| Filter type |
Filter sizes (mm) |
Characteristics |
Analyses methods* |
| Chemical |
Physical |
| Ringed Teflon membrane |
25
37
47 |
- Low blank levels
- Low blank weight
- Low hygroscopic tendency
- Inert to gas absorption
|
- Thin membrane
- High particle collection efficiency
- High flow resistance
- Melts at ~60oC
- Cannot be accurately sectioned
- Multiple pore sizes available
|
Gravimetry, XRF, PIXE, NAA, AAS, ICP/AES, ICP-MS, IC |
| Teflon membrane-polypropylene backed |
47 |
- Low blank levels
- High blank weight
- Inert to gas absorption
- High background levels for PIXE and XRF
- Low hygroscopic tendency
|
- Thin membrane
- High particle collection efficiency
- Melts at ~60oC
- High flow resistance
|
Gravimetry, PIXE, XRF, NAA, AAS, ICP/AES, ICP-MS, IC |
| Nylon membrane |
25
37
47 |
- Low blank weight
- Low hygroscopic tendency
- High HNO3 collection efficiency
|
- Thin pure nylon membrane
- High flow resistance
- Melts at ~60oC
|
IC |
| Silver membrane |
25
37 |
- Resistant to chemical attack
- Passive adsorption of organic vapours
- High blank weight
- Low hygroscopic tendency
|
- Thin membrane
- High flow resistance
- Melts at ~350oC
|
Gravimetry |
| Cellulose esters membrane (cellulose nitrate mixed esters and cellulose acetate |
37
47 |
- Dissolved by several organic solvents
- Negligible ash content
- Hygroscopic
- Low blank weight
|
- Thin membrane
- Multiple pore size available
- High flow resistance
- Melts at ~70oC
|
Gravimetry, SEM, TEM |
| Poly-carbonate membrane |
47 |
- Low blank levels
- Low blank weight
- Low hygroscopic tendency
|
- Smooth, thin surface with straight capillary holes
- Multiple pore sizes available
- Used for particle size classification
- Low particle collection efficiency for some pore sizes
- Retains static charge
- Moderate flow resistance
- Melts at ~60oC
|
Gravimetry, XRF, PIXE and SEM |
| Pure quartz filter |
25
37
47
203 x 254 |
- Contains large variable quantities of Al and Si
- Low blank levels for ions
- Passive absorption of organic vapours
- Little absorption of HNO3
- Low hygroscopic tendency
|
- Edges of filter flake in holders
- High particle collection efficiency
- Moderate flow resistance
- Melts at > 900oC
|
ICP/AES, ICP-MS, IC |
| Mixed quartz filter (quartz filters with 5% borosilicate content) |
203 x 254 |
- Contains large and variable quantities of Na, Al and Si plus variable levels of other metals
- Passive adsorption of organic vapours
- Little adsorption of HNO3
- High blank weight
- Low hygroscopic tendency
|
- High particle collection efficiency
- Low flow resistance
- Becomes brittle on heating
- Can melt at ~500oC
|
Gravimetry, XRF, PIXE, AAS, ICP/AES, ICP-MS, IC |
| Teflon-coated glass fibre (borosilicate glass fibre mat with surface layer of Teflon) |
37
47 |
- Inert to absorption of HNO3
- Low blank levels for ions
- High blank weight
- Low hygroscopic tendency
|
- Low flow resistance
- High particle collection efficiency
- Melts at ~60oC
|
Gravimetry, IC |
| Glass fibre (borosilicate glass fibre) |
203 x 254 |
- Adsorbs HNO3 and organic vapours
- High blank levels
- High blank weight
- Low hygroscopic tendency
|
- Low flow resistance
- High particle collection efficiency
- Melts at ~500oC
|
Gravimetry, XRF, PIXE, NAA, AAS, ICP/AES, IC |
| Cellulose fibre (paper filter) |
25
37
47 |
- Low blank levels (high purity)
- High blank weight
- Hygroscopic
- Adsorbs gases, particularly water vapour
|
- High mechanical strength
- Low particle collection efficiency
- Variable flow resistance
- Burns at ~150oC
|
Gravimetry, XRF, PIXE, NAA, AAS, ICP/AES, ICP-MS, IC |