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| Here we take a brief look at the history of the laboratory to help give perspective about ''why'' they're important to modern life.
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| <div align="center">-----Return to [[User:Shawndouglas/sandbox/sublevel4|the beginning]] of this guide-----</div>
| | ==Sandbox begins below== |
| __TOC__
| | {{raw:wikipedia::Detection limit}} |
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| ==Laboratories: A historical perspective==
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| ===Introduction===
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| Take note of your surroundings. If you're indoors, what objects are nearby? If you're outdoors, what objects are on your person? Are you in a vehicle such as an automobile, bus, or airplane? Are you using a mobile phone, desktop computer, tablet, or laptop? What of the clothes you wear, the food you eat, and the water you drink?
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| What do all these things have in common? A laboratory was likely involved at some point before you made observation of them.
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| For some this will be an obvious but uninteresting point. "Why should I care that a laboratory was somehow involved in a product's creation?" some may say. For others the association isn't as obvious. "How is a laboratory involved with the ink pen on my desk or water I drink?" they might ask.
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| Both of these questions are valid and productive, particularly to the inquisitive mind. To the first, we could simply reply with something about quality assurance, safety, and more efficient design regarding the items we interact with on a daily basis. But it's a bit more complicated than that. And so is the reply to the second question: it's more than just research and design (R&D) and quality control.
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| Laboratories play an important role in modern life, ubiquitous and often unseen by the average person. They improve quality of life, act as hotbeds of discovery, and help us make sense of our universe, particularly in the capable hands of the tens of thousands of professionals who work in them. But the laboratory as we know it today is actually a relatively new concept. It wasn't always as sectionally organized, well staffed, and well equipped. To gain a better sense of how common the laboratory is to our lives, we first briefly look at the past history of laboratory research and how it developed from a philosophical and more selfish endeavor to one more focused on analysis and the benefits to society.
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| ===Origins of the laboratory===
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| Among the earliest known organized scientific study was that under the rule of the early Ptolomies of Alexandria in the third century B.C. While little to no evidence seems to exist for public or organized laboratories during this time period, researchers and historians widely accept the idea that at least organized and individual research (meaning "direct personal contact with the objects of study, and by the aid of such appliances as were then available"<ref name="WelchTheEvolution20">{{cite book |url=http://books.google.com/books?id=utc0AQAAMAAJ&pg=200 |chapter=The Evolution of Modern Scientific Laboratories |title=Papers and Addresses by William Henry Welch |author=Welch, William Henry |volume=3 |publisher=The Johns Hopkins Press |year=1920 |pages=200–211}}</ref>) into anatomy, physiology, and medicine occurred.<ref name="ZilselTheSocial03">{{cite book |title=The Social Origins of Modern Science |chapter=The Genesis of the Concept of Scientific Progress and Cooperation |series=Boston Studies in the Philosophy of Science |author=Zilsel, E. |editor=Cohen, R.S., Wartofsky, M.W. |publisher=Kluwer Academic Publishers |year=2003 |pages=130–171 |isbn=1402013590}}</ref><ref name="MartinSomeThoughts1888">{{cite book |url=https://books.google.com/books?id=Raw-AQAAMAAJ&pg=PA256 |title=Physiological Papers |chapter=Some Thoughts About Laboratories |author=Martin, H.N. |publisher=The John Hopkins Press |pages=256–264 |year=1895}}</ref><ref name="WelchTheEvolution20" /><ref name="SerageldinAncient13">{{cite journal |title=Ancient Alexandria and the dawn of medical science |journal=Global Cardiology Science & Practice |author=Serageldin, I. |volume=2013 |issue=4 |pages=395–404 |year=2013 |doi=10.5339/gcsp.2013.47 |pmid=24749113 |pmc=PMC3991212}}</ref> Dissections and experiments took place, but certainly not in an organized teaching or research laboratory setting like today. Early twentieth-century philosopher of science Edgar Zilsel suggested that scientific endeavor was non-collaborative in this early era, and the laboratory as a collaborative environment simply didn't exist<ref name="ZilselTheSocial03" />:
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| <blockquote>No publications, no astronomical or geographical investigation which are the work of several collaborating scientists are known. Even the learned compendia of the Roman period (Varro, Pliny, Celsus) and the encyclopedias of late antiquity (Boëthius) were composed by single polyhistors. There is no evidence that the Alexandrian Museum conjointly carried out investigations. Laboratories, the birth places of scientific co-operation in the modern era, existed neither in the Alexandrian Museum, nor in the Academy, nor in the Lyceum. As far as the fellow scholars of the museum did not work each for himself they might have contented themselves with dinners and debates. And of course, there were in antiquity no scientific periodicals in which new findings could have been discussed.</blockquote>
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| With scientific advancement and discovery still largely a personal (i.e., prestigious) goal, even through to the Renaissance humanists of the fourteenth through sixteenth century A.D.<ref name="ZilselTheSocial03" />, it took quite some time for both the private and public laboratory to evolve. To be certain, private laboratories surely existed, from Aristotle<ref name="WelchTheEvolution20" /> (third century B.C.) to the anatomical laboratory — "the first scientific laboratory" — that began to take hold in the late thirteenth to early fourteenth century<ref name="WelchTheEvolution20" /><ref name="WalkerClinical90">{{cite book |url=https://www.ncbi.nlm.nih.gov/books/NBK201/ |title=Clinical Methods: The History, Physical, and Laboratory Examinations |chapter=Chapter 1: The Origins of the History and Physical Examination |author=Walker, H.K. |editor=Walker, H.K.; Hall, W.D.; Hurst, J.W. |edition=3rd |publisher=Butterworths |year=1990 |isbn=040990077X}}</ref>, all the way to the "zenith" of the alchemical research laboratory in the second half of the sixteenth century.<ref name="Martinón-TorresA16th03">{{cite journal |title=A 16th century lab in a 21st century lab: Archaeometric study of the laboratory equipment from Oberstockstall (Kirchberg am Wagram, Austria) |journal=Antiquity |author=Martinón-Torres, M.; Rehren, T.; von Osten, S. |volume=77 |issue=298 |url=http://antiquity.ac.uk/projgall/martinon298}}</ref> But it wouldn't be until the late sixteenth to early seventeenth century that collaboratory science and the first university-affiliated labs would appear.
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| Zilsel claimed that Italian polymath Galileo Galilei, while teaching at the University of Padua from 1592 to 1610, founded the first university-affiliated laboratory in his own home, with help from craftsmen who aided in researching architectural and mechanical concepts.<ref name="ZilselTheSocio00">{{cite journal |title=The Sociological Roots of Science |journal=Social Studies of Science |author=Zilsel, E. |volume=30 |issue=6 |pages=935–949 |year=2000 |url=http://www.jstor.org/stable/285793}}</ref> As Galileo was nearing completion of his professorship at Padua, chemist Johannes Hartmann opened up a university laboratory for students at the University of Marburg in 1609, albeit for "instruction not in [chemical] analysis — still in a very rudimentary state — but in pharmaceutical preparations."<ref name="IhdeTheDevelop84">{{cite book |url=https://books.google.com/books?id=89BIAwAAQBAJ&pg=PA262 |title=The Development of Modern Chemistry |chapter=Chapter 10: The Diffusion of Chemical Knowledge |author=Ihde, A.J. |publisher=Dover Publications |pages=259–276 |year=1984 |isbn=0486642356}}</ref> One of the first actual public laboratories dedicated to chemical instruction was founded later that century, in 1683, hosted at the University of Altdorf, created and directed by physician and professor Johan Moritz Hofmann.<ref name="IhdeTheDevelop84" /><ref name="WiechmannChemistry1899">{{cite book |url=https://books.google.com/books?id=z4k-AAAAYAAJ&pg=PA83 |title=Chemistry: Its Evolution and Achievements |author=Wiechmann, F.G. |series=Science Sketches |publisher=William R. Jenkins |location=New York |pages=176 |year=1899}}</ref><ref name="LockemannFriedrich53">{{cite journal |title=Friedrich Stromeyer and the history of chemical laboratory instruction |journal=Journal of Chemical Education |author=Lockemann, G.; Oesper, R.E. |volume=30 |issue=4 |pages=202–204 |year=1953 |doi=10.1021/ed030p202}}</ref> That same year the (Old) Ashmolean played host to Britian's first university laboratory, directed by chemistry chair Robert Plot.<ref name="BowenTheBalliol70">{{cite journal |title=The Balliol-Trinity Laboratories, Oxford 1853-1940 |journal=Notes and Records of the Royal Society of London |author=Bowen, E.J. |volume=25 |issue=2 |pages=227–236 |year=1970 |url=http://www.jstor.org/stable/530877}}</ref><ref name="Martinón-TorresTheArch11">{{cite journal |title=The Archaeology of Alchemy and Chemistry in the Early Modern World: An Afterthought |journal=Archaeology International |author=Martinón-Torres, M. |volume=15 |pages=33–36 |year=2011-2012 |doi=10.5334/ai.1508}}</ref>
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| By the end of the seventeenth century, textbooks on various subjects such as anatomy<ref name="BartholinTheAnat15">{{cite book |url=https://books.google.com/books?id=Y9o_CgAAQBAJ&pg=PA20 |title=he Anatomy House in Copenhagen |author=Bartholin, T. |publisher=Museum Tusculanum Press |pages=222 |year=2015 |isbn=9788763542593}}</ref> and chemistry<ref name="WiechmannChemistry1899" /> had become more notable, and numerous vital scientific measurement and observation devices — including astronomy equipment — had been created.<ref name="BronfenbrennerTheRole1913">{{cite book |url=https://books.google.com/books?id=-v4CAAAAIAAJ&pg=PA11 |title=The Role of Scientific Societies in the Seventeenth Century |author=Bronfenbrenner, M.O. |publisher=University of Chicago Press |location=Chicago |pages=308 |year=1913}}</ref> And most importantly, as early twentieth century political science researcher Martha Ornstein put it, after much build-up, finally "the [public] chemical and physical laboratory existed in embryonic form."<ref name="BronfenbrennerTheRole1913" />
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| ===Eighteenth- and nineteenth-century laboratories===
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| The eighteenth century saw the "embryonic" laboratories develop further, but in truth in wasn't until the nineteenth century that the age of the laboratory in academic, hospital, and — particularly in the latter half of the century<ref name="WelchTheEvolution20" /><ref name="MMJSimon">{{cite journal |url=http://books.google.com/books?id=dooRAAAAYAAJ&pg=PA55 |journal=Maryland Medical Journal |title=The Importance of Laboratory Methods in Diagnosis |author=Simon, Charles E. |volume=35 |issue=4 |pages=55–57 |date=9 May 1896 |accessdate=28 June 2017}}</ref><ref name="ShoemakerChemical1884">{{cite journal |url=http://books.google.com/books?id=DmQWAAAAYAAJ&pg=PA277 |journal=The Medical Bulletin: A Monthly Journal of Medicine and Surgery |title=Chemical Department at Jefferson Medical College |author=Shoemaker, John V. (ed.) |volume=6 |issue=11 |pages=277–278 |date=November 1884 |accessdate=28 June 2017}}</ref><ref name="ElliottEditorial1898">{{cite journal |url=http://books.google.com/books?id=bcjRAAAAMAAJ&pg=PA57 |journal=Journal of Applied Microscopy |title=Editorial |author=Elliott, L. B. |volume=1 |issue=3 |date=March 1898 |pages=57–58 |accessdate=28 June 2017}}</ref> — physician settings began to bloom. Some historians describe the changes that took place during these centuries as a transition from natural philosophy — sometimes referred to as "experimental philosophy" — and its "philosophical instruments" to natural or empirical science (or "physics," but not in the modern sense<ref name="BuchwaldPhysics03">{{cite book |url=https://books.google.com/books?id=k5qgGcZVOugC&pg=PA163 |title=From Natural Philosophy to the Sciences: Writing the History of Nineteenth-Century Science |chapter=Chapter 6: Physics |author=Buchwald, J.Z.; Hong, S. |editor=Cahan, D. |publisher=University of Chicago Press |year=2003 |pages=163–195 |isbn=9780226089287}}</ref>) and the laboratory instruments used to better analyze and describe the physical and life sciences.<ref name="BuchwaldPhysics03" /><ref name="BennettCabinets13">{{cite book |url=https://books.google.com/books?id=DJKiWjpCgAkC&pg=PA4 |title=Cabinets of Experimental Philosophy in Eighteenth-Century Europe |chapter=Cabinets for Experimental Philosophy in the Netherlands |author=Zuidervaart, H.J. |editor=Bennett, J.; Talas, S. |publisher=Brill |year=2013 |pages=1–26 |isbn=9789004252974}}</ref><ref name="KleinTheLab08">{{cite journal |title=The Laboratory Challenge: Some Revisions of the Standard View of Early Modern Experimentation |journal=Isis |author=Klein, U. |volume=99 |issue=4 |pages=769-782 |year=2008 |doi=10.1086/595771}}</ref>
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| Even by the late eighteenth century, the laboratory was still viewed as a "workshop," a place for material (chemicals, colored glass, etc.) production.<ref name="SchmidgenTheLab11">{{cite web |url=http://www.ieg-ego.eu/schmidgenh-2011-en |title=The Laboratory |work=European History Online (EGO) |author=Schmidgen, H. |publisher=Institute of European History |date=08 August 2011 |accessdate=28 June 2017}}</ref> However, instances of scientists beginning to view laboratory teaching and hands-on analysis as vital slowly began to spring forth. For example, the laboratory teaching of practical or "physical chemistry" — separating itself even further by several decades from alchemical study — first took place in St. Petersburg, Russia in 1751 under the professorship of Mikhail Lomonosov. Two years prior he had built for him a small 15 x 9 meter brick structure where he developed colored glasses for mosaics, but he quickly turned his focus towards using the laboratory to teach students in physical chemistry, "a science which must explain by means of physical laws and experiments the cause of changes produced by chemical operations in composite bodies."<ref name="MenschutkinARussian1927">{{cite journal |title=A Russian physical chemist of the eighteenth century |journal=Journal of Chemical Education |author=Menschutkin, B.N. |volume=4 |issue=9 |pages=1079–1087 |year=1927 |doi=10.1021/ed004p1079}}</ref> Three years later in Berlin, the Prussian Academy of Sciences' academic laboratory was founded with materials from a previously associated artisanal lab, signalling a shift "from commercial production to systematic observation and experimental exploration of the properties and chemical transformations of material substances."<ref name="KleinTheLab08" />
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| Speaking of German kingdoms, universities and associated laboratories in the region continued to build a renowned reputation on into the early and mid-nineteenth century.<ref name="SchmidgenTheLab11" /><ref name="MechanicsTheLab1884">{{cite journal |url=https://books.google.com/books?id=yAZHAQAAMAAJ&pg=PA290 |title=The Laboratory in Modern Science |journal=Mechanics |publisher=David Williams |volume=5 |issue=120 |date=19 April 1884 |page=290}}</ref> In 1806, Friedrich Stromeyer, fresh from being named "extraordinary professor" after the death of Johann Friedrich Gmelin, took over as director of University of Göttingen's chemical laboratory. Stromeyer's strong opinion that students could only learn chemistry best through practice and self-analysis led to a subtle but significant change: the development of one of the first university laboratories in Germany to offer students hands-on chemical analysis.<ref name="LockemannFriedrich53" /><ref name="IhdeTheDevelop84" /> Following a similar path, Czech physiologist Johannes Evangelista Purkinje, upon being appointed a professor at the University of Breslau (then a part of Germany), set up a private physiology laboratory in 1824 within his own house and taught students from it. Impressed by his work, the government eventually helped Purkinje set up the world's first professional physiology laboratory in 1842, known as the Physiological Institute.<ref name="GarrisonAnIntro1921">{{cite book |url=https://books.google.com/books?id=JvoIAAAAIAAJ&pg=PA486 |title=An Introduction to the History of Medicine |author=Garrison, F.H. |publisher=W.B. Saunders Company |chapter=XI: The Nineteenth Century: The Beginnings of Organized Advancement of Science |edition=3rd |year=1921 |pages=486–488}}</ref><ref name="MechanicsTheLab1884" /> And in 1826, at the University of Giessen, influential chemist Justus Liebig began perhaps not the first but definitely one of the more influential teaching and analysis laboratories, his work influencing the future direction of German as well as international universities and institutes.<ref name="HolmesTheComp89">{{cite journal |title=The Complementarity of Teaching and Research in Liebig's Laboratory |journal=Osiris |author=Holmes, F.L. |volume=5 |pages=121-164 |url=http://www.jstor.org/stable/301795}}</ref><ref name="IhdeTheDevelop84" /> That carried over to Wilhelm Weber's physics lab at Göttingen University (1833), Franz Neumann's physics lab in Königsberg (1847), Robert Bunsen's chemical teaching and research laboratory in Heidelberg (c. 1850), and Johann N. Czermak's ''spectatorium'' for physiology teaching in Leipzig (c. 1870).<ref name="SchmidgenTheLab11" />
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| By the late eighteenth century, other countries were marveling at the laboratories of the German-speaking countries.<ref name="SchmidgenTheLab11" /><ref name="MechanicsTheLab1884" /> Industrial labs were beginning to pop up around the world, including the United States, with researchers "interested in getting patents recognized so as to have commercial control of the processes and products involved in their research."<ref name="SchmidgenTheLab11" /> Even physician laboratories were beginning to take shape at the turn of the century as instruments such as centrifuges, microscopes, and microtomes became slightly easier to acquire.<ref name="ElliottEditorial1898" /><ref name="BartleyManualOfClin1899">{{cite book |url=http://books.google.com/books?id=FqPVAAAAMAAJ&pg=PA53 |title=Manual of Clinical Chemistry |author=Bartley, Elias H. |publisher=P. Blakiston's Son & Co |year=1899 |page=53 |accessdate=28 June 2017}}</ref> The role-based division of responsibilities within laboratories was also becoming entrenched into labs by the end of the century.<ref name="SchmidgenTheLab11" /><ref name="MechanicsTheLab1884" />
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| ===Modern laboratories and their importance===
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| The twentieth century saw laboratories of all kinds grow, develop, and mature, though not without their share of difficulties. In the 1920s, for example, some U.S. physicians, specialists, and dentists complained heavily of the lack of quality standards, regulations, and ethics inherent in for-profit clinical, chemical, and radiological laboratories.<ref name="TaylorAdvert1920">{{cite journal |url=http://books.google.com/books?id=LbEDAAAAYAAJ&pg=PA229 |journal=Texas State Journal of Medicine |title=Advertising Medical Laboratories (Encore) |author=Taylor, Holman (ed.) |volume=16 |issue=6 |date=October 1920 |pages=229–230 |accessdate=28 June 2017}}</ref><ref name="SondernCommer1921">{{cite journal |url=http://books.google.com/books?id=j7hYAAAAYAAJ&pg=PA390 |journal=New York State Journal of Medicine |title=Commercial Laboratories |author=Sondern, Frederic E. (ed.) |volume=21 |issue=10 |date=October 1921 |page=390 |accessdate=28 June 2017}}</ref><ref name="WhiteTheRole1922">{{cite journal |url=http://books.google.com/books?id=OTMTAAAAYAAJ&pg=PA755 |journal=Kentucky Medical Journal |title=The Role of the Nonmedical Graduate in the Medical Laboratory |author=White, Courtland Y. |volume=25 |issue=11 |date=August 1922 |pages=755–760 |accessdate=28 June 2017}}</ref><ref name="SundelofTheBus1922">{{cite journal |url=http://books.google.com/books?id=E741AQAAMAAJ&pg=PA442 |journal=The Boston Medical and Surgical Journal |title=The Business Side of X-ray Diagnosis and Treatment |author=Sundelof, E. M. |volume=186 |issue=13 |date=30 March 1922 |pages=442–444 |accessdate=28 June 2017}}</ref> Other changes took place there too, particularly after World War II, when a fundamental transition took place, shifting many perceptions of what was the "Western" world from Europe to the U.S. This post-war shift also saw focus from the philosophical and theoretical laboratorian to the experimental and practical lab researcher, according to Pestre<ref name="PestreScience13">{{cite book |url=https://books.google.com/books?id=ZYUfAgAAQBAJ&pg=PA71 |title=Science in the Twentieth Century |chapter=Chapter 4: Science, Political Power and the State |author=Pestre, D. |editor=Krige, J.; Pestre, D. |publisher=Routledge |year=2013 |pages=61–76 |isbn=9057021722}}</ref>:
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| <blockquote>Fundamental theorists were still essential, and they were highly respected, but they no longer had that mythical status which was accorded to the founders of quantum mechanics. They were also in minority with those (the "phenomenologists") whose job it was to deal with the mass of experimental results produced in the laboratories. Seeking theories which were locally coherent and which could be immediately useful and produce numbers, their role was to display a practical efficiency. They thus participated in the development of a science which was increasingly integrated into its economic and political environment, and contributed to the multiplications of the sites where knowledge was produced. These were now the universities and the technical institutes, the national laboratories and the industrial laboratories (Siemens or General Electric), but also the myriad of small firms established as a result of government contracts.</blockquote>
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| This transition carried on to other parts of the world, where the Industrial Revolution gave way to the Scientific-Technical Revolution of the '50 and '60s, and that to the Information Age in roughly the late '70s to early '80s. Through all of these time periods to present day, we've seen the amount of information moving in and out of laboratories multiply drastically as well, particularly with the advent of data-producing analytical devices and data management tools, including genomics equipment such as DNA sequencers.<ref name="PollackDNA11">{{cite web |url=http://www.nytimes.com/2011/12/01/business/dna-sequencing-caught-in-deluge-of-data.html |title=DNA Sequencing Caught in Deluge of Data |author=Pollack, A. |work=The New York Times |publisher=The New York Times Company |date=30 November 2011 |accessdate=28 June 2017}}</ref>
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| Most importantly, however, is the ubiquity of the laboratory in our lives today. The previous quote from Pestre is important to note when thinking about this concept; today we see labs in all the places he mentioned as well as in other unexpected locations and fields of research, including the expanding cannabis industry.<ref name="DouglasPast17">{{cite web |url=https://www.limswiki.org/index.php/LII:Past,_Present,_and_Future_of_Cannabis_Laboratory_Testing_and_Regulation_in_the_United_States |title=Past, Present, and Future of Cannabis Laboratory Testing and Regulation in the United States |author=Douglas, S.E. |work=LIMSwiki.org |date=April 2017 |accessdate=28 June 2017}}</ref> Like the idea of the ubiquitous transistor and how easy it is to take for granted<ref name="GaudinTheTrans07">{{cite web |url=http://www.computerworld.com/article/2538123/computer-processors/the-transistor--the-most-important-invention-of-the-20th-century-.html |title=The transistor: The most important invention of the 20th century? |author=Gaudin, S. |work=Computerworld |publisher=IDG Communication, Inc |date=12 December 2007 |accessdate=28 June 2017}}</ref>, the laboratory is also found everywhere, sometimes obvious (when you need to have blood drawn for a medical test) and other times not at all (the U.S. Navy's Arctic Submarine Laboratory<ref name="USNArctic">{{cite web |title=Arctic Submarine Laboratory |publisher=United States Navy |accessdate=28 June 2017}}</ref>).
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| And these labs are important, positively impacting industry, government, and the public. Take for example the United States' Argonne National Laboratory in Illinois, which claims in 2010 to have created nearly 5,000 jobs and $695 million total economic impact for the state, while bringing in 5,500 researchers from all around the world.<ref name="ArgonneOurImpact">{{cite web |url=https://www.anl.gov/community/our-impact |title=Our Impact |work=Argonne National Laboratory |publisher=UChicago Argonne, LLC |accessdate=29 June 2017}}</ref> Looking to the past, we find that Bell Telephone Laboratories at its peak employed some 1200 PhDs and was responsible for the creation of vital technologies such as solid state components, wireless telephony technology, the C programming language, and the Unix operating system (thanks to Bell researchers like Ken Thompson and Dennis Ritchie).<ref name="GertnerTheIdea13">{{cite book |url=https://books.google.com/books?id=OkECDAAAQBAJ |title=The Idea Factory: Bell Labs and the Great Age of American Innovation |author=Gertner, J. |publisher=Penguin |year=2013 |pages=422 |isbn=9780143122791}}</ref> In fact, laboratories are often at the heart of a company's research and development (R&D) efforts towards bringing people new products. Vehicle<ref name="VolvoMaterials">{{cite web |url=http://www.volvogroup.com/en-en/about-us/r-d-and-innovations/materials-technology.html |title=Materials Technology |work=Volvo Group |publisher=AB Volvo |accessdate=29 June 2017}}</ref> and makeup<ref name="LOrealUSAResearch">{{cite web |url=http://www.lorealusa.com/group/discover-l%27or%C3%A9al-usa/l%E2%80%99or%C3%A9al-usa-research-and-innovation |title=L’Oréal USA Research And Innovation |publisher=L’Oréal Group |accessdate=29 June 2017}}</ref> users alike are affected by manufacturing laboratories that research, design, test, and quality control their products. Clinical labs help keep current and future generations healthy, and forensic labs help bring justice to the wronged. And calibration laboratories are vital to ensuring the precise measurement and production values of any equipment those other laboratories strongly depend on.
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| In a quest to further put the prevalence of laboratories into perspective, we use examples similar to above to describe 20 common industries that find laboratories vital to their activities. But before we can do that, we need to first build a framework for better visualizing and understanding how labs intersect our lives, which we do in the next section.
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| ==Further reading==
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| * {{cite book |url=https://books.google.com/books?id=DJKiWjpCgAkC&pg=PA4 |title=Cabinets of Experimental Philosophy in Eighteenth-Century Europe |editor=Bennett, J.; Talas, S. |publisher=Brill |year=2013 |pages=296 |isbn=9789004252974}}
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| * {{cite journal |title=The Laboratory Challenge: Some Revisions of the Standard View of Early Modern Experimentation |journal=Isis |author=Klein, U. |volume=99 |issue=4 |pages=769-782 |year=2008 |doi=10.1086/595771}}
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| * {{cite web |url=http://www.ieg-ego.eu/schmidgenh-2011-en |title=The Laboratory |work=European History Online (EGO) |author=Schmidgen, H. |publisher=Institute of European History |date=08 August 2011}}
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| * {{cite book |url=http://books.google.com/books?id=utc0AQAAMAAJ&pg=200 |chapter=The Evolution of Modern Scientific Laboratories |title=Papers and Addresses by William Henry Welch |author=Welch, William Henry |volume=3 |publisher=The Johns Hopkins Press |year=1920 |pages=200–211}}
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| ==References==
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| {{Reflist|colwidth=30em}}
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| <!--Place all category tags here-->
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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
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
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