Ash and Mineral Analysis by Ulfa Andayani
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Ash and Mineral
Analysis
by Ulfa Andayani
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TOPICS DESCRIPTION
Minerals Metode analisa mineral.
Prinsip dan aplikasi
spektrofotometri serapan atomatau spektrometri nyala
dan metode kimia untuk unsur
renik .
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Definitions
• Ash: kadar mineral total; residu inorganic sisa setelahpengabuan atau oksidasi sempurna materi organik.
• Minerals:
– Macro minerals (>100 mg/day)
• Ca, P, Na ,K, Mg, Cl, S – Trace minerals (mg/day)
• Fe, I, Zn, Cu, Cr, Mn, Mo, F, Se, Si
– Ultra trace minerals• Va, Tn, Ni, Sn, B
– Toxic mineral• lead, mercury, cadmium, aluminum
3
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Kadar mineral :• jumlah total mineral dalam makanan,
• dihitung sebagai komponen anorganik
spesifik,• misal :Ca, Na, K and Cl.
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Alasan mineral perlu dianalisis ?
• Nutritional labeling .
• Konsentrasi dan jenis mineral yang ada harus
dicantumkan dalam label suatu bahan makan.
• Quality.
• Kualitas beberapa bahan makan tergantung pada
konsentrasi dan jenis mineral yang terkandung,rasa, tampilan, tekstur dan stabilitas.
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Microbiological stability
Kandungan mineral yang tinggi, terkadang digunakan
untuk retard pertumbuhan certain microorganisms.
NutritionBeberapa mineral sangat essensial terhadap diet (mis :
calcium, phosphorous, potassium and sodium)
sedangkan yang lain bersifat toxic (e.g., lead,
mercury, cadmium and aluminum).
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• Processing
• Penting untuk mengetahui kandungan mineral
dalam makanan selama proses karena berpengaruh
pada sifat fisikokimia suatu makanan.
• Peraturan pemerintah
• Setiap produk makanan harus disertai identifikasi
sesuai standar
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• Pengembangan riset
• Peningkatan mutu produk yang lama dan membuat
produk baru
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Penentuan Kadar Mineral
•Abu merupakan residu anorganik yang tersisasetelah air dan materi organik dihilangkandengan proses pemanasan dengan bahan
pengoksidasi.
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• Teknik analisaà informasi kandungan totalà fakta : mineral (analit) dapat didistinguished dari semua komponen (matriks)yang terkandung dalam bahan makan.
• Mineral tidak dapat didekstruksi melaluipemanasan, dan tingkat volatilitas yang lebih
rendah dibandingkan komponen bahanmakanan yang lain.
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Ash Contents in Foods
Wheat flour, whole grain 1.6%
Macaroni, dry, enriched 0.7%
Milk, whole, fluid 0.7%
Butter, with salt 2.1%Apple, raw with skin 0.3%
Banana, raw 0.8%
Egg, whole, raw 0.9%
Hamburger, regular, plain 1.7%
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Methods for Determining Ash
– Dry ashing
• high temperature
– Wet ashing
• oxidizing agent and/or acid
– Low-temperature plasma ashing
• dry ashing in partial vacuum at low
temperature
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Dry Ashing
• Principles – High temperature (>525°C) overnight (12-18 hr)
– total mineral content
• Instrumentation
– Muffle furnace
– Crucible
• quartz
• porcelain
• steel
• nickel
• platinum
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General Procedure for Dry Ashing
1. 5-10g pretreated sample into a crucible
2. Ignite crucible to constant weight at ~550°C
for 12-18 hr
3. Cool in desiccator
4. Weigh cooled crucible
% ash (db) = × 100%
wt after ashing - crucible wt
Sample wt - berat air
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Dry Ashing
• Advantages
– safe and easy
– no chemical
– many samples handled at one time
– resultant ash for further mineral analysis
• Disadvantages
– loss of volatiles
– interaction
– long time and expensive equipment
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Color spectrometry for determination of
P
conve rts organic P to
inorganic or thophosphate
(PO4
3- )
P is de te rmine d by forming a
color comple x that abs orbs light
at a s pecific wave le ngthaccording to Be e r’s Law
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Color spectrometry for determination of
P
Nature of complex -- Coordination of molybdateions with P as the central coordinating ion.
1. H3PO4 + 12 H2MoO4è H3P(Mo3O10)4 + 12 H2O
yellow blue
2. Reduce Mo6+ to Mo3+ to form a blue color.
3. Read absorbance (A) at 880 nm wavelength)
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PRINSIP ANALISA MINERAL METODE AAS
• Sampel dilakukan pengabuan basah atau
kering,
• residu dilarutkan asam encer
• dibakar dengan nyala api alat AAS,
• absorpsi atau emisi logam diukur pada
panjang gelombang tertentu.
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P
P0
MonochromaterDetector
(Photomultiplier)Hollow cathode lamp
Sample
Chopper
Flame
Emits light at a
wavelength specific
to the element to be
determined.
Converts the sampleelement to an atomic
vapor
Electronics and
readout
Splits the beam into
a sample beam and
a reference beam in
order to compensate
for variations in the
electrical current.
Isolates the correct
wavelength for the
element being
determined.
Detects the light
energy and converts
it to electrical energy.
The output is the ratio
of two beams, P/P0.
Converts the
electrical signal
to readable data.
Ground State
Energy level = E0 Excited State
Energy level = E1
Atomic Absorption
Spectrophotometry
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Prinsip kerja :
• PEREAKSI:
– HCl 6 N, 3N DAN 0,3 N
– LANTANUM KHLORIDA 10% w/v
– Kertas saring Whatman No541, cuci kertas saringdgn HCl 3N
• Larutan stok STD 1000 mg/L = 1 g/L (pa)
spt tabel 1
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Tabel 1
Logam Larutan stok/standart berat g/250 m l
Ca CaCO3 kering 0.624
Cu CuSO4.5H2O 0,981
Fe Fe2(SO4) 3(NH4) 2SO4.24H20 2,158
Mg MgSO4.7H2O 2,530
Zn ZnSO4.7H2O 1,100
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• Lar. STD diencerkan dengan air utk sampel
pengabuan basah
• atau dgn HCl 0,3N (pengabuan kering) sampaikonsentrasi dalam kisaran konsentrasi (Tabel
2)
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Tabel 2
Panjang gelombang Limit deteksi Kisaran
kerja
(nm) (ug/ml) (ug/ml)
—Ca 422,7 0,01 0,05-5
—Cu 324,8 0,005 0,05-5
—Fe 248,3 0,03 0,05-5
—Mg 285,2 0,001 0,02-2
—Zn 213,9 0,004 0,1-2
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Peralatan
• AAS (MODEL, BUATAN MANA?) Alat sudah
dikalibrasi dengan lar. STD yg telah diketahui
kadarnya untuk masing-2 jenis logam
• Alat gelas yg telah dicuci dengan asam nitrat
encer sebelum dipakai.
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PRINSIP KERJA
• A. Pengabuan basah: – pindahkan abu larutkan dgn labu takar
sampai diperoleh kons. Logam sesuai dgntabel 2. encerkan sampai tanda tera dengan
air, tutup labu takar.• B. lakukan pengabuan kering sesuai prosedur
• Siapkan blanko spt cara pengabuan kering.
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KALIBRASI ALAT DAN PENETAPAN SAMPEL
1. SET ALAT SESUAI DENGAN MANUAL
2. UKUR LAR. STD MASING-2 LOGAM DAN
BLANKO
3. UKUR ABSORBANSI SAMPEL
4. BUAT KURVA LARUTAN STD REG LINEAR
(Absorbansi Vs [larutan standar]
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PERHITUNGAN
1. TENTUKAN KONS LOGAM DALAM SAMPELDARI KURVA STD YG DIPEROLEH.
2. KADAR LOGAM (mg/100 g) =
(a-b) x V/ 10 W3. KADAR LOGAM (mg/1000 g) =
(a-b) x V/ W
W = berat sampel; V= Vol ekstrakkons. Lar. sample (ug/ml) = a
Kons. lar. Blanko (ug/ml) = b
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LATIHAN PERHITUNGAN
A ANALISA MINERAL Fe metode AAS
A LARUTAN STOCK Fe STD : 1000 mg/L
A Buat larutan Fe STD yg mengandung 0,05; 0,1; 0,5;1,0;
2,0;3,0;4,0 dan 5 ug/ml
A Bagaimana caranya?
A Ukur Abs Lar STD tsb dgn AAS pada panjang gelombang 248,3.
Hasilnya : 0,005; 0,098;0,156;0,560;0,685;0,719;0,815 & 0,968
A Abs blanko : 0,085
AAbs sampel : 0,634 & 0,937
A Berapa kadar Fe dalam sampel ? Ppm/ug/ml