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  2. Parts-per notation - Wikipedia

    en.wikipedia.org/wiki/Parts-per_notation

    For example, the conversion factor between a mass fraction of 1 ppb and a mole fraction of 1 ppb is about 4.7 for the greenhouse gas CFC-11 in air (Molar mass of CFC-11 / Mean molar mass of air = 137.368 / 28.97 = 4.74). For volume fraction, the suffix "V" or "v" is sometimes appended to the parts-per notation (e.g. ppmV, ppbv, pptv).

  3. Explosives trace detector - Wikipedia

    en.wikipedia.org/wiki/Explosives_trace_detector

    It is expressed in terms of nano-grams (ng), pico-grams (pg) or femto-grams (fg) with fg being better than pg better than ng. It can also be expressed in terms of parts per billion (ppb), parts per trillion (ppt) or parts per quadrillion (ppq). Sensitivity is important because most explosives have a low vapor pressure .

  4. Electrochemical stripping analysis - Wikipedia

    en.wikipedia.org/wiki/Electrochemical_stripping...

    Stripping analysis has the following properties: sensitive and reproducible (RSD<5%) method for trace metal ion analysis in aqueous media, 2) concentration limits of detection for many metals are in the low ppb to high ppt range (S/N=3) and this compares favorably with AAS or ICP analysis, field deployable instrumentation that is inexpensive ...

  5. Purified water - Wikipedia

    en.wikipedia.org/wiki/Purified_water

    Combinations of a number of these processes have come into use to produce ultrapure water of such high purity that its trace contaminants are measured in parts per billion (ppb) or parts per trillion (ppt). Purified water has many uses, largely in the production of medications, in science and engineering laboratories and industries, and is ...

  6. List of file formats - Wikipedia

    en.wikipedia.org/wiki/List_of_file_formats

    PDAX – Portable Document Archive (PDA) document index file; PDF ... Microsoft PowerPoint Presentation; PPTX ... it is usually 64 bytes in size. (.bca)

  7. Odor detection threshold - Wikipedia

    en.wikipedia.org/wiki/Odor_detection_threshold

    The odor detection threshold is the lowest concentration of a certain odor compound that is perceivable by the human sense of smell.The threshold of a chemical compound is determined in part by its shape, polarity, partial charges, and molecular mass.

  8. PDF - Wikipedia

    en.wikipedia.org/wiki/PDF

    Interactive Forms is a mechanism to add forms to the PDF file format. PDF currently supports two different methods for integrating data and PDF forms. Both formats today coexist in the PDF specification: [38] [53] [54] [55] AcroForms (also known as Acrobat forms), introduced in the PDF 1.2 format specification and included in all later PDF ...

  9. National Ambient Air Quality Standards - Wikipedia

    en.wikipedia.org/wiki/National_Ambient_Air...

    The EPA first set primary and secondary standards in 1971. Dual primary standards were set at 140 ppb averaged over a 24-hour period, and at 30 ppb averaged annually. The secondary standard was set at 500 ppb averaged over a 3-hour period, not to be exceeded more than once a year.