Editing Glucose (section)

===Instrumental quantification===
====Refractometry and polarimetry====
In concentrated solutions of glucose with a low proportion of other carbohydrates, its concentration can be determined with a polarimeter. For sugar mixtures, the concentration can be determined with a [[refractometer]], for example in the [[Oechsle scale|Oechsle]] determination in the course of the production of wine.

====Photometric enzymatic methods in solution====
{{main|Glucose oxidation reaction}}
The enzyme glucose oxidase (GOx) converts glucose into gluconic acid and hydrogen peroxide while consuming oxygen. Another enzyme, peroxidase, catalyzes a chromogenic reaction (Trinder reaction)<ref>{{Cite journal |doi=10.1177/000456326900600108 |title=Determination of Glucose in Blood Using Glucose Oxidase with an Alternative Oxygen Acceptor |journal=Annals of Clinical Biochemistry |volume=6 |pages=24–27 |year=1969 |last1=Trinder |first1=P. |issue=1 |s2cid=58131350 |doi-access=free }}</ref> of [[phenol]] with [[4-Aminoantipyrine|4-aminoantipyrine]] to a purple dye.<ref name="purpuled">{{cite book |doi=10.1016/bs.pmbts.2019.01.004 |chapter=Fasting blood glucose levels in patients with different types of diseases |title=Glycans and Glycosaminoglycans as Clinical Biomarkers and Therapeutics - Part A |series=Progress in Molecular Biology and Translational Science |date=2019 |volume=162 |pages=277–292 |isbn=978-0-12-817738-9 | vauthors = Zhang Q, Zhao G, Yang N, Zhang L |publisher=Elsevier |pmid=30905457 }}</ref>

====Photometric test-strip method====
The test-strip method employs the above-mentioned enzymatic conversion of glucose to gluconic acid to form hydrogen peroxide. The reagents are immobilised on a polymer matrix, the so-called test strip, which assumes a more or less intense color. This can be measured reflectometrically at 510&nbsp;nm with the aid of an LED-based handheld photometer. This allows routine blood sugar determination by nonscientists. In addition to the reaction of phenol with 4-aminoantipyrine, new chromogenic reactions have been developed that allow photometry at higher wavelengths (550&nbsp;nm, 750&nbsp;nm).<ref name="purpuled"/><ref>{{Cite journal |doi=10.1039/A709038B |title=Water-soluble chromogenic reagent for colorimetric detection of hydrogen peroxide—an alternative to 4-aminoantipyrine working at a long wavelength |journal=Analytical Communications |volume=35 |issue=2 |pages=71–74 |year=1998 |last1=Mizoguchi |first1=Makoto |last2=Ishiyama |first2=Munetaka |last3=Shiga |first3=Masanobu}}</ref>

====Amperometric glucose sensor====
The electroanalysis of glucose is also based on the enzymatic reaction mentioned above. The produced hydrogen peroxide can be amperometrically quantified by anodic oxidation at a potential of 600 mV.<ref>{{Cite journal |pmid=18154363 |year=2008 |last1=Wang |first1=J. |title=Electrochemical glucose biosensors |journal=Chemical Reviews |volume=108 |issue=2 |pages=814–825 |doi=10.1021/cr068123a}}.</ref> The GOx is immobilized on the electrode surface or in a membrane placed close to the electrode. Precious metals such as platinum or gold are used in electrodes, as well as carbon nanotube electrodes, which e.g. are doped with boron.<ref>{{Cite journal |doi=10.1016/j.talanta.2008.04.023 |pmid=18656655 |year=2008 |last1=Chen |first1=X. |title=Amperometric glucose biosensor based on boron-doped carbon nanotubes modified electrode |journal=Talanta |volume=76 |issue=4 |pages=763–767 |last2=Chen |first2=J. |last3=Deng |first3=C. |last4=Xiao |first4=C. |last5=Yang |first5=Y. |last6=Nie |first6=Z. |last7=Yao |first7=S.}}</ref> Cu–CuO nanowires are also used as enzyme-free amperometric electrodes, reaching a detection limit of 50&nbsp;μmol/L.<ref>{{Cite journal |doi=10.1007/s00604-009-0260-1 |title=Enzyme-free amperometric sensing of glucose using Cu-CuO nanowire composites |journal=Microchimica Acta |volume=168 |issue=1–2 |pages=87–92 |year=2010 |last1=Wang |first1=Guangfeng |last2=Wei |first2=Yan |last3=Zhang |first3=Wei |last4=Zhang |first4=Xiaojun |last5=Fang |first5=Bin |last6=Wang |first6=Lun |s2cid=98567636 }}</ref> A particularly promising method is the so-called "enzyme wiring", where the electron flowing during the oxidation is transferred via a molecular wire directly from the enzyme to the electrode.<ref>{{Cite journal |doi=10.1021/ac00087a008 |pmid=8092486 |year=1994 |last1=Ohara |first1=T. J. |title="Wired" enzyme electrodes for amperometric determination of glucose or lactate in the presence of interfering substances |journal=Analytical Chemistry |volume=66 |issue=15 |pages=2451–2457 |last2=Rajagopalan |first2=R. |last3=Heller |first3=A.}}</ref>

====Other sensory methods====
There are a variety of other chemical sensors for measuring glucose.<ref name="Borisov">{{Cite journal |doi=10.1021/cr068105t |pmid=18229952 |year=2008 |last1=Borisov |first1=S. M. |title=Optical biosensors |journal=Chemical Reviews |volume=108 |issue=2 |pages=423–461 |last2=Wolfbeis |first2=O. S.}}</ref><ref>{{Cite journal |doi=10.1177/193229681100500507 |pmc=3208862 |pmid=22027299 |year=2011 |last1=Ferri |first1=S. |title=Review of glucose oxidases and glucose dehydrogenases: A bird's eye view of glucose sensing enzymes |journal=Journal of Diabetes Science and Technology |volume=5 |issue=5 |pages=1068–76 |last2=Kojima |first2=K. |last3=Sode |first3=K. }}</ref> Given the importance of glucose analysis in the life sciences, numerous optical probes have also been developed for saccharides based on the use of boronic acids,<ref>{{Cite journal |doi=10.1007/s00604-008-0947-8 |title=Boronic acid based probes for microdetermination of saccharides and glycosylated biomolecules |journal=Microchimica Acta |volume=162 |issue=1–2 |pages=1–34 |year=2008 |last1=Mader |first1=Heike S. |last2=Wolfbeis |first2=Otto S. |s2cid=96768832 }}</ref> which are particularly useful for intracellular sensory applications where other (optical) methods are not or only conditionally usable. In addition to the organic boronic acid derivatives, which often bind highly specifically to the 1,2-diol groups of sugars, there are also other probe concepts classified by functional mechanisms which use selective glucose-binding proteins (e.g. concanavalin A) as a receptor. Furthermore, methods were developed which indirectly detect the glucose concentration via the concentration of metabolized products, e.g. by the consumption of oxygen using fluorescence-optical sensors.<ref>{{Cite journal |doi=10.1016/S0956-5663(99)00073-1 |pmid=10826645 |title=Sol–gel based glucose biosensors employing optical oxygen transducers, and a method for compensating for variable oxygen background |journal=Biosensors and Bioelectronics |volume=15 |issue=1–2 |pages=69–76 |year=2000 |last1=Wolfbeis |first1=Otto S. |last2=Oehme |first2=Ines |last3=Papkovskaya |first3=Natalya |last4=Klimant |first4=Ingo}}</ref> Finally, there are enzyme-based concepts that use the intrinsic absorbance or fluorescence of (fluorescence-labeled) enzymes as reporters.<ref name="Borisov" />

====Copper iodometry====
Glucose can be quantified by copper iodometry.<ref name="Galant">{{Cite journal |doi=10.1016/j.foodchem.2015.04.071 |pmid=26041177 |year=2015 |last1=Galant |first1=A. L. |title=Glucose: Detection and analysis |journal=Food Chemistry |volume=188 |pages=149–160 |last2=Kaufman |first2=R. C. |last3=Wilson |first3=J. D.}}</ref>