Talk:Detection limit

Incorrect definition

The current description of detection limit is fundamentally wrong in the sense that the detection limit is not the level at which the detection decision is taken. The detection decision is a one-sided test (Ho: analyte is absent) that only considers false positives. Assume for example that a risk of 5% is accepted to report a positive when in fact the analye is absent. Further assume that the distribution is Gaussian, as is done in the figure. Then the decision should be taken at about 1.65 sigma. This is called the critical level or decision limit. The detection limit is the level that will lead to false non-detects with a certain probability (say 5%) if the decision is taken at the critical level. Assuming two identical Gaussian distributions (the second one for Ha: analyte present at this level) leads to a detection limit of about 3.30 sigma. Klaas Faber 80.126.235.235 (talk) 16:13, 24 January 2008 (UTC)

Merge proposal

I suggest that Detection limit and Detection Limits be merged. Biscuittin 18:32, 5 July 2007 (UTC)

Support Added templates. --Kkmurray 14:51, 19 August 2007 (UTC)

While the initial definition on the Detection Limits entry seems OK, most of the information appears to be related to the amount of material being probed, rather than a description of what a detection limit (or detection limits) is. Perhaps the heading for that entry is in appropriate. Mattj63 23:43, 23 August 2007 (UTC)

In looking closer, it seems perhaps the intent of the table with different techniques was to list the detection limit of each technique. If that's the case, then this information would be better suited to an entry on the individual technique or groups of techniques (e.g. surface analysis). I think the Detection Limit entry should be limited to what a detection limit actually is and how it is defined. Mattj63 03:14, 24 August 2007 (UTC)

The relationship between the different definitions of detection limit (IDL, LLD, MDL, LOQ) is misleading since the relationship is not that simple. Estimating an instrument detection limit does not necessarily tell you anything about the method detection limit or the lower limit of detection. I will remove this if no objections. Mattj63 15:22, 1 September 2007 (UTC)

The Material at the end

I don't know what the material at the end of this article is or means. Perhaps the material at the end should just be removed? What I am referring to, is the list of analytical methods. There doesn't really seem to be any information related to detection limit in that section. --Chris (talk) 22:20, 10 January 2008 (UTC)

Agreed - I removed it just now. It still contained no data a year after the cleanup tag was added, and (as a list) it was inherently unmaintainable anyway. -- Jaeger5432 | Talk 17:57, 3 September 2008 (UTC)

Method Reporting Limit

The LOQ may be more common in research labs, but a more general approach to the sticky issue of reporting results as they near the MDL is the Method Reporting Limit. Method Reporting Limits (MRL) are generally about ten times the MDL. There is a formula for computing the MRL based on the MDL for EPA compliance labs, but I don't recall exactly what it is. Reporting results near the MDL aren't a sticky issue just because of the LOQ, but also because the claimed uncertainty for a method begins to break down at low levels. If a method claims +/-10% uncertainty, then in the most simple terms what that really means is +/-10% or +/- the MDL, whichever is greater. Of course, +/- the MDL is probably too generous even if the result is slightly above the LOQ, but the problems with the relationship between the MDL and the claimed uncertainty will normally continue well above the LOQ.

For example, a hypothetical method has an MDL of 1ppm, a claimed uncertainty of +/-10%, and an LOQ of 5ppm. I get a result of 8ppm. What is the uncertainty for that measurement? Common sense tells you that the resolution of the reported results should never be better than the MDL, so I can't say that the range is 7.2ppm - 8.8ppm, since I know I can't measure fractions of a ppm. At best it can only be 8ppm +/-1ppm, but 1ppm is more than 10% of 8ppm.

That may all seem very technical, but arguments over uncertainty will inevitably occur if MRL's are not in place. An MRL of 10ppm for the above example would quiet most of these arguments, because the uncertainty is at least equal to the MDL.

--Rataan (talk) 17:41, 1 August 2008 (UTC)

False reference number 3

The cited article Gary L. Long & J.D Winefordner; Analytical Chemistry, 55(7), 713A - 724A, (1983) is not to be found in Analyt. Chem.Silin2005 (talk) 13:27, 8 August 2008 (UTC)

Gll1955 (talk) 01:47, 11 April 2010 (UTC)The paper is in Analytical Chemistry. I am the one of the authors. Here is the citation:

G. L. Long and J. D. Winefordner, Limit of Detection: A Closer Look at the IUPAC Definition, Anal. Chem., 1983, 55, 713A-724A. 01:44, 11 April 2010 (UTC) —Preceding unsigned comment added by Gll1955 (talk • contribs)

Incorrect use of IUPAC and ACS definitions

Gll1955 (talk) 01:58, 11 April 2010 (UTC). There is no mention of the correct limit of detection (cL). The LOQ is incorrectly described. There is no mention of the limit of indentification (cI). —Preceding unsigned comment added by Gll1955 (talk • contribs) 01:57, 11 April 2010 (UTC)

Improper Referenceing?

Much of this article (espcially the Instrument detection limit section) appears to be copy-pasted from here: http://www.chem.agilent.com/Library/technicaloverviews/Public/5990-7651EN.pdf Proper references/quotations/paraphasing should be included.Piyrwq (talk) 17:21, 8 November 2011 (UTC)

Reference to Lloyd A. Currie's paper is a must!

Lloyd A. Currie, Limits for Qualitative Detection and Quantitative Determination: Application to Radiochemistry, Anal. Chem. 40, 586-593 (1968)</ref> obtained from

"Until Lloyd Currie’s paper Limits for Qualitative Detection and Quantitative Determination: Application to Radiochemistry was published, there was enough inconsistency in the definition of “detection limit” to conceal a great deal of disagreement. In just over seven pages, this tightly written communication established a high level of uniformity in answering these questions.

The paper contains fundamental information that has made it influential far beyond its size, and it is rich enough to be discussed actively in e-mail news groups over 30 years later. This is surely one of the most often cited publications in analytical chemistry"

Until Lloyd defined the terms it was a mess. Bestshot (talk) 21:03, 4 February 2012 (UTC)

References

Need for improvement Comment

After finding this article in research for other material on LOD, I have reluctantly taged the article as factually inaccurate. Several discussion posts have pointed to incorrect definition or implementation, and to lack of citation of IUPAC references. While there are so many LOD definitions out there that this article may be accurate for some sectors, anyone seeking reference information could be seriously misled. I hope to address some of this in the medium term but in the mean time, tagging seems sensible just as a warning to less expert readers.

Some wiki links don't support the text they're embedded in

Specifically in the section "Significance in analytical chemistry"

• "analytical sensistivity" links to the article about Specificity and Sensitivity which IMO is not relevant
• "calibration plot" links to something about machine learning which also seems to be irrelevant (I don't know anything about that topic)

Unfortunately I do not if there is a better wikipedia link (obviously if I did know I wouldn't need to be reading the article) 82.22.157.112 (talk) 13:56, 15 December 2022 (UTC)