MULTI PHYSICAL-CHEMICAL PROFILER FOR REAL-TIME CONTINUOUS IN SITU MONITORING

MULTI PHYSICAL-CHEMICAL PROFILER FOR REAL-TIME CONTINUOUS IN SITU MONITORING OF SPECIFIC FRACTIONS OF TRACE METALS AND MASTER VARIABLES

Marylou Tercier-Waeber1, Fabio Confalonieri2, Giuliano Riccardi2, Antonio Sina2, Flavio Graziottin2, Jacques Buffle1

1Dept. of Inorganic and Analytical Chemistry, University of Geneva, 30 Quai E. Ansermet, 1211 Geneva 4, Switzerland.2Idronaut Srl, Via Monte Amiata 10, Brugherio (MI), Italy.

IDRONAUT

CHIMIE ANALYTIQUE ET BIOPHYSICOCHIMIE

DE

L’E

NV

IRO

NN

EM

ENT

MULTI PHYSICAL-CHEMICAL PROFILER MAIN COMPONENTS

Schematic diagram of the gel-integrated microsensors

AC

ID

LIGA

ND

Mixing coil(V = 4.5 ml)

Heating coil( V = 4.5 ml)

Cooling coil(V = 4.5 ml/min)

To VIP cell

Raw Arve sample 2.3 ml/min

150 µM TRIEN 2.3 ml/min

0.03 M HNO3

2.3 ml/min

Sample + L eq. t = 5 min; T = 20°C

Sample + L + Acid eq. t = 5 min; Tf = 22°C

Sample + L + Acid eq. t = 5 min; T = 60°C

Schematic diagram of the submersible FIA and example of analytical conditions used for measurements of total extractable metal concentrations in Arve river samples.

Schematic diagram of the MPCP harware

The MPCP probe harware and firmware have been developed to allow simultaneous measurement cycles on the three channels.

Integrated multiparameter probe

MPCP management software

Agarose gelMercury layer

Si3N4

IrSi3N4

Silicon 5 µm

Mercury layer

Ir

Silicon

Agarose gel

Chelating resin

5 µm

Si3N4

Si3N4

100-interconnectedIr-microdisk electrode array

Al or Au bonding

4 m

m

1.8 mm

electrical contact epoxy resin

containment ring

150 µm

GIME (MPCP cells 1 and 3)

CGIME(MPCP cell 2)

0

20

40

60

80

100

Cu/Cutot Pb/Pbtot

4.12.2001

pH 2, 15 min FIA, 15 min pH 2, 62 h

Ratios of total extractable Me conc. (voltammetry) to total Me conc. (ICP-MS ) obtained in an Arve river sample after sample pre-treatments based on: i) acidification and ii) ligand exchange followed by acidification and heating of the sample.

Cell-1GIME

Cell-2CGIME

Cell-3FIA-GIME

Submarine connectors for:Telemetry, Serial interface,FIA, Fluorescence probe

Main CPU boardFSK telemetry boardFluidic & FIA device drive board

Smart potentiostat boards

Mother board & Power supply

Mechanical & signal connectors

VIP cell

Preamplifier

Multiparameter probe board

Incorporation of the MPCP voltammetric probe with external/integrated probes for measurements of master variables into a buoy supported automated monitoring system which can be controlled from a land station.

for simultaneous in situ measurements of the above three specific fractions of trace metals Development of an improved VIP voltammetric probe based on 3 flow-through cells and three individual potentiostats (MPCP voltammetric probe) Development of a submersible FIA system coupled to one cell for in situ measurements of total extractable metal concentrationsDevelopment of a novel chelating resin-gel integrated microsensor (CGIME) for in situ measurements of free metal ion concentrations

The following analytical and technical developments are under way to improve the capability of the VIP probe: .

Land Station

Buoy Profiler Labile (M -L)

Free (M z+ )

Colloids Particles/Aggregates

CoagulationM icrobial activity

Shear stressM icrobial activity

Sedim entation

DYNAM IC – MSPECIES

COLLO IDAL – MSPECIES

PARTICULATE -MSPECIES

4 nm 0.2 µm/(0.45 µm )

MICROO RGANISM

M ads

Diffusion

Labile (M -L)

Free (M z+ )

Colloids Particles/Aggregates

CoagulationM icrobial activity

Shear stressM icrobial activity

Sedim entation

DYNAM IC – MSPECIES

COLLO IDAL – MSPECIES

PARTICULATE -MSPECIES

4 nm 0.2 µm/(0.45 µm )

MICROO RGANISM

M ads

Diffusion

INTRODUCTIONDevelopment of novel analytical tools allowing real-time and detailed temporal/spatial evolution monitoring of the distribution of specific metal species and master variables is of prime interest. They will enable us to better understand the role and the fate of trace metals in aquatic systems, to develop more accurate predictive models based on biogeochemical processes, to evaluate the impact of human activity on coastal ecosystems and therefore to optimize industrial/social developments. With these goals in mind, we recently started the development of an automated Multi Chemical-Physical Profiler (MPCP). The MPCP is based on the Voltammetric In situ Profiling System (VIP System), which was developed during an European MAST-III project and is now commercialised by Idronaut. The VIP probe is based on a gel integrated microelectrode (GIME) which allows the specific measurement of the concentration of the dynamic fraction of trace metals, defined as the sum of the free metal ions and the small labile complexes with size of few nanometers.

PRELIMINARY FIELD TESTS OF THE MPCP

Measurements of trace metal speciation and master variables in Gullmarsfjorden

0

2

4

6

8

10

12

14

Con

cent

ratio

n (n

M)

Pontoon Ingela's5m-22

Ingela's30m-22

Alsbäck5m-23

Alsbäck35m-23

Ingela's5m-26

Ingela's30m-26

Cutot pH2 2hCutot FIA 7minCudyn VIP/MPCPCufree CGIME

3.5m-21

0

20

40

60

80

100

120

140

Cu

spec

ific

frac

tions

/ C

u tot p

H 2

(%)


Ingela's30m-22

Alsbäck5m-23

Alsbäck35m-23

Ingela's5m-26

Ingela's30m-26

Cutot FIA 7minCudyn VIP/MPCPCufree CGIME

3.5m-21

0

20

40

60

80

100

120

140

Pb sp

ecifi

c fr

actio

ns /

Pbto

t pH

2 (%

)


Ingela's30m-22

Alsbäck5m-23

Alsbäck35m-23

Ingela's5m-26

Ingela's30m-26

Pbtot FIA 7minPbdyn VIP/MPCPPbfree CGIME

3.5m-21

0

0.5

1

1.5

2

2.5

3

Con

cent

ratio

n (n

M)


Ingela's30m-22

Alsbäck5m-23

Alsbäck35m-23

Ingela's5m-26

Ingela's30m-26

Pbtot pH2 2hPbtot FIA 7minPbdyn VIP/MPCPPbfree CGIME

3.5m-21

Example of Cu and Pb specific fraction concentrations measured in Gullmarsfjorden stations, August 21-26 2002

60

50

40

30

20

10

0

Temperature (°C) Salinity (psu)

Dep

th (m

)

0 5 10 15 20 25 30 35 40

Ingela’s 22.08.0260

50

40

30

20

10

00 5 10 15 20 25 30 35 40

Dep

th (m

)


Ingela’s 26.08.02120

100

80

60

40

20

00 5 10 15 20 25 30 35 40


Dep

th (

m)

Alsbäck 23.08.02

Typical temparature and salinity profiles measured in two stations of Gullmarsfjorden

timeConc. of Cu dynamic fraction (nM)

Channel 1 Channel 2 Channel 3 Av. conc. RSD %

11h3012h3013h3014h3015h30

4.915.144.394.744.30

4.304.794.514.59 -

5.364.454.274.364.28

4.854.794.394.57

-

10.93 7.10 2.73 4.16 -

Av. conc. RSD %

4.697.46

4.554.57

4.5410.10

timeConc. of Pb dynamic fraction (nM)


11h3012h3013h3014h3015h30

0.430.460.390.430.43

0.440.420.340.40 -

0.480.480.370.410.36

0.450.450.370.41

-

5.78 5.78 6.86 3.70 -

Av. conc. RSD %

0.435.81

0.439.76

0.4211.91

timeConc. of Cd dynamic fraction (nM)


11h3012h3013h3014h3015h30

0.170.190.170.220.20

0.200.220.190.23 -

0.210.170.21 -

0.21

0.190.190.19

10.31 11.30 10.32

Av. conc. RSD %

0.1911.05

0.218.57

0.20 9.01

- - - -

Reproducibility of the MPCP voltammetric probe

Typical example of the measurement reproducibility of the individual channels and between the three channels of the MPCP voltammetric probe obtained for in situ autonomous measurements over 5 hours using one GIME sensor in each MPCP probe channel. Kristineberg pontoon August 22 2002, deployment depth 3.5 m, SWASV measurement time 20 min.

Preliminary field tests of the MPCP analytical and technical developments have been performed during a campaign performed at Kristineberg Marine Station – Sweden, August 19-28 2002. The MPCP system integrating 3 GIME sensors was deployed, together with VIP systems, in Gullmarsfjorden at various locations and depths. Laboratory measurements of total extractable Me and free Me ion concentrations using a FIA prototype coupled to the MPCP channel 3 and a CGIME sensor respectively were performed in freshly collected samples.

Kristineberg Marine Station Entrance of Gullmarsfjorden

ACKNOWLEDGEMENTSThe authors thank: Olivier Guenat and Milena Koudelka-Hep, IMT - University of Neuchâtel, who produce and supply the Ir-interconnected microelectrode arrays used to prepare the GIME and CGIME sensors; David Turner, AMK-University of Göteborg, for all facilities during field work in Sweden; the financial support of the European Commission and the OFES – Switzerland (European EESD program- IMTEC project Contract n° EVK3-CT-2000-00036).

Contact: [email protected]

Example of voltammogram obtained bymeasurements in Arve river sample using GIME sensor

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MULTI PHYSICAL-CHEMICAL PROFILER FOR REAL-TIME CONTINUOUS IN SITU MONITORING