Module 4

Question 1

What are the steps of an analytical process

Answer 1

1. Formulating the question
2. Selecting analytical procedure
3. Sampling
4. Sample preparation
5. Analysis
6. Reporting and interpretation
7. Drawing conclusion

Question 2

What is used for the statistical treatment of data (4)

Answer 2

1. Outliers
2. Confidence interval
3. RSD
4. Uncertainty

Question 3

What is standardizing analytical methods and how is it done

Answer 3

Determine the relationship between the measured signal and amount of target analyte present
Done by using analytical standards of known amounts of the target analytem

Question 4

3 types of standardization

Answer 4

1. External standards
2. Internal standards
3. Standard addition

Question 5

What are the two types of reagents used in analytical standards

Answer 5

1. Primary reagents - reagent of known purity that can make a solution of known concentration
   - known stoich, purity and stability in long term storage
2. Secondary reagents- reagents whose purity must be determined relative to a primary reagent

Question 6

What are external standards

Answer 6

Most common used method for standardization
- solutions prepared across a range of concentrations the measures
- Linear relationship will be established

Question 7

What is the slope of line ‘k’

Answer 7

Sensitivity

Question 8

What does linear working range imply

Answer 8

The methods of sensitivity remains constant throughout the standards concentration range

Question 9

What is sensitivity

Answer 9

Rate at which signal changes with concentration

Question 10

What is an internal standard

Answer 10

A compound different from the target analyte purposely added to the sample in a known amount

Question 11

Criterial for a good internal standard:

Answer 11

1. Must be stable
2. Not present in the sample
3. Not interfere with target analyte
4. Similar chemical physical properties to target analyte

Question 12

What does an internal standard track

Answer 12

All loses that occur because of extraction and sample purification
Any loses that occur with target analyte also occurs with internal standard

Question 13

What is standard addition

Answer 13

Known quantities of target analyte are added to the sample

Question 14

3 approaches to standard addition

Answer 14

1. Single addition to a single solution
2. Multiple point addition to multiple solutions
3. Multiple point addition to single solution

Question 15

What is the matrix effect

Answer 15

Change in signal caused by anything other than the target analyte

Question 16

When is multiple addition to multiple solutions used

Answer 16

When only a small volume of sample is present

Question 17

How is multiple addition to single solution prepared

Answer 17

Preparing a series of spiked samples containing increasing amounts of the standard

Question 18

Pros and cons of standard addition

Answer 18

Pros: can mitigate influence of matrix
- can be used when matrix effect is complex

Cons: time consuming
- inaccurate preparation of standards and additions can lead to indeterminate errors

Question 19

Pros and cons of internal standards

Answer 19

Pros: accounts for matrix
-accounts for loss

Cons: hard to find standard with similar chemical physical properties

Question 20

Pros and cons of external standards

Answer 20

Pros: simple
-inexpensive
- fast

Cons:
Does not account for matrix

Question 21

What is a sampling error

Answer 21

When improper or non representative sample is collected and analyzed