Intro to Instrumental Analysis and Quality Assurance - Flashcards

A set of practice flashcards covering key concepts from Lecture No. 1 and 2 notes on Instrumental Analysis and Quality Assurance.

What is instrumental analysis?

The determination of chemical composition and/or relative concentrations by applying a stimulus (optical, electrical, magnetic, or thermal) and detecting induced responses to identify or quantify analytes.

What stimuli are used in instrumental analysis?

Optical (light, hν), electrical (I or V), magnetic (B), and thermal (heat, q).

What are the typical components of an instrumental analysis workflow?

A detector signal, an amplifier, a digitizer, data processed by a PC or meter, enabling qualitative identification and quantitative results.

What is the purpose of calibration in instrumental analysis?

To provide quantitative results by relating instrument signal to analyte concentration through a calibration curve.

What is an external standard calibration curve?

A calibration curve built from known standards measured outside the sample to relate signal to concentration (also called a standard curve).

What are the four steps of external standard calibration as described in the notes?

1) Prepare known samples over a concentration range; 2) Subtract blank signal; 3) Plot data and assess linearity; 4) Measure the unknown and interpolate within the linear range.

Why might sample preparation be necessary for analysis?

Because a complex sample matrix can affect measurements; techniques like Solid Phase Extraction or Liquid Chromatography are used for preparation.

What is the purpose of a standard curve in quantitative analysis?

To relate instrument response to concentration and enable calculation of unknown concentrations within the curve's linear range.

What are the general steps in chemical analysis according to the notes?

Question formulation, analytical procedure selection, sampling, sample preparation, analysis, and reporting & interpretation.

What is QA in analytical chemistry?

Quality Assurance: a process to ensure a procedure meets objectives and specifications, including data collection and verification of results.

What is a specification in QA?

A defined tolerance or requirement (an analytical figure of merit) that results must satisfy.

What is assessment in QA?

The process of collecting data to show compliance with specifications and verifying that results meet objectives.

What is a false positive in QA terminology?

An incorrect result where the test indicates a concentration above the limit when it is truly below.

What is a false negative in QA terminology?

An incorrect result where the test indicates a concentration below the limit when it is truly above.

What does precision measure?

How well replicate measurements agree with one another, usually described by the standard deviation.

What does accuracy measure?

How close a measurement is to the true value, often assessed with reference materials or known values.

What is specificity in method validation?

The ability of a method to distinguish the analyte from everything else that might be present.

What is selectivity in method validation?

The relative sensitivity of the response to one species over another.

What is robustness in method validation?

The ability of a method to remain unaffected by small, deliberate changes in operating parameters.

What are LOD and LOQ in method validation?

LOD (Limit of Detection): the lowest concentration that can be detected (often defined as 3s/m). LOQ (Limit of Quantitation): the lowest concentration that can be quantified with acceptable precision (often 10s/m).

What is linearity in a calibration curve?

The range over which the instrument response is proportional to concentration, typically evaluated with R^2 and a linear slope.

What does the slope and R^2 indicate in a calibration curve?

Slope indicates sensitivity; R^2 indicates goodness of fit to a linear model.