Before selecting a transmitting material as window for a cell or ATR prism in infrared spectroscopic application, the following parameters should be taken into consideration useful transmission range, refractive index, solubility, reactivity and cost. Depending on the application, mechanical and thermal properties of the material may be important. The table below is provided as a selection guide and Medway Optics will not only offer you quality products but experts technical support at value-to-cost ratios among the most competitive in the marketplace.
Material
Useful Transmission range (~ 2mm thick)
Refractive Index @ 5µ
m
Solubility in H2O g/100g @ 20ºC
(cm-1)
(µm)
Sodium Chloride (NaCl)
40,000-625
0.25-16
1.52
36.0
Potassium Bromide (KBr)
40,000-385
0.25-26
1.54
65.2
Potassium Chloride (KCl)
40,000-500
0.25-20
1.47
34.7
Caesium Iodide (CsI)
33,000-200
0.30-50
1.75
160@61ºC
Calcium Fluoride (CaF2)
62,500-1,000
0.16-10
1.40
0.0017
Barium Fluoride (BaF2)
50,000-835
0.2-12
1.45
0.12 @ 25ºC
Thallium Bromoiodide (KRS-5)
16,000-250
0.6-40
2.38
0.05
AMTIR-1 (GeAsSe Glass)
11,400-830
0.9-12
2.51
Insoluble
Silver Chloride (AgCl)
20,800-400
0.48-25
2.00
Insoluble
Zinc Selenide (ZnSe)
10,000-525
1.0-19
2.41
Insoluble
Germanium (Ge)
5000-870
2.0-11.5
4.01
insoluble
Silicon (Si)**
10,000-100
1.0-100
3.42
Insoluble
IR-Fused Silica (SiO2)
40,000-2,500
0.25-4.0
1.42 @ 3µm
insoluble
Sapphire (Al2O3)
3,300-1,800
0.30-5.5
1.60
Insoluble
Diamond (C)(synthetic)**
45,000-FIR
0.22-FIR
2.4
Insoluble
** Transmission is not continuous. Bands occur between 6-28µm for Si and 4-6µm for C
In pressure applications, the following formulae for calculating window thickness apply for circular windows.
For clamped window:
tclamped = 0.866 x D x (P/M)1/2
For unclamped window:
tunclamped = 1.05 x D x (P/M)1/2
where: t = window thickness
D = unsupported diameter
P = pressure
M = modulus of rupture or apparent elastic limit depending on nature of material.
The criteria for selection of prism material to obtain a good FT-IR ATR spectrum is outlined below. For a good spectrum, it is essential to select conditions to achieve optimum depth of penetration (dp).
The useful wavenumber (cm-1)/wavelength (l
) range of the material. The wider the useful transmission wavelength range, the better the material for general purpose uses. The depth of penetration increases with decreasing wavenumber/ increasing wavelength.
Refractive index of material (h
1). This determines the critical angle (q
c) of the material at which total internal reflection phenomena begins to occur. The higher the material refractive index, the lower the critical angle. It is desirable for the angle of incidence to far exceed the critical angle to avoid spectrum distortion when working with high refractive index (h
2) samples
Angle of incidence (q
i). Increasing angle of incidence will decrease the depth of penetration and number of reflections. These will decrease effective pathlength and therefore decrease the absorbance intensity of the spectrum
Effective sample contact. It is important to achieve a good sample contact all over the ATR prism sample contact area to obtain a good spectrum. In solid samples it is important to choose an ATR material that will permit sufficient pressure to be applied without causing damage to the prism or sample in order to obtain a good spectrum. The hardness of the material is important.
Material reactivity. When dealing with liquid samples, careful attention should be paid to solubility in water, the reactivity of the ATR materials to acids, bases, oxidising and reducing agents and complexes.
l
h2
dp =
--------------------------------------
q
c = sin-1
----------
2p
h
1 (sin2 q
i - (h
2/h
1)2)1/2
h
1
N = L/T tan q
i Where N = number of reflections, L = length (centre to centre), T = thickness
Ordering information
Prism Size
45º ATR Prism (30º, 60º and other sizes available on request)
L x W x T (mm)
KRS-5
ZnSe
Ge
Si
KRS-5
ZnSe
Ge
Si
Parallelogram
Trapezoid
50 x 20 x 1
A010
A030
A050
A070
72 x 10 x 6*
A020
A040
A060
A080
50 x 20 x 2
A011
A031
A051
A071
50 x 20 x 1
A021
A041
A061
A081
50 x 20 x 3
A012
A032
A052
A072
50 x 20 x 2
A022
A042
A062
A082
50 x 10 x 1
A013
A033
A053
A073
50 x 20 x 3
A023
A043
A063
A083
50 x 10 x 2
A014
A034
A054
A074
50 x 10 x 1
A024
A044
A064
A084
50 x 10 x 3
A015
A035
A055
A075
50 x 10 x 2
A025
A045
A065
A085
25 x 10 x 2
A016
A036
A056
A076
50 x 10 x 3
A026
A046
A066
A086
25 x 10 x 3
A017
A037
A057
A077
Note: L is measured tip-to-elbow (or centre-to-centre) except* measured tip-to-tip.
Technical information
Transmission technique offers one of the most reliable and accurate means of quantitative and qualitative analysis by infrared spectroscopy. Evacuable pellet dies allow small amounts of solid samples blended with suitable infrared transmitting powder medium such as KBr or KCl to be pelleted for transmission analysis. A hydraulic press is required for pelleting.
Medway Optics offers dies with the following features and options:
Sample evacuation prior to pressing to remove traces of water vapour that could interfere with sample analysis.
Vacuum hardened 440C Stainless Steel parts resistant to scratches and chemical attack from vast majority of laboratory samples.
Highly polished Stainless Steel pellets for scatter free and good surface finish samples.
Easy removal of sample for analysis and dismantling of die parts for cleaning.
Optional tungsten carbide polished pellets for extra hard samples.
Optional 15 tons and 25 tons presses for infrared and X-ray fluorescence (XRF) sample pressing applications.
Ordering information
A Die set comprises of body (with black anodised sleeve), base, O-rings (2 off), plunger, one face polished pellets (2 off) and an extractor ring. 3* mm Die set uses one polished pellet and a polished plunger.
KBr Dies for Infrared
XRF Dies for sample cups
Die Set Size (mm)
3*
5
8
10
13
16
25
32
40
P/N
D010
D020
D030
D040
D050
D060
D070
D080
D090
Pellets
D011
D021
D031
D041
D051
D061
D071
D081
D091
Plunger
D012
D022
D032
D042
D052
D062
D072
D082
D092
O-rings
D013
D023
D033
D043
D053
D063
D073
D083
D093
Extractor ring
D014
D024
D034
D044
D054
D064
D074
D084
D094
Sample holder
D015
D025
D035
D045
D055
D065
D075
D085
D095
Tungsten Carbide
On Request
On Request
Hydraulic Presses
(15 tons) On Request
(25 tons) On Request
P/N D056 13mm KBr Starter Kit comprising of
13mm Die set
-P/N D050
100gm KBr powder
-P/N D201
Spatula
-P/N D202
Tweezers
-P/N D203
Disc holder
-P/N D204
Handpress Evacuable Die set
Technical information
This is a low cost but effective way of producing a pellet die for infrared analysis without the use of a hydraulic press. The set comprises of a precision honed stainless steel cylinder body with evacuation tube, two 9/16 UNF hardened stainless steel bolts with optically polished ends with seals, two spanners and a slide die holder. The die set will produce a 8mm diameter pellet inside the cylinder. The sample is trapped inside the body (poured from one end) in between the two bolts. Vacuum is introduced into the chamber through the evacuation tube for a short while and the two bolts are turned against each other to press the sample. The result is a clear pellet formed in the cylinder. The two bolts are removed and the sample in the cylinder is placed on the slide die holder, which locates in the infrared spectrometer for analysis. The sample can be washed away with water after analysis. This Handpress die set is most suitable for teaching laboratories and in industries where the demand for frequent pelleting of samples is low.
Ordering information
D210
Handpress 8mm Die set comprising of:
Die body, polished bolts with seals (2 off), spanners (2 off),
Technical information
This optical polishing kit contains all the accessories needed for buffing and re-polishing soft materials that do not require pitch polishing such as NaCl, KBr and KCl windows for spectroscopic application. Polishing form blank materials will require a bit of skill from grinding, smoothing and polishing but buffing and re-polishing require minimal skill. Polishing from blank also requires a glass optical flat. The kit is not recommended for cleaning KRS-5.
Technical information
The oil in water analysis kit allows trace amounts of hydrocarbon in water effluents originating from petroleum products such as oil or grease to be analysed by the method certified by the Environmental Protection Agency (EPA) of the United States of America. The kit comprises of one matched pair of 10mm pathlength rectangular cuvette, one matched pair or 50mm pathlength two ports circular cuvette, one matched pair of 100mm pathlength two ports circular cuvette, 1 universal cuvette holder for rectangular and circular cuvettes from 10mm to 100mm pathlength, 1 instruction manual and a carry case. All the cuvettes have round neck stoppers to prevent evaporation, and are made from infrared grade fused quartz.
Ordering information
O110
Oil in water/hydrocarbon analysis kit
O111
Matched pair if 10mm pathlength rectangular IR Quartz cuvette
O112
Matched pair of 50mm pathlength circular IR quartz cuvette
O113
Matched pair of 100mm pathlength circular IR Quartz cuvette
O114
Universal cuvette holder for 10mm to 10mm pathlength rectangular/circular cuvettes
Technical information
Two types of cells for gas analysis are available as standard. Stainless Steel gas cell is made of 316 Stainless Steel suitable for most gas applications. For more corrosive gases, our Teflon gas cell provides an ideal solution. Both are available is 10cm pathlength, and are fitted with leak free easy fit valves for flow or static laboratory applications. The cells are supplied with two tubes with rifle ends for connection to laboratory tubing packaged in a carry case.
Specification
Material of body
316 SS Stainless Steel
Teflon
End caps
Black anodised aluminium
Black anodised aluminium
Vacuum valves
Two Nupro plug valves
Two PFA valves
Window-to-cell seal
Viton O-ring seal (Nitrile optional)
Viton O-ring seal (Nitrile optional)
Window-to-cap seal
Teflon
Teflon
Clear aperture
25mm diameter
25mm diameter
Pathlength
100mm
100mm
Volume
50cc
50cc
Outlet valves connection
1/4" (6.35mm) Swagelok
1/4" (6.35mm) tubing
Supplied connection
two 1/4" s/s tube with rifle ends
two 1/4" Teflon tubes with rifle ends
Supplied cell mount
Slide holder with cell grip screw
Slide holder with cell grip screw
Ordering information
G010
10cm Stainless Steel gas cell kit without windows
G011
10cm Teflon gas cell kit without windows
G012
Set of Viton O-ring seals (6 off)
G013
Set of Nitrile O-ring seals (6 off)
G014
Set of Teflon seals (6 off)
Window (pair) for 10cm gas cells
NaCl
KBr
CaF2
BaF2
ZnSe
Si
IR-Quartz
Sapphire
G020
G021
G022
G023
G024
G025
G026
G027
Other Common Gas Cell Windows
D x T
NaCl
KBr
KCl
CaF2
BaF2
ZnSe*
IR-Quartz
Sapphire*
25 x 4
W105
W135
W165
W195
W225
W285
W375
W405
25 x 5
W106
W136
W166
W196
W226
-----
W376
W406
29.7 x 4.2**
W107
-----
-----
W197
W227
W287
-----
------
29.7 x 6.1
W108
W138
W168
W198
W228
-----
-----
------
38 x 4
W111
W141
W171
W201
W231
W291
W381
W411
38 x 6
W112
W142
W172
W202
W232
-----
W382
W412
47.5 x 5
W113
W143
W173
W203
W233
W293
-----
W413
47.5 x 7.5**
W114
W144
W174
W204
W234
-----
W384
-----
47.5 x 10
W115
W145
W175
W205
W235
-----
-----
-----
49 x 6
W115
W146
W176
W206
W236
W296
W386
-----
ZnSe* is offered at 3mm thick or less except where indicates **. Sapphire* is offered at 3mm thick or less.
Technical information
The Diamond EX-Press is an excellent sample preparation tool for FTIR micro analysis. The diamond is a high quality Synthetic Type IIa Sumi-crystal with excellent physical and infrared transmission properties. Samples of solids and film (e.g. mineral stones, polymers and pharmaceutical materials) can be compressed to thin uniform films by using only finger tight pressure for good infrared analysis without prior sample preparation.
The cell is fitted with 1mm thick diamonds, has a working distance of only 11mm and fitted with a 3" x 2" backplate making it ideal for FTIR spectrometers without a beam condenser and Infrared Microscopes with 15X and 32X objectives.
Technical information
This patented innovative sample holder allows samples of various types (films, Nujol mulls, KBr pellet disc) and sizes from 13mm to 40mm diameter, and up to 13mm thick to be held and analysed by transmittance in infrared spectrometers. The cone shaped clip holder is gimballed and can be turned over for use in the opposite direction for different sample sizes. The spring loaded clip holder sits on an interchangeable magnetic base which gives 10mm or 22mm clear aperture depending on the direction on use.
Viton O-ring protects the sample from the retaining clip and a thumb screw provides an adjustable pressure on the sample. The holder has a 3" x 2" backplate for easy insertion into all infrared spectrometers.
Technical information
The K Holder is a simple but versatile accessory for holding liquid and solid samples including pellets for analysis in IR, UV, NIR and Raman instruments. The unit consists of an adjustable slide mount with a 2-position sample block attached to a 3" x 2" backplate. The sample block has a V shape on one end that allows circular shaped samples (e.g. discs, pellets, circular cuvettes) to be securely mounted and a flat end on the opposite side for holding flat objects such as cuvette. The two ends are interchangeable.
Depending on the size and shape of the sample, the slide mount can be adjusted 25mm along the 3" x 2" backplate to position the sample precisely in the 13mm diameter aperture of the backplate and secured tight using a thumb screw.
Technical information
This accessory provides a quick, easy and inexpensive way of mounting window discs, pellets and films for transmission analysis in infrared spectrometers. The samples are held on a 3" x 2" backplate using a spring loaded clip and a Viton O-ring protects samples from the clip. Two sample holder models are available, a 25mm diameter aperture more suitable for windows and films and a 13mm diameter for pellets.
Ordering information
P/N J025 P/N J026
EZ-Clip Sample Holder with 13mm diameter clear aperture EZ-Clip Sample Holder with 25mm diameter clear aperture
Technical information
The table press is a compact efficient mini-press designed for laboratories with small budgets but with frequent need of making KBr pellets quickly. It is sturdy on a bench table, with small footprint it occupies minimum space and is easy and safe to use.
Good KBr pellets are produced in KBr Dies using light press pressure by smooth operation of the press handle effortlessly single handed. It is ideal for making 1mm to 16mm KBr. It is oil free and no maintenance is required.