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==1. Introduction to food and beverage laboratories==
==Sandbox begins below==
 
{{raw:wikipedia::Detection limit}}
 
===1.1 Food and beverage labs, then and now===
The history of laboratory-based food and beverage tasting is a scattered one, with little being documented about foodborne illness and food safety until the nineteenth century. With a better understanding of bacteria and their relationship to disease, however, more was being said about the topic by the mid- to late-1800s.<ref name="RobertsTheFood01">{{Cite book |last=Roberts |first=Cynthia A. |date=2001 |title=The food safety information handbook |pages=25-28 |publisher=Oryx Press |place=Westport, CT |isbn=978-1-57356-305-5}}</ref> In the U.S. Northeast during the 1860s, recognition was growing concerning the threat that tainted milk originating from dairy cows being singularly fed distillery byproducts had to human health. Not only was the milk generated from such cows thin and low in nutrients, but it also was adulterated with questionable substances to give it a better appearance. This resulted in many children and adults falling ill or dying from consuming the product. The efforts of Dr. Henry Coit and others in the late 1800s to develop a certification program for milk—which included laboratory testing among other activities—eventually helped plant the seeds for a national food and beverage safety program.<ref>{{Cite book |last=Lytton |first=Timothy D. |date=2019 |title=Outbreak: foodborne illness and the struggle for food safety |chapter=Chapter 2: The Gospel of Clean Milk |publisher=The University of Chicago Press |place=Chicago ; London |pages=24-64 |isbn=978-0-226-61154-9}}</ref>
 
Roughly around the same time, during the 1880s, Britain saw more public health awareness develop in regards to digestive bacterial infections. "As deadlier infections retreated," argues social historian Anne Hardy, "food poisoning became an increasing concern of local and national health authorities, who sought both to raise public awareness of the condition as illness, and to regulate and improve food handling practices."<ref name="HardyFood99">{{Cite journal |last=Hardy |first=A. |date=1999-08-01 |title=Food, Hygiene, and the Laboratory. A Short History of Food Poisoning in Britain, circa 1850-1950 |url=https://academic.oup.com/shm/article-lookup/doi/10.1093/shm/12.2.293 |journal=Social History of Medicine |language=en |volume=12 |issue=2 |pages=293–311 |doi=10.1093/shm/12.2.293 |issn=0951-631X}}</ref> This led to further efforts from public health laboratories to promote the reporting and tracking of food poisoning cases by the 1940s.<ref name="HardyFood99" />
 
With the recognition of bacterial and other forms of contamination occurring in foodstuffs, beverages, and ingredients, as well as growing acknowledgement of the detrimental health effects of dangerous adulterations with toxic substances, additional progress was made in the realm of regulating and testing produced food and beverages. Events of interest along the way include<ref>{{Cite book |last=Stanziani, A. |date=2016 |editor-last=Atkins, P.J.; Lummel, P.; Oddy, D.J. |title=Food and the city in Europe since 1800 |url=https://books.google.com/books?hl=en&lr=&id=OPYFDAAAQBAJ&oi=fnd&pg=PA105 |chapter=Chapter 9. Municipal Laboratories and the Analysis of Foodstuffs in France Under the Third Republic: A Case Study of the Paris Municipal Laboratory, 1878-1907 |language=English |publisher=Routledge |place=London; New York |isbn=978-1-315-58261-0 |oclc=950471625}}</ref><ref name=":0">{{Cite book |last=Redman |first=Nina |date=2007 |title=Food safety: a reference handbook |url=https://www.worldcat.org/title/mediawiki/oclc/ocm83609690 |chapter=Chapter 1: Background and History |series=Contemporary world issues |edition=2nd ed |publisher=ABC-CLIO |place=Santa Barbara, Calif |isbn=978-1-59884-048-3 |oclc=ocm83609690}}</ref><ref name=":1">{{Cite book |last=Stevens, K.; Hood, S. |date=2019 |editor-last=Doyle |editor-first=Michael P. |editor2-last=Diez-Gonzalez |editor2-first=Francisco |editor3-last=Hill |editor3-first=Colin |title=Food microbiology: fundamentals and frontiers |chapter=Chapter 40. Food Safety Management Systems |edition=5th edition |publisher=ASM Press |place=Washington, DC |pages=1007-20 |isbn=978-1-55581-997-2}}</ref><ref>{{Cite book |last=Detwiler |first=Darin S. |date=2020 |title=Food safety: past, present, and predictions |chapter=Chapter 2: "Modernization" started over a century ago |publisher=Academic Press |place=London [England] ; San Diego, CA |pages=11-23 |isbn=978-0-12-818219-2}}</ref><ref name="FDABackFSMA18">{{cite web |url=https://www.fda.gov/food/food-safety-modernization-act-fsma/background-fda-food-safety-modernization-act-fsma |title=Background on the FDA Food Safety Modernization Act (FSMA) |publisher=Food and Drug Administration |date=30 January 2018 |accessdate=14 August 2022}}</ref><ref name="DouglasFDA22">{{cite web |url=https://www.limswiki.org/index.php/LII:FDA_Food_Safety_Modernization_Act_Final_Rule_on_Laboratory_Accreditation_for_Analyses_of_Foods:_Considerations_for_Labs_and_Informatics_Vendors |title=FDA Food Safety Modernization Act Final Rule on Laboratory Accreditation for Analyses of Foods: Considerations for Labs and Informatics Vendors |author=Douglas, S. |work=LIMSwiki.org |date=21 February 2022 |accessdate=14 August 2022}}</ref>:
 
*By 1880, the first of many municipal laboratories dedicated to testing food and beverage adulteration came into use in France. A focus was made on watered-down wines early on, but Frances's municipal food safety labs quickly began addressing other foods, beverages, and ingredients.
*The Pure Food and Drug Act and Beef Inspection Act were passed in 1906 in response to food quality issues in packing plants, on farms, and other areas of food production.
*In 1927, the U.S. Food, Drug, and Insecticide Administration (shortened to the U.S. Food and Drug Administration or FDA not long after) was formed to better enforce the Pure Food Act.
*By 1945, ''Clostridium perfringens'' was being identified as a common cause of foodborne illness<ref name="RobertsTheFood01" />, and today it is recognized by the [[Centers for Disease Control and Prevention]] (CDC) as one of the top five provocateurs of foodborne illness.<ref name="CDCFood20">{{cite web |url=https://www.cdc.gov/foodsafety/foodborne-germs.html |title=Foodborne Germs and Illnesses |publisher=Centers for Disease Control and Prevention |date=18 March 2020 |accessdate=13 August 2022}}</ref>
*The seeds of the Hazard Analysis and Critical Control Points (HACCP) quality control method were planted in 1959, when Pillsbury began working with NASA to ensure safe foods for astronauts. The value of Pillsbury and NASA's methodology became apparent to the food and beverage industry by 1972, and other organizations began adopting HACCP for food safety.
*The Fair Packaging and Labeling Act of 1966 brought standardized, more accurate labeling to food and beverages.
*The Food Quality Protection Act of 1996 mandated HACCP for most food processors and improved pesticide level calculations.
*FDA Food Safety Modernization Act (FSMA) was enacted in 2011, giving the FDA more enforcement authority and tools to improve the backbone of the U.S. food and water supply.
*In December 2021, the Laboratory Accreditation for Analyses of Foods (LAAF) amendment to the FSMA was approved, providing for an accreditation program for laboratories wanting to further participate in the critical role of ensuring the safety of the U.S. food supply through the "testing of food in certain circumstances."
 
This progression of scientific discovery and regulatory action has surely managed to reduce risks to U.S. food and beverage consumers, though not without complication and complexity.<ref name="LyttonAnIntro19" /><ref>{{Cite journal |last=Floros |first=John D. |last2=Newsome |first2=Rosetta |last3=Fisher |first3=William |last4=Barbosa-Cánovas |first4=Gustavo V. |last5=Chen |first5=Hongda |last6=Dunne |first6=C. Patrick |last7=German |first7=J. Bruce |last8=Hall |first8=Richard L. |last9=Heldman |first9=Dennis R. |last10=Karwe |first10=Mukund V. |last11=Knabel |first11=Stephen J. |date=2010-08-26 |title=Feeding the World Today and Tomorrow: The Importance of Food Science and Technology: An IFT Scientific Review |url=https://onlinelibrary.wiley.com/doi/10.1111/j.1541-4337.2010.00127.x |journal=Comprehensive Reviews in Food Science and Food Safety |language=en |volume=9 |issue=5 |pages=572–599 |doi=10.1111/j.1541-4337.2010.00127.x}}</ref> As the U.S. population has grown over the past 100 years, it has become more difficult to have a sufficient number of inspectors, for example, to examine every production facility or farm and all they do, necessitating a risk assessment approach to food and beverage safety.<ref name=":0" /><ref name=":1" /><ref>{{Cite book |date=1998 |title=Food Safety: Current Status and Future Needs |url=http://www.ncbi.nlm.nih.gov/books/NBK562616/ |series=American Academy of Microbiology Colloquia Reports |publisher=American Society for Microbiology |place=Washington (DC) |pmid=33001600}}</ref> As such, the laboratory is undoubtedly a critical component of risk-based safety assessments of food and beverage products.
 
===1.2 Laboratory roles and testing in the industry===
Sources: [[LIMS FAQ:What is the importance of a food and beverage testing laboratory to society?]] and [[LIMS FAQ:What types of testing occur within a food and beverage laboratory?]]
 
====1.2.1 R&D roles and testing====
 
 
====1.2.2 Pre-manufacturing and manufacturing roles and testing====
 
 
====1.2.3 Post-production regulation and security roles and testing====
 
 
====1.2.4 Tangential laboratory work====
 
 
==References==
{{Reflist|colwidth=30em}}

Latest revision as of 18:25, 10 January 2024

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Template:Short description

"LOQ" redirects here. For the company listed as LOQ on the London Stock Exchange, see Lo-Q. For the airport in Botswana with IATA code LOQ, see Lobatse Airport.

The limit of detection (LOD or LoD) is the lowest signal, or the lowest corresponding quantity to be determined (or extracted) from the signal, that can be observed with a sufficient degree of confidence or statistical significance. However, the exact threshold (level of decision) used to decide when a signal significantly emerges above the continuously fluctuating background noise remains arbitrary and is a matter of policy and often of debate among scientists, statisticians and regulators depending on the stakes in different fields.

Significance in analytical chemistry

In analytical chemistry, the detection limit, lower limit of detection, also termed LOD for limit of detection or analytical sensitivity (not to be confused with statistical sensitivity), is the lowest quantity of a substance that can be distinguished from the absence of that substance (a blank value) with a stated confidence level (generally 99%).[1][2][3] The detection limit is estimated from the mean of the blank, the standard deviation of the blank, the slope (analytical sensitivity) of the calibration plot and a defined confidence factor (e.g. 3.2 being the most accepted value for this arbitrary value).[4] Another consideration that affects the detection limit is the adequacy and the accuracy of the model used to predict concentration from the raw analytical signal.[5]

As a typical example, from a calibration plot following a linear equation taken here as the simplest possible model:

where, corresponds to the signal measured (e.g. voltage, luminescence, energy, etc.), "Template:Mvar" the value in which the straight line cuts the ordinates axis, "Template:Mvar" the sensitivity of the system (i.e., the slope of the line, or the function relating the measured signal to the quantity to be determined) and "Template:Mvar" the value of the quantity (e.g. temperature, concentration, pH, etc.) to be determined from the signal ,[6] the LOD for "Template:Mvar" is calculated as the "Template:Mvar" value in which equals to the average value of blanks "Template:Mvar" plus "Template:Mvar" times its standard deviation "Template:Mvar" (or, if zero, the standard deviation corresponding to the lowest value measured) where "Template:Mvar" is the chosen confidence value (e.g. for a confidence of 95% it can be considered Template:Mvar = 3.2, determined from the limit of blank).[4]

Thus, in this didactic example:

There are a number of concepts derived from the detection limit that are commonly used. These include the instrument detection limit (IDL), the method detection limit (MDL), the practical quantitation limit (PQL), and the limit of quantitation (LOQ). Even when the same terminology is used, there can be differences in the LOD according to nuances of what definition is used and what type of noise contributes to the measurement and calibration.[7]

The figure below illustrates the relationship between the blank, the limit of detection (LOD), and the limit of quantitation (LOQ) by showing the probability density function for normally distributed measurements at the blank, at the LOD defined as 3 × standard deviation of the blank, and at the LOQ defined as 10 × standard deviation of the blank. (The identical spread along Abscissa of these two functions is problematic.) For a signal at the LOD, the alpha error (probability of false positive) is small (1%). However, the beta error (probability of a false negative) is 50% for a sample that has a concentration at the LOD (red line). This means a sample could contain an impurity at the LOD, but there is a 50% chance that a measurement would give a result less than the LOD. At the LOQ (blue line), there is minimal chance of a false negative.

Template:Wide image

Instrument detection limit

Most analytical instruments produce a signal even when a blank (matrix without analyte) is analyzed. This signal is referred to as the noise level. The instrument detection limit (IDL) is the analyte concentration that is required to produce a signal greater than three times the standard deviation of the noise level. This may be practically measured by analyzing 8 or more standards at the estimated IDL then calculating the standard deviation from the measured concentrations of those standards.

The detection limit (according to IUPAC) is the smallest concentration, or the smallest absolute amount, of analyte that has a signal statistically significantly larger than the signal arising from the repeated measurements of a reagent blank.

Mathematically, the analyte's signal at the detection limit () is given by:

where, is the mean value of the signal for a reagent blank measured multiple times, and is the known standard deviation for the reagent blank's signal.

Other approaches for defining the detection limit have also been developed. In atomic absorption spectrometry usually the detection limit is determined for a certain element by analyzing a diluted solution of this element and recording the corresponding absorbance at a given wavelength. The measurement is repeated 10 times. The 3σ of the recorded absorbance signal can be considered as the detection limit for the specific element under the experimental conditions: selected wavelength, type of flame or graphite oven, chemical matrix, presence of interfering substances, instrument... .

Method detection limit

Often there is more to the analytical method than just performing a reaction or submitting the analyte to direct analysis. Many analytical methods developed in the laboratory, especially these involving the use of a delicate scientific instrument, require a sample preparation, or a pretreatment of the samples prior to being analysed. For example, it might be necessary to heat a sample that is to be analyzed for a particular metal with the addition of acid first (digestion process). The sample may also be diluted or concentrated prior to analysis by means of a given instrument. Additional steps in an analysis method add additional opportunities for errors. Since detection limits are defined in terms of errors, this will naturally increase the measured detection limit. This "global" detection limit (including all the steps of the analysis method) is called the method detection limit (MDL). The practical way for determining the MDL is to analyze seven samples of concentration near the expected limit of detection. The standard deviation is then determined. The one-sided Student's t-distribution is determined and multiplied versus the determined standard deviation. For seven samples (with six degrees of freedom) the t value for a 99% confidence level is 3.14. Rather than performing the complete analysis of seven identical samples, if the Instrument Detection Limit is known, the MDL may be estimated by multiplying the Instrument Detection Limit, or Lower Level of Detection, by the dilution prior to analyzing the sample solution with the instrument. This estimation, however, ignores any uncertainty that arises from performing the sample preparation and will therefore probably underestimate the true MDL.

Limit of each model

The issue of limit of detection, or limit of quantification, is encountered in all scientific disciplines. This explains the variety of definitions and the diversity of juridiction specific solutions developed to address preferences. In the simplest cases as in nuclear and chemical measurements, definitions and approaches have probably received the clearer and the simplest solutions. In biochemical tests and in biological experiments depending on many more intricate factors, the situation involving false positive and false negative responses is more delicate to handle. In many other disciplines such as geochemistry, seismology, astronomy, dendrochronology, climatology, life sciences in general, and in many other fields impossible to enumerate extensively, the problem is wider and deals with signal extraction out of a background of noise. It involves complex statistical analysis procedures and therefore it also depends on the models used,[5] the hypotheses and the simplifications or approximations to be made to handle and manage uncertainties. When the data resolution is poor and different signals overlap, different deconvolution procedures are applied to extract parameters. The use of different phenomenological, mathematical and statistical models may also complicate the exact mathematical definition of limit of detection and how it is calculated. This explains why it is not easy to come to a general consensus, if any, about the precise mathematical definition of the expression of limit of detection. However, one thing is clear: it always requires a sufficient number of data (or accumulated data) and a rigorous statistical analysis to render better signification statistically.

Limit of quantification

The limit of quantification (LoQ, or LOQ) is the lowest value of a signal (or concentration, activity, response...) that can be quantified with acceptable precision and accuracy.

The LoQ is the limit at which the difference between two distinct signals / values can be discerned with a reasonable certainty, i.e., when the signal is statistically different from the background. The LoQ may be drastically different between laboratories, so another detection limit is commonly used that is referred to as the Practical Quantification Limit (PQL).

See also

References

  1. ↑ IUPAC, Compendium of Chemical Terminology, 2nd ed. (the "Gold Book") (1997). Online corrected version:  (2006–) "detection limit".
  2. ↑ "Guidelines for Data Acquisition and Data Quality Evaluation in Environmental Chemistry". Analytical Chemistry 52 (14): 2242–49. 1980. doi:10.1021/ac50064a004. 
  3. ↑ Saah AJ, Hoover DR (1998). "[Sensitivity and specificity revisited: significance of the terms in analytic and diagnostic language."]. Ann Dermatol Venereol 125 (4): 291–4. PMID 9747274. https://pubmed.ncbi.nlm.nih.gov/9747274. 
  4. ↑ 4.0 4.1 "Limit of blank, limit of detection and limit of quantitation". The Clinical Biochemist. Reviews 29 Suppl 1 (1): S49–S52. August 2008. PMC 2556583. PMID 18852857. https://www.ncbi.nlm.nih.gov/pmc/articles/2556583. 
  5. ↑ 5.0 5.1 "R: "Detection" limit for each model" (in English). search.r-project.org. https://search.r-project.org/CRAN/refmans/bioOED/html/calculate_limit.html. 
  6. ↑ "Signal enhancement on gold nanoparticle-based lateral flow tests using cellulose nanofibers". Biosensors & Bioelectronics 141: 111407. September 2019. doi:10.1016/j.bios.2019.111407. PMID 31207571. http://ddd.uab.cat/record/218082. 
  7. ↑ Long, Gary L.; Winefordner, J. D., "Limit of detection: a closer look at the IUPAC definition", Anal. Chem. 55 (7): 712A–724A, doi:10.1021/ac00258a724 

Further reading

  • "Limits for qualitative detection and quantitative determination. Application to radiochemistry". Analytical Chemistry 40 (3): 586–593. 1968. doi:10.1021/ac60259a007. ISSN 0003-2700. 

External links

Template:BranchesofChemistry Template:Authority control

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