Analytical Chemistry II

1. Analytical Chemistry II Budi Hastuti, S.Pd., M.Si.

2. INTRODUCTION

3. Two step analysis: 1. Identify Qualitative Analysis2. EstimationQuantitative Analysis MethodClassical / conventionalModern Analytical scale Macro, semimakro Ultramikro,Micro Submikro

4. Definition • ANALYSIS covers 3 aspects comprehensively:1. Data collection2. Data processing, interpretation3. Judgement, decision making / conclusions

5. Classification of Analytical Methods • AnalyticalChemystry is a science that identify the types of components in a sample (qualitative analysis) and determine the relative amounts of each component (quantitative analysis). • Generally, phase separation is necessary to isolate the components in the samples analyzed. • The method used distinguished role in 2 groups namely:Classical Methods Instrumental Methods

6. Classification of Analytical Methods • CLASSICAL METHODS - also called wet method • Separation of analytes - extraction, distillation, precipitation (precipitation), filtration (filtering), etc.. • Qualitative Analysis - boiling point, freezing point, color, odor, density, reactivity, refractive index, etc.. • Quantitative Analysis - gravimetric and volumetric analysis.

7. The different of classical analytical and analytical instruments (modern)

8. Profit of Analytical Instrument: • Sensitive • Fast • Selective and specific • Objective • Often non-destructive • Easily automated

9. Lack of Instrumental method: • expensive tools • Utilization and complexmaintenance • Need a special technician • Need additional tools, calibration and standardization of cheese (sometimes difficult) • needs a good environment

10. Classification of Analytical Methods • Instrumental Methodexploit the physical properties of an analyte to obtain information, both qualitative and quantitative. • Separation of analytes- Can be done in 2 ways:a. Physical separation: - Chromatography - Electrophoresisb. Spectroscopic separation: isolate the signal that appears in spectroscophy

11. Classification of Analytical Methods • Instrumental Method 1. Separation of analytes 2. Qualitative Analysis * X-Ray Spectroscopy * Infrared Spectroscopy (IR) * mass spectroscopy (MS) * nuclear magnetic spectroscopy (NMR) 3. Quantitive Analysis * UV-Vis Spectroscopy * Atomic absorption & emission spectroscopy (AAS and AES) * mass spectroscopy (MS) * Conductivity (pH)

12. Classification of Analytical Methods • Type method of Instrumental

13. Instrumentation Components

14. Analytical Method Selection • To determine the appropriate analytical method (the best), the analyst should ask the following things:a. Is accuracy required?b. How many samples are available?c. How much range of concentrations found in the sample?d. Are there any components in the sample that cause interference?e. How physical and chemical properties of the matrix contained in the sample?f. How many samples to be analyzed?

15. Performance characteristics The criteria used to compare several analytical methods • Precision • Absolute standard deviation • Relative standard deviation • Coefficient of variation • Variance • Accuracy/Bias • Absolute systematic error • Relative systematic error • Sensitivity • Calibration • Analytical • Detection Limit • Blank plus three times Std. Dev. of blank • Limit of Linearity (LOL) • Selectivity • Effects of interferences • Coefficient of Selectivity

16. Performance characteristics The other criteria that need to be considered in the selection of analytical methods: a Velocity analysis b Convenience analysismethods c Operator skill level d Cost and availability of equipment (instruments) e Cost of analysis every sample

17. N _ å - 2 ( x x ) i = = s i 1 - N 1 s = RSD _ x s = ´ CV 100 % _ x = SE s / n Performance characteristics 1. PRECISION Measure reproducibility of a determination set a) Absolute standard deviation (s) b) Relative standard deviation (RSD) c) Coefficient of variance (CV) c) Standard error of mean (SE)

18. Performance characteristics 2. ACCURACY (BIAS) Measure the error of an analytical method. a) Absolute bias (Ea) a) Persen bias (% error)

19. a) Calibration sensitivity (m) S = signal or instrument response Sbl = signal from blank sample c = sample concentration m = calibration sensitivity (slope of calibration curve) DSm1 DSm2 DC g = analytical sensitivity m = calibration sensitivity sS = std. dev. in signal measurement b) Analytical sensitivity (g) Performance characteristics 3. SENSITIVITY The ability to distinguish effect of increasing concentration on instrument response.

20. a) Minimum detectable signal (Sm) Sm= minimum detectable signal Savg,bl = average signal of the blank sbl = standard deviation in the blank signal k = multiple of variation in the blank signal • The analytical signal must be larger than the blank signal (Savg,bl) by some factor (k) of the standard deviation in the blank (sbl). kis usually set to a value of three. • Expressed in terms of sbl Performance characteristics 4. DETECTION LIMIT Concentration / minimum analyte mass that still can be detected (still can be distinguished from the noise) by a analysis method based on certain confidence level (usually 95%) b) Minimum detectable concentration (cm) cm= minimum detectable concentration m = slope of the calibration curve • Limit of Detection (LOD)

21. mA = slope = + + + S m c m c m c S A A B B C C bl S mB = slope = / k m m B , A B A = k m m / mC = slope , C A C A = + + + S ( ) m c k c k c S , , A A B A B C A C bl Sbl cA cB cC Performance characteristics 5. SELECTIVITY Degree an analytical method is free from interference that contained on the sample matrix kis the selectivity coefficient K value ranging from 0 (not selective) up to a certain figure. Increase k, the methods more selective