Differential mobility detector
Encyclopedia
Differential Mobility Detector (DMD) is a type of microelectromechanical system, radio frequency modulated IMS (MEMS RF-IMS) device.
Due its small size, it easily fits into portable units, such as transferable gas chromatographs or drug/explosives sensors. For instance, it was incorporated by Varian
in its CP-4900 DMD MicroGC, and by Thermo Fisher
in its EGIS Defender system, designed to detect narcotics and explosives in transportation or other homeland security applications.
However, independent researchers report that RSD
for such compounds as hydrogen sulfide
, methyl mercaptan
, and ethyl mercaptan
is from 4 to 11%.
|Type of source>
|Capsule Type
|Holder Type
|Isotope (radio nuclide)63Ni or Nickel 63)
>-
|Source Manufacturer
|Amount of activity per source
|Physical State of Source
|Half life Ni – 63
|Energy of beta for Ni – 63 (average / max)
|Minimum Specific Activity
|Type of decay
|Progeny (Ni – 63 decays to)
|ISO – 2919 : 1999 Testing Classification
|Maximum temperature of the source
|ISO – 2919 : 1999 Radio Toxicity Classification Group
emitted from 63Ni. In this, it is very similar to the ECD
. Varian
has given the following specifications:
Due its small size, it easily fits into portable units, such as transferable gas chromatographs or drug/explosives sensors. For instance, it was incorporated by Varian
Varian
Varian may refer to:People:* Varian Fry , American journalist who helped thousands escape from Nazi-occupied Europe during World War II...
in its CP-4900 DMD MicroGC, and by Thermo Fisher
Thermo Fisher Scientific
Thermo Fisher Scientific is a large life sciences supply company that was created in 2006 by the merger of Thermo Electron and Fisher Scientific.-Predecessors and merger:...
in its EGIS Defender system, designed to detect narcotics and explosives in transportation or other homeland security applications.
Specifications for DMD as part of Varian CP-4900 MicroGC
- Detection limit: 100 ppb for MES
- Dynamic range: 103
- RSDRelative standard deviationIn probability theory and statistics, the relative standard deviation is the absolute value of the coefficient of variation. It is often expressed as a percentage. A similar term that is sometimes used is the relative variance which is the square of the coefficient of variation...
< 2% at 10 times the LDL - Gas requirements: 400 mL/min ‘Zero’ Air or N2.
However, independent researchers report that RSD
Relative standard deviation
In probability theory and statistics, the relative standard deviation is the absolute value of the coefficient of variation. It is often expressed as a percentage. A similar term that is sometimes used is the relative variance which is the square of the coefficient of variation...
for such compounds as hydrogen sulfide
Hydrogen sulfide
Hydrogen sulfide is the chemical compound with the formula . It is a colorless, very poisonous, flammable gas with the characteristic foul odor of expired eggs perceptible at concentrations as low as 0.00047 parts per million...
, methyl mercaptan
Methanethiol
Methanethiol is a colorless gas with a smell like rotten cabbage. It is a natural substance found in the blood and brain of humans and other animal as well as plant tissues. It is disposed of through animal feces. It occurs naturally in certain foods, such as some nuts and cheese...
, and ethyl mercaptan
Ethanethiol
Ethanethiol is an organic compound with the formula CH3CH2SH. It consists of an ethyl group, CH3CH2, attached to a thiol group, SH. Its structure parallels that of ethanol, but with S instead of O. The presence of S leads to many different properties, most notably the infamous odour of EtSH...
is from 4 to 11%.
Radioactive source in DMD
|Capsule Type
|Holder Type
|Isotope (radio nuclide)
>-
|Source Manufacturer
|Amount of activity per source
|Physical State of Source
|Half life Ni – 63
|Energy of beta for Ni – 63 (average / max)
|Minimum Specific Activity
|Type of decay
|Progeny (Ni – 63 decays to)
|ISO – 2919 : 1999 Testing Classification
|Maximum temperature of the source
|ISO – 2919 : 1999 Radio Toxicity Classification Group
Detectable Substances
DMD is able to analyze the substances which can be ionized by the β particlesBeta particle
Beta particles are high-energy, high-speed electrons or positrons emitted by certain types of radioactive nuclei such as potassium-40. The beta particles emitted are a form of ionizing radiation also known as beta rays. The production of beta particles is termed beta decay...
emitted from 63Ni. In this, it is very similar to the ECD
Electron capture detector
An electron capture detector is a device for detecting atoms and molecules in a gas through the attachment of electrons via electron capture ionization. The device was invented in 1957 by Dr. James E...
. Varian
Varian
Varian may refer to:People:* Varian Fry , American journalist who helped thousands escape from Nazi-occupied Europe during World War II...
has given the following specifications:
| Analyzer | Application | Detection Limit DMD | Why | Markets |
|---|---|---|---|---|
| Sulfur odorants in Natural Gas | THT | 0.5 mg/m3 (100 ppb) | Safety | Gas transportation |
| TBM | Environmental | Gas Distribution | ||
| MES | City gates | |||
| Fuel cells | ||||
| Sulfur-free odorants in Natural Gas | Methyl Acrylate | 0.35 mg/m3 (100 ppb) | Catalysts | |
| 0.45 mg/m3 (100 ppb) | ||||
| Ethyl Acrylate | ||||
| Anesthetic gases in air | Halotane | 100 ppb | Safety | Operating Theaters |
| Enflurane | Anesthetic gas companies | |||
| Isoflurane | Recovery rooms | |||
| Desflurane | ||||
| Sevoflurane | ||||
| Sulfur hydrocarbons in HC matrices | Hydrogen Sulfide | 200 ppb | Safety | Petro-chemical processes |
| Carbonyl sulfide | Environmental | Catalysts | ||
| Methyl Mercaptan | Corrosion | Fuel cells | ||
| De-sulfurisation companies | ||||
| Mercaptanes C1-C4 in gas | Methyl Mercaptan | 100 ppb | ||
| Ethyl Mercaptan | ||||
| iso-Propyl Mercaptan | ||||
| n-Propyl Mercaptan | ||||
| TBM, tert-Butyl Mercaptan | ||||
| CFC’s & HCFC’s in air | For example | 100 ppb | Safety | Personal monitoring |
| CFC-11 | Environmental | Environmental companies | ||
| CFC-12 | Emission control companies | |||
| CFC-113 | CFC & HCFC Producers | |||
| CFC-114 | ||||
| CFC-115 |