Ehrlich测试 - 定义，原理，过程，结果，使用

Ehrlich测试定义

Ehrlich测试is a biochemical test used for the detection of amino acid, tryptophan, in aproteinsample. Ehrlich test is also termed the p-dimethylamino benzaldehyde test, named after the Ehrlich reagent. The test is named after the Nobel Prize winner Paul Ehrlich, who identified this test during the distinction of typhoid from simple diarrhea. It is also called a specific amino acid test as it detects a certain amino acid, tryptophan. This test has been used in laboratories for medical tests, some for drug testing while others for diagnosis of various diseases. Diagnosis of liver diseases, carcinoid syndrome, hemolytic processes, and occlusion of the common bile duct can also be performed with the Ehrich test. One of the common forms of the Ehrlich test is the spot test used for the detection of psychoactive compounds like tryptamines and ergoloids (like, LSD). A positive Ehrlich test is obtained for natural opium as it contains tryptophan. The Ehrlich reagent is also used for the identification of indoles and urobilinogen (found in urine).

Ehrlich测试的目标

To detect the presence of tryptophan in a given sample.
To distinguish between typhoid and diarrhea.
To identify the presence of urobilinogen in a urine sample.

Principle of Ehrlich Test

Ehrlich试剂由P-二甲基氨基苯甲醛组成。在测试中发生的反应是基于以下原理：在酸性条件下，Ehrlich的试剂经历了亲电取代。替代发生在色氨酸的吲哚或苄基吡咯环，以产生蓝紫色的冷凝产物。通过添加纳米，进一步增强了反应后形成的冷凝产物₂.

Reaction

色氨酸 + Ehrlich试剂（P-二甲基氨基苯甲醛）→蓝紫色凝结产物

要求

Reagents

Ehrlich试剂：Ehrlich试剂是通过在50 mL的95％乙醇中添加约0.5至2.0克P-二甲基氨基苯甲醛来制备的。为此，50毫升10％h₂SO₄is added.
Protein sample
Concentration HCl
NaNO₂

Materials required

试管
Test tube stand
Pipettes

Ehrlich测试的过程

About 3-4 ml of diluted protein solution or urine sample is added to a test tube.
The liquid is then boiled with 1 ml of concentrated HCl.
A few drops of the Ehrlich reagent (p-dimethylamino benzaldehyde in H₂SO₄) are added to the test tube.
然后将测试管摇动以正确将内容物正确混合在一起。
The test tube is observed for the color change. If a blue-violet color is observed, a few drops of NaNO₂将溶液添加到试管中以获得蓝色。

Result and Interpretation of Ehrlich Test

Positive result:A positive result in the Ehrlich test is indicated by the appearance of red to purple or blue-violet color. The color then changes to blue with the addition of NaNO₂. This indicates that the sample contains tryptophan.
Negative result:Ehrlich测试中的负结果是通过在添加Ehrlich试剂中没有蓝色紫色的颜色来指示的。这表明样品不包含任何色氨酸。

用途

该测试是用于检测蛋白质样品中色氨酸的醛测试。
该测试用于诊断诸如伤寒的疾病和其他胆汁胆管阻塞过程的疾病。
该测试还可以用于检测精神活性化合物和药物（例如色素和ergoloids）。
Ehrlich test detects the presence of indoles and urobilinogen. The presence of urobilinogen in high concentration in urine sample helps in the diagnosis of hepatic jaundice and hepatitis.

限制

The false-negative reaction might occur in the presence of urinary tract infection as nitrites oxidize urobilinogen to urobilin.
抗生素治疗期间的假阴性结果可能会破坏一些肠道细菌。
This test is a specific test for aldehyde or tryptophan, and it doesn’t detect other amino acids or proteins.

References and Sources

Nigam S. C. and Omkar (2003). Experimental Animal Physiology and Biochemistry. New Age International Pvt. Limited. New Delhi.
Tiwari A. (2015). Practical Biochemistry. LAP Lambert Academic Publishing.
Wilson，T M和L S P Davidson。“ Ehrlich的尿泡蛋白原测试。”英国医学杂志, Vol. 1, 4611 (1949): 884-7. doi:10.1136/bmj.1.4611.884
2％ -https://medlineplus.gov/lab-tests/urobilinogen-in-urine/
2％ -https://fac.ksu.edu.sa/sites/default/files/Qualitative_tests_of_amino_acids_Lab_1.pdf
1%——https://www.sigmaaldrich.com/analytical-chromatography/microbiology/microbiology-products.html?TablePage=17928001
1% – https://www.sciencedirect.com/topics/neuroscience/urobilinogen
1% – https://www.organic-chemistry.org/synthesis/heterocycles/benzo-fused/indoles.shtm
1% – https://nutrientsinfooddoubelc.weebly.com/food-testing-lab.html
1％ - https://en.wikipedia.org/wiki/urine_test_strip
1% – https://en.wikipedia.org/wiki/Ehrlich%27s_reagent
1％ - http://wwwchem.uwimona.edu.jm/courses/chem2402/crime/reagent_kits.html
1% – http://www.urology-textbook.com/urinary-tract-infection-causes.html
<1% – https://www.thoughtco.com/calculating-concentration-and-dilution-608178
<1% – https://answers.yahoo.com/question/index?qid=20110506072319AAJSsLM

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