Appendix I
Septa Septa Selection Guide Septum Material
Description
Temperature (°C)
PTFE/Red Rubber
Most popular and economical choice for general GC and HPLC applications. Used for routine analysis in GC with FID, TCD and FPD detectors or HPLC with UV/Vis and RI detectors. They offer moderate resealability and excellent chemical inertness prior puncture. Low durometer of rubber allows ease of needle penetration. PTFE/Red Rubber septa are not recommended for multiple injections or storage of samples. Ideal for use in GC and HPLC applications for its high resealability even after repeated punctures. Good for sensitive analysis (lower background) and storage of samples. PTFE/Silicone septa are soft and more easily punctured, and protects the needle in autosampler. Share the same chromatographic characteristics, physical and chemical property as non-slit PTFE/Silicone septa. The cross-slit aid in needle penetration for low coring, and prevent formation of vacuum when multiple injection or large volume of sample is withdrawal from vial. However, the pre-slit septa are not recommended for storage of samples due to evaporation of volatile organic solvents through the slit. Recommended for ultra trace analysis, or where there is a longer time between injections. PTFE liners on both sides of Silicone resist coring during penetration, and protects Silicone from chemical attacks. The PTFE barrier provides excellent chemical resistance to most solvents. Butyl/PTFE septa has good resealability and suitable for gas sampling due to low permeability.
-40 to 110
PTFE/Silicone
-60 to 200
PTFE/Silicone, pre-slit
-60 to 200
PTFE/Silicone/PTFE
-60 to 200
Butyl/PTFE
-40 to 120
Physical Characteristic and Solvent Compatibility of Materials used for Caps and Septa. The chart below displayed the physical characteristic and solvent compatibility of materials used for caps and septa. You might want to test your product under actual conditions of use as there are many factors that can affect chemical resistance. Physical Characteristic of Caps and Septa
Method Dependent
Medium hard
No resealability No resealability
PP
Polypropylene Polytetra- fluorethylene Synthetic Red Rubber/PTFE
Translucent
135
-20 Yes No No Yes Yes
Low
Very hard (Very thin)
PTFE
White
260
-200 Yes Yes Yes Yes Yes Very high
Low
Medium hard Soft to medium
RR
Red/beige
110
-30 No No No No No Medium
Medium Low to Medium Low to Medium
Medium
Method Dependent
Highly resealable Highly resealable
Butyl Grey Butyl
Opaque grey
125
-20 Yes No Yes Yes Yes
T/S
Silicone/PTFE
White/Red
200
-60 Yes Yes Yes Yes Yes High
Soft
T/S/T PTFE/Silicone/PTFE Red/White/Red 200
-60 Yes Yes Yes Yes Yes High
Very low Soft
Good
* Due to hardness and molecular structure (coring) † Needle penetration ‡ In case of multiple injection
Chemical Resistance of Vials and Caps Chemical Glass PP
Chemical Diacetone
Glass PP
Chemical
Glass PP
1,2-Dichloroethane 1,2,4-Trichlorobenzene
EE EE EE EE EE EE EE EE EE
NN NN GF FN NN
EE EE EE EE EE EE EE EE EE
GF EF NN NN NN GG GN GF EE
n-Amyl Acetate
EE EE EE EE EE EE EE EE EE
GF EE GF FN FF EE FF FN NN
Diacetone Alcohol Dibutylphthalate Diethyl Benzene Diethyl Ether Diethyl Ketone Diethyl Malonate
n-Butanol
1,4-Dioxane
n-Butyl Acetate
2,2,4-Trimethylpentane
n-Decane n-Heptane
2,4 Dichlorophenol
2-Butanol
EE EE EE
Nitric Acid, 10% Nitric Acid, 20% Nitric Acid, 50% Nitric Acid, 70%
2-Methoxyethanol
2-Propanol
Diethylamine
Acetaldehyde
GN
Diethylene Dioxide
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