Karbon-14 (¹⁴C)

Data nuklida

Unsur

Karbon (C, Z = 6)

Nomor massa (A)

14

Proton (Z)

6

Neutron (N)

8

Massa atom

14.00324198862 ± 0.00000000403 u

Waktu paruh

5,7 ribu tahun (± 0,03 ribu tahun)

Mode peluruhan

Peluruhan beta minus (β⁻) ( 100 %)

Inti anak

Nitrogen-14 (¹⁴N)

Tahun penemuan

1936

Sumber data

IAEA Atomic Mass Data Center (NUBASE) and IUPAC CIAAW, via PubChem

Kegunaan isotop karbon

• Because of above-ground nuclear bomb testing, the neutrons released reacted with CO2 to increase atmospheric 14C via the 14N (n, p) 14C reaction, and 14C started rising in about 1955 (Fig. IUPAC.6.1) and reached a peak in the mid-1960s. With the curtailment of above-ground nuclear testing in the 1960s, the atmospheric 14C concentration has since been decreasing exponentially (Fig. IUPAC.6.1). This variation in 14C concentration is used to establish when cells in biology were born and how quickly they are renewed. This technique is commonly called carbon-14 bomb pulse biology and it has provided information on the age of cells and their regeneration. Figure 4.6.2 shows the average age of selected cells in a 30-year-old human.
• Because molecules, atoms, and ions of the stable isotopes of carbon possess slightly different physical and chemical properties, they commonly will be fractionated during physical, chemical, and biological processes, giving rise to variations in isotopic abundances and in atomic weights. Carbon in natural terrestrial materials shows a substantial variation in isotopic abundance (Fig. IUPAC.6.3), providing many different ways of distinguishing sources of materials and processes affecting them. Variations in the isotope-amount ratio n(13C)/n(12C) in tree rings and in CO2 trapped in ice cores have been used to study causes of variations in atmospheric CO2 levels. Variations in the isotope-amount ratio n(13C)/n(12C) and in the 14C concentration of surface ocean waters have been used to trace the incorporation and movement of atmospheric CO2 in the ocean.
• Variations in the isotope-amount ratio n(13C)/n(12C) of biological products can be observed using isotope-ratio mass spectrometry (IRMS) to detect adulteration (the addition of inferior ingredients) in honey and other food products. The isotope-amount ratio n(13C)/n(12C) can fluctuate between carbon sources, for example C3 plants (found in temperate climates and which use atmospheric carbon dioxide to make a 3-carbon molecule during photosynthesis — examples include rice, potatoes, tomatoes, and sugar beets), C4 plants (found in hot climates and which use atmospheric carbon dioxide to make a 4-carbon molecule during photosynthesis — examples include corn and sugar cane), animal carbon, atmospheric CO2, etc. This commonly makes it possible to detect whether these different carbon sources have been mixed by using isotope or mass balance to distinguish, for example, between beet sugar and cane sugar. Complications in source identification can arise with plants that open stomata at night to collect carbon dioxide to use a third mechanism to fix atmospheric carbon dioxide (CAM or crassulacean acid metabolism). The isotope-amount ratio n(13C)/n(12C) of CAM plants overlaps that of C3 or C4 plants — examples include pineapples and jade plants. The following adulterations are commonly detected using stable carbon isotope IRMS: –Variations in the isotope-amount ratio n(13C)/n(12C) of honey are used to detect the addition (and potential adulteration) of high fructose corn syrup, corn, or sugar cane. –Variations in the isotope-amount ratio n(13C)/n(12C) of fruit juice have been used to detect the addition of a sugar. –Variations in the isotope-amount ratio n(13C)/n(12C) of natural vanilla extract have been used to detect the addition of artificial vanillin or p-hydroxybenzaldehyde. –Variations in the isotope-amount ratio n(13C)/n(12C) of beer are used to detect C4 carbon, which would indicate that a beer company may have added ingredients that are not traditionally used in brewing beer. Therefore, this ratio is used to detect the misrepresentation of a product as being pure,. Stable carbon IRMS has been used to determine if the botanical origin of an alcoholic spirit has been mislabeled and if chaptalization (the process of adding sugar to increase the alcoholic content) of wine has occurred,. 14C scintillation counting has been used to determine the age of wine and alcoholic spirits,. Variations in the isotope-amount ratio n(13C)/n(12C) of urine has been used to determine if steroids in urine are natural or of synthetic origin. These measurements enable anti-doping laboratories to perfect their methods for detecting steroid doping in athletes,,. Variations in the isotope-amount ratio n(13C)/n(12C) of marijuana can provide information to determine if the plants were grown “inside” a building or greenhouse or were “open grown” (Fig. IUPAC.6.4). Plant carbon isotopic compositions are controlled by atmospheric CO2 and the supply and demand of CO2 in photosynthesis (the process used by plants to convert light energy from the sun into chemical energy). “Open grown” plants are grown in an area that is well ventilated and receives natural CO2. In contrast, plants grown “inside” receive supplemented CO2 and the photosynthesis process is more confined. Additionally, CO2 from a tank of compressed gas used to augment atmospheric CO2 to increase the growth of marijuana plants is commonly highly depleted in 13C as a refinery by-product. These differences change the carbon isotope ratios of the plants and the ratios vary enough to enable the determination of the growing and cultivation process of marijuana,.
• Radioactive 14C is the basis for the radiocarbon dating method to determine the ages of carbon-bearing materials. 14C is formed naturally in the atmosphere by cosmic-ray interactions and was also released by above-ground, nuclear weapons testing (Fig. IUPAC.6.1). Atmospheric 14C is incorporated into plants, animals, soils, groundwater, and ocean water, and it decays with a half-life of ~5700 years. This makes it useful for dating objects, such as archaeological remains and water masses in oceans and aquifers, on time scales ranging from hundreds of years to tens of thousands of years. Plants and animals living since the 1950s can be identified by bomb-peak 14C in their cells.
• 14C is used to create isotopically labeled drugs to study their uptake and metabolism in humans,,. 13C is used in breath tests to detect Helicobacter pylori bacteria (bacteria in the stomach linked to ulcers), which can cause cancers.

Reaksi inti

• Peluruhan beta karbon-14

Isotop karbon lainnya

⁸C, ⁹C, ¹⁰C, ¹¹C, ¹²C, ¹³C, ¹⁵C, ¹⁶C, ¹⁷C, ¹⁸C, ¹⁹C, ²⁰C, ²¹C, ²²C, ²³C

Pelajari

Kimia inti Simulasi peluruhan ¹⁴C Bagan nuklida