1983, gas chromatography in water analysis--ii

8/6/2019 1983, Gas Chromatography in Water Analysis--II

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Water Res. Vol. 17, No. 12, pp. 1905-1916, 1983 0043-1354/83 $3.00+0,00Printed in Great Britain Pergamon Press Ltd

G A S C H R O M A T O G R A P H Y I N W A T E R A N A L Y S I S - - I IS E L E C T IV E D E T E C T IO N M E T H O D S

PAUL BURCHILL, ALAN A. HEROD, KAREN M. MARSHan0 ERNEST PRITCHARD

National Coal Board, Coal Research Establishment, Stoke Orchard, Cheltenham, Gloucester GL52 4RZ,England(Rece i ved Apr i l 1983)

A~t raet --Gas chromatographic methods using selective detectors have been applied successfully o thedetermination of haloforms, herbicides and chlorophosphate esters in water extracts.Electron capture detection has been used for the determination of the four haloforms, CHC13, CHC12Br,CHCIBr2 and CHBr 3 in pentane extracts. The very low detection limits render both the extracts andcalibration solutions highly susceptible o contamination, and precautions necessary for their handling andstorage are described.Mass spectrometric single ion monitoring of gas chromatographic efltuents has been used for thedetermination of the herbicides MCPA, MCPB and Mecoprop in methylated ether extracts. Possibleinterference from other components of the water extracts is discussed, and it is concluded that more thanone ion should be monitored for each herbicide to minimise the interference.A flame photometric method involving detection at 528 nm has been developed for the determinationof chlorophosphate esters in dichloromethane extracts. The method is extremely specific for phosphoruscompounds, but some interference from sulphur compounds may be observed. This can be minimised bythe use of high efficiency capillary columns.Detection limits and linear response ranges for the methods are given, and detector selectivities arediscussed. Typical chromatograms are shown, and representative results for raw and treated waters arealso given.

INTRODUCTIONAs part of the contri butio n by Thomas Ness Ltdto the Anglian Water Authority Trent-Witham-Ancholme (TWA) Potability Study, a method hasbeen developed at the Coal Research Establishment(CRE) laboratories of the National Coal Board forthe routine chromatographic scanning of watersources for trace organic compounds, The method,which is described in detail in Part I (Burchill e t a l . ,1983), involves solvent extraction of the water withdichloromethane, followed by analysis of the concen-trated extract by gas chromatography on a glassSCOT capillary column with flame ionisation de-tection to yield a "water profile". Over 600 extractsfrom the TWA system and various treatment regimeswithin the Elsham pilot plant, together with samplesfrom the reference sites at Brampton and Ardleigh,were examine d in this way between January 1978 andOctober 1980. The profiles were quant ified usingn-paraffin standards and a computerised data system,and mass spectrometry was used to identify chemicaltypes in over 60 of the extracts.

Although this technique has proved extremelyvaluable in giving an overall picture of the morevolatile organic compounds present in water sources,it has a number of disadvantages for the routineanalysis of specific components.

(i) The extreme complexity o f many o f the profilesand the low selectivity of the detection system resultin a specific component being very liable to inter-ference from other species with similar chromato-graphic retention times, particularly if it is present atvery low concentrations.

(ii) The method is only semi-quantit ative since itassumes a response factor of unity relative to then-paraffin standard. This was the only feasible ap-proach for unidentifiable compounds, and otherswhich were identified, but for which reference materi-als were unavailable.(iii) Although the quantitative aspects of themethod could be improved for specific compo unds bythe use of response factors, a num ber of compou ndsof particular interest have high heteroatomic con-tents, and give low responses with flame ionisationdetection. For example, the fire retardant Tris(2-chloroethyl)phosphate, which was identified in anumber of samples, has a specific response lower bya factor of 5 than that for the paraffin standard. Thischaracteristic reduces the sensitivity with which thesecompounds may be detected, and tends to increasethe level of interference in their measurement by thismethod.

(iv) The general purpose, non-polar SE-30 liquidphase used for the "water profile" work is not idealfor polar components, which may be subject to1905


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1906 PAUL BURCHILL t al .a d s o r p t i o n e f fe ct s, a n d t h e u s e o f m o r e p o l a r l i q u idp h a s e s w o u l d b e p r e f e r r e d f o r s u c h c o m p o u n d s .

( v) T h e t e m p e r a t u re p r o g r a m m i n g n e c e ss a ry t oc o p e w i t h c o m p o u n d s c o v e r i n g a w i d e b o il in g r a n g eresu l t s i n l ong ana lys i s t imes fo r t he wa te r p rof i l e s .

T h e s e p r o b l e m s m a y b e o v e r c o m e b y t h e u s e o fs e le c ti v e d e t e c t o r s f o r i s o t h e r m a l g a s c h r o m a t o -g r a p h y o n s u i t a b l e l i q u i d p h a s e s . S u c h d e t e c t o r sr e s p o n d s e le c ti v el y t o s o m e p r o p e r t y o f th e e l u t e dspec ie s such a s t he p re sence o f a cha rac t e r i s t i c e le -m e n t o r g r o u p . T h e y a r e u s u a l l y v e r y s e n s i t i v e , a n di s o t h e r m a l o p e r a t i o n a t a s u i t a b l e c o l u m n t e m p e r a -t u r e a ll o w s t h e r a p i d a n a l y s i s o f c o m p o u n d s w i th i n al imi t ed bo i l i ng range .Thi s pap e r desc r ibes the ap p l i ca t ion o f t h ree sel ec -t i v e d e t e c t i o n m e t h o d s f o r t h e g a s c h r o m a t o g r a p h i ca n a l y s is o f w a t e r e x t r a c ts f r o m t h e T W A p r o j e c t .E l e c t r o n c a p t u r e d e t e c t i o n h a s b e e n u s e d f o r t h ed e t e r m i n a t i o n o f h a l o f o r m s i n p e n t a n e e x t r a c ts , m a s ss p e c t r o m e t r i c s in g l e i o n m o n i t o r i n g h a s b e e n u s e d f o rt h e d e t e r m i n a t i o n o f h e r b ic i d e s i n m e t h y l a t e d e t h e re x t r a c t s a n d a f l a m e p h o t o m e t r i c m e t h o d h a s b e e nd e v e lo p e d f o r t h e m e a s u r e m e n t o f c h l o r o p h o s p h a t ees t e r s i n d i ch lo rome thane ex t rac t s . De tec t ion l imi t sa n d l i n ea r r e s p o n s e r a n g e s f o r t h e m e t h o d s a r e g iv e n ,and de t ec to r se lec tivi ti es and poss ib l e sources o fi n t e r f e r e n c e a r e d i s c u s s e d . T y p i c a l c h r o m a t o g r a m sa r e s h o w n , a n d r e p r e s e n t a t i v e r e s u l t s f o r r a w a n dt rea t ed wa te r s a re a l so g iven .In recen t yea r s , cons ide rab le i n t e re s t has beens h o w n i n t h e a n a l y s i s o f l o w l e v e l s o f h a l o f o r m s i ndr ink ing wa te r . Th i s conce rn fo l lowed the iden t i f i -c a t io n o f a n u m b e r o f h a l o f o r m s i n d r i n k i n g w a t e r inH o l l a n d a n d t h e U . S . A . , w h i c h p r o m p t e d a n E P As u r v e y o f t h e d i s t r ib u t i o n o f h a i o f o r m s i n d r i n k i n gw a t e r t h r o u g h o u t t h e U . S . A . T h e r e su l ts o f th i ss u r v e y , w h i c h d e m o n s t r a t e d t h e w i d e s p r e a d o c c u r -r e n c e o f h a l o f o r m s i n d r i n k i n g w a t e r , h a v e b e e nr e v i e w e d b y S y m o n s e t a l . (1975).H a l o f o r m s a r e d e f i n e d a s t r i h a l o g e n a t e d m e t h a n e so f t h e f o r m u l a CHX3, wh ere X = C1 , Br , I o r F .T h e s e c o m p o u n d s , p a r t i c u l a r l y c h l o r o f o r m , d i c h l o -r o b r o m o m e t h a n e , d i b r o m o c h l o r o m e t h a n e a n d b r o -m o f o r m , h a v e b e e n s h o w n t o b e a l m o s t u b i q u i t o u s

c o m p o n e n t s o f t re a t e d w a t e r s , b ei n g p r o d u c e d i ns i d e - re a c t io n s d u r i n g t h e d i s i n f e c ti o n o f w a t e r b yc h l o r i n e a t t h e t r e a t m e n t w o r k s . R o o k ( 1 9 7 4 ) h a ss h o w n t h a t c h l o r i n e r e a c t s w i t h o r g a n i c m a t e r i a l ,p a r t i c u la r l y h u m i c s u b s t a n c e s , p r e s e n t i n t h e w a t e r t op r o d u c e t h e c h l o r i n a t e d c o m p o u n d s , a n d h a s s u g -ges t ed tha t t he b romina ted de r iva t ives a r i se e i the rf r o m t h e p r e s e n c e o f b r o m i d e s i n t h e w a t e r o r f r o mb r o m i n e i m p u r i t y i n t h e c h l o r i n e .T h e h u m a n h e a l t h r i s k s a r i s i n g f r o m h a l o f o r m shave no t , a t p re sen t , been fu l ly i nves t iga t ed , bu t t hec a r c i n o g e n i c i ty o f c h l o r o f o r m i n a n i m a l s h a s b e e nrepor t ed by Morr i s (1975) , NCI (1976) and Pie rce(1978). S ince the l eve ls o f t hese com po un ds can bere l a t ive ly h igh in t r ea t ed wa te r , e .g . con cen t ra t ions ine xc es s o f 3 0 0 / ~ g 1 ~ f o r c h l o r o f o r m h a v e b e e n r e -p o r t e d b y H o e h n e t a l . ( 19 7 7) , m e a s u r e m e n t o f th ema jor ha lo forms p re sen t i n wa te r supp l i e s i s c l ea r lydesi rable .

T h e m a j o r i t y o f a n a l y t ic a l t e c h n i q u e s d e v e l o p e df o r t h e d e t e r m i n a t i o n o f h a l o f o r m s i n w a t e r h a v ei n v o lv e d t he u s e o f g as c h r o m a t o g r a p h y a n d / o r m a s ss p e c t r o m e t r y . A n u m b e r o f m e t h o d s a r e d e sc r i b e d b yK e i t h ( 1 9 7 7 ) . T h e m e t h o d r e p o r t e d h e r e i s b a s e d o nt h o s e d e v e l o p e d b y F i e l d i n g e t a l . (1977) , Richarda n d J u n k ( 1 9 7 7 ) a n d S a n d e r e t a l . (1977) . I t involvest h e s o l v en t e x t r a c ti o n o f th e h a l o f o r m s f r o m w a t e ru s i n g n - p e n t a n e , f o l lo w e d b y a n a l y s is o f th e e x t r a c tb y g a s c h r o m a t o g r a p h y w i t h e l e c t r o n c a p t u r e d e -t ec t ion (ECD) us ing a f ree fa t ty ac id l i qu id phase( F F A P ) p a c k e d c o l u m n .

T h e h er b ic id e s, M C P A , M e c o p r o p a n d M C P B , a r eused a s se lec tive w eedki l le r s fo r t he con t ro l o f b ro ad-l e a v e d w e e d s . T h e c o m p o u n d s a r e 4 - m e t h y l ,2 - c h l o r o p h e n o x y d e r iv a t iv e s o f a l k a n o i c a c i d s a n dthe i r s t ruc tu re s a re shown in F ig . 1 . Th i s r epor td e s c r i b e s a m e t h o d f o r t h e i r m e a s u r e m e n t i n w h i c ht h e m e t h y l e s t e r s a r e s e p a r a t e d b y g a s c h r o -m a t o g r a p h y a n d d e t e c t e d b y m a s s s p e c t r o m e t r y b yo b s e r v i n g a p a r t i c u l a r i o n c h a r a c t e r is t i c o f e a c he s t e r - - a s i ng l e i o n m o n i t o r i n g m e t h o d . I t is b a s e d o na n u n p u b l i s h e d m e t h o d d e v e l o p e d b y t h e W a t e rResea rch Cent re (F ie ld ing , 1977) . The mass spec -t r o m e t e r i s t u n e d t o d e t e c t o n l y o n e m / z va lue ,p r e f e r a b l y o n e u n i q u e t o t h e c o m p o u n d t o b e i n -

M C P A4 - M e t h y l , 2 - c h l o ro -p h e n o x y a c e t i c a c i d

C H 3 -" ~ O C H 2 C OO Hci

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CI

CIIHI303CIM W . 2 2 8 . 0 5 5 2

Fig. 1. Structures of herbicide acids.


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1 9 0 8 PA U L BU RCI -I IL L e t a l .

T a b l e 1 . C o n d i t i o n s f o r g a s c h r o m a t o g r a p h y : h a l o f o r m a n a l y s i sI n s t ru m e n t : P e r k i n - E l m e r F - 1 7 g a s c h r o m a t o g r a p hD e t e c t o r : 6 3N i E C D ( n o m a k e - u p g a s u s e d )D e t e c t o r p u l s e i n t e r v a l : 1 2 5 # sC a r r i e r g a s : N i t r o g e nI n j e c t i o n v o l u m e : 1 .0 # 1

C o l u m n 1 C o l u m n 2Co l u m n d i m e n s i o n s : 4 m x 1 .7 5 m m i . d . x " o .d . 4 m x 1 .7 5 m m i . d . x 4" o .d .L i q u i d p h a s e / s u p p o r t: 5 ~ F F A P o n 8 0 - 1 0 0 m e s h 1 0 ~ F F A P o n 1 0 0 - 12 0 m e s hU n i v e r sa l s u p p o r t C h r o m o s o r b W - H P8 0 C 1 0 0 C1 7 5 - 3 3 8 C 2 2 5 C6 4 m l m i n - i ( 4 0 p . s . i. ) 4 0 m l m i n - ~ ( 5 0 p . s . i .)C o l u m n t e m p e r a t u r e :I n j e c t o r / d e t e c t o r t e m p e r a t u r e :C a r r i e r f l o w :R e t e n t i o n t i m e s :C H C I 3C H C I 2 B rC H C I B r 2C H B r 3

1 .4 m i n 2 .7 m i n2 .9 m i n 5 .3 m i n6 .5 m i n 1 1 .2 m i n1 4 .8 m i n 2 3 .7 m i n

1 - 1 0 0 / t g 1 - 1 w e r e p r e p a r e d t a k i n g t h e p r e c a u t i o n sa l r e a d y d e s c r i b e d t o a v o i d c o n t a m i n a t i o n . T h e s t a n -d a r d s w e r e a n a ly s e d b y G C / E C D u s in g 1 .0 # l i n je c -t i on s o n t h e 1 0 ~ F F A P c o l u m n u n d e r t h e c h r o -m a t o g r a p h i c c o n d i t i o n s gi v en in T a b l e l , C o l u m n 2 .

T h e r e s p o n s e s , a s p e a k h e i g h t x a t t e n u a t i o n , w e r em e a s u r e d , a n d c a l i b r a t i o n g r a p h s c o n s t r u c t e d f o re a c h h a l o f o r m a f t e r c o r r e c t i o n fo r t h e s o l v e n t b l a n k .N o r m a l l y o n l y c h l o r o f o r m w a s d e t e c t e d i n t h e s o l -v e n t . T h e c a l i b r a t i o n g r a p h s , w h i c h a r e s h o w n i n F i g .3 , a r e l i n e a r o v e r t h e c a l i b r a t i o n r a n g e u s e d , b u t s o m ed e v i a t i o n f r o m l i n e a r i t y w a s o b s e r v e d a t h i g h e r l e v e lsa n d w i t h i n c r e a s i n g c o n c e n t r a t i o n t h e r e s p o n s e s a p -p r o a c h e d a m a x i m u m v a l u e c o r r e s p o n d i n g t o s a t u r -a t i o n o f th e d e t e c t o r w i t h s t r o n g l y e l e c t r o n - c a p t u r i n gs p ec ie s. D i e h l o r o b r o m o m e t h a n e a n d d i b r o m o c h l o r o -

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F i g . 2, V a r i a t i o n o f E C D r e s p o n s e w i t h t e m p e r a t u r e f o rh a l o f o r m s .

m e t h a n e g i v e l a r g e r E C D r e s p o n s e s t h a n c h l o r o f o r ma n d b r o m o f o r m . T h e m i n i m u m d e t e c ti o n l im i ts fo rt h e f o u r h a l o f o r m s h a v e b e e n e s t i m a t e d o n t h e b a s i so f a p e a k h e i g h t o f 4 m m a t a n a t t e n u a t i o n o f 1 6 x l ,a n d a r e g i v e n in T a b l e 2 . A f u l l c a l i b r a t i o n w a sn o r m a l l y c a r r i e d o u t p r i o r t o t h e a n a l y s i s o f e a c hb a t c h o f e x tr a c t s , a n d s t a n d a r d s o l u t i o n s w e r e i n te r -s p e r s e d w i t h t h e s a m p l e s a s a r u n n i n g c h e c k .

T h e e x t r a c t i o n s w e r e g e n e r a l ly c a r r i e d o u t a t t h eA W A E l s h a m l a b o r a t o r y . A l l w a t e r s a m p le s , in c l u d -i n g d i s t il l e d w a t e r b l a n k s , w e r e t r e a t e d w i t h t h i o -s u l p h a t e t o r e m o v e e x c e s s f r e e c h l o r i n e a n d t h u st e r m i n a t e r e a c t i o n s w h i c h m i g h t l e a d t o i n c r e a s i n gh a l o f o r m l e ve l s o n s t o r a g e . 5 m l d e c h l o r i n a t e d w a t e rs a m p l e s w e r e p i p e t t e d i n t o s c r e w - t o p p e d g l a s s p h i a l sf i t te d w i t h P T F E - f a c e d s e p t a , t o g e t h e r w i t h 5 m ln - p e n t a n e . P a r t i t i o n o f t h e h a l o f o r m s t o t h e u p p e rl a y e r t a k e s p l a c e r a p i d l y o n s h a k i n g a n d t h e p h i a l sw e r e t h e n t r a n s p o r t e d to C R E v i a A W A r o a d t r a n s -p o r t .

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F i g . 3 . E C D c a l i b r a t i o n g r a p h s f o r h a l o f o r m s .


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Gas chrom atography in wa te r ana ly s i s - - I I 1909Table 2. Haloform detection limits

Detection limitComponent (g)

Minimum detectableconcen tration inwater, assuming1 1 extraction ratioand 1.0#1 injection(#g 1 r)CHC I 3 12 I0 -13 1.2CHCI 2Br 3 x 10 ]3 0.3CHC IBr 2 5 x 10 -I~ 0.5CH Br 3 20 x 10 ~3 2

T h e m a j o r i t y o f h a l o f o r m s a m p l e s fr o m t h e A W Aw e r e r e c e i v e d a s 1 :1 r a t i o e x t r a c t s , a n d t h i s r a t i oa p p e a r s t o b e t h e m o s t s a t i s f a c t o r y . O c c a s i o n a l l y at r e a t e d w a t e r s a m p l e m a y r e q u i r e d i l u t i o n in o r d e r t ob r i n g s o m e o f t h e h a l o f o r m s i n t o t h e i r l i n e a r E C Dc a l i b r a t i o n r a n g e s b e f o r e q u a n t i f i c a t i o n . H i g h e r e x -t r a c t i o n r a t i o s w e r e u s e d t o c o n c e n t r a t e s o m e s a m p l e sw i t h v e r y l o w h a l o f o r m l e v el s , b u t r e s u l ts h a v e s h o w nt h i s t o b e g e n e r a l l y u n n e c e s s a ry .

T h e e x t r a ct s w er e a n al y s e d b y G C / E C D o n t h e1 0 ~ F F A P c o l u m n u n d e r t h e c a li b r a t i o n c o n d i t io n sd e t a i l e d i n T a b l e 1 . T h e r e s p o n s e f o r e a c h h a l o f o r mw a s m e a s u r e d a n d t h e c o n c e n t r a t i o n o f t h e h a l o f o r mi n t h e e x t r a c t s d e t e r m i n e d f r o m t h e a p p r o p r i a t eg r a p h . T y p i c a l c h r o m a t o g r a m s o f t r e a te d w a t e r sf r o m t h e E l s h a m p l a n t a r e i l l u s t ra t e d i n F i g s 4 a n d5 , a n d t h e c o n c e n t r a t i o n s o f h a l o f o r m s m e a s u r e d f o rt h e s a m p l e s a r e g i v e n i n T a b l e 3 . T h e e l u t i o n o fp e n t a n e l m i n a f t e r i n j e c t i o n m o m e n t a r i l y s w a m p st h e E C D , a s i n d i c a t e d b y t h e f i r s t n e g a t i v e p e a k . T h i si s f o l l o w e d b y s e v e r a l , o f t e n i n t e n s e , p e a k s p r i o r t o

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Fig. 4 . GC/ECD chromatogram of a t reated water extract :Elsham m ain w orks f i l tered water , 27 July 1979. Chro-matog raphic condit ions given in Table 1, Column 2; 1:1extract ra t io .

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t.)

L . ,I~ o ~ ' ~ 2 ' 0 , ~ , S ~ '

Reten t ion t i m e ( m i n )Fig. 5 . GC/ECD chromatogram of a t reated water extract :Elsham pilot pla nt carbon filtrate 133, 13 M ay 1979.Chromatographic condit ions given in Table 1, Column 2;7:1 extract ratio,

t h e e l u t i o n o f c h l o r o f o r m . T h e i d e n t i t y o f a l l t h e s ee a r l y p e a k s i s n o t c e r t a i n , b u t t h e y a r e p r o b a b l y d u et o v o l a t i l e h a l o g e n a t e d c o m p o u n d s s u c h a s C H 2C 1 2.E x t r a c t s c o n t a i n i n g p a r t i c u l a r l y h i g h c o n c e n t r a t i o n so f h a l o f o r m s m a y r e q u i r e d i l u t io n t o b r i n g s o m ec o n s t i t u e n t s in t o t h e i r l i n e a r E C D c a l i b r a t i o n r a n g e sb e f o r e q u a n t i f i c a t i o n . A l l i n j e c t i o n s o f t h e s a m p l e sw e r e m a d e i n d u p l i c a t e a n d t h e r e p r o d u c i b i l i t y w a si n v a r i a b l y w i t h i n 5 ~ .H er bi c i de ana l ys i s w i t h s i ng l e i on m oni t or i ng m as ss p e c t r o m e t r i c d e t e c t i o nT h e h e r b i c i d e s w e r e f i r s t e x t r a c t e d f r o m a 4 0 0 m lw a t e r s a m p l e i n t o 5 0 m l e t h e r , f o l l o w e d b y m e t h y l -a t i o n . M e t h y l a t i o n w a s u s e d b e c a u s e o f t h e p o o rc h r o m a t o g r a p h i c b e h a v i o u r o f th e u n e s t er i f ie d a c id s .T h e c h r o m a t o g r a p h i c c o l u m n u s e d w a s a 4 m p a c k e dc o l u m n c o a t e d w i t h O V - 1 7 p h a s e , a n d t h e o p e r a t i n gc o n d i t i o n s a r e l i s t e d i n T a b l e 4 . T h e c o l u m n w a si n s ta l le d i n a P e r k i n - E l m e r F - 1 7 c h r o m a t o g r a p h a n dw a s c o u p l e d t o a m a s s s p e c t r o m e t e r ( M S - 3 0 ) b y a j e ts e p a r a t o r .M a s s s p e c t r a o f t h e t h r e e e s t e r s w e r e o b t a i n e d b yG C - M S o f a c o n c e n t r a t e d m ix t u r e a n d a r e s ho w n , i no r d e r o f e l u t io n , in F i g s 6 ( A ) - ( C ) f o r M e c o p r o p ,M C P A a n d M C P B , r e sp e c ti v el y . I n t h e M e c o p r o pe s t e r s p e c t r u m , t h e r e a r e s e v e r a l r e l a t i v e l y l a r g e p e a k sa n d t h r e e h a v e b e e n u s e d , n a m e l y t h e 3 5C 1 m o l e c u l a r


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1 9 1 0 P A U L B U R C H I L L e t a l .

T a b l e 3 . H a l o f o r m l e v e l s i n t y p i c a l r a w a n d t r e a t e d w a t e r s a m p l e sH a l o f o r m c o n c e n t r a t i o n ( # g l - I )S a m p l e T y p e C H C I 3 C H C I 2 B r C H C I B r 2 C H B r 3

E l s h a m m a i n w o r k sf i l te r e d w a t e r , C1 7 3 , T r e a t e d 5 9 .8 3 5 .6 1 9 .0 < 12 7 J u l y 1 9 7 9 ( 1 : 1 e x t r a c t i o nrat io ; see Fig . 3 )E l s h a m p i l o t p l a n t c a r b o nf i l te r e d w a t e r , Y 1 3 3 , T r e a t e d 1 .3 0 .9 1 .7 1 .31 3 M a y 1 9 7 9 ( 7 : 1 e x t r a c t i o nr a t i o ; s e e F i g . 4 )O v e r a l l r a n g e R a w 0 - 3 0 - 1 0 - 1 N DO v e r a ll r a n g e T r e a t e d 0 - 1 0 4 0 - 5 0 0 - 2 5 0 - 2N D = n o t d e t e c t e d .

io n m/z 2 2 8 a n d t h e f r a g m e n t i o n s m/z 142 and m/z1 4 1 . T h e l a t t e r i o n w a s u s e d b e c a u s e i t i s l e s s l i a b l et o i n t e r f e r e n c e f r o m f a t t y a c i d e s t e r s w h i c h c a n b ep r e s e n t i n s u r f a c e w a t e r s . I n t h e M C P A e s t e r s p e c -t r u m , t h e i o n s m/z 2 1 4 a n d 1 4 1 h a v e b e e n u s e d . I nt h e M C P B e s t e r s p e c t r u m , t h e r e i s o n l y o n e i o n o fh i g h i n t e n s i t y a n d n o t t o o l o w m a s s a n d t h i s i s t h ep e a k a t m/z 101.

T o s e l e c t t h e c o r r e c t m/z v a l u e s i n t h e m a s ss p e c t r o m e t e r , a s a m p l e w a s i n t r o d u c e d w h i c h p r o -d u c e d t h e r e q u i r e d i o n f o r a l o n g e n o u g h p e r i o d t oa l l o w f o r t u n i n g a n d o p t i m i s i n g t h e i n s t r u m e n t . T h er e s o l u t i o n o f t h e m a s s s p e c t r o m e t e r w a s s e t a t 1 0 00 ,t h a t i s , t h e b e a m d e f i n i n g s l i t s w e r e w i d e o p e n t om a x i m i s e t h e i o n c u r r e n t . A l l o f th e i o n s m o n i t o r e df o r t h e es te r s o f M C P A a n d M e c o p r o p c a n b e f o u n di n t h e f r e e a c i d s a n d t h e s e w e r e i n t r o d u c e d i n t o t h ei o n s o u r c e u s i n g t h e s o l i d s i n j e c t io n p r o b e t o g e n e r a t et h e a p p r o p r i a t e m/z v a l u e s f o r t u n i n g . I n t h e c a s e o fM C P B m e t h y l e s t e r , t h e i o n c h o s e n f o r m o n i t o r i n gc a n o n l y b e p r o d u c e d b y i n t r o d u c t i o n o f t h e e s te ri ts e lf , a n d n o r m a l p r a c t i c e h a s b e e n t o d o t h e i n it i a lt u n i n g u s i n g m/z 1 0 1 i n p e r f l u o r o k e r o s e n e ( P F K )w h i c h i s 0 . 0 5 8 8 m a s s u n i t s l o w e r t h a n t h a t i n t h ee s te r , a n d t h e n p e r f o r m t h e fi n a l t u n i n g o n G C p e a k sf r o m s t a n d a r d s o l u t i o n s o f t h e e s te r .

T h e s y s t e m w a s c a l i b r a t e d b y p r e p a r i n g s t a n d a r ds o l u t i o n s o f e a c h e s t e r w i t h c o n c e n t r a t i o n s i n t h er a n g e 5 - 5 0 n g p l ~. 0 . 0 2 g o f t h e f re e a c i d w a sd i s s o l v e d i n 1 m l o f a m e t h y l a t i n g s o l u t i o n , " M e t h y l8 " f r o m t h e P i e r c e C h e m i c a l C o . , a n d d i l u t e s o l u t io n sw e r e p r e p a r e d b y d i s s o l v i n g 1 -3 /~ 1 o f t h i s s o l u t i o n i n1 , 2 o r 3 m l o f t e t r a h y d r o f u r a n . A l l s o l u t i o n s w e r e

p r e p a r e d i n 3 m l g l a ss P T F E - f a c e d s e p t u m c a p p h i a l sa n d s t o r e d u n d e r r e f r i g e r a t i o n .

1# 1 i n j e c ti o n s o f t h e s t a n d a r d s o l u t i o n s w e r e m a d eu n d e r t h e c h r o m a t o g r a p h i c c o n d i t i o n s g iv e n i n T a b l e4 , a n d t h e i r r e s p o n s e s m e a s u r e d a s p e a k h e i g h t . T h ec a l i b r a t i o n g r a p h s f o r a l l t h e i o n s m o n i t o r e d w e r es t r a i g h t l i n e s p a s s i n g t h r o u g h t h e o r i g i n a n d t h e i rs l o p e s w e r e i n th e r a n g e 1 . 8 - 7 . 4 m m n g - L T h e c a l i -b r a t i o n g r a p h s f o r t h e t h r e e e s te r s a r e s h o w n i n F i g .7 f o r s e l e c t e d i o n s . S o m e 5 # 1 i n j e c t i o n s o f t h es t a n d a r d s o l u t i o n s w e r e a l s o m a d e s i n c e m o s t o f t h eA W A s a m p l e s w e r e f o u n d t o r e q u i r e t h e l a r g e ri n j e c ti o n v o l u m e t o g i v e a d e t e c t a b l e r e s p o n s e . I t w a se s t a b l i sh e d t h a t t h e 5 / ~ 1 i n j e c ti o n s o f t h e s t a n d a r ds o l u t i o n s la y o n t h e c a l i b r a t i o n g r a p h s d r a w n f o r t h e1 /~ 1 s t a n d a r d s . T h e c a l i b r a t i o n w a s n o r m a l l y c h e c k e de a c h d a y .T h e l i m i t s o f d e t e c t i o n o f t h e t e c h n i q u e c a n b ee s t i m a t e d b y a s s u m i n g t h a t t h e m i n i m u m d e t e c t a b l ep e a k h e i g h t i s 1 m m , w h i c h c o r r e s p o n d s t o 0 . 1 - 0 . 4 n go f M C P A , 0 . 2 - 0 .5 n g o f M e c o p r o p a n d 0 . 4 n g o fM C P B , d e p e n d i n g o n w h i c h i o n i s m o n i t o r e d . A s -s u m i n g t h a t e a c h o r i g i n a l 4 0 0 m l w a t e r s a m p l e w a se x t r a c t e d b y 5 0 m l e th e r w h i c h w a s t h e n c o n c e n t r a t e dt o 1 m l , o f w h i c h 5 # 1 w e r e in j e c t e d o n t o t h e c o l u m n ,t h e n t h e l i m i t s o f d e t e c t i o n w o u l d c o r r e s p o n d t oa b o u t 0 .1 # g 1 ~ o f e a c h a c i d i n t h e o r i g i n a l w a t e r .

T h i r t y - s i x w a t e r e x t r a c t s c o l l e c t e d d u r i n g t h e1 9 7 7 -1 9 7 9 c r o p s p r a y i n g s e a s o n s w e r e a n a l y s e d . T h es a m p l e s w e r e r e ce i ve d f ro m t h e A W A a s m e t h y l a t e de t h e r e x t r a c ts d e r i v e d f r o m 4 0 0 m l w a t e r s a m p l e s a n dw e r e c o n c e n t r a t e d t o 1 m l p r i o r t o a n a l y s i s . 1 o r 5 # 1i n j e c ti o n s o f th e e x t r a c t s w e r e m a d e u n d e r t h e c h r o -

T a b l e 4 . C o n d i t i o n s f o r g a s c h r o m a t o g r a p h y : h e r b i c i d e a n a l y s i sM C P A M e c o p ro p M C P B

4 m p a c k e d c o l u m n : 3% O V - 1 7 o n8 0 - 10 0 m e sh C h r o m o s o r b W - A WO v e n t e m p e r a t u r e 2 0 0 2 0 0 2 0 0I n j e c t o r t e m p e r a t u r e 2 5 0 2 5 0 2 5 0H e c a r r i e r g a s p r e s s u r e ( p s ig ) 2 0 2 0 4 0S e p a r a t o r t e m p e r a t u r e ( C ) 1 8 0 1 8 0 1 80A p p r o x i m a t e r e t e n t i o n t i m e s 8 6 . 5 9( m i n )


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Ga s chromatography in water ana lysis --II 1911C I I . H I 3 . O : 3 . C L M E eO P R OP , M E E S T ER

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~ 214> , i 1 2 5 i 1 5 5" N 5 0 4 7 7 ]~- ' i 8 9 !e -

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51 6 3 ' i i i9 9 i ! i ~ i ~i iC l 2 . H I 5 . 0 3 . C L M C P B , M E E S TE RI0 1I O O i

i 6 9 7 7 i 1 0 7 14 2; 5 1 ~ i 8 9 L , ! . : . i ! i5 o

( B )

( c )

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m / zFig. 6. M ass spectra o f herbicide methyl esters.

m a t o g r a p h i c c o n d i t i o n s u s e d f o r t h e c a l i b r a t i o n( T a b l e 4 ). T h e h e i g h t o f t h e p e a k i n t h e s a m p l e a t t h er e t e n t i o n t im e o f t h e s t a n d a r d w a s t a k e n t o b ei n d i c at i v e o f th e c o n c e n t r a t i o n o f t h e a c i d. T h e p e a kh e i g h t w a s c o n v e r t e d t o w e i g h t o f a c id i n t h e o r i g i n a ls a m p l e b y d i v i d in g b y t h e s l o p e o f t h e c a l i b r a ti o ng r a p h ( m m n g - ~ ) a n d m u l t i p l y i n g b y t h e r a t i o o f

E 2 oEI - - I 0 O1 "(, 9

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0 i ~ / i i i i i i i i i i, o 2 0 3 0 4 o 5 0 6 o r oW E I G H T I N J E C T E D ( r i g )

Fig. 7. GC-MS calibration graphs for herbicide methylesters.

s a m p l e v o l u m e t o v o l u m e i n j e ct e d . R e s u l t s f o r t h r e etyp ica l samples a re g iven in Tab le 5 . In some samplese x a m i n e d f o r M e c o p r o p a n d M C P B i n t h e 1 9 7 8b a t c h , t h e p e a k s h a p e s w e r e n o t s i m p l e b u t a p p e a r e das incomple t e ly re so lved double t s . In t he case o fM C P A , t h e p e a k s h a p e s i n t h e s a m p l e s w e r e g e n e r a ll ys l i g h t l y b r o a d e r t h a n t h o s e i n t h e s t a n d a r d s . I n t h e1979 samples , t he re was aga in ev idence f rom the pea ks h a p e s t h a t s o m e i n t e r f er e n c e w a s t a k i n g p l a c e in t h ed e t e rm i n a t io n o f M e c o p r o p u s i n g m/z 228.Chlorophosphate analysis with flame photometricdetection

T h e P e r k i n - E l m e r f l a m e p h o t o m e t r i c d e t e c t o r w a si n s t a l l e d i n a P e r k i n - E l m e r m o d e l F - 1 7 g a s c h r o -m a t o g r a p h , a n d w a s u s e d i n c o n j u n c t i o n w i t h a nS G E S P 2 2 5 0 g l a s s S C O T c a p i l l a r y c o l u m n a n d a nSGE sp l i t l e ss i n j ec to r . He l ium was employed a sca r r i e r gas .

T h e F P D o p e r a t in g c o n d i t io n s w e r e o p t im i s e d f o rm a x i m u m r e s p o n s e b y in j e c ti n g a s t a n d a r d T r i s -( 2 - c h l o r o e t h y l ) p h o s p h a t e s o l u t i o n u n d e r t h e i s o -t h e r m a l c o n d i t i o n s g i v e n in T a b l e 6 . W i t h t h e h y d r o -g e n f l o w a t t h e o p t i m u m v a l u e o f 1 0 3 m l m i nes t ab l i shed fo r su lphur de t ec t ion , t he oxygen f lowwas va r i ed f rom 4 .6 to 23 .1 ml ra in -~, g iv ing am a x i m u m r e s p o n s e a t 1 5 . 5 m l m i n - 1. U s i n g t h e o p t i -m i s e d o x y g e n f l o w , t h e h y d r o g e n f l o w w a s t h e nv a r ie d f r o m 7 8 to 1 9 4 m l m i n - ~, w it h a m a x i m u mr e s p o n s e a t 1 2 0 m l m i n - L C o m p a r i s o n w i t h e a r l i e rw o r k o n s u l p h u r d e t e c t i o n ( B u r c h i l l et aL, 1982a,b)ind ica t ed tha t s imi l a r f l ame condi t ions a re requ i redf o r d e t e c t i o n o f t h e t w o e l e m e n t s .


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1912 P A U L B U R C H I L L e t a l .T a b l e 5 . H e r b i c i d e c o n c e n t r a t i o n s i n t y p i c a l w a t e r s a m p l e s

H e r b i c i d e c o n c e n t r a t i o n ( # g l - I )M C P A M e c o p ro p M C P BI o n m o n i t o r e d 2 1 4 1 41 2 2 8 1 4 2 1 4 1 1 0 1B a r r o w N o . 3 b o r e 1 0 M a y 7 9 0 .3 0 . 5 1 . 4 0 . 4 < 0 . 2 < 0 . 1S n i t t e r b y C a r r s 1 0 M a y 7 9 0 . 5 0 . 6 3 . 5 0 . 8 0 . 4 0 . 3C a d n e y I n t a k e 1 0 M a y 7 9 0 . 4 0 , 4 3 . 0 0 , 5 0 . 5 0 . 2

S t a n d a r d s o l u t i o n s o f T C E P a n d T C P P i n te t-r a h y d r o f u r a n w e r e p r e p a r e d c o v e r i n g t h e c o n c e n -t r a t i o n r a n g e 0 . 7 - 1 4 0 0 n g k tl - I . 1 . 0 / t l i n je c t io n s o ft h e s t a n d a r d s o l u t i o n s w e r e m a d e u n d e r t h e c h r o -m a t o g r a p h i c c o n d i t i o n s g i v e n i n T a b l e 6 , a n d t h ec a l i b r a t io n g r a p h o f l o g re s p o n s e ( a s d a t a s y s t e m a r e ac o u n t i n / ~ V ) v s l o g w e i g h t o f T C E P i n je c t ed i s s h o w nin Fig . 8 . The s t ra igh t l i ne p lo t wi th a s lope o f 0 .992c o n f i r m s t h e l i n e a r it y o f th e d e t e c t o r r e s p o n s e o v e r3 .5 d e c a d e s o f c o n c e n t r a t i o n .B e t w e e n N o v e m b e r 1 9 79 a n d O c t o b e r 1 98 0 , t h i rt y -s ix wa te r ex t rac t s were ana lysed quan t i t a t i ve ly fo rT C E P a n d T C P P . T h e e x t r a c t s , w h i c h c o n s i s t e dl a r g el y o f T r e n t , T o r k s e y a n d E l s h a m r a w w a t e rs a m p l e s, w e r e s u p p l i e d o r ig i n a l ly b y t h e A W A f o rwa te r p rof i l e ana lys i s , and were de r ived f rom 201 . o fw a t e r e x t r a c t e d w i t h d i c h l o r o m e t h a n e . T h e y w e r em a d e u p t o 0 . 5 m l p r i o r t o a n a l y s is f o r c h l o r o -p h o s p h a t e s .

1 .0 / z l i n j ec t ions o f t he samples were a l t e rna t edw i t h s t a n d a r d T C E P a n d T C P P s o l u t i o n s u n d e r t h ec h r o m a t o g r a p h i c c o n d i t i o n s u s e d f o r t h e c a l i b r a t i o n( T a b l e 6 ) . T y p i c a l c h r o m a t o g r a m s r e c o r d e d u n d e rt h e s e c o n d i t i o n s a r e s h o w n f o r T r e n t , T o r k s e y ( 1 7J a n u a r y 1 9 8 0 ) a n d E l s h a m r a w w a t e r ( 2 J a n u a r y1980) in F ig . 9 (A) and (B) , r e spec t ive ly . Peak a reasw e r e u s e d f o r q u a n t i f ic a t i o n , a n d w e r e m e a s u r e d w i t ha H e w l e t t - P a c k a r d 3 35 3 c h r o m a t o g r a p h y d a t a sy s -t em . T h e c o n c e n t r a t io n s o f T C E P a n d T C P P i nT r e n t , T o r k s e y a n d E l s h a m r a w w a t e r s a m p l e s b e -t w e e n N o v e m b e r 1 9 7 9 a n d O c t o b e r 1 9 8 0 a r e s h o w ng r a p h i c a l l y in F i g . 1 0, t h e p e r i o d s o f T r e n t t r a n s f e ri n t o t h e T W A s y s t e m b e i n g d e m o n s t r a t e d c l e a r l yb y t h e h i g h e r l ev els o f th e s e c o m p o u n d s r e a c h i n gE l s h a m ,

T a b l e 6 . C o n d i t i o n s f o r g a s c h r o m a t o g r a p h y : c h l o r o p h o s p h a t ea n a l y s i sC o l u m n l e n g t h ( m ) 6 7C o l u m n i n t e r n a l d i a m e t e r ( m m ) 0 . 5L i q u i d p h a s e S P - 2 2 5 0Sa m p l e v o l u m e i n j e c t e d ( /z l) 1 .0I n j e c t o r t e m p e r a t u r e ( C ) 3 0 0H e l i u m c a r r i e r g a s p r e s s u r e ( p s i) 2 4H e l i u m c a r r i e r g a s l i n e a r v e l o c i t y ( c m s - ~ ) 4 4 . 7C o l u m n t e m p e r a t u r e ( C ) 2 1 0D e t e c t o r t e m p e r a t u r e ( C ) 2 5 0F P D H 2 p r e s s u r e ( p s i) 5FP D H 2 f l o w ( m l r a i n - ~ ) 1 2 0F P D O : p r e s s u r e ( p si ) 1 7FP D 0 2 f l o w ( m l r a i n ] ) 1 5 .5T i m e t a k e n f o r e l u t i o n o f T C P P ( r a i n )T i m e t a k e n f o r e l u t i o n o f T C E P ( r a i n ) 10 .711.5

The ex t rac t ion e f f i c i enc ie s were de t e rmined bys p i k i n g a w a t e r s a m p l e w i t h t h e c h l o r o p h o s p h a t e s a tc o n c e n t r a t i o n s o f a p p r o x i m a t e l y 3 .5 # g 1 - 1 . T h e r e -cove r i e s were found to be 100 .8 and 100 .0% forT E C P a n d T C P P , r e s p e c t i v e l y , t h u s c o n f i r m i n g t h a te x t r a c t io n o f t h e se c o m p o u n d s f r o m w a t e r w i t h d i-ch lo rome thane i s e ssen t i a l ly quan t i t a t i ve .

D I S C U S S I O NHalo orm analysis

B e t w e e n F e b r u a r y a n d A u g u s t 1 9 7 9 1 2 6 s a m p l e sf rom the E l sham p lan t and the re fe rence s i t e s a tB r a m p t o n a n d A r d l e i g h w e r e r e c e i v e d a s p e n t a n ee x t r a c t s a n d a n a l y s e d b y G C / E C D f o r t h e f o u rh a l o f o r m s . T h e s a m p l e s i n c l u d e d r a w a n d t r e a t e dwa te r s , and d i s t i l l ed wa te r and pen tane b l anks . Ther a n g e o f c o n c e n t r a t i o n l e ve ls f o u n d f o r e a c h h a l o -fo rm a re g iven in Tab le 3 . The ha lo form l eve l s i n t het rea t ed samples a re i n most ca ses a t l ea s t an o rde r o fm a g n i t u d e h i g h e r t h a n i n t h e r a w w a t e r .

The re su l t s a l so show tha t unexpec ted ly h igh l eve l so f b r o m i n a t e d c o m p o u n d s a r e o f t e n p re s en t . T h eo c c u r r e n c e o f th e s e b r o m i n a t e d d e r i v at iv e s i s c o n s i d -e red by Rook (1974) to a r i se e i the r f rom the p re sence

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F ig . 9. G C /F P D ch ro m ato g ram s o f tw o r aw w a te r ex t rac t s ; (A ) T ren t , T o rk sey , 1 7 Jan u a ry 1 9 80 ; (B )E l sh am raw w a te r , 2 J an u a ry 1 9 8 0 . C h ro m ato g rap h ic co n d i t i o n s g iv en in T ab le 6 . P eak id ent it ie s :I - - T C P P ; 2 - - T C E P 3 - - N - ( n - b u t y l ) b e n ze n e s u l ph o n a m i de .

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10/12

1914 PAUL BURCHILLet al.o f b r o m i d e s i n th e w a t e r o r f r o m b r o m i n e i m p u r i t yi n t h e c h l o ri n e . T h e c h l o r i n a t i o n o f w a t e r a t t h et r e a t m e n t w o r k s p r o d u c e s h y p o c h l o r o u s a c i d a n dc o m p a r a t i v e l y sm a l l a m o u n t s o f h y p o b r o m o u s a c i d .H o w e v e r , t h e r e a c t iv i t y o f h y p o b r o m o u s a c i d isr e l a t iv e l y m u c h g r e a t e r t h a n h y p o c h l o r o u s a c i d a n di t w i l l r e a c t m o r e r a p i d l y w i t h o r g a n i c m a t e r i a lp r e s e n t t o f o r m b r o m i n a t e d h a l o f o r m s .

T h e d e t e c t i o n l i m i t s g i v e n i n T a b l e 2 h a v e b e e nc a l c u l a t e d o n t h e b a s i s o f a s i g n a l : n o i s e ra t i o o f 2 : 1a n d i n d i c a t e t h a t a b s o l u t e q u a n t i t i e s a s l o w a s 1 0 ,2 gm a y b e d e t e c t e d , c o r r e s p o n d i n g t o a c o n c e n t r a t i o n o f1 /~ g 1 ~ n t h e w a t e r s a m p l e s , a s s u m i n g a 1 1 e x t r a c -t i o n r a t i o a n d a 1 p l i n j e c t i o n . T h e s e n s i t i v i t y o f t h em e t h o d m a y b e f u r t h e r i n c r e a s e d b y t h e u s e o f h i g h e re x t r a c t i o n r a t i o s a n d l a r g e r i n j e c t i o n v o l u m e s .

T h e v e r y l o w d e t e c t i o n l i m i t s e m p h a s i s e t h e n e e d t oa v o i d c o n t a m i n a t i o n o f t h e s a m p l es a n d s t a n d a r ds o l u t i o n s . I n t e r f e r e n c e is m o s t l i k e l y t o a r i s e f r o mh a l o g e n a t e d h y d r o c a r b o n s w h i c h m u s t , t h e r e f o r e , b er i g o r o u s ly e x c lu d e d f r o m t h e l a b o r a t o r y e n v i r o n -m e n t .

T h e s a m p l e s w e r e t r a n s p o r t e d a n d s t o r e d i n g l a s sP T F E - f a c e d s e p t u m c a p p h i a l s . H a l o f o r m s o l u t i o n sa r e p a r t i c u l a r l y s u s c e p t ib l e to p h o t o c h e m i c a l r e a c -t i o n s a n d s h o u l d b e s t o r e d i n t h e d a r k . M i l d r e f r i g -e r a t i o n ( 0 - 5 C ) i s d e s i r a b l e f o r lo n g t e r m s t o r a g e , b u td e e p f r e e z in g o f a q u e o u s s a m p l e s s h o u l d b e a v o i d e dt o p r e v e n t b r e a k a g e s o n t h a w i n g . R e p e a t e d a n a l y s i so f a d e c h l o r i n a t e d s a m p l e s to r e d u n d e r t h e s e c o n d i -t i o n s sh o w e d n o s i g n i f i c a n t c h a n g e i n h a l o f o r m c o n -c e n t r a t i o n s o v e r a p e r i o d o f n e a r l y 3 m o n t h s .Herbicide analysis

A l t h o u g h t h e s i n g l e i o n m o n i t o r i n g t e c h n i q u e i sp o t e n t i a l l y v e r y s e n s i t i v e a n d s p e c i f i c , t h e r e s u l t sr e v e a l e d s o m e i n c o n s i s t e n c i e s . I n p a r t i c u l a r , t h e r e -s u l t s f o r M e c o p r o p d i s p l a y s i g n i f i c a n t v a r i a t i o na m o n g t h e m s e l v e s . H o w e v e r , t h o s e f o r M C P A ( m / z2 1 4 a n d 1 4 1 ) a r e i n b e t t e r a g r e e m e n t .S o m e o f t h e p e a k s h a p e s w e r e i r r e g u l a r a n d o c c a -s i o n a l l y e x t r a p e a k s a p p e a r e d . T h o s e o b t a i n e d f o rM e c o p r o p a n d M C P A a t m /z 1 4 1 g a v e r e a s o n a b l ys h a p e d p e a k s w i t h n o e v i d e n c e f o r u n r e s o l v e d c o m -p o n e n t s . T h e t w o e s t e r s a r e c h r o m a t o g r a p h i c a l l yr e s o l v e d f r o m e a c h o t h e r b u t n o i s e l e v e l s a r e c o m -p a r a b l e t o t h e M e c o p r o p p e a k h e i g h ts o n s o m e o f t h es a m p l e s . T h e i o n m /z 2 1 4 u s e d t o e s t i m a t e t h e M C P Ae s t e r a l s o g a v e n o o b v i o u s i n d i c a t i o n t h a t p a r t i a l l yr e s o l v e d c o m p o n e n t s w e r e p r e s e n t i n t h e s a m p l e s ,a l t h o u g h t h e l a rg e s t p e a k h e i g h t s o b s e r v e d w e r e o n l yt w o o r t h r e e t i m e s t h e n o i s e le v e ls . H o w e v e r , t w o o ft h e io n s u s e d to e s t i m a t e M e c o p r o p , m /z 142 an d m / z2 2 8 , d i d s h o w e v i d e n c e t h a t o t h e r c o m p o n e n t s w e r eo n l y p a r t i a l l y r es o l v e d f r o m t h e h e r b i c i d e p e a k a n dm o s t p r o b a b l y i n t e r f e r e d w i t h t h e e s t i m a t i o n . T h e i o nm / z 101 s e l e c te d f o r e s t i m a t i o n o f M C P B w a s t h eo n l y o n e o f s u i t a b l e in t e n s i ty . P e a k s h a p e s o f s t a n -d a r d s o l u t i o n s w e r e g o o d , b u t t h e p e a k h e i g h t sd e t e c t e d i n t h e s a m p l e s w e r e o f a s i m i l a r m a g n i t u d e

t o t h e n o i s e l e v e l s a n d t h e a c c u r a c y o f h e r b i c i d em e a s u r e m e n t s i s o b v i o u s l y l i m i te d a t t h e s e l o w l e ve l so f c o n c e n t r a t i o n . L i t t l e e v i d e n c e w a s f o u n d t o i n d i -c a t e th e p r e s en c e o f p e a k s o t h e r t h a n t h a t f o r M C P Bw h i c h c o u l d i n t e r f e r e w i t h t h e d e t e r m i n a t i o n .

T h e s i n g l e i o n m o n i t o r i n g m e t h o d w i ll r e s p o n d t oa n y i o n i c s p e c ie s o f w h i c h t h e g a u s s i a n - s h a p e d m a s ss p e c t r a l p e a k o v e r l a p s t h e n a r r o w m a s s r a n g e " w i n -d o w " s e t f o r t h e s p ec i fi c h e r b i c i d e p e a k , t h e w i n d o ww i d t h b e i n g a f u n c t i o n o f s li t w i d t h s a n d r e l a t e d tor e s o l u t io n . S i n ce t h e m a s s s p e c t r o m e t r i c r e s o l u t i o n i s1 0 00 , t h e e f f ec t i v e w i n d o w w i d t h s f o r e a c h a c i d e s t e ra r e a p p r o x i m a t e l y a s f o l lo w s : M C P A 2 1 4 .0 3 9 6 +0 . 10 7 m a s s u n i t s , M e c o p r o p 2 2 8 .0 5 5 2 _+ 0 . 1 1 4 m a s sun i t s and M CP B 101 .0602 _+ 0 .051 m ass un i t s . W hi lem a n y m o l e c u l a r a n d f r a g m e n t i o n s c a n b e l i s t e d f o re a c h o f t h e m a s s r a n g e s o f t h e i o n s w h i c h h a v e b e e nm o n i t o r e d , t h e l i k e l i h o o d o f su c h m o l e c u l es b e i n gp r e s e n t i n a r a w w a t e r s a m p l e a n d t h e i r c h r o -m a t o g r a p h i c p r o p e r t i e s a r e g e n e r a l l y u n k n o w n .H o w e v e r , o n e cl a ss o f c o m p o u n d w h i c h i s k n o w n t ob e p r e s e n t i n r a w w a t e r a n d w h i c h w o u l d r e a d i l ym e t h y l a t e t o g i v e s p e c i e s w i t h s a t i s f a c t o r y c h r o -m a t o g r a p h i c p e r f o r m a n c e a n d s i m i l a r r e t e n t i o n t im e st o t h e h e r b i c i d e a c i d e s t e r s is t h e f a t t y a c i d s . T h u s t h em o l e c u l a r i o n s f r o m t h e m e t h y l e s t e r s o f t h e C ~ 2 a n dC13 f a t t y a c i d s c o u l d i n t e r f e r e w i t h rn/z 2 1 4 a n d m / z228 re spec t ive ly .

H e r b i c i d e c o n c e n t r a t i o n s , d e t e rm i n e d f r o m c h r o -m a t o g r a m s w h e r e a n i o n w h i c h s u f f e r s f r o m i n t e r -f e r e n c e is m o n i t o r e d , a r e l i k e l y t o b e o v e r e s t i m a t e s .F o r a h e r b i c i d e w h e r e s e v e ra l i o n s h a v e b e e n m o n -i t o r e d , t h e p e a k g i v i n g t h e l o w e s t r e s u l t w i l l s u f f e rf r o m t h e l e a s t i n t e r f e r e n c e a n d c o n s e q u e n t l y s h o u l dg i v e t h e m o s t a c c u r a t e c o n c e n t r a t i o n . H o w e v e r , t h ep r e s e n c e o f a s i n g le c h r o m a t o g r a p h i c p e a k d o e s n o tp r e c l u d e t h e p o s s i b i l i ty o f i n t e r f e re n c e b y a n i o n f r o ma c o m p o n e n t w i t h i d e n t ic a l e l u t i o n t im e .

T h e p r o b l e m s e n c o u n t e r e d i n t h e m e a s u r e m e n t o ft h e h e r b i c i d e s a r e e x a c e r b a t e d b y t h e i r e x t r e m e s o fd i l u t i o n a n d t h e p r e s e n c e o f i n t e rf e r i n g i o n s. T h em e t h o d c o u l d b e i m p r o v e d b y u s e o f h i g h e r e f fi c ie n c yc h r o m a t o g r a p h i c c o l u m n s a n d b y u s i n g a m a s s s p e c -t r o m e t e r w i t h h i g h e r r e s o l u t i o n a n d h i g h e r s e n s i -t i v i t y . D u e t o i n t e r f e r e n c e , i t i s a d v i s a b l e t o m o n i t o rm o r e t h a n o n e i o n i f p o s s i b le .Chlorophosphate analysis

T h e c a l i b r a t i o n g r a p h ( F i g . 8 ) sh o w s t h a t a l i n e a rr e l a t i o n s h i p b e t w e e n r e s p o n s e a n d t h e w e i g h t o fc o m p o n e n t i n j e c te d is o b t a i n e d f o r p h o s p h o r u s c o m -p o u n d s o v e r a c o n c e n t r a t i o n r a n g e o f a t l e a st 3. 5d e c a d e s . T h i s l i n e a r r a n g e a p p r o a c h e s t h a t o f t h ef l a m e i o n i s a t i o n d e t e c t o r , a n d t h e u s e o f i n t e r n a ls t a n d a r d t e c h n i q u e s w o u l d b e p o s si b l e , a l t h o u g h t h e yw e r e n o t a t t e m p t e d i n t h e p r e s e n t w o r k . T h e l i n e a r i tyo f t h e d e t e c t o r f o r p h o s p h o r u s i s i n m a r k e d c o n t r a s tt o t h a t f o r s u l p h u r d e t e c t i o n . F o r s u l p h u r , t h e r e -s p o n s e i s n o r m a l l y r o u g h l y p r o p o r t i o n a l t o t h es q u a re o f t h e c o n c e n t ra t i o n o f s u l p h u r c o m p o u n d s ,


11/12

Gas chrom atography in wa te r ana ly s i s - - I f 1915b u t r e s p o n s e c h a r a c t e r i s t i c s i n t e r m e d i a t e b e t w e e n al i n e a r a n d a s q u a r e l a w r e l a t i o n s h i p h a v e b e e n r e -p o r t e d f o r s o m e c o m p o u n d s b y S e v c i k ( 1 97 6 ). H o w -e v e r , d e t e c t o r d r i f t d u e t o f l u c t u a t i n g l ev e l s o f s t r a yl i g h t w a s f o u n d t o b e m o r e o f a p r o b l e m i n t h ep h o s p h o r u s m o d e t h a n f o r su l p h u r d e t e c ti o n , po s s i-b l y d u e t o t h e d i f f e r e n t w a v e l e n g t h b e i n g m o n i t o r e db y t h e d e t e c t o r . T h i s p r o b l e m w a s o v e r c o m e b ys h i e ld i n g t h e d e t e c t o r h o u s i n g .

A s s u m i n g t h a t t h e m i n i m u m d e t e c t i o n li m i t i sr e p r es e n t ed b y a p e a k h e i g h t o f 5 m m a t m a x i m u md e t e c t o r s e n s i ti v i ty , a v a l u e o f 0 . 1 0 n g h a s b e e nc a l c u l a t e d f o r T C E P . S i n c e th e e l e c t r o n i c n o i se l ev e lo f t h e d e t e c t o r is v e r y l o w , < 1 X F S D w h e n u n -a t t e n u a t e d , a n d l o n g - t e r m d r i f t i s n o t e x c e s s iv e , p a r -t i c u l a r l y u n d e r i s o t h e r m a l c o n d i t i o n s , i t s h o u l d b ep o s s i b l e to r e a l is e th i s l i m it . T h e m i n i m u m d e t e c t i o nl i m i t c o r r e s p o n d s t o a l e ve l o f 0 . 0 0 2 # g 1 ~ i n t h eo r i g i n a l w a t e r , a s s u m i n g a s a m p l e v o l u m e o f 2 0 1. a n da c o n c e n t r a t e d e x t r a c t v o l u m e o f 5 0 0/ ~ I, 1 .0 p l i n j e c -t i o n s b e i n g u s e d .

I n t e r f e r e n c e f r o m h y d r o c a r b o n s i n t h e d e t e c t i o n o fp h o s p h o r u s c o m p o u n d s a p p e a r s t o b e m i n i m a l , a n dt h e m a s s i v e s o l v e n t p e a k w h i c h c h a r a c t e r i s e s a l l t h eG C / F I D w a t e r p r of i le s i s a b s e n t in t h e G C / F P Dc h r o m a t o g ra m s . H o w e v e r , th e G C / F P D c h r o m a t o -g r a m o f E l s h a m r a w w a t e r , s h o w n i n F i g . 9 ( B ),c o n t a i n s a l a r g e p e a k e l u t e d a f t e r a p p r o x . 1 2 .5 r a i n ,w h i c h w a s n o t o b s e r v e d i n t h e o t h e r s a m p l e s f r o m t h es a m e s o u r c e a n a l y s e d f o r c h l o r o p h o s p h a t e s . I t ist h o u g h t t h a t t h i s m a y b e d u e t o N - ( n - b u t y l ) b e n z e n e -s u l p h o n a m i d e , w h i c h w a s i d e n ti f ie d b y G C - M S a s am a j o r c o m p o n e n t o f t h e s a m p l e . T h e p o s s i b i l it y o fi n t e r f e r e n c e f r o m h i g h l e v e l s o f s u l p h u r - c o n t a i n i n gc o m p o n e n t s i n t h e s e l e ct i ve d e t e r m i n a t i o n o f p h o s -p h o r u s c o m p o u n d s m u s t , t h e r e f o r e , b e c o n s i d e r e d .N a t u s c h a n d T h o r p e ( 1 9 7 3 ) h a v e s u g g e s t e d t h a t t h i si n t e r f e re n c e m a y a r i s e f r o m a n o v e r l a p o f t h e H P Oa n d $2 s p e c t r a l b a n d s w i t h i n t h e b a n d p a s s o f t h eo p t i c a l f il te r e m p l o y e d . U n f o r t u n a t e l y , a p u r e s a m p l eo f N - ( n - b u t y l ) b e n z e n e s u l p h o n a m i d e w a s n o t a v a i l -a b l e , b u t t h e s e l e c t i v it y o f t h e p h o s p h o r u s d e t e c t i o nw a s c h e c k e d u s i n g d i b e n z o t h i o p h e n e a t 1 00 n g p l - ~.I t w a s f o u n d t h a t t h e p h o s p h o r u s / s u l p h u r a t o m i cr e s p o n s e r a t i o w a s 1 3.2 w h e n t h e d e t e c t o r w a s o p e r -a t e d f o r m e a s u r i n g p h o s p h o r u s . I t m u s t b e c o n c l u d e dt h a t i n t e r f e r e n c e f ro m h i g h l e v el s o f s u l p h u r c o m -p o u n d s m a y b e a p r o b l e m i n t h e s el e c ti v e d e t e c t i o no f p h o s p h o r u s c o m p o u n d s . H o w e v e r , a s i n t h ep r e s e n t c a s e , t h e u s e o f h i g h e f f ic i e n c y c a p i l l a r yc o l u m n s s h o u l d g e n e r a l l y a l l o w c o m p l e t e s e p a r a t i o no f t h e c o m p o u n d o f i n te r e s t fr o m t h e i n t e r fe r i n gc o m p o n e n t . I t s h o u l d b e n o t e d t h a t c o m p a r a t i v e l yf ew s u l p h u r c o m p o u n d s h a v e b e e n i d e n t if i e d i n t h ew a t e r s a m p l e s a n a l y s e d d u r i n g t h e T W A p r o j e c t .

GENERAL CONCLUSIONST h r e e s e l e c t iv e d e t e c t o r s h a v e b e e n u s e d s u c c e s s -f u l l y f o r t h e a n a l y s i s o f w a t e r e x t r a c t s b y g a s c h r o -

m a t o g r a p h y , T h e q u a n t i t a t iv e p e r f o r m a n c e o f e a cho f t h e d e t e c t o r s w a s s a t i s f a c t o r y i n t e r m s o f d e t e c t i o nl i m i t s a n d l i n e a r c a l i b r a t i o n r a n g e s . T h e s e l e c t i v ed e t e c t i o n m e t h o d s w e r e a l l s i g n i fi c a n t ly m o r e s e n si -t i v e f o r t h e c o m p o u n d s d e t e r m i n e d t h a n t h eG L C - F I D p r o c e d u r e u se d f o r tr a c e o r g a n ic s a na l y si s( P a r t I , B u r c h i l l e t a l . , 1 9 8 3 ) , a n d i n s o m e c a s e sf u r t h e r i m p r o v e m e n t s i n s e n s i t i v it y c o u l d b ea c h i e v e d . T h e d e g r e e o f s e l e c t i v it y o f e a c h o f t h ed e t e c t o r s i s h i g h , a n d t h e r e q u i r e d c o m p o u n d s c a nn o r m a l l y b e a n a l y s e d w i t h m i n i m a l i n te r f e r e n c e fr o mo t h e r c o m p o n e n t s . N e v e r t h e le s s , in s o m e c a s e s i n t e r-f e r en c e i n t h e d e t e r m i n a t i o n w a s o b s e r v e d , a n d w a y so f m i n i m i s i n g t h i s h a v e b e e n d i s c u ss e d . T h e v e r y l o wd e t e c t i o n l i m i t s w h i c h a r e a c h i e v a b l e w i t h s e l e c t i v ed e t e c t o r s r e n d e r t h e s a m p l e s a n d s t a n d a r d s s u s -c e p t i b l e t o c o n t a m i n a t i o n , a n d p a r t i c u l a r a t t e n t i o nn e e d s t o b e p a i d t o t h e q u a l i t y o f t h e s o l v e n t s u s e df o r t h e w a t e r e x t r a c t i o n s a n d t o t h e g e n e r a l l a b o r a -t o r y e n v i r o n m e n t .

A c k n o w l e d g e m e n t s - - D u r i n g the course of this work helpfuldiscussions were held with staff from the W ater ResearchCentre lab oratories a t Medmenham and Stevenage, and theSeve rn-Tren t W ate r Author i ty l abora to ry a t F inham . The i radvice and co-ope rat ion is gra teful ly acknowledged. W e arealso indebted to the Agrochemical Division of Fisons Ltd,Cambridge, for the gif t of herbicide s tandards , an d to theSeve rn-Tren t Wate r Author i ty fo r the g i f t o f ch lo ro -phosphate es ters . The authors a lso wish to thank theAngl ian Wate r Au thor i ty and the Na t iona l Coa l Board fo rpermission to p ublish this paper ; the view s expressed aretheir own and not necessari ly those of the Board.REFERENCES

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1983, gas chromatography in water analysis--ii

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