Experiment 7: Analysis of Chlorapyrifos in Water by Solid-Phase Extraction (SPE) and Gas
Chromatography-Electron Captre !etector (GC-EC!)
Introduction
Chlorapyrifos
Chlorpyrifos is a crystalline organophosphate insecticide that acts on the ner"os system of insects by inhibiting acetylcholinesterase# Chlorpyrifos is moderately toxic to hmans and the exposre $ill case nerological effects sch as persistent de"elopmental disorders atoimmne disorders and children mental de"elopment retard de to the exposre dring pregnancy# %n agricltre& chlorpyrifos remains as one of the most $idely sed as the pesticide# Solid-phase extraction (SPE) is an extraction method that ses solid and li'id phase to isolate analyte from soltion# %t is a rapid and selecti"e sample preparation# he prpose of sing the SPE is to prify& trace enrichment& sol"ent exchange and deri"atiation# he ad"antages of the SPE are high reco"ery of analyte& concentration of analyte& ease of atomation and redction of organic sol"ent consmption# he general procedre of SPE is the loading of soltion throgh SPE phase& $ash a$ay ndesired components& and lastly $ash off the desired analytes $ith other sol"ent into the collection tbe# Steps of SPE are from colmn sol"ation and e'ilibration& sample loading& interference eltion and lastly& the analyte eltion#
Procedure
*# he $ater sample is filter throgh a glass fibre filter paper# +# ,or solid-phase extraction procedre& the C* SPE catridge in conditioned by passing *. m/ of methanol# 0# he 1. m/ filtered $ater sample is passed throgh the preconditioned colmn sing a "acm manifold at 2 m/ per min (3 drops4min)# the colmn is ma5e sre to not dry dring sample enrichment step# 3# hen& the colmn is dried by "acm for *1 mintes# 1# he inteference is remo"ed by elting the colmn $ith *. m/ of deionied $ater and again the "acm is dried for *. mintes# 2# he pesticide is elted sing 1 m/ of hexane# hen& the sample is concentrated to * m/ by blo$ing do$n sing gentle nitrogen# 6# he instrment is set p for in7ector temperatre is +. oC# he detector temperatre is set 0.. oC# While& the carrier gas flo$ rate is fixed +.#. m/ min -* sing nitrogen gas# And the colmn temperatre initially *21 oC for 0 min& then it is increased to +2. o
C at 0 oC min-* $ith a final time of + min#
# he 'antitati"e analysis of chlorpyrifos# ,irstly& * 8/ of sample is in7ected onto the colmn# he in7ection is repeated to get reprodcible pea5 areas# 9# * 8/ of standard chlorpyrifos is in7ected# he in7ection is repeated to get reprodcible pea5 area# *.# sing the data from the standard soltion& the concentration of chlorpyrifos in the sample is calclated#
Result
A# Comparison in retention time of standard and samples: ;etention time of
Sample
;etention
standard
time
of
sample A"erage
(min)
retention
(ppm)
of
time
sample
(min) 2#696 2#696 2#696
rial * 2#96. 2#92 2#922
* + 0
rial + 2#966 2#929 2#92+
2#963 2#929 2#923
<# Calclation of response factor for standard compond:
amount peak area
;esponse ,actor (;,) =
30
=
748063
=
4.01 × 10
−5
ppm4>?s
C# Amont of chlorpyrifos in sample: Amont of chlorpyrifos in sample = ;, standard @ pea5 area sample
Sample
* + 0
Area (>?s)
rial * *0*61 **.991 600021
rial + *+319 *.2.9 60+*9
A"erage
Amont
area
chlorpyrifos
(>?s)
(ppm)
*0*02#1 *.9.+ 600.9+
1#+29 3#3.0 +9#096
of
5.269 + 4.403 + 29.397
A"erage amont of chlorphyrifos in sample =
3
= *0#.+0 ppm Percentage reco"ery of samples: Percentage reco"ery =
amount of chlorpyrifos ∈ sample × 100 amount of chlorpyrifos ∈ standard
Amont of chlorpyrifos in standard = 0. ppm sample * + 0
Amont of chlorpyrifos 1#+29 3#3.0 +9#096
Percentage reco"ery *6#12 *3#2 96#99
17.56 + 14.68+ 97.99
A"erage percentage reco"ery of sample =
= 30#3*
3
Discussion
%n this analysis& GC $ith Electron Captre detector is sed becase the analyte $hich is chlorpyrifos is to be analysed is halogenated compond& $hich is only EC! can detect analytes# he EC! contain electronegati"e fnctional grops that can captre electrons sch as halogens& peroxides& 'inones and nitro grops $hich can detect the analyte (chlorpyrifos)# he Electron Captre detector (EC!) is it in"ol"e $ith radioacti"e component# he amont of chlorpyrifos in samples is calclated by sing response factor calclation that base on the standard compond# he a"erage amont of chlorpyrifos in the sample is *0#.+0 ppm& that is abot half from the amont of chlorpyrifos in the standard# he percentage reco"ery calclated is 30#3* in a"erage# %n order to get higher amont of chlorpyrifos or the percentage reco"ery& the SPE mst be carried ot careflly so it $ill extract more chlorpyrifos efficiently#
Conclusion
he a"erage amont of chlorpyrifos in the sample is *0#.+0 ppm& $hile the percentage reco"ery is 30#3* in a"erage#
Reference
*# Solid-Phase Extraction (SPE)# ni"ersity of %oannina# ;etrie"ed at http:44$$$#oi#gr4research4labs4en"itech4SPE#htm 2.
