a centrifugal lab-on-a-disc device for the in situ...

A centrifugal lab-on-a-disc device for the in situ determination of dissolved

reactive phosphate in water

Gillian Duffy, Brendan Heery, Ivan Maguire, Charles Nwankire, Jens Ducrée, Fiona Regan 1

Contents Background information

Centrifugal microfluidics

Analytical method on disc

Detection system

Integrated system

2

Phosphorus in water Growth limiting nutrient:

• algal bloom

• hypoxic waters

• death of aquatic animals

• toxic blooms

3 http://serc.carleton.edu/microbelife/topics/redtide/general.html

http://www.natureworldnews.com/articles/15693/20150717/toxic-algae-expected-lake-erie-potentially-worst.htm

http://sites.duke.edu/biology217_01_s2011_mkg14/ecological-impacts/eutrophication/

Traditional analysis

Grab sample

Travel

Storage

Analysis

Travel

4

• Time intensive

• Labour intensive

• Expensive

instrumentation

• Low sampling

frequency

• Contamination

Centrifugal microfluidics

5

Centrifugal force

Direction of rotation

Analytical method

6

Four methods:

High sensitivity

Selectivity

Simplicity

LOD and LOQ

Linear range

Analytical method

7

R² = 0.9983

R² = 0.9583

R² = 0.9377

R² = 0.9872 0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

0 100 200 300 400 500 600

Ab

sorb

an

ce (

AU

)

Concentration (µg L-1 PO4-P)

0

0.0002

0.0004

0.0006

0.0008

0.001

0.0012

0.0014

0.0016

0.0018

Se

nsi

tiv

ity

(A

U (

µg

L-1)-1

)

= ascorbic acid method

= stannous chloride method

= stannous chloride-hydrazine method

= yellow method

Analytical method

8

PO43- + 2(NH4)6Mo7O24.4H2O

𝑯𝟐𝑺𝑶𝟒 H3PMo12O40

1.

H3PMo12O40 + 2C6H8O6 + C8H4K2O12Sb2.3H2O

H7PMoV

4MoVI8O40 + 2C6H6O6 + 4H+ 2.

Detection system

9

increase

Microfluidic disc

10

Reservoir

Microchannel

Air vent

Detection chamber

11

Detection system

12

Roithner 880 nm laser Radionics 880 nm LED

Radionics photodiode

Optical path length study

LED (B)

Laser (A)

Photodiode B

Photodiode A

Optical path length 13

Optical path length study

R² = 0.9809

R² = 0.9985

-0.001

0

0.001

0.002

0.003

0.004

0.005

0.006

0.007

0 20 40 60 80 100

Se

nsi

tiv

ity

(AU

L µ

g-1)

Optical path length (mm)

Laser

LED

14

R² = 0.9098

R² = 0.796

0

0.001

0.002

0.003

0.004

0.005

0.006

0 20 40 60 80 100 120

Se

nsi

tiv

ity

(AU

L µ

g-1)

Optical path length (mm)

LED

Laser

Integrated NutriSense system

15

Black 3D printed container

Motor to be incorporated for disc rotation

Optical detection system is aligned on the stage

Electronics stored beneath, away from wet chemistry

Conclusion Analytical method

Disc design optimised Mixing

bubble formation

Optical path length

Integrated system designed – first prototype fabricated

16

Future work Incorporate motor into system

Investigate system robustness in situ

Adapt disc design for other analytes for water quality analysis

17

Acknowledgements Brendan Heery

Ivan Maguire

Prof. Fiona Regan

18

Thank you! 19