Laboratory Methods for Analytical Instrumentation
One of the most practical documents regarding the use of analytical instrumentation in a laboratory is the method outlining the operation of the instrument. While there are many examples of standard analytical procedures (for example, Australian Standard or ISO methods), these generally describe sample preparation and instrument settings (for example, the temperature an instrument should be operated at; the time a sample should be held at temperature; the molarity and type of an acid used for a digestion) in detail but will not outline the specifics of physically operating a particular brand or model of instrument. The reason for this is simple – laboratories will not necessarily use the same brand of equipment for a particular analysis, and even if there is an “industry standard” instrument, differences between models of that instrument can lead to different steps for its operation. As a result, laboratories who use standard laboratory methods will often have a separate instrumental method that describes how to use the brand and model of instrument they have.
Laboratory methods follow a standard structure, generally including (but not limited to) the following sections.
The Introduction outlines the reason for completing the analysis and how the results are used by the lab or its refinery.
Health, safety and environmental considerations will depend upon the process being described, but there are several common areas. These include the type, concentration and quantity of chemicals are used and the conditions (heat, electricity, outputs such as laser beams or x-rays) that pose potential hazards to people or the environment. This section may also reference any risk assessments that were carried out regarding the operation of the instrument or the analysis.
The Theory section of the method outlines the chemistry behind the analytical process, how and why each step functions.
A laboratory method may also include a section outlining Interferences that may impact the result achieved. Some examples of this are sample properties (for example, high iron content), sample collection conditions (temperature, storage) or other potential sample issues (for example, analysing acidic versus alkaline samples).
The reliability of an analysis is described in terms of its Repeatability and Reproducibility. This section will also outline considerations such as the limit of detection and limit of the method, the accepted error in analysis of a standard sample and other statistical descriptions of the method’s reliability.
The Sample preparation section of a method may include both preparation and representative sample of the bulk sample (washing, drying and and rotary splitting a solid) and preparation for analysis (sample digestion or dilution).
Instrument operation will cover preparing the instrument for operation, including calibration and/or check sample analysis, analysing samples and instrument shutdown. Emergency procedures, such as emergency shutdown, may also be outlined in this section.
Collecting Results will be explained, along with any manipulations or calculations that are required.
Finally, the method will include any References used and a table or section outlining Document Modifications for auditing purposes and document control.
Laboratory methods are detailed and often lengthy documents that contain significant information or references to documents containing additional information. They also require regular review and updating when modifications are made to methods. These documents are useful for initial training requirements but are often not used as the day-to-day reference by an experienced operator. Other more simplified documents, such as checklists or one-page procedures, are often the more commonly used documents in the laboratory, rather than the entire method.