D E M O U N T A B L E L I Q U I D C E L L

OPER ATION AND USER MANUAL

Introduction

The Spectral Systems Demountable Liquid

Cell is an ideal accessory for the analysis of

liquids when a wide range of component

concentrations is encountered and when the

sample type varies frequently. The pathlength

of the analysis is defined by your choice of

spacer included with the accessory. Spacers

are composed of Teflon® which is inert and

compatible with all sample types.

Spectral Systems offers a complete

selection of window materials for analysis in

the mid-, near- and far-infrared spectral

regions and to provide compatibility with

organic and aqueous solvents. All windows

offered for our Demountable Liquid Cell are

edge rounded and finished for exceptional

durability and improved seal.

Maximum Sampling Pathlength Flexibility• Easy spacer change for flexible sampling pathlength

• Complete selection of window materials for all sample types

• Standard rectangular slide mount configuration to fit your FT-IR spectrometer

S PECI F I C AT I O NS

Plate Geometry Rectangular

Plate Dimensions 2.0" W × 3.0" H

IR Beam Port Dimension 9.5 × 21 mm

Spacer Thickness, mm 0.015, 0.025, 0.050, 0.10, 0.20, 0.50, 1.0

Nominal Pathlength Spacer thickness

Seal Type Friction, Teflon

Fill Port Type Luer Lock

Window Dimensions 32 × 3.0 mm circular

Window Flatness λ/5 at 10.6 micron (Except KRS-5 and Polyethylene)

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Unpacking Your Product

The Demountable Liquid Cell will be packaged

in a plastic storage container. If IR windows

are ordered with the cell they will be

packaged separately. When the IR windows

are not in use they should be stored in a low

humidity environment such as a desiccator

to protect the long-term integrity of the IR

windows.

What’s included?

• Cell holder (base and cap)

• Needle plate with Luer Lock fittings

• Alignment pins

• Teflon gasket

• Teflon o-ring

• 2 Teflon stoppers for cell

• 2 each of 0.015, 0.025, 0.050, 0.10, 0.20,

0.50 and 1.0 mm Teflon spacers

Assembling the Cell

The Demountable Liquid Cell is easily

assembled with your choice of spacer

thickness which provides the nominal

infrared sampling pathlength.

In Figure 1 we show the assembly process;

1. Lay the Demountable Liquid Cell (DLC)

base onto a flat working surface and

install a Teflon o-ring into the DLC base.

2. Gently install an undrilled window into the

DLC base.

3. Install your choice of Teflon spacer over

the undrilled window.

4. Install a drilled window over the Teflon

spacer with the drill holes oriented left/

right with respect to the length of the DLC.

5. Insert alignment pins one each into the

drill holes of the drilled window.

6. Install the drilled Teflon apacer over the

alignment pins and over the drilled window.

7. Install the needle plate over the alignment

pins and over the drilled Teflon spacer

fitting the needle plate alignment pin into

the slot of the DLC base.

8. Install the optional aluminum o-ring

(only if using 2 mm thick windows) over

the needle plate. The optional aluminum

o-ring is not used with the standard 3 mm

thick windows.

9. Install the DLC cap onto the DLC base and

turn to begin seal of the cell. Slowly

continue finger/hand turning until tight.

10. Pull the alignment pins out of the needle

plate and your Demountable Liquid Cell

is ready to use.

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Figure 1. Demountable Liquid Cell (DLC) assembly

Determining Cell Pathlength

The nominal cell pathlength of your

Demountable Liquid Cell is determined by

the thickness of your choice of Teflon spacer.

You can determine its precise pathlength by

using the following procedure.

1. Collect an open beam background

spectrum on your FT-IR

2. Collect the spectrum of the empty cell.

The resulting spectrum will exhibit a

fringing pattern resulting from the

reflection of the IR beam between the

opposing surfaces of the open cell.

3. Select a region of the spectrum where

the fringing pattern is distinct – free of

interference (water bands, etc.) and note

beginning and ending point values in cm-1

for a significant number of fringes. Figure 2

shows the spectrum of a 0.1 mm

Demountable Liquid Cell.

4. The pathlength of the cell can be

calculated from the following equation1:

Pathlength = 10 N/2(λ1 – λ2)

Where;

Pathlength = value in mm

N = number of fringes between λ1 and λ2

λ1 = starting value in cm-1 for measurement

λ2 = ending value in cm-1 for measurement

In the example shown in Figure 2, λ1 =

2534.38 cm-1, λ2 = 1138.93 cm-1 and N = 29.

From this we calculate the actual pathlength

to be 0.104 mm.

Note: In order to exhibit the spectral fringing pattern described above sufficient spectral resolution must be selected. See required values in Table 1.

Figure 2. Spectrum of 0.1 mm pathlength Demountable Liquid Cell

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Minimum Spectral Resolution Required

CELL MINIMUM PATHLENGTH SPECTR AL (mm) RESOLUTION (cm -1)

10 0.25

5 0.5

1 2.5

0.5 5.0

Table 1. Minimum spectral resolution required for measuring fringe pattern

Sampling Procedures

Samples measured in the Demountable

Liquid Cell are generally a component in a

base liquid, for example an additive in fuel

for a combustion engine. Generally the

pathlength of the liquid cell is chosen to

optimize the absorbance of the component

which needs to be measured. Often the

components of interest are at low concen-

trations within the base liquid; parts per

million (ppm) and low percentage levels are

typical. Therefore, we generally need to

choose longer pathlength cells to “see” and

measure these low concentration levels. The

primary absorbance bands from the base

liquid generally are out of the linear range of

the spectrometer and therefore cannot be

used to internally calibrate the pathlength of

the measurement. The Demountable Liquid

Cell is ideal for “finding” the appropriate cell

pathlength for the quantitative analysis.

When this is completed it may be beneficial

to move to a fixed cell path cell offered by

our Super-Sealed™ Liquid Cell. In some sample

measurements weakly absorbing bands of

the base liquid can be used as a measure of

the liquid cell pathlength. In these cases the

absorbance of the component of interest

can be ratioed to an absorbance band of the

base liquid to determine concentration and a

fixed pathlength cell aids in the precision of

the quantitative measurements.

Using the Demountable Liquid Cell

The assembled Demountable Liquid Cell is

configured with two Luer Lock ports for

connection with Luer Lock style syringes. It

is very important to use proper procedure

for filling the cell.

• Gently connect a Luer Lock style syringe

with your liquid sample onto one of the

Luer Lock fittings of the cell.

• Gently connect an empty Luer Lock style

syringe onto the other Luer Lock fittings

of the cell.

• Filling the cell must be pull via the empty

syringe to prevent damage to the cell.

• Slowly pull the plunger of the empty

syringe upward to draw the liquid into

the cell as shown in Figure 3.

• Remove the Teflon stoppers and install

one each Teflon stoppers into the

Luer Lock ports to seal the liquid

sample in the cell. Examine the

filled cell to ensure liquid

maintains fill in the cell and

that no bubbles are present.

• To remove sample from the

flow cell, remove the Teflon

stoppers from the Luer Lock

fittings and install an empty

glass syringe onto the lower

port and slowly pull the

plunger in the out direction

to remove the sample.

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Figure 3. Filling the Demountable Liquid Cell

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Cleaning and Storing the Liquid Cell

Before storing the liquid flow cell after use it

is important to remove all sample residue to

prevent long-term damage to the cell.

• Pull a suitable cleaning solvent through

the cell using the following method;

• Install a Luer Lock glass syringe with

solvent onto the lower port of the

Demountable Liquid Cell. Install an empty

glass syringe onto the upper port of the

cell. Gently pull the plunger of the upper

syringe out to draw the solvent into the

cell. It is recommended this be done three

times using three times the volume (each

time) of the liquid cell to completely

remove sample residue.

• Store the Demountable Liquid Cell in a

desiccator to protect the long-term

integrity of the IR windows. Alternately,

disassemble the cell and store the IR

windows in a desiccator.

Product Configurations

The Demountable Liquid Cell is available

with your selection of window materials.

Table 2 shows a complete list of Spectral

Systems part numbers for these configurations.

Each of the window materials have of

course unique properties and capabilities

relative to spectral range and water

solubility. For your convenience we have

listed some of these properties for each of

the materials in Table 3.

Safety Precautions

It is essential to utilize safe laboratory

procedures when using the Demountable

Liquid Cell. Safety protective eyeglasses and

laboratory gloves are required.

Follow proper cell flowing and emptying

procedures as outlined in Sampling

Procedures. Failure to do this may cause

liquid flow cell damage and or exposure to

the liquid sample.

Make sure your sample is compatible with

the window material of the flow cell. Failure

to do this may cause liquid flow cell damage

and or exposure to the liquid sample.

Maintenance

When IR sampling is completed with the

Demountable Liquid Cell, empty and clean

the cell as detailed in Sampling Procedures.

The cell and or windows should be stored in

a desiccator to prevent damage to hygro-

scopic IR windows.

If any damage to the cell is detected, please

contact Spectral Systems for assistance.

References:

1. Conley, Robert T., Infrared Spectroscopy

(Allyn & Bacon, 1966).

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Part Numbers List for Demountable Liquid Cell Windows

WINDOW UNDRILLED DRILLED MATERIAL PART NO. PART NO.

BaF2 915-3716 915-3717

CaF2 920-3716 920-3717

CsI 935-3716 935-3717

Ge 940-3716 940-3717

IR-Quartz 965-3716 965-3717

KBr 945-3716 945-3717

KRS-5 950-3716 950-3717

NaCl 955-3716 955-3717

Polyethylene 957-3716 957-3717

Si 960-3716 960-3717

ZnSe 975-3716 975-3717

ZnS 971-3716 971-3717

Table 2. Special versions of these windows are also available from Spectral Systems. Versions with specialized coatings to increase IR throughput and versions with window wedging to improve performance for high-resolution measurements are available. Please contact us for more information for your requirements.

Spectral Range and Solubility for Demountable Liquid Cell Windows

SHORT LONG WINDOW WAVELENGTH, WAVELENGTH, SOLUBILITY, MATERIAL CM-1 CM-1 G/100 G

BaF2 66,600 782 0.17

CaF2 79,500 1025 0.0017

CsI 42,000 172 44

Ge 5,500 574 0

IR Quartz 50,000 2,677 0

KBr 48,800 388 53

KRS-5 17,900 232 7.4

NaCl 52,600 584 36

Polyethylene 700 ~0 0

Si 8,900 969 0

ZnSe 15,000 508 0

ZnS 17,000 722 0

Table 3. Spectral range and water solubility for Demountable Liquid Cells where SWL = highest wavenumber, LWL = lowest wavenumber and Solubility is the value at room temperature.

Replacement Spacers for Demountable Liquid Cells

SPACER THICKNESS PART NO.

0.015 097-3713

0.025 097-3714

0.050 097-3715

0.10 097-3716

0.20 097-3717

0.50 097-3718

1.0 097-3719

Spacers include 12 each. Spacers are composed of Teflon which is compatible with organic and aqueous solvents.

Replacement Parts and Options for Demountable Liquid Cells

DESCRIP TION PART NO.

Teflon Stoppers (12 each) 097-3711

Teflon Gaskets (12 each) 097-3712

Teflon O-Rings (12 each) 097-3737

Aluminum O-Rings (12 each) 097-3723

Needle Plate 097-3727

Alignment Pins (12 each) 097-3709

Glass Syringe, 1 mL 097-3801

Glass Syringe, 5 mL 097-3805

Glass Syringe, 10 mL 097-3810

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©2015 Spectral Systems. Super-Sealed is a trademark Spectral Systems. Teflon is a registered trademark of E.I. du Pont de Nemours & Co.