+ ... + x

3 nd MeetingChemical AnalysisSteps and issues

STEPS IN CHEMICAL ANALYSIS1. Sampling2. Preparation3. Testing/Measurement4. Data analysis2. Error in chemical analysis3. Statistics for chemistry

SAMPLINGPrerequisite: sample should be representativeExample:Main sampleA B CPrimary sample1324Bulk samplea ba bcd2 + 3 1 + 4cdSub-bulk sampleLab sample

Preparation for Solid Sample1. 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 digestingAshing (Furnace) in certain temperature(+“ashing aid”. if necessary), solving in acids,and diluting quantitatively

TESTING/MEASUREMENTPurpose : Qualitative and quantitativeanalysisQualitative Analysis: Spot test AnalysisQuantitative Analysis:Conventional Methods: Volumetri danGravimetriPhysico-chemical methods (modern) :Elektrokimia, Spektrofotometri

Calculatioan and Data InterpretationDATA CAN BE ACHIEVED(quantitative analysis): volume, (volumetric),mass, (Gravimetric)Absorption (Spectrometric)Potential Cell (Electrochem)Should bechanged in toConcentration,(M, ppm)content(% mass/mass, % vol/mass)

Error in chemical analysis1. Indeterminate Error error can be exactly definedExamples:- Noise and deviation in electronic circuits- Vibration of building- environment change2. Determinate Error/Systematical error- Error in methods: Interfere agents ( can be + or -)3. Operational Error: Operators/Analysts4. Instrumental Error: Uncalibated/ un-standardizedinstruments

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

Simple Statistics in chemical analysis1. Mean (harga rata-rata, x ),x 1 + x 2 + x 3 + ... + x nX =n2. Standard Deviation (S), Variability of analysis resultS = ( x – x ) 2n – 1S =JKn - 1

3. Relative Standard Deviation (R.S.D)sR.S.D =x4. Coefficient of Variation (C.V.)s x 100C.V. =xExample :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%

5. Batas Kepercayaan, merupakan daerah di sekitar harga yangsesungguhnya = x + t (s x )ss x = nNilai t diperoleh dari Tabel t pada derajat kebebasan (D.B.) = n - 1Contoh:Hasil analisis massa nikel (mg) yang terkandung dalam 1 g suatu bahangalian adalah : 5,0 ; 5,3 ; 5,7 ; 4,8 ; 5,2Hitung batas kepercayaan pada tingkat kepercayaan 95%

ANSWER• x = 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.

8.PresisionThe similarity of value/data in one set of data,shown by standard of deviation9. AcurationThe nearness of data measurement tothe true value

x xxx xx xxx xXXXXXXXXXXAB C D

x xxx xx xxx xXXXXXXXXXXAB C DKeterangan:A : Presisi baik, akurasi baikB : Presisi baik, akurasi tidak baikC : Presisi tidak baik, akurasi baik (rata-rata)D : Presisi tidak baik, akurasi tidak baik

SEKIAN DULUTerima Kasih