Transcript Sterilization Device for Liquid Chromatography Solvents

Sterilization Device for Liquid
Chromatography Solvents
Design Team
Nick Roulleau, Michael Vose
Michael Racette, Michael McKay
Advisor
Professor Mohammad Taslim
Introduction
• Background
• Problem Statement
• Past Art
• Design Requirements
• Design Concepts
• Prototype Design
• Component Analysis
• Recommendations
What is Liquid Chromatography?
A substance comprised of components A and B is dissolved
in a solvent and enters the analytical column, where it is
separated
Basic Components of an HPLC System
From http://www.waters.com/WatersDivision
Problem
From http://www.waters.com/WatersDivision
Design Goal
To mitigate the risk of blockage at the
inlet frit due to bacterial contamination
and extend the useful life of the UPLC
column.
Existing Solutions
• In-line filters
• Guard columns and cartridges
• Pre-filtration of samples and
mobile phase liquids
Product Requirements
• Mandatory:
» Must be adaptable for use worldwide
» Must extend the useful life of columns
» Must meet safety standards (ISO, UL and CE)
» Must operate for 1 year w/o user intervention
• Desirable:
» Should be able to filter two bottles simultaneously
» Should meet customer acceptance criteria
– Low-maintenance
– Easy to use
– Cost
Constraints
• Cannot change the chemical composition
» Of the solvent
» Of the sample
• Cannot create risk of causing pump cavitation
• Cannot hinder bottle accessibility
• Cannot negatively impact system resolution
Initial Design Concepts
UV Probe
Pump/filter--Cap enclosure
Pump/filter--External enclosure
Preliminary Design – UV Probe
• Inexpensive
• Simple Design
Why Not Use Ultraviolet Radiation as a
Primary Solution?
• Degradation of organic solvent modifiers
(Low Risk)
• Degradation of aqueous additives
(Low Risk)
• User safety from UV-C exposure
(Medium Risk)
• UV can inactivate but not remove
bacteria
Filter Sizing
• How many bacteria could be generated per year?
• Logarithmic growth:
» Assuming worst case
– 100% replicating
– Short generation time
– Neglecting lag phases and cell death
• Filter capacity = 107 CFU/cm2
Filter Sizing
With logarithmic bacterial growth, filter area
becomes exceptionally large in a short period
Current Design
External Filter Enclosure with UV
Dual-head
brushless DC
pump
UV lamp
with multiple
sterilization
lines
Pall AcroPak 200 filters
Filter Selection
• Membrane with material
compatibility
• Sufficient capacity to contain 1
year of inactivated bacteria
Pump Selection
Micro-diaphragm pump
• Dual pump heads
• Ability to run dry
• DC brushless motor for
long life
Pump Pressure Requirements
• Pump must deliver sufficient differential
pressure (Δp) to move fluid through filter
• Darcy’s equation for porous media:
kA( p1  p2 )
Q
 ( L)
Q = flow rate
k = permeability constant for filter
A = effective filter area (EFA)
µ = viscosity
L = membrane thickness
p1 = pump-side pressure
p2 = outlet pressure
UV Block Design-Initial Concept
UV Block Design
• 99.99% inactivation requires a UV dose of at least 40
mJ/cm2 for nearly all species of bacteria
• Dose is a function of the irradiance (mW/cm2) and time of
exposure (in seconds)
Dose = Irradiance x time
Fd 1 2
1
L
L  X  2H
1

tan
 
tan 1
H
H 2  1   H XY
X  (1  H )2  L2
Y  (1  H ) 2  L2
h
H
r
l
L
r
X ( H  1) 1
H 1
1
 tan

Y ( H  1) H
H 1
A
dA
UV Block Design
UV Block Design
13 loops necessary with an 18W UV bulb and thin wall FEP tubing
Test Planning
• Verification Test
»
Does the Device Meet
Design Requirement?
»
Pump Particle-Laden
Water from Bottles With
and Without Device
Device
Pump
Sensor
Column
»
Compare Backpressure
and/or Flow Rate
PRESSURE
80
70
60
50
40
30
20
10
0
0
100
200
300
Test Results
Backpressure Test
12
10
Backpressure (PSI)
8
6
No Device
Device (Norm)
4
2
0
1
599
1197 1795 2393 2991 3589 4187 4785 5383 5981 6579 7177 7775 8373 8971 9569 10167 10765 11363 11961
Elapsed Time (s)
Backpressure was reduced by 28% when our device was used
Cost Analysis
• Developed target costs by estimating:
» Annual costs without the assistance of our device
(excluding operational costs)
» Savings in material costs by implementing our device
• Potential savings for high-end users = $44,000
• Minimum estimated annual savings = $600
• Target production cost = $500
• Target prototyping cost = <$1500
Recommendations for Further
Development
• Improve manufacturability of the design
» Simplify tubing system
» Smaller pump
» Custom filter size
• Analyze effectiveness of UV with
microbiological testing
Summary
• Introduction to liquid chromatography
• The problem and its source
• Requirements of a good solution
• Design considerations
• Prototype design and analysis
• Recommendations
Questions???