**Instrumental Analysis****The course is designed to introduce the student to modern methods of instrumental analysis****In modern analytical chemistry. The focus of the course is in trace analysis, and therefore methods for the identification, separation and quantitation of trace substances will be described.**# Scope and Relevancy of

# Instrumental Analysis

# Instrumental Methods

# Instruments

**Calibration Methods**# Method Validation

# Specificity

# Linearity

# Accuracy

# Precision

# Range

# Limits of Detection and Quantitation

# Method Validation – Specificity

# How well an analytical method distinguishes the analyte from everything else in the sample.

# Baseline separation

# Method Validation- Linearity

# How well a calibration curve follows a straight line.

# R2 (Square of the correlation coefficient)

# Method Validation- Linearity

# Method Validation- LOD and LOQ

# Limit of Detection (LOD)

# Limit of Linear Response (LOL)

# Useful Range of an Analytical Method

# Method Validation- Linearity

# Method Validation- Accuracy and Precision

# Precision – reproducibility

# Method Validation- LOD and LOQ

# Standard Addition

**Standard addition**is a method to determine the amount of analyte in an unknown.

# –In standard addition, known quantities of analyte are added to an unknown.

# –We determine the analyte concentration from the increase in signal.

# Standard addition is often used when the sample is unknown or complex and when species other than the analyte affect the signal.

# –The **matrix** is everything in the sample other than the analyte and its affect on the response is called the **matrix effect**

# The Matrix Effect

# The matrix effect problem occurs when the unknown sample contains many impurities.

# If impurities present in the unknown interact with the analyte to change the instrumental response or themselves produce an instrumental response, then a calibration curve based on pure analyte samples will give an incorrect determination

# Calibration Curve for Perchlorate with Different Matrices

# Calculation of Standard Addition

# The formula for a standard addition is:

# [X] is the concentration of analyte in the initial (i) and final (f) solutions, [S] is the concentration of standard in the final solution, and I is the response of the detector to each solution.

# But,

# If we express the diluted concentration of analyte in terms of the original concentration, we can solve the problem because we know everything else.

# Standard Addition Example

# Serum containing Na+ gave a signal of 4.27 mv in an atomic emission analysis. 5.00 mL of 2.08 M NaCl were added to 95.0 mL of serum. The spiked serum gave a signal of 7.98 mV. How much Na+ was in the original sample?

# Standard Additions Graphically

# Internal Standards

# An

**internal standard**is a known amount of a compound, different from the analyte, added to the unknown sample.# Internal standards are used when the detector response varies slightly from run to run because of hard to control parameters.

# –*e.g.* Flow rate in a chromatograph

# But even if absolute response varies, as long as the

*relative*response of analyte and standard is the same, we can find the analyte concentration.# Response Factors

# Internal Standard Example

# In an experiment, a solution containing 0.0837 M Na+ and 0.0666 M K+ gave chromatographic peaks of 423 and 347 (arbitrary units) respectively. To analyze the unknown, 10.0 mL of 0.146 M K+ were added to 10.0 mL of unknown, and diluted to 25.0 mL with a volumetric flask. The peaks measured 553 and 582 units respectively. What is [Na+] in the unknown?

# First find the response factor,

*F*# Internal Standard Example (Cont.)

# Now, what is the concentration of K+ in the mixture of unknown and standard?

# Now, you know the response factor,

*F*, and you know how much standard, K+ is in the mixture, so we can find the concentration of Na+ in the mixture.# Na+ unknown was diluted in the mixture by K+, so the Na+ concentration in the unknown was:

…