What is an SOP?


Text Authors: Noreen Warren and Lisa A. Seidman, Ph.D.
SOP authors: Michael Barazia (Identification Methods for Copper Sulfate) and Jay Bucher, Senior Metrologist, Promega Corporation (Balance and Scale Calibration Procedure)
E-Mail: lseidman@madisoncollege.edu
Madison Area Technical College, Madison, WI 53704
Revision November 8, 2012

This page describes Standard Operating Procedures (SOPs) and their component sections and provides examples of a SOP for students to review.

Documentation, that is, a system of written records, is essential in all laboratories and production environments. A Standard Operating Procedure (SOP) is a certain type of document that describes in a step-by-step outline form how to perform a particular task or operation. Everyone in a company must follow the same procedures to assure that tasks are performed consistently and correctly. Most companies have a wide variety of SOPs that describe how to do different tasks. In many companies technicians and operators are trained in how to follow individual SOPs and their training record specifies which SOPs they are trained on and are authorized to use.

There is no federally approved format for a SOP but there are expectations within the industry how a SOP should be written. The SOP is written in imperative sentences rather than a narrative style. A cookbook format is used and sentences should start with a task specific verb that tells what to do. The instructions are numbered in the order that they will be followed.

There are certain sections and types of information that are typically included in an SOP. These sections are illustrated in the SOP below entitled "Balances and Scale Calibration Procedure". Print out this SOP and look for the following components:


The title of the procedure, "Balances and Scale Calibration Procedure", is clearly written at the top of the procedure.


Each procedure should be also contain a unique identification number. The SOP ID number SOP11C002 is written at the top of the "Balances and Scale Calibration Procedure".


When a procedure becomes outdated and is revised, the new procedure should reflect the difference with an updated revision number or date. It is essential that companies have systems in place to prevent operators from using outdated revisions of an SOP. A revision number and effective date are shown at the top of the "Balances and Scale Calibration Procedure". This SOP also includes a history of the various revisions in Section 8.


Each page of the procedure should be numbered. The usual format is to say p. x of p. xx where x is the page number and xx is the total number of pages. This pagination is not illustrated in the "Balances and Scale Calibration Procedure", however, you can see it in another SOP, "Identification Methods for Copper Sulfate".


A statement of the purpose of the procedure should be clearly indicated on the SOP. The purpose of the "Balances and Scale Calibration Procedure" is "To describe the responsibilities of the Metrology Department as they relate to the calibration of all balances and scales".


A statement of what the SOP covers. The "Balances and Scale Calibration Procedure" "applies to all balances and scales that impact the quality of the goods supplied by Acme Widget Corp., Eatmorecheese, WI."


The persons who are responsible for the procedure should also be included. These persons may require specialized education or training for using the procedure. In the "Balances and Scale Calibration Procedure", the responsibilities are defined in Section 3.1.


Any important words or abbreviations are defined. In the "Balances and Scale Calibration Procedure", definitions are in Section 4.


SOPs should inform operators of any hazards associated with the materials or the completion of the procedure and how to protect themselves from dangers. This information is included in Section 3.2 of "Balances and Scale Calibration Procedure", but would often be included in a separate safety information section.


A list of references or other document required to complete the task should also be included as well as any forms or calculations necessary for completion of the task. The "Balances and Scale Calibration Procedure" lists a Related Procedure in Section 6.2.


The SOP should include any required forms associated with the task. The "Balances and Scale Calibration Procedure" lists an associated worksheet entitled "Balances and Scale Calibration Worksheet" in Section 6.1 (although it might place this information in Section 7). The worksheet is a form that is filled out by the analyst as the calibration procedure is performed.


The core of the SOP details the procedure in full in a step-by-step chronological manner. The following associated information will also be present:

  • A materials list indicating the materials or reagents needed.
  • If equipment is needed to complete the task, a list of the equipment is included. Details may be necessary to include the manufacture or location of the equipment.

The "Balances and Scale Calibration Procedure" has an incomplete procedure because it illustrates the overall format and the types of information that are important in a calibration SOP. A more complete procedure with all the steps can be found in another SOP, "Identification Methods for Copper Sulfate".

For more information about writing a good SOP, see:

1. DeSain, Carol, and Charmaine Vercimak Sutton, Documentiation Practices, AVANSTAR Communications, Duluth, 1996.

2. Seidman, Lisa A., and Cynthia Moore, Basic Laboratory Methods for Biotechnology, , http://www.pearsonhighered.com/educator/product/Basic-Laboratory-Methods-for-Biotechnology/9780321570147.page. See especially Chapter 6.

3. Nilsen, Clifford L., "Writing SOPs: Keep it Simple", Food Quality, Volume 6, Number 3, April 99, pp. 50-51.


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