Development of Instruments for

Real-time Water Monitoring

S. Mitra

New Jersey Institute of Technology

Newark, NJ 07102

mitra@njit.edu

Acknowledgements: US EPA, NSF, US Army

On-line Real-time Monitoring

Process

Or

Process Stream

Instrument

or sensor

Real-time Monitoring of VOCs Ground Water Using Gas Injection Membrane Extraction (GIME)

Gas

Pulse

Heating

Nitrogen

Injector

Membrane Module

Portable GC

Detector

Microtrap

Sample Out

Sample In

Data System

Sample out

1. K. Hylton and S. Mitra. J. Chromatogr. A, 2007, 1152, 199–214.

2. D. Kou and S. Mitra, Anal. Chem. 2001

Continuous Monitoring by GIME

Compounds MDLs (ug/l) RSD (%)

Benzene 0.1 1.7

Toluene 0.1 2.3

Ethylbenzene 0.9 2.8

Field Testing of Gime-GC System at a Superfund Site

The on-line real-time monitoring system A groundwater treatment facility at the Naval

and Engineering Station in Lakehurst, NJ,

where the field study was conducted.

I1 I4I2 I5I3 I6 I7 I9I8

0 3618 9054 10872 126 144

Time (min)

1

2

3

1. 1,1 Dichloroethylene

2. cis 1,2 Dichloroethylene

3. Trichloroethylene

Typical chromatograms from on-line analysis of water entering the treatment facility. Injections were made at I1, I2 etc.

0.00

0.50

1.00

1.50

2.00

2.50

3.00

0.00 50.00 100.00 150.00 200.00 250.00 300.00 350.00 400.00

Time (min)

Co

ncen

trati

on

(p

pb

)

cis 1,2 Dichloroethylene

0.00

0.20

0.40

0.60

0.80

1.00

1.20

1.40

0.00 50.00 100.00 150.00 200.00 250.00 300.00 350.00 400.00

Time (min)

Co nc en tra tio n (p pb )

Trichloroethylene

Concentration Profiles over a six hour monitoring period

Continuous Monitoring by GIME-GC

Steps in Trace Semi Volatile Measurements

Extraction -LLE, SPE, SPME

Concentration -Evaporative, Membrane

Detection -GC, HPLC, MS

Membrane Extraction

Membrane Feed side Permeate side

Schematic Diagram of ME-LC

Organic

Extractant

Water

Sample

Detector

HPLC mobile phase

HPLC Column

Solvent Exit

Analyte

Laden

Solvent

Sample Exit

Hollow Fiber

Membrane Module

Injection Valve

X. Guo and S. Mitra, Journal of Chromatography A,904 (2000) 189-196.

Continuous monitoring by ME-LC

X. Guo and S. Mitra, Journal of Chromatography A, 904 (2000) 189-196

Simultaneous Extraction and Concentration

Analyte

Acceptor (solvent)

Donor

(water)

Membrane

Extract

Solvent

Analyte

Solvent

Donor

D. Kou and S. Mitra, Analytical Chemistry (2003).

Solubility and Solvent Loss

Kow

(Log P)

Hexane BA MIBK

IPA

EE EF EE EF EE EF EE EF

PCP 5.12 68.1 36.3 69.5 101.6 43.7 153.3 26.1 203.4

Atrazine 2.61 6.5 3.5 56.2 82.2 N/A N/A 31.6 246.6

Naphthalene 3.30 46.3 24.6 81.3 119 33.9 119 37.4 292

Water Solubility

9.5 mg/l 8.4 g/l 19 g/l 30.9 g/l

Solvent

Loss (%)

26.7 73.3 88.9 95

Ref: D. Kou and S. Mitra, Analytical Chemistry (Nov, 2003)

Analytical Performance

Compounds MDL (μg/L ) RSD (%)

Atrazine 0.5 4.6

PCP 1.0 7.8

Naphthalene 0.9 6.3

Total Analyitical System

Integrating Extraction and Concentration

Extraction with On-line Membrane

Concentration

membrane concentration

Organic solvent

Water sample

Water sample exit

Inert gas

Gas out

Injection valve HPLC

membrane extraction Extract

Concentrated extract

Wang and Mitra, Journal of Chromatography A, 1068 (2005), 237-242

Wang and Mitra, Journal of Chromatography A, 1068 (2005), 237-242

Total Analytical System

Organic

Extractant Sample Exit

Extraction Module

Detector

HPLC Mobile Phase

HPLC Column

Injection Valve

Water

Sample

Injec. Loop

Overflow

Concentration

Module

N2

N2 Stripping

Flow Analyte

Laden

Solvent

Extraction Concentration Detection

Wang and Mitra, Journal of Chromatography A, 1068 (2005), 237-242

Mass transfer in the TAS

Wang and Mitra, Journal of Chromatography A, 1068 (2005), 237-242

Comparison of EF

in three experimental modes

Mode 1:membrane extraction only;

Mode 2: membrane extraction and pervaporation without N2 stripping;

Mode 3: and membrane extraction and pervaporation with a N2 flow rate of 45 mL/min. Naphthalene

Biphenyl

Mode 1

Mode 2

Mode 3

0

20

40

60

80

100

120

140

160

180

200

EF

Real Time Monitoring of Haloacetic Acids

Continuous SLME-HPLC

Wang, Kou and Mitra.Journal of Chromatography A (2005).

Series of Chromatograms from Continuous

SLME of the Nine HAAs

Lab-on-a-chip, Total Analytical System

Sample

Extraction

Sample

Concentration

Separation/

Processing

Detection

On-Chip SLMME

In Review- Anal. Chem. (2004)