Fully automated system for the continuous monitoring of ammonium ion in fish farming plant sea water by flow-injection analysis

345

Analytrca Chunxa Acta, 261(1992) 345-349

Elsevier Saence Pubhshers B V , Amsterdam

Fully automated system for the continuous monitoring of ammonium ion in fish farming plant sea water by flow-injection analysis Hldelu Murals * Sanukr Industry Co, Ltd, 3-4-13

Muiongaoka, Hamura-macht,

Nrrhrtama-gun, Tokyo MI-11 (Japan)

Kelro Hlguchl Tokyo Kaset Kogyo Co, Ltd, 6-15-9

Toshlma, kIta-ku, Tokyo 114 (Japan)

Masanorl Sasalu Kelyu Industry Co, Ltd, 992-l

Takada, Kashlwa-shr, Chlba 277 (Japan)

Takashl Korenaga Centre for Envrronmental Scrence and Technology, Okayama Unruersrty, 3-l-l

Txushrmanaka, Okayama 700 (Japan)

KYOJIThei Faculty of Liberal Arts and Scrence, Okayama Umversr@ of Scrence, Rtdatcho, Okayama 7W (Japan)

(Recewed 12th September 1991)

An automated system for the contmuous momtormg of ammonmm eon m fish farming plant sea water IS described The sample IS Introduced mto a carrier stream by an automated sample Injector and merged with a reagent solution contammg sochum sahcylate and sodium mtroprusslde The sample stream IS then muted with a second reagent solution contammg sodium hypochlorlte and heated at 50°C The absorbance of the resultmg solution IS momtored at 660 nm The cahbratlon graph was lmear up to at least 3 0 mg 1-l NH:-N The relative standard devlatlon for 20 mjectlons of samples contammg 1 0 mg 1-I NH:-N was 0 35% The interference from Ca*+ and Mg*+ was masked with potassmm sochum tartrate The Interference due to ammo aads and protems present m fish foods and wastes was ehrtunated by adlustmg the pH to 6-7 when the sample merged wth the tirst reagent solution Keywords

Flow system, Spectrophotometry, Ammomum, Fish farmmg, Sea water, Waters

The development of fish cultwatlon plants m recent years has let to the need for a fully automated system to monitor and control the breedmg environment Ammomum Ion 1s one of the most unportant parameters controllmg the optlmum condltlons m fish farming plants However, no fully automated continuous momtormg system has been built for the determmatlon of various

controllable components m sea-water samples In this paper, a contmuous momtormg system for ammonium ion usmg flow-inJectIon analysis (FIA) 1s reported Several methods for the determmatlon of ammonium Ion by FIA have been proposed, based on Nessler’s reagent [l], phenol-hypochlorlte reactlon [2], spectrofluorometry using derlvatlzatlon

0003-2670/92/$05 00 0 1992 - Elsevier Science Pubhshers B V All rights reserved

H Murakr et al /Anal Chun Acta 261 (1992) 345-349

346

with o-phthalaldehyde [3,4] and spectrophotometry with a gas-dlffusron unit using a microporous PTFE membrane [5,6] However, these methods require the use of mercury, dlstdlatlon or a fluorescence detector The method mvolvmg spectrophotometry wth a gas-dlffuslon unit is unsuitable for a continuous momtormg system because of the maintenance requnements We therefore studied the development of a system that does not require a condensation process and provides simple and maintenance-free operation with highly accurate measurement results The spectrophotometrx method usmg sodium sahcylate-hypochlorlte 1s better than that wth phenol-hypochlonte because of the mstablhty of the latter reagent, it 1s also very sensitive In this study, the sodium sahcylate-hypochlorlte reaction was employed and equipment was designed for the maintenance-free, fully automated measurement of ammomum ion m fish farming plant sea water

EXPERIMENTAL

metric detector (Model S-3250) The reaction cod and flow system consisted of 1 mm 1 d tubes and parts to prevent blockmg of the FIA system durmg long periods of momtormg [7] Reagents

All reagents were of analytlcal-reagent grade Carrzer dutwn Sodmm chloride (35 g) was dissolved m 1 1 of dlstdled water This solution has the same specific gravity as sea water Reagent solutwn Z Sodium sahcylate (200 g) and potassmm sodium tartrate (38 g) were each dissolved m 1 1 of distilled water Reagent solution I was prepared by mnnng equal volumes of the two solitions Just before use Reagent solutwn ZZ Sodmm hypochlorlte solution (10 ml) (containing 6% of active chlorme) was diluted to 1 1 with 0 5 M sodium hydroxide solution Standard solutwn A stock solution containing 1000 mg 1-l NH:-N was prepared by dlssolvmg 3 8189 g of ammomum chloride m 1 1 of artlflcal sea water Workmg standard solutions were prepared by dllutlon with artlflcal sea water as required

Apparatus

A flow diagram of the experimental FIA system 1s shown Fig 1 The system was mamly composed of a Sanuk~ FIA reactor (Model FI30001, a Sanulu double-plunger pump (Model DMX-23OOT) and a Soma Kogaku spectrophoto-

A

RESULTS

AND DISCUSSION

Effect of concentratwn of reagent The effect of the concentration of sodium sah-

cylate m reagent solution I from 67 to 300 g 1-l

s

PI

CS

RC

8O.C

SP

P2 RS2

Fig 1 Schematic diagram of the flow system CS, carrier solution (dlstdled water), RSl, sodmm sahcylate-sodmm mtroprusslde solution, RS2, sodmm hypochlorlte, Pl, double-plunger pump (flow-rate 0 7 ml nun-‘), P2, double-plunger pump (flow-rate 0 5 ml mm -l), S, Sample Injector (200 PI), RC, reaction cod (2 m X 1 mm I d ), SP, spectrophotometer (660 run), R, recorder, W, waste

347

H Murakt et al /AnaL Chm Acta 261 (1992) 345-349

was examined The peak height increased linearly with mcreasmg concentration up to 150 g l-l, then decreased A concentration of sodium sahcylate of 200 g 1-l was chosen

c

Effect of reactwn cod length The reaction co11length vvlth a 1 mm I d tube

was varied from 1 to 5 rn A length of 2 m gave the maximum peak height and was therefore chosen Effect of reaction temperature The effect of temperature m sodium sahcy-

late-hypochlonte reactlon was examined m the range 30-100°C The peak height increased up to SO’C, then decreased A reaction temperature of 80°C was therefore adopted Effect of jlow-rate The flow-rate of reagent solution II was varied

from 0 2 to 0 7 ml mm-’ with the flow-rates of both carrier and reagent solution I fnced at 0 7 ml mm -I The peak height decreased with mcreasmg flow-rate From conslderatlon of the stablhty of the pumps and the analytlcal speed, the flowrate of reagent solutlon II was adjusted to 0 5 ml mm-’ Cabbratzon graph for ammomum wn

Figure 2 mdlcates that the flow signals for ammonium ion show good reproduclblhty under the above optmuzed condltlons The cahbratlon graph was linear up to 3 0 mg I-’ NH:-N The relative standard deviation for 20 mJectlons of samples containing 10 mg l- ’ NH:-N was 0 35% Effect of dzverse lolls

The Interferences due to various ions at concentratlons usually found m sea water were exammed The concentrations of Ions that did not interfere m the determmatlon of 10 pg ml-’ NH: -N were Ca’++ sodmm sahcylate, Mg2+ + sodmm sahcylate, NO;, SOi- and H,POz- 10m2 M and Fe3+ and HCO; 10m3 M Na+ and Cldid not mterfere when 3 5% sodium chloride was added to the carrier solution Ca’+ and Mg2+ caused negative errors, but the mterference was masked with potassmm sodmm tartrate

FIE 2 Flow signals for standard solution of ammoniacal nitrogen NH:-N (mg I-*) (A) 0, ( B) 0 5, (0 10, (D) 15, (E)2O,(F)25,(G)30

Determtnatlon of ammonium ton tn fish farmmg plant water

Figure 3 shows the flow diagram of the system An automated sample m]ector, conslstmg of a Sanulu automatic sample exchange valve (Model SVA-4M2R), an automated samphng valve (Model SVA-6M2H), a single-plunger pump (Model lP3M-9054) and a sequencer (Sanulu Industry), was used for automated water samphng The reactor was mamtamed at 50°C to prevent Interference due to the side-reactions between ammo acrds and the chromogenic reagent

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H Murakt et al /Anal

Chtm Acta 261 (1992) 345-349

P3

I I

0.751l/rin

-

RB(SO'C)

I I

cs RSt RC

SP

Fig 3 Schemattc dtagram of automated contmuous momtormg system for ammomum ton m fish famung plant sea water Sl-S4, water tangs, SV, selector valve, CS, carrier solution (3 5% NaCl solution), RSl, sodmm sahcylate-sodmm mtroprusstde-potassmm sodium tartrate, Pl,P2, double-plunger pumps, P3, single-plunger pump, RC, reaction cot1 (2 m X 1 mm 1d 1, SP, spectrophotometer

Some preclpltatlon was observed during the reaction of the chromogenic reagent wth sea water contaming proteins and ammo acids ongl-

natmg from fish foods and wastes An amon-exchange resm column has been used to prevent interference from ammo acids, etc [31, but this

Fig 4 Representattve examples of contmuous momtonng of ammoniacal mtrogen (a) 10 mg 1-l NH: (b-d) fish farming sea water

m artrfictal sea water,

H Murakr et aL/Anal Chm Acta 261 (1992) 345-349

method IS not suitable for long periods of momtormg The effect of pH m causmg the preapltatron was exammed by using real fish farming sea water and it was found that precipitates were formed whenever the pH rose to lo-11 In the proposed system, therefore, poor to merging with reagent solution I adJustment of the pH to 6-7 was necessary Four different samples were consecutively mtraduced mto the earner stream of the FIA system Figure 4 shows the flow signals for the continuous monitoring of ammonium nitrogen in fish farming plant water

349

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