Definitions in Analytical Chemistry

Study Notes

Analytical Chemistry is a branch of chemistry focused on the identification, quantification, and characterization of chemical substances.
Analyte: Substance of interest being examined in a sample.
Assay: Method for measuring a specific analyte in a sample.
Interference: Substance in a sample that can cause inaccurate analysis, impacting the analyte measurement.
Sample Matrix: Composition of the sample, excluding the specific analyte, which can affect the analysis.
Blank: Sample with all components except the analyte, used to account for background interference in measurements.

Classical Method: Methods that involve chemical reactions and visual/analytical techniques for determining analyte concentrations.
Instrumental Method: Methods that use sophisticated instruments to analyze chemical substances and determine concentrations.

Sampling: Collecting a representative sample of the material to be analyzed.
Sample preparation: Transforming the sample into a suitable form for analysis.
Analysis: Measuring the specific analyte of interest based on chosen methods.
Data processing: Analyzing the collected data, interpreting the results, and reporting findings.
Selection of Analytical Method:
- Purpose of the analysis: What is the analyte of interest?
- Type of sample: What are the properties of the sample and the analyte?
- Sensitivity needed: How low of a concentration can be accurately measured?
- Cost: How much can be spent for analysis?
- Speed: How quickly are the results needed?
- Accuracy: How precise and accurate should the measurements be?

Instrument Calibration: To verify and adjust the instrument’s performance to ensure consistent and accurate measurements.
External Standard Method: A series of known analyte concentrations with standard solutions are measured for their response. This establishes a calibration curve, which is then used to determine concentrations of unknowns.
Internal Standard Method: To account for variations in the analysis process. Involves adding a known amount of a reference standard (internal standard) to the sample and the standards. By comparing analyte signal to the internal standard signal, it corrects for variations.
Standard Addition: A method commonly used when the sample matrix may interfere with the analysis. A known quantity of a standard solution is added to a series of aliquots of the sample. This helps overcome matrix effects by establishing a calibration curve in the sample matrix.

Used to assess the quality and effectiveness of analytical methods
Accuracy: How close a measurement is to the true value.
Precision: How close a measurement is to other measurements taken under similar conditions.
Specificity: Ability to measure a specific analyte without interference from other substances.
Sensitivity: Ability to detect a low concentration of the specific analyte being measured.
Limit of Detection (LOD): Minimum concentration of the analyte that can be reliably detected by the analytical method.
Concentration Range and Linearity: The span of analyte concentrations the method is reliable for and linearity refers to the relationship between the measured signal and the analyte concentration.

Parameters: Key aspects evaluated in validating an analytical method such as accuracy, precision, linearity, range, specificity, sensitivity, LOD, limit of quantification (LOQ), robustness, and system suitability.
Critical Components:
- Method development
- Method validation
- Method qualification

Analytical Chemistry is crucial in the pharmaceutical industry for ensuring the quality, efficacy, and safety of drugs.
The field is essential for:
- Drug development and optimization
- Manufacturing quality control
- Formulation of medications
- Pharmacokinetic studies (study of drug absorption, distribution, metabolism, and excretion)
- Bioavailability and bioequivalence analysis
- Therapeutic drug monitoring (TDM)
- Toxicology testing