR ( 2007 ) , inorganic arsenic signifier is more unsafe than organic arsenous anhydride. This fact is ever confirmed dose-response consequence survey. One survey on dose-response consequence shows the consumption of inorganic arsenic causes respiration tissue harm in liver and kidney of a rat ( WHO 1981b ) . Further researches provide grounds that suggest the inorganic arsenous anhydride in trivalent signifier is more toxic than pentavalent inorganic arsenous anhydride ( Hymer & A ; Caruso 2004 ) . Arsenic ( III ) oxide fatal dosage for human through consumption includes from 1 to 2.5 milligrams As/kg organic structure weight ( WHO 1981b ) . Since the consumption measure is low to do fatal, therefore, a decision can be drawn that trivalent arsenous anhydride is pose more toxic that pentavalent arsenous anhydride. This information is strengthen by mutagenicity survey, where a survey carried out on human chromosome by in vivo and in vitro ( WHO 1981b ) . There is an addition in chromosome scratch when it is exposed to arsenic ( III ) oxide ( WHO 1981b ) . However, no inauspicious consequence was observed in rat that was ingested with nutrient incorporating “ seafood arsenic ” , besides known as organic arsenous anhydride ( WHO 1981b ) . The rat on this survey was fed with shrimp that contained 14 milligram As/kg for 12 months. Monomethylarsinic acid, organic arsenous anhydride, found to travel through placenta of the studied rat ( WHO 1981b ) . This methyl signifier arsenous anhydride is presumed every bit harmless as its degree of acute toxicity is well low ( Codex 2007 ) .

When arsenous anhydride is consumption, inorganic arsenous anhydride will travel through a methylation procedure, which is said to be an of import detoxification procedure in human organic structure ( Hymer & A ; Caruso 2004 ) and it is besides a major metabolic tract for inorganic arsenous anhydride ( Sirot 2008 ) . In this procedure, arsenate, arsenic ( V ) is reduced to arsenite, arsenic ( III ) signifier, followed by add-on of methyl group to organize monomethylarsonic acid and dimethlyarsinic acid ( MMA and DMA ) which will be excreted through nephritic tract ( Sirot 2008 ) . Minimal elimination is observed in fecal matters, nails and hair ( Sirot 2008 ) .

2.2 Arsenic taint beginning and rhythm in aquatic environment

In this twenty-first century, arsenous anhydride is an component that is widely distributed in the surface of Earth. Arsenic being in the environment is due to natural causes such as stones, deposits and human activity for illustration coal combustion, Cu smelting and mineral ore processing ( FSA 2005 ; Hymer & A ; Caruso 2004 ; Reilly 1980 ) . Volcanic activity has become a beginning of arsenic distribution to the environment through air. In add-on of geological beginning, use of inordinate pesticides ( which contains arsenic constituent ) can lend to high degree of arsenic in the dirt ( NZFSA 2005 ) . Other beginnings of arsenic taint are commercial use of antifungals, weedkillers, insectides and wood preservatives ( Reilly 1980 ) .

Arsenic can non be destroyed in the environment, it can merely alter signifier. When arsenic being released into the environment, it settles down to earth or transport out into the infinite via rain ( Reilly 1980 ) . Most of the arsenic compound is H2O soluble and aquatic beings have the inclination to absorb arsenic from its home ground ( Reilly 1980 ) . Since the metabolic procedure occurs of course in the biosphere, arsenic ( inorganic and organic ) is easy found in nutrient concatenation ( Codex 2007 ) . Aquatic being bio accumulates arsenic from its nutrient. This bioaccumulation demonstrates the metabolic transmutation concatenation when arsenic enters the aquatic being ‘s nutrient concatenation ( Borak & A ; Hosgood 2007 ) . Besides that, wood combustion besides releases arsenic particularly inorganic pentavalent, to the ambiance, due to its present in wood preservatives ( WHO 1981b ) .

In general, arsenic is circulated into the environment through H2O ( WHO 1981b ) . Arsenite is more overriding in oxygenated aquatic country, while arsenate is widely distributed in deep Waterss ( WHO 1981b ) . Aquatic country such as sea can be divided into 5 zones, which are epipelagic, mesopelagic, bathypelagic, abbyssopelagic and hadopelagic as shown in figure 2.1.

Epipelagic or suface zone is the country where the photosynthesis occurs because of sufficient sunshine and O supply. In this zone, chief sphere of aquatic being are tuna fish, shark and jelly fish

At mesopelagic zone, sunlight incursion is non sufficient for photosynthesis procedure. Aquatic being that lives in this country normally has efficient gills and limited motion such as calamari, sword fish and woffish.

Bathypelagic zone Iowa dark zone. There is no flora here and the aquatic animate beings that live in this zone are elephantine octopus and giant.

No visible radiation can perforate abbyssopelagic zone and this country is known as bottomless zone.

Hadopelagic zone is assumed to hold deepness of 6000 m. No species is believed to populate in this country.

Figure 2.1: Zones in aquatic country

Inorganic methylation procedure frequently related with biological activities in the H2O ( WHO 1981b ) . Some of the aquatic being is said have the capablenesss to transform inorganic arsenic to complex organic arsenic compound such as arsenobetaine and arsenocholine ( WHO 1981b ) . Arsenic biomethylation started to be known when arsine was produced from Scopulariopsis brevicaulis fungi civilization. Arsenate methylation mechanism is as shown in the tract below:

2e CH3+ 2e CH3+

AsVO43- — – & gt ; AsIIIO33- — – & gt ; CH3AsVO32- — – & gt ; CH3AsIIIO22- — – & gt ;

— O2- — O2-

2e CH3+ 2e

( CH3 ) 2AsVO2- — – & gt ; ( CH3 ) 2AsIIIO- — – & gt ; ( CH3 ) 3AsVO — – & gt ; ( CH3 ) 3AsIII

— O2- — O2-

Figure 2.2: Arsenic methylation procedure

Mechanism in figure 2.2, shows AsV is reduced to AsIII before methylation. The find of methylarsenic acid in sea H2O and fresh H2O proves that arsenic compound have undergone other procedures besides decrease and oxidization ( WHO 1981b ) . Methylation procedure is related with plankton, whether in sea or fresh H2O ( WHO 1981b ) . This is because plankton or algae can easy uptake arsenic in arsenate signifier and during detoxification procedure, arsenate is reduced and methylated which produce arsenic sugar and DMA and other methylated arsenic ( Borak & A ; Hosgood 2007 ) . Bioaccumulation occurs in nutrient concatenation, when lower degree being which contains arsenic is consumed by higher degree animate being in nutrient concatenation. Figure 2.3 shows arsenic distribution and biomethylation in the environment.

Figure 2.3: Arsenic distribution and biomethylation in the environment

2.2 Contamination degree of arsenic in fish

In Malaysia, fish is mostly consumed because of its copiousnesss, cheap and healthy protein beginning ( Hajeb et al. 2009 ) . Food ingestion statistics of Malaysia 2002/2003 for grownup population, aged 18 to 59 old ages indicates prevalence per centum for marine fish consumption is more than 90 % with estimated consumption of 60.67 g/day as shown in table 2.2. Marine fish shows highest degree of estimated consumption ( g/day ) and prevalence ( % ) as compared of other type of seafoods.

Table 2.2: Food ingestion statistic for fish and fish merchandises in Malaya

Type of nutrient

Estimate consumption ( g/day )

Prevalence ( % )

Marine fish

60.67

94.66

Fresh H2O fish

12.11

53.13

Anchovies

4.90

85.64

Canned fish

4.30

75.56

Cockles

4.70

58.81

Fresh shrimp

3.00

67.51

Fresh calamari

12.94

72.45

Dried calamari

5.65

25.95

Crab

3.94

62.79

Dried fish

2.93

67.77

Fish ball/cake

10.70

63.76

Keropok Lekor

4.17

55.10

Beginning: Ministry of Health 2006

Though devouring fish promotes good wellness benefits, there were legion studies on taint of fish by heavy metals in the environment, peculiarly, arsenic ( Hajeb et al. 2009 ) . Malaya criterions have set maximal permitted proportion ( MPP ) for arsenous anhydride for fish and fish merchandise as 1 mg/kg ( Malaysia Food Act and Regulation 1985. ) .

Two nutrient safety activities were conducted by Ministry of Health, which clearly shows the taint degree of arsenic in Malaysia. First activity is Entire Diet Study ( TDS ) , conducted in 2006 ( KKM 2006 ) . It was found in this survey, that 80 % of fish and fish merchandise analysed contains entire arsenic transcending maximal permitted proportion for arsenous anhydride for fish and fish merchandise stated in Schedule Fourteen, Regulation 38, Food Regulation 1985, which is 1 mg/kg ( KKM 2006 ) .

In continuance of the above mentioned survey, in 2007, a national monitoring plan was conducted to find the taint degree of arsenic in fish and fish merchandise that is retail around Federal States, Selangor, Negeri Sembilan and Melaka. The type of sample studied are sea fish ( ikan kerisi, ikan kembung, ikan sardin, ikan susu, ikan bawal putih dan ikan bawal hitam ) , fresh H2O fish ( ikan talapia merah, ikan Tilapia hitam, ikan keli, ikan lampan jawa, ikan patin, ikan siakap ) , squid, crustaceans ( pediculosis pubis and shrimps ) and seafood merchandises ( dried runts and anchovies ) . From 96 sample analysed, it was found that about 20 % of the samples violate arsenic taint degree as stated in Schedule Fourteen, Regulation 38, Food Regulation 1985. However, this degree refers to entire arsenic. At the present, there is no information obtained for inorganic arsenous anhydride or arsenic species taint in fish in Malaysia.

Even though, arsenic degree is high in aquatic being, harmonizing to Food Standard Agency, who conducted a study on entire arsenic and inorganic arsenous anhydride in fish and fish merchandise in 2005 shows that about 1-3 % of entire arsenous anhydride is inorganic arsenous anhydride ( FSA 2005 ) . Most of the arsenic signifier found in the fish sample are arsenobetaine and arsenocholine, which sometimes refered as “ fish arsenous anhydride ” .

In the twelvemonth of 2003, dietetic exposure survey for entire arsenic in seafood was conducted in Europe. The part of arsenic in seafood exceeds 50 % ( Sirot et al. 2008 ) . Where, organic arsenous anhydride is dominant to the part particularly AsB, AsC, MMA dan DMA, as compared to inorganic arsenic ( Sirot et al. 2008 ) . Harmonizing to Sirot et Al. ( 2008 ) , scientific research reported the per centum of inorganic arsenous anhydride in seafood is between 0.4 to 5.3 % and the remainder is in organic signifier particularly AsB. In the twentieth Total Diet Study conducted in Australia, the inorganic arsenic degree in fish, shrimp and canned tuna fish was found to be lower than bound of describing that 0.05 mg/kg.

Even though, some of the survey shows that inorganic arsenic degree is low in aquatic being, research on arsenic species is invariably conducted by scientist. This is because, in methylation procedure, which is a detoxicification mechanism is a metamorphosis concatenation, arsenic green goods intermediates in the signifier of active metabolites such free groups which releases O, which can be a accelerator for toxic consequence ( Gong et al. 2002 ) . This reaction is observed in toxicology survey conducted on rats, where carcinogen metabolite in rat red blood cell was found as a merchandise of arsenic metabolic activity ( Borak & A ; Hosgood 2007 ) . Harmonizing to Gong et al. ( 2002 ) , this metabolite is more toxic than inorganic arsenous anhydride.

2.4 Health affect

International Agency for Research on Cancer ( IARC ) has classified arsenic as carcinogenic agent for homo ( category 1 ) ( Sirot 2008 ) . This is because arsenic has the capableness to work certain cell pathway, bind with protein and distrupt molecule system ( Newman 2005 ) . In general, 75 % of arsenous anhydride is excreted through kidney and small per centum through fecal matters ( WHO 1981b ) . Arsenic elimination rate in homo is slow as compared with animate beings and is being stored in certain variety meats ( WHO 1981b ) . A survey conducted on rat and human confirms that inorganic arsenic can be transferred from female parent to fetus through placenta ( WHO 1981b ) . DMA besides have the capableness to go through through the placenta barrier, this has been proved by comparison trial of female parent and foetus blood ( WHO 1981b ) .

Both pentavalent and trivalent signifier of arsenic is easy absorbed in digestion system ( Reilly 1980 ) . However, trivalent arsenous anhydride is considered more toxic than pentavalent arsenic ( Reilly 1980 ) . When arsenous anhydride is being absorbed, it spreads to variety meats and tissue in the signifier of complex protein, likely with I±-globulin ( Reilly 1980 ) . It binds with sulphyryl group in protein and inhibits enzymatic activity, particularly those related to metamorphosis and chondriosome respiration ( WHO 1981b ) . Below is the tract of how arsenic compound binds with sulphyryl group enzyme.

SR ‘

/

R – As = O + 2R’SH & lt ; == & gt ; R – As + H2O

SR ‘

After 24 hours exposure, arsenic concentration in most variety meats will be reduced, nevertheless, accretion in tegument, nails and hair may increase after few yearss of digestion ( Reilly 1980 ) . The most sensitive index is skin skining for systematic toxicity due to chronic arsenic exposure. Chiefly, skin malignant neoplastic disease instances reported through medical intervention exposure is due to trivalent arsenic compound ( WHO 1981b ) .

Arsenic have no biological map and prolong exposure may be hazardness to wellness ( FSA 2005 ) . Prolong exposure or consumption of arsenous anhydride will do some inauspicious consequence to some variety meats ( Newman 2005 ) . Classical marks of ague arsenic toxic condition are sickness, puke, diarrhea, low blood force per unit area and eventually decease ( Newman 2005 ) . Chronic arsenic toxic condition symptoms are lost appetite, weight lost, distrupt to digestion system, oculus upset and others diseases. Exposure to inorganic arsenic can do assorted effects to wellness such as colon and tummy disease, decrease of ruddy and white blood cell production, alterations to clamber which is related to clamber that can take to skin malignant neoplastic disease and lung disease ( Hung et al. 2004 ; Reilly 1980 ) .

Arsenic in the signifier of inorganic can do DNA distruption and is known to do malignant neoplastic disease such as tegument, lungs, liver and lien ( FSA 2005 ; Hung et Al. 2004 ) . This is because Deoxyribonucleic acid contains protein with sulphyryl bond and arsenous anhydride have the possible to adhere with this bond, later, disturpt DNA mechanism.

There are few incident related to arsenic toxic condition. In the late nineteenth century, 1000s of United Kingdom citizens experience arsenic toxic condition caused by amylum that is hydrolysed by arsenic tainted acid and used in beer agitation procedure ( Reilly 1980 ) . Another serious instance occurs in 1955 in Japan, involves more than 12 000 babes given milk that was contaiminated with arsenic trioxide. This compound was used accidentally in Na phosphate to stabilise the milk pulverization ( Reilly 1980 ) . A profound instance occurred in Bangladesh around 1970s, where a monolithic arsenous anhydride poisnoning took topographic point when good H2O was contaminated with arsenic.

Entire Arsenic Analysis

Mineralization process in biological sample is critical in obtaining desirables consequences. Assorted sample readying processs can be employed such as dry ashing, wet digestion and micro-cook digestion. In dry ashing process, high temperature is applied to the sample and digested for long hours. In some instances, the temperature can be rised up to 500°C and digested for more that 16 hours ( Demirel et al. 2008 ) . Wet digestion is fundamentally an unfastened digestion system, which requires high volume of acerb mixture with digestion clip of 4 to 6 hours. Microwave digestion AIDSs digestion with microwave radiation normally provides a closed digestion system. This process requires short clip and little volume of acid for digestion.

Harmonizing to Soylak et Al. ( 2004 ) , wet and dry ashing processs are time-consuming as compared to micro-cook digestion. Microwave digestion has the characteristics for fast and efficient sample decomposition method for hint metals finding ( Tuzen 2002 ) . Study conducted by Soylak et Al. ( 2004 ) in comparing microwave, dry and wet digestion, proves the recoveries of the hint metals utilizing microwave digestion were in the scope of 95-103 % with criterions divergences less than 10 % . The writer concluded that dry and wet digestion processs are slow, complicated and less efficient than microwave digestion.

In another survey by Reyes et Al ( 2009 ) , microwave digestion was employed to digest DOLT-3 ( Dogfish Liver ) and BCR-627 ( Tuna Fish Tissue ) with recovery of entire arsenous anhydride was 98 % and 100 % severally. Harmonizing to Demirel et Al. ( 2008 ) , microwave digestion process was preferred to dry ashing and wet digestion processs because it provides more accurate consequences, shorter digestion clip and accomplish better recovery in the samples. Microwave digestion method is suited for digestion of volatile component such as arsenic ( Demirel et al. 2008 ) , because it provides closed digestion system which minimize lost as compared to dry or wet digestion.

There are many spectrometry instrumentality techniques that can be employed to observe entire arsenous anhydride in fish. Some of the techniques are hydride generation-atomic soaking up spectroscopy ( HG-AAS ) , graphite furnace atomic soaking up spectroscopy ( GFAAS ) , inductively coupled plasma optical emanation spectroscopy ( ICP-OES ) and inductively coupled plasma mass spectroscopy ( ICP-MS ) ( EFSA 2009 ) . ICP-MS is the best technique because the analytical public presentation is stable and robust, with low LoQ and broad dynamic additive scope ( EFSA 2009 ) .

2.6 Speciation Technique

International Union for Pure and Applied Chemistry ( IUPAC ) suggested definition for speciation analysis as activity for finding and mensurating measure of one or more individu chemical species in sample. Elemental speciation construct in distinguishing entire element fraction, exist bit by bit tardily fiftiess. Merely in 1980s, analytical instrumentality achieved required finding rate to calculate hint element fraction in the environment and biological sample.

Speciation technique requires instrumentality with separation device and sensing instrumentality ( Gong et al. 2002 ) . Matching of this analytical technique is needed to accomplish sensitiveness and selectivity in single arsenic species finding ( Gong et al. 2002 ) . Normally, speciation technique involves matching of separation chromatographic and finding spectroscopy ( Gong et al. 2002 ) .

High public presentation liquid chromatography ( HPLC ) frequently used as separation tool in arsenic speciation ( Gong et al. 2002 ) . While, instrument such as gas chromatography, supercritical fluid chromatography and capillary cataphoresis besides used in arsenic speciation, though, the use is non broad. Separation modes utilised in HPLC are ion-pairing, ion-exchange and size exclusion ( Gong et al. 2002 ) . In arsenic species analisis, ion-exchange is normally used, followed by ion-pairing ( Hymer & A ; Caruso 2004 ) .

In the basic design of chromatography, ion-exchange is employed to divide ion and easy ionized compound ( Hymer & A ; Caruso 2004 ) . It utilizes equilibrium exchange mechanism between stationary stage which contains surface ion and ion with rearward charge nomadic stage ( Hymer & A ; Caruso 2004 ) . Ion-exchange chromatography can applied in two separation manner, that is, anion kation exchange ( Hymer & A ; Caruso 2004 ) . Ionic strength in solution, nomadic stage pH, flow rate, concentration and ionic strength of buffer solution and temperature influences the separation and keeping clip in ion-exchange HPLC ( Hymer & A ; Caruso 2004 ) . Anion exchange chromatography typically use for separation of arsenite arsenit ( AsIII ) , arsenate ( AsV ) , monomethylarsonic ( MMAV ) dan dimethlyarsenic ( DMAV ) , where else, kation exchange is emplyed in separation of AsB, AsC and trimethylarsine oxide ( TMAO ) ( Hymer & A ; Caruso 2004 ) .

Ion exchange chromatography system utilizes isocratic and gradient system in separation of arsenic compound ( Hymer & A ; Caruso 2004 ) . Most survey is base on isocratic system, though ; gradient separation allows a better declaration clip and peak public presentation ( Hymer & A ; Caruso 2004 ) . Harmonizing to Reuter et Al. ( 2003 ) , gradient system is employed to find AsB, AsIII, DMA, MMA dan Asv ; it require clip for column re-equilibration ; long analysis clip nevertheless, gradient system produce better declaration clip as shown in figure 2.4.

Figure 2.4: Chromatograhy of five arsenic species at five difference concentration utilizing gradient system

Beginning: Reuter et Al. ( 2003 )

Study conducted by Cao et Al. ( 2009 ) and Hymer et Al. ( 2001 ) explains chromatography technique of anion exchange with gradient system could divide both anion and kation arsenous anhydride. This is achieved by modifying flow rate and buffer solution concentration that is ammonium carbonate ( Hymer et al. 2001 ) . Flow rate at 0.8, 1.0 and 1,5 with concentration scope of ammonium carbonate ( buffer ) at 5.00, 10.0, 15.0, 20.0 dan 30.0 mmol-1 is used to measure the separation between AsB, AsC, AsIII, Asv, DMA dan MMA ( Hymer et al. 2001 ) .

Isocratic system has advantage in term of clip, where entire tally clip is less than gradient system ( Reuter et al. 2003 ) . Even though, this system is clip salvaging, declaration clip is less satisfactory as compared to gradient system ( Reuter et al. 2003 ) a can be observed in figure 2.5 that shows chromatography of arsenic species at individual concentration and clean utilizing isocratic system. The declaration clip diference between gradient system and isocratic system is preponderantly observed in AsB AsIII, DMA and Asv.

Figure 2.5: Chromatography of arsenic species at individual concentration and clean utilizing isocratic system

Beginning: Reuter et Al. ( 2003 )

Buffer system that is usually used in ion exchange chromatography ( to divide polar arsenic compound ) , including phosphate, carbonate, trimethylammonia hydrated oxide and formate ( Hymer & A ; Caruso 2004 ) . Potassium phosphate is non suited to be employed as buffer because it leave residue on skimmer and sampling station cone in ICP-MS, where else carbonate does non go forth much hint ( Hymer & A ; Caruso 2004 ) .

ICP-MS has become an efficient sensing technique in arsenic speciation ( Gong et al. 2002 ) . It is extremist sensitive and has the capableness to find assorted elements ( Hymer & A ; Caruso 2004 ) . This ability allows coincident finding of assorted elements such as arsenic species ( Hymer & A ; Caruso 2004 ) . Arsenic is prone to spectral perturbation in certain conditions during sensing in ICP-MS ( Hymer & A ; Caruso 2004 ) . This is indirectly related to arsenous anhydride of being monoisotopic with mass of 75 amu ( Hymer & A ; Caruso 2004 ) . Argon gas from plasma and Cl from sample matric have the ability to unite to organize Ar chloride, 40Ar35Cl, with similiar mass-to-charge ratio to arsenic, which is 75 amu ( Hymer & A ; Caruso 2004 ) . In supervising the signal at 75 m/z, the beginning of signal is from 2 beginnings which are arsenic compound and argon chloride perturbation ( Hymer & A ; Caruso 2004 ) . Introduction to reaction cell or hit cell at mass spectroscopy quadrapole will decide this polyatomic reaction ( Hymer & A ; Caruso 2004 ) . Reuter et Al. ( 2003 ) suggest the dynamic reaction cell ( DRC ) engineering can “ reassign ” arsenic ion from Ar+Cl- by reaction of arsenic ion with O to organize arsenic oxide, 75As16O+ , which can be determine at 91 m/z.

Figure 2.6: HPLC-ICP-MS yoke operation strategy

HPLC-ICP-MS yoke mechanism is illustrated in figure 2.6. The constituents in the strategy are HPLC with nomadic stage to transport the sample to column with the assistance of pump ( Reuter et al. 2003 ) . Sampel that base on balls through the column will continue to ICP plasma in aerosol signifier ( Hymer & A ; Caruso 2004 ) . After the ionisation procedure in plasma, arsenic ions will go on to mass spectroscopy ( Hymer & A ; Caruso 2004 ) . Then, informations can be interpretated with specific package employed consequently to the instrument theoretical account.

Harmonizing to Hymer & A ; Caruso ( 2004 ) , there are 2 attacks in sample extraction for arsenic speciation that is traditional technique and enhanced technique. Traditional techniques are:

Liquid-liquid or solid-liquid extraction, besides know as sonification technique – this technique utilizes dissolver such as methyl alcohol, propanone and trichloromethane.

Solid stage extraction ( SPE )

Solid-phase microextraction

Enhance technique consist of:

Pressurized liquid extraction ( PLE ) or besides known as automatic extraction utilizing Automated Solvent Extraction ( SPE )

Microwave-assisted extraction ( MAE ) and Supercritical fluid extraction ( SFE )

The sum-up of extraction method from other surveies in table 2.2 shows that in traditional extraction, the sonification technique exhibit highest recovery per centum ( 100.9 % ) as compared to other method. While, recoveray rate for MAE extraction method is excessively broad.

Table 2.3: Summary of extraction method from other surveies

Sample

Extraction method

Arsenic species

Recovery scope