Closed System HPLC
Colosed
To Completely contain solvent vapor for an HPLC unit, we need to address the two “open” solvent containers:
1) the Solvent Reservoir (the “inlet”), and
2) the Solvent Waste Container.
Since we’re dealing with the flow of liquid, closing either of those containers requires addressing two separate issues:
a) fluid connections (i.e., tubing and fittings)
b) air inlet /vent at the Reservoir, and vapor vent at the Waste Container
I’ll use that basic framework to describe the Closed System
1) SOLVENT RESERVOIR
Regarding the Solvent Reservoir,
1a) RESERVOIR FLUID CONNECTIONS
For a closed system on a bottle, each container first needs a bottle cap with ports made to fit the specific
tubing sizes. We recommend caps with fittings, as the fittings may be changed to accommodate the different
diameters of tubes. Caps with “slip-through” ports (non-threaded holes drilled or molded into a cap) are
acceptable, provided the holes fit the tubing sizes. Most Slip-through caps are made to accommodate 1/8”
OD or 1/16” OD tubing.
FLOW
SOLVENT FLOW
SOLVENT FLOW
VAPOR
VAPOR FL OW
CLOSED-SYSTEM HPLC
2b
1b
1a
2a
1
t el: 800.5 41 .8 42 1
PUMP
f ax: 800.5 42.8 42 1
DETECTOR
email: jus tus@HPL Csuppl y.com
2
w ebsit e: www.HPL Csuppl y.com
BCS-300
GL45 2-inlet cap
For 1/8” OD tubing
With luer port
SLIP-THROUGH CAP
BC-313
GL45 3-ported cap
For 1/8” OD tubing
CAP WITH THREADED PORTS
In some labs, most of the bottles have caps already in place. These are caps with 3 threaded ports for fittings. In
other labs, a number of caps were provided with the systems on purchase. These are all the gray “Slip-through”
variety, made for two 1/8” OD tubing lines. The current bottle situation is that each system has two 4-liter bottles
and one 1-liter, all with the same “GL45” bottle cap. using two 1/8 lines in each 4-liter container. The third bottle
has an odd-sized tubing, and will require a new bottle cap with fittings.
1b) RESERVOIR VAPOR VENT
To complete the closed system on the bottles, secondly each container needs a device to control the bottle cap
vent. A closed bottle has to work exactly like a coffee travel mug -- liquid goes out through one hole, and air
comes in through a pinhole to displace the liquid removed. Because air only has to come in to the reservoir, not
out, the simplest answer is a check valve made to occupy a threaded bottle cap port. The check valve allows air to
enter the bottle as the HPLC pump moves the liquid phase out to the system. It also prevents vapors contained in
the bottle from escaping. The problem, however, is that we need a safety “relief” valve if the bottle is ever exposed
to pressure. That could happen because of a fire or rise in lab temperature, a chemical reaction, or a sparging line
accidentally connected. To prevent explosion, the relief valve will allow pressure to escape. The Justrite safety
waste containers are an example of this, as they will automatically vent at 5 psi when under pressure.
To this end, we developed a “dual check valve” which allows air to enter the bottle while the system is in use, but
also allows vapor to escape through a relief valve if a pressure buildup occurs. A pressure of 0.5 psi to 0.8 psi
is maintained in the bottle. It is constructed of a PEEK casing with Viton check elements, which will resist most
solvents. We can make a version with Chemraz seals also, but this will be about twice the price as the Viton.
The current design will work very well in any case, more than likely sealing above 99% of the vapor contained.
APPLICATIONS IN LABS:
Because many bottle caps are already in place, to avoid purchasing more caps here are two examples of how
the dual check valve can be adapted. In the labs that have mostly caps with threaded ports, so the valve can be
threaded directly into the cap. The“slip-through” bottle caps will require an adapter, as shown below.
In either lab, whenever a bottle cap is not currently in place, w recommend using a bottle cap with more ports than
the tubing lines require, with plugs for unused ports. This allows for more tubing lines to be accommodated at a
later date if necessary. We can provide caps in 2, 3, 4, 6, and 9-port configurations, with options to incorporate
additional lines when required.
BOTTLE CAP WITH DUAL
CHECK VALVE
VAPOR “RELIEF” VENT
SOLVENT
FLOW
SOLVENT
FLOW
CHECK VALVE ASSEMBLY
AIR INLET
2) SOLVENT WASTE CONTAINER
You are more familiar with our progress so far on the system waste, but we have a few new developments:
2a) WASTE FLUID CONNECTIONS
Most labs have standardized on the Justrite 2- and 5- gallon HPLC waste containers, with Polypropylene
quick disconnects. This standard should work well for most solvents, except those which cause swelling in
Polypropylene. We’ve had issue with Hexane, for example, which swells the quick disconnects as much as 30%,
causing the disconnect to “stick” inside and restricting fluid flow.
Most of the HPLCs have waste tubing in dimensions of 1/8”, 1/16”, and 0.085” OD, and also 1/4” ID. The 6-port
manifolds (made for both polypropylene and stainless disconnects) will adapt to tubing sizes up to 1/2” ID or OD,
PA R T # D V- 1 0 0
D u a l C h e c k Va l v e
for 1/4-28 ports.
PA R T # D V- 1 0 1
D u a l C h e c k Va l v e
for luer ports.
PRICE: $50.00
PRICE: $63.50
M-1 BOTTLE CAP
PA-11 BOTTLE CAP
and can be stacked to accept additional lines.
we can offer an alternative that is readily available, The list price would be much higher than
our new version shown on left.
RECOMMENDED 4-PORT CAP
Valve can ship within 2-3 weeks
TEMPORARY SOLUTION
Valve can ship within 3 days
Some of the fittings are molded in one piece, as with the barbed
fittings, and others are in several components, but in every
case there is a self-sealing “NPT” (National Pipe Thread) which
screws into the manifold. Even though the threads are selfsealing, we’ve learned it is important to first wrap each thread
in Teflon tape 3-4 times, then wrench tighten till flush. A socket
wrench with a 9/16” hex socket is the simplest way to do this.
SOCKET SET
9/16” Socket and
standard wrench
WASTE
MANIFOLD
Shown in stacked
configuration
2b) WASTE CONTAINER VAPOR VENT
The most significant vapor generator is the waste can,
where solvents draining to the container may volatilize
rapidly. Solvent entering forces vapor out of the can into
the lab, and many of the waste containers used are not
located near a fume hood. Our main concern in dealing
with this problem is preventing toxic vapor exposure to
those working in the lab.
Activated carbon has excellent adsorptive properties for organic solvents. With a gas Chromatograph, we tested
a number of carbon types for vapor breakthrough under a flow of Acetonitrile vapor, one of the more common
solvents used in HPLC. After determining the appropriate carbon type, we tested it for breakthrough on four other
common solvents, shown below. The data we acquired is based on use of 100% concentration of each solvent, at
a flow rate of 1 mL per minute (most analytical HPLCs run at 1-2 mL /min).
The recommended replacement period per each solvent is less than the actual breakthrough time recorded -- a
margin for safety and liability reasons. Because of this safety factor, because most HPLC systems are not in constant use, and because frequently solvents are not used at 100% concentration, in most cases the filters will last
longer than the replacement period. Those factors considered, the table below serves as a conservative “rule of
thumb” when replacing the filter. For most systems using Acetonitrile , for example, I recommended replacement
every two weeks.
RECOMMENDED CARTRIDGE REPLACEMENT PERIODS, BY SOLVENT
Based on a vapor stream flow rate of 1mL/min
150 (6.25 days)
Methylene Chloride
Acetone
230 (9.5 days)
Acetonitrile
300 (12.5 days)
TetrahydraFuran
340 (14 days)
Ethyl Acetate
420 (17.5 days)
Methanol
600 (25 days)
TIME IN HOURS
COLOR INDICATOR
Although we know the table above is an effective method of replacement, it requires that the user record the installation and replacement dates for each filter, considering such factors as solvent type and system flow rate. To simplify
replacement,a chemical indicator in incorporated in the end of the filter that will change color when breakthrough occurs. We will more than likely continue to sell the standard filter (without the indicator) for the budget-minded user.