3 nd Meeting Chemical Analysis Steps and issues STEPS IN CHEMICAL ANALYSIS 1. Sampling 2. Preparation 3. Testing/Measurement 4. Data analysis 2. Error.

Presentasi berjudul: "3 nd Meeting Chemical Analysis Steps and issues STEPS IN CHEMICAL ANALYSIS 1. Sampling 2. Preparation 3. Testing/Measurement 4. Data analysis 2. Error."— Transcript presentasi:

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2 3 nd Meeting Chemical Analysis Steps and issues

3 STEPS IN CHEMICAL ANALYSIS 1. Sampling 2. Preparation 3. Testing/Measurement 4. Data analysis 2. Error in chemical analysis 3. Statistics for chemistry

4 SAMPLING Prerequisite: sample should be representative Example: Main sample AB C Primary sample 1 4 3 2 2 + 3 1 + 4 dc b a a b c d Bulk sample Sub-bulk sample Lab sample

5 Preparation for Solid Sample 1.Wet Digesting Direct solvation with water Solvation with: oxydator acids (HNO3, H 2 SO 4, HCl, HClO 4, its mixtures) and base. Destruction with aqua regia: HNO 3 : HCl = 1 : 3. 2. Dry digesting Ashing (Furnace) in certain temperature (+“ashing aid”. if necessary), solving in acids, and diluting quantitatively

6 TESTING/MEASUREMENT Purpose : Qualitative and quantitative analysis Qualitative Analysis: Spot test Analysis Quantitative Analysis: Conventional Methods: Volumetri dan Gravimetri Physico-chemical methods (modern) : Elektrokimia, Spektrofotometri

7 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)

8 Every steps in analysis steps always face error. Need Statistic calculation to help in decision making Error in data interpretation

9 Error in chemical analysis 1.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

10 Relative Error True value – measurement value % Error = x 100% True value

11 Simple Statistics in chemical analysis 1. Mean (harga rata-rata, x ), x 1 + x 2 + x 3 +... + x n X = n 2.Standard Deviation (S), Variability of analysis result  ( x – x ) 2 S = n – 1 JK S = n - 1

12 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%

13 5.Batas Kepercayaan, merupakan daerah di sekitar harga yang sesungguhnya  = x + t (s x ) s s x =  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%

14 ANSWER x = 5,2 ; s = 0,3 ; s x = 0,134x = 5,2 ; s = 0,3 ; s x = 0,134  = 5,20 + 0,37 So 95% believe that % mass of Iron is between : 4,83 – 5,57.  = 5,20 + 0,37 So 95% believe that % mass of Iron is between : 4,83 – 5,57.

15 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

16 x x xx x X X X X X X X X X X A BCD

17 X X X X X X X X X X A BCD 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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