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CHAPTER 2

CHAPTER 2 . INTRODUCTION TO CHEMICAL ANALYSIS. NURUL AUNI ZAINAL ABIDIN FACULTY OF APPLIED SCIENCE UITM NEGERI SEMBILAN. What is chemical analysis???. Chemical analysis is more than just detecting or determining the general composition or a specific component of a sample.

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CHAPTER 2

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  1. CHAPTER 2 INTRODUCTION TO CHEMICAL ANALYSIS NURUL AUNI ZAINAL ABIDIN FACULTY OF APPLIED SCIENCE UITM NEGERI SEMBILAN

  2. What is chemical analysis??? • Chemical analysis is more than just detecting or determining the general composition or a specific component of a sample. • It is the resolution or interpretation of a given problem.

  3. Why it is important? • Analytical chemists must use a systematic approach to obtain the required information from samples. • This approach consists of a series of steps and processes. • Let we see the step in analytical analysis.

  4. Step in chemical analysis…. Understanding and defining the problem NOV 2005 Familiarize with background of problem and history of sample Literature search (selecting the analytical procedures) Sampling (obtain and store sample) Preparation and pretreatment of sample

  5. Analysis (perform measurement and compare results with standards) Apply required statistical techniques Verify results Reporting

  6. 1. Understanding and Defining Problem • The goal of every chemical analysis is to obtain the required information within a period of time acceptable to the customer. • Many problem do not require complete identification and many cases require only a general classification. • It is important for the analyst to determine the information required by the client. • For example, in water analysis, only the total hardness is required rather than the concentration of individual Ca2+ and Mg2+ ion concentration is not necessary.

  7. 2. Sample History and Background of the Problem • Should know the origin of the sample. • Sample history include information on how, where, and when the sample were collected, transported and stored. • Analyst will use the sample history to maximize advantage in solving the problem.

  8. 3. Literature Search • Literature search is essential to find an appropriate procedures. • Patents or commercial literature usually help in determination of the composition of industrial materials. • Others: - book - review articles - standard organization : i) Association of official Analytical Chemists (AOAC) ii) Food and Drug Administration (FDA) - electronic media

  9. 4. Sampling OCT 2007 APR 2007 • Definition: Process of selecting representative material from the lot and storing the sample. • The suitable sampling method differ from one substance to another depending on homogeneity. • Homogeneous : Substance that has the same composition throughout the sample. • Heterogenous : Substance that has different composition from one reagent to another reagent. • Proper procedure must be used to store both samples and standards. • All sample must be properly labeled and recorded.

  10. 5. Sample Preparation and Pretreatment APR 2007 • Step of sample preparation involved bulk materials: 1. Bulk sample must be reduced in size to obtain a laboratory sample of several grams. 2. From which a few grams to milligrams will be taken to be analyzed (analysis sample). 3. The size reduction may require taking portions (eg, two quarters) and mixing, in several steps, as well as crushing and sieving to obtain a uniform powder for analysis.

  11. Why sample pretreatment is important? • Laboratory samples are often subjected to physical or chemical pretreatment where it is converted to a form that is suitable for the measurement. • During pretreatment: i) reduce and remove interferences ii) adjust analyte concentrations to a range suitable for measurement iii) produce species from analyte that have quantitatively measurable properties.

  12. 6. Analysis • Analysis: Incorporates the measurement of the concentration of the analyte in replicates and comparing with standards. • Replicate measurement: the practice of taking multiple readings. • The replicate measurements are necessary to obtain the measurement uncertainty. • The uncertainty important as it indicates the reliability of the measurements.

  13. APR 2006 • Suitable standardization methods should be selected to ensure the precision and accuracy of results. i) CALIBRATION CURVE – An graph of detector response as a function of analyte concentration. ii) EXTERNAL STANDARDIZATION iii) INTERNAL STANDARDIZATION iv) STANDARD ADDITION - Addition of a known quantity of analyte to a real sample undergoing analysis. v) BLANKS – A blank contains the reagents and solvents use in analysis, but no analyte. vi) CONTROL CHARTS

  14. 7. Reporting and Interpretation • Deliver a clearly written, complete report and their limitations.

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