The measurement technique that involves withdrawing a sample from the process for its determination. It is used in monitoring a process in which continuous measurement is either not possible or not required. For example, solid, liquid or gas samples can be taken and analyzed using various analytical techniques such as gas or liquid chromatography. These procedures require the discrete processing of samples and it may take many minutes to return a result. In-line analysis, on the other hand, involves immediate and direct sensing and reading of process parameters. This form of continuous (p. 263) process monitoring has the advantage of eliminating errors caused by delays. Examples of in-line analysis probes include thermocouples, pressure gauges, pH probes, and dissolved oxygen probes.