3 nd meeting chemical analysis
DESCRIPTION
3 nd Meeting Chemical Analysis. Steps and issues. STEPS IN CHEMICAL ANALYSIS. Sampling Preparation Testing/Measurement Data analysis 2. Error in chemical analysis 3. Statistics for chemistry. SAMPLING. Prerequisite: sample should be representative Example: Main sample. - PowerPoint PPT PresentationTRANSCRIPT
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33ndnd Meeting MeetingChemical Analysis Chemical Analysis
Steps and issuesSteps and issues
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STEPS IN CHEMICAL ANALYSIS
1. Sampling
2. Preparation
3. Testing/Measurement
4. Data analysis
2. Error in chemical analysis
3. Statistics for chemistry
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SAMPLING
Prerequisite: sample should be representative
Example: Main sample
A B C Primary sample
1
43
2
2 + 3 1 + 4
dc
ba a b
c d
Bulk sample
Sub-bulk sample
Lab sample
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Preparation for Solid Sample
1.Wet Digesting
• Direct solvation with water
• Solvation with: oxydator acids (HNO3, H2SO4, HCl, HClO4, its mixtures) and base.
• Destruction with aqua regia: HNO3 : HCl = 1 : 3.
2. Dry digesting
Ashing (Furnace) in certain temperature (+“ashing aid”. if necessary), solving in acids, and diluting quantitatively
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TESTING/MEASUREMENT
Purpose : Qualitative and quantitative
analysisQualitative Analysis: Spot test Analysis
Quantitative Analysis:
Conventional Methods: Volumetri dan Gravimetri
Physico-chemical methods (modern) :
Elektrokimia, Spektrofotometri
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Calculatioan and Data Interpretation
DATA CAN BE ACHIEVED (quantitative analysis):
volume, (volumetric),mass, (Gravimetric)Absorption (Spectrometric)Potential Cell (Electrochem)
Should be changed in to
Concentration, (M, ppm)
content (% mass/mass, % vol/mass)
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Every steps in analysis steps
always face error.
Need Statistic calculation to help in
decision making
Error in data interpretation
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Error in chemical analysis1. Indeterminate Error error can be exactly defined
Examples:
- Noise and deviation in electronic circuits
- Vibration of building
- environment change
2. Determinate Error/Systematical error
- Error in methods: Interfere agents ( can be + or -)
3. Operational Error: Operators/Analysts
4. Instrumental Error: Uncalibated/ un-standardized instruments
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Relative Error
True value – measurement value% Error = x 100% True value
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Simple Statistics in chemical analysis
1. Mean (harga rata-rata, x ),
x1 + x2 + x3 + ... + xn
X = n
2. Standard Deviation (S), Variability of analysis result
( x – x )2
S =
n – 1
JK
S =
n - 1
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3. Relative Standard Deviation (R.S.D) s R.S.D = x
4. Coefficient of Variation (C.V.) s x 100 C.V. = x
Example :
Analysis of iron ores produce % mass of Iron:
7,08 ; 7,21 ; 7,12 ; 7,09 ; 7,16 ; 7,14 ; 7,07 ; 7,14 ; 7,18 ; 7,11.
Calculate: means, Standard of deviation, and coefficient of variation !
Jawab :
X = 7,13 % ; s = 0,045 % ; C.V. = 0,63%
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5. Batas Kepercayaan, merupakan daerah di sekitar harga yang sesungguhnya
= x + t (sx)
s
sx = n
Nilai t diperoleh dari Tabel t pada derajat kebebasan (D.B.) = n - 1
Contoh:
Hasil analisis massa nikel (mg) yang terkandung dalam 1 g suatu bahan galian adalah : 5,0 ; 5,3 ; 5,7 ; 4,8 ; 5,2
Hitung batas kepercayaan pada tingkat kepercayaan 95%
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ANSWERANSWER
• x = 5,2 ; s = 0,3 ; sx = 5,2 ; s = 0,3 ; sxx = 0,134 = 0,134
= 5,20 = 5,20 ++ 0,37 0,37 So So 95% 95% believe that % mass of Iron is believe that % mass of Iron is between : between : 4,83 – 5,57.4,83 – 5,57.
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8.Presision
The similarity of value/data in one set of data, shown by standard of deviation
9. Acuration
The nearness of data measurement to the true value
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x x xx x
x x xx x
X
XX
XX
X
X
XX
X
AB C D
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x x xx x
x x xx x
X
XX
XX
X
X
XX
X
AB C D
Keterangan:
A : Presisi baik, akurasi baik
B : Presisi baik, akurasi tidak baik
C : Presisi tidak baik, akurasi baik (rata-rata)
D : Presisi tidak baik, akurasi tidak baik
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SEKIAN DULUSEKIAN DULU
Terima Kasih
Terima Kasih