Izotop-nisbati massa spektrometriyasi ( irms )
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- Izotop nisbatli massa spektrometriyasi Magnit sektor massa spektrometri issiqlik ionizatsiyasi orqali izotop nisbatlarini tahlil qilishda ishlatiladi . Qisqartma
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Izotop nisbatli massa spektrometriyasi Izotop-nisbati massa spektrometriyasi ( IRMS ) - mass-spektrometriyaning ixtisoslashuvi bo'lib , unda ma'lum bir namunadagi izotoplarning nisbiy ko'pligini o'lchash uchun mass- spektrometrik usullar qo'llaniladi. [1] [2] Ushbu texnikaning er va atrof-muhit fanlarida ikki xil qo'llanilishi mavjud. " Barqaror izotoplar " tahlili odatda tabiiy tizimlarda massaga bog'liq bo'lgan izotop fraksiyasidan kelib chiqadigan izotopik o'zgarishlarni o'lchash bilan bog'liq . Izotop nisbatli massa spektrometriyasi Magnit sektor massa spektrometri issiqlik ionizatsiyasi orqali izotop nisbatlarini tahlil qilishda ishlatiladi . Qisqartma IRMS Tasniflash massa spektrometriyasi Boshqa tomondan, radiogen izotop tahlili [3] tabiiy radioaktivlikning parchalanish mahsulotlarining ko'pligini o'lchashni o'z ichiga oladi va ko'pchilik uzoq muddatli radiometrik tanishish usullarida qo'llaniladi. Kirish CO 2 ni o'lchash uchun izotop nisbati massa spektrometrining sxemasi Izotop nisbati massa spektrometri (IRMS) tabiiy izotoplarning aralashmalarini aniq o'lchash imkonini beradi. [4] Izotoplar nisbatlarini aniq aniqlash uchun ishlatiladigan asboblarning aksariyati magnit sektor turiga tegishli . Ushbu turdagi analizator ikki sababga ko'ra ushbu tadqiqot sohasida to'rt kutupli tipdan ustundir . Birinchidan, u bir nechta kollektorli tahlil uchun o'rnatilishi mumkin, ikkinchidan, u yuqori sifatli "cho'qqi shakllari" ni beradi. Bu ikkala mulohazalar ham juda yuqori aniqlik va aniqlikda izotop nisbatlarini tahlil qilish uchun muhimdir. [3] Alfred Nier tomonidan ishlab chiqilgan sektor tipidagi asbob mass-spektrometr dizaynida shu qadar ilg'or ediki , bu turdagi asbob ko'pincha "Nier tipi" deb ataladi. Umuman olganda, asbob qiziqish namunasini ionlashtirish, uni kilovolt diapazonidagi potentsialda tezlashtirish va hosil bo'lgan ionlar oqimini ularning massa-zaryad nisbati (m/z) bo'yicha ajratish orqali ishlaydi. Yengilroq ionli nurlar og'irroq ionli nurlarga qaraganda kichikroq radiusda egiladi. Har bir ion nurining oqimi " Faraday kubogi " yoki multiplikator detektori yordamida o'lchanadi . Ko'pgina radiogen izotop o'lchovlari qattiq manbani ionlash orqali amalga oshiriladi, yorug'lik elementlarining barqaror izotop o'lchovlari (masalan, H, C, O) odatda gaz manbai bo'lgan asbobda amalga oshiriladi. "Ko'p yig'uvchi" asbobda ion kollektori odatda bir vaqtning o'zida bir nechta izotoplarni aniqlash imkonini beruvchi Faraday stakanlari qatoriga ega. [5] Measurement of natural variations in the abundances of stable isotopes of the same element is normally referred to as stable isotope analysis. This field is of Gaz manbalarining massa spektrometriyasi interest because the differences in mass between different isotopes leads to isotope fractionation, causing measurable effects on the isotopic composition of samples, characteristic of their biological or physical history. As a specific example, the hydrogen isotope deuterium (heavy hydrogen) is almost double the mass of the common hydrogen isotope. Water molecules containing the common hydrogen isotope (and the common oxygen isotope, mass 16) have a mass of 18. Water incorporating a deuterium atom has a mass of 19, over 5% heavier. The energy to vaporise the heavy water molecule is higher than that to vaporize the normal water so isotope fractionation occurs during the process of evaporation. Thus a sample of sea water will exhibit a quite detectable isotopic- ratio difference when compared to Antarctic snowfall. Samples must be introduced to the mass spectrometer as pure gases, achieved through combustion, gas chromatographic feeds, [6] or chemical trapping. By comparing the detected isotopic ratios to a measured standard, an accurate determination of the isotopic make up of the sample is obtained. For example, carbon isotope ratios are measured relative to the international standard for C. The C standard is produced from a fossil belemnite found in the Peedee Formation, which is a limestone formed in the Cretaceous period in South Carolina, U.S.A. The fossil is referred to as VPDB (Vienna Pee Dee Belemnite) and has 13 C: 12 C ratio of 0.0112372. Oxygen isotope ratios are measured relative the standard, V-SMOW (Vienna Standard Mean Ocean Water). Yüklə 237,94 Kb. Dostları ilə paylaş:
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