Parts per billion ppb

The requirements placed on the performance and reliability of CVD coatings are continuously upgraded. For one thing, this means the need for an ever increasing degree of purity of the precursor materials since impurities are the maj or source of defects in the deposit. The purity of a gas is expressed in terms of nines, for instance, six nines, meaning a gas that is 99.9999% pure, which is now a common requirement. It is also expressed in ppm (parts per million) or ppb (parts per billion) of impurity content. 

Even lower concentrations in a gas mixture are expressed in parts per billion (ppb). Parts per billion measures how many molecules of substance are present in one billion molecules of sample. 

Minute quantities are sometimes quoted in ppb, parts per billion. Care is needed here, as the billion is usually an American billion (109), not the UK billion (1012). 

To help prevent this, the U. S. Public Health Service has recommended a maximum limit of 0.5 ppm mercury in any food. If the fish are to have less than this level of methyl mercury and the concentration factor is 3,000, then the surrounding water in which the fish live should have less than 0.16 ppb (parts per billion). Currently the oceans have about 0.1 ppb, but it is not known whether this is in the form of organic or inorganic compounds.8 It is also not known whether fish can convert inorganic mercury into methyl mercury.8 However, a large number of microorganisms can do this, so possibly its usual form is unimportant. 

ECD = electron capture detector ELISA = enzyme-linked immunosorbent assay GC = gas chromatography HRGC = high resolution gaschromatography MS = mass spectrometry MTBE = methyl-tert-butyl ether ppb = parts per billion ppm = parts per million ppt = parts per trillion SPE = solid phase extraction... 

GC = gas chromatography EC = electrochemical (detector ECD = electron capture (detector HCD = Hall conductivity detector HFBA = heptafluorobutyric anhydride HPLC = high performance liquid chromatography NCI-MS = mass spectrometry in the negative chemical ionization mode NPD = nitrogen-phosphorus detector ppb = parts per billion UV = ultraviolet absorption SPE = solid phase extraction wt wt = weight weight... 

SHIP = Separator for Heavy Ion Products (Germany) JINR = Joint Institute for Nuclear Research (Russia) ppm = parts per million ppb = parts per billion % = percent A= heat... 

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