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Mass-spektrometriya

Molekulyar massa • Izotopik taqsimot • Fragmentatsiya • HRMS • m/z fizikasi

Birikmalarning mass-spektr tahlili

Kompleks birikmalarning to'liq mass-spektr talqini: molekulyar ion aniqlash, ketma-ket fragmentatsiya yo'llari, izotopik cluster simulyatsiyasi va HRMS orqali molekulyar formula tasdiqlash — har bir birikma uchun batafsil.

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20+ ta birikmaIzotopik clusterFragmentatsiya sxemasiHRMS ppmm/z hisob-kitobiESI+/ESI− rejimlar

📖 Mass-spektrometriyaning fizik asosi

Mass-spektrometriya — moddaning atom-molekulyar tarkibini ionlarning massa-zaryad nisbati (m/z) bo'yicha aniqlaydigan analitik usul. Har qanday mass-spektrometr uchta asosiy bosqichdan iborat: ionlashtirish → massalarga ajratish → aniqlash. Ilk mass-spektrograf J. J. Thomson tomonidan 1912-yilda yaratilgan; F. W. Astonbuning uchun 1922-yilda Nobel mukofoti bilan taqdirlandi. Kompleks birikmalar kimyosida bu usul molekulyar identifikatsiyaning oltin standartiga aylandi.

🔑 Asosiy fizik tenglamalar

Lorentz kuchi:

F = q(E + v × B)

Kinetik energiya (tezlashuv):

½mv² = zeV → v = √(2zeV/m)

Magnit sektor m/z:

m/z = (r²B²e) / (2V)

Rezolyutsiya (FWHM):

R = m / Δm

ppm xatosi:

Δppm = (mobs − mcalc)/mcalc × 10⁶

Massa turlari (aniqliklar iyerarxiyasi)

  • Nominal massa

    Butun sonli: H=1, C=12, N=14, O=16. Past aniqlikdagi asboblarda ishlatiladi.

  • O'rtacha (average) massa

    Barcha izotoplarning tabiiy o'rtachasi: C = 12.011. Molar massa bilan bir xil.

  • Monoizotopik massa

    Faqat eng ko'p tarqalgan izotoplar: ¹H, ¹²C, ¹⁴N, ¹⁶O. HRMS ishlatadi.

  • Aniq (exact) massa

    Nazariy hisoblangan (4–6 xona): ¹²C = 12.00000, ¹H = 1.00783. HRMS ma'lumotlari bilan solishtiriladi.

🧮 Halqa va π-bog'lar soni (RDBE — Ring + Double Bond Equivalents)

HRMS orqali topilgan molekulyar formuladan to'yinmaganlik darajasini (halqalar + qo'shbog'lar sonini) hisoblash mumkin. Bu kompleks birikmaning struktura taxminini tekshirishda hal qiluvchi ahamiyatga ega.

RDBE = C − H/2 − X/2 + N/2 + 1

(C — uglerod, H — vodorod, X — galogenlar, N — azot)

Benzol (C₆H₆)

RDBE = 6 − 3 + 1 = 4 (3π + 1 halqa) ✓

bpy (C₁₀H₈N₂)

RDBE = 10 − 4 + 1 + 1 = 8 (2 halqa + 6π) ✓

Ferrosen (C₁₀H₁₀Fe)

RDBE = 10 − 5 + 1 = 6 (2 Cp halqa + 4π koordinatsion)

Azot qoidasi (Nitrogen Rule)

Agar organik molekulada toq sonda N atom bo'lsa, uning nominal molekulyar massasi ham toq son bo'ladi. Bu qoida N sonini tez baholash uchun ishlatiladi. Kompleks birikmalarda ammiakli komplekslar ([Co(NH₃)₆]³⁺, [Ni(en)₃]²⁺) uchun ham amal qiladi — masalan, [Co(NH₃)₆]Cl₃ da 6 ta N (juft) → M = 267 (toq bo'lmaydi, lekin Cl ekvivalentini hisobga olish kerak).

📚 Ilmiy manbalar

  • • J. H. Gross — Mass Spectrometry: A Textbook (3rd ed., Springer, 2017)
  • • E. de Hoffmann, V. Stroobant — Mass Spectrometry: Principles and Applications (3rd ed., Wiley)
  • • F. W. McLafferty, F. Tureček — Interpretation of Mass Spectra (4th ed., University Science Books)
  • • W. Henderson, J. S. McIndoe — Mass Spectrometry of Inorganic and Organometallic Compounds (Wiley, 2005)
  • • R. A. W. Johnstone, M. E. Rose — Mass Spectrometry for Chemists and Biochemists (2nd ed., CUP)
  • • IUPAC Gold Book — Mass spectrometry terminology (2013 tavsiyalari)
  • • NIST 2021 — Atomic Weights and Isotopic Compositions (CODATA)
  • • J. B. Fenn — Nobel Lecture (2002, ESI kashfi)
  • • K. Tanaka — Nobel Lecture (2002, MALDI kashfi)
  • • M. Yamashita, J. B. Fenn — J. Phys. Chem. 88 (1984) 4451
  • • A. G. Marshall — FT-ICR: Anal. Chem. 74 (2002) 252A
  • • A. Makarov — Orbitrap: Anal. Chem. 72 (2000) 1156
  • • W. Paul — Nobel Lecture (1989, kvadrupol va ion tutqich)