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Barfoed’s test for monosaccharides

February 25, 2015 by Dr Hamza Arshad 40 Comments

Barfeod’s test is a qualitative test used to check the presence of monosaccharides in an unknown solution.Barfeod’s reagent react with monosaccharide and precipitate is formed.It also react with disaccharide but the reaction is slow and monosaccharides can be easily distinguished from disaccharides and polysaccharides.

Principle of barfoed’s test:

When barfoed reagent mix with solution of monosaccharide or disaccharide, and heated in boiling water bath, they react and crystal precipitate is formed. Copper acetate which is present in barfoed’s reagent convert to copper oxide and give brick red precipitate when react with monosaccharide or disaccharides.Monosaccharde react fast while disaccharide react slowly.

Reagents for barfeod test:

3 to 5 ml of barfoed’s reagent which is composed of:

  • Copper acetate
  • Acetic acid.

Original sugar solution.

Procedure of barfeod’s test:

  • Take 3 to 5 ml of barfoed’s reagent in a test tube.
  • Add 3-4 drops of original solution to the test tube.
  • Then put the test tube in boiling water bath for boiling.The reaction will occur and precepitate would be formed.

barfoad's test for monosaccharides

Monosacchardies give brick red precipitate with copper acetate and acetic acid.They usually appear within seven minutes.If they appear within seven minutes, it means that monosaccharide is present in the solution.If brick red precipitate are formed after seven minutes, it means that disacchaides are present in the original solution.And if precipitates are not formed, it means that solution doesn’t contains either monosaccharides or disaccharides.

Precautions:

Here are a few important things you must keep in mind while performing this test:

  1. Add more amount of barfoed reagent as compared to solution. As mentioned in procedure above.
  2. Keep a stop watch or just watch with yourself and note time when you put test in boiling water bath.
  3. Water should be boiling. Don’t put test tube in water if it is not boiling.
  4. Remove the test tube regularly and check if precipitates are formed or not. If ppt are not formed, keep it in water bath again quickly.

Results of barfoed test:

If precipitate appear in 7 minutes, it means monosaccharde is present in the original solution.But if precipitate appear after seven minutes, it means that disaccharide is present in the original solution.

 

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Filed Under: Biochemistry Tagged With: barfoed's test, test for monosaccharides

About Dr Hamza Arshad

Hamza is the writer and owner of this blog. He is a hobby blogger and student of MBBS in BMC (Bannu Medical college). He blogs to help others and share his knowledge with others.

Comments

  1. pankaj panday says

    December 9, 2015 at 12:40 pm

    why barfoed reagent give the red ppt..?
    why we not use the fehling solution inthe place pf barfoed reagent??

    Reply
    • Admin says

      December 9, 2015 at 1:59 pm

      barfoed reagent gives red ppt because Copper acetate which is present in barfoed’s reagent convert to copper oxide and give brick red precipitate when react with monosaccharide or disaccharides…
      we don’t use fehling solution here because fehling test is used for detection of reducing carbohydrates and does not react with non-reducing carbohydrates while barfoed test is for the detection of monosaccharides and disaccharides.
      Hope this helps…

      Reply
      • PANKAJ PANDAY says

        January 2, 2016 at 5:20 am

        is the fehling solution is more basic than barfoed reagent

        Reply
    • Shailesh biradar says

      October 26, 2017 at 1:14 am

      Why monosachharide react faster than diasachharide…?

      Reply
  2. U.Kishokkumar says

    December 25, 2015 at 1:29 pm

    Dear Sir I have one doubt also face very difficult situation.

    my problem is, I was receive milk from collecting center but those peoples are adulterate by glucose. can i used this method for finding it? you are mention mono & Di saccharides test but already milk has lactose it is Di saccharides so how can find which is adulterate glucose?

    please say some think I m waiting for your prompt reply.
    my e mail ID kishofst05@gmail.com

    Reply
    • Admin says

      December 25, 2015 at 2:46 pm

      This test would be positive for both glucose and lactose…but it would not be useful if both glucose and lactose are present..if you want to know that milk has glucose or not then you can use this test…if ppt are formed before 7 minutes then it means that both glucose and lactose are present (as lactose would be definitely present) but if ppt are formed after 7 minutes then it means that only lactose is present.
      Hope this helps…if you have further questions, feel free to ask.
      Do visit our site again for more medical related stuff.

      Reply
  3. Chanel says

    January 21, 2016 at 1:46 pm

    What is the negative result for this test?

    Reply
    • Admin says

      January 31, 2016 at 10:32 am

      precipitate will not form…

      Reply
      • ayshatu says

        February 11, 2016 at 8:19 pm

        Pls I wnt introduction for benedict an barfoed test

        Reply
        • Admin says

          February 14, 2016 at 6:53 pm

          read the first para of this post.

          Reply
  4. Ahmad says

    February 13, 2016 at 2:35 pm

    need more discussion on the result of both Benedict and barfoed tesr

    Reply
    • Admin says

      February 14, 2016 at 6:51 pm

      compared the results of both…there is nothing logical in it.

      Reply
  5. HAMMANI says

    February 14, 2016 at 7:41 pm

    Pls.i need barfoed test discussion

    Reply
    • Admin says

      February 16, 2016 at 9:58 am

      you can collect discussion from this post…pick important points from here.

      Reply
  6. David sarpong says

    February 27, 2016 at 10:44 pm

    Why is that the monosaccharides forms ppt faster than the disaccharides?

    Reply
    • Admin says

      March 1, 2016 at 4:11 pm

      read the principle of this test above, it is clearly written then monosaccharides reacts faster then dissaccharides.

      Reply
      • bobbyb says

        March 5, 2016 at 9:09 pm

        That didn’t answer the question, which was WHY?

        Reply
        • Admin says

          March 6, 2016 at 6:11 pm

          sorry, i don’t have the exact answer but will ask for you from someone..

          Reply
    • Salmin Alshalmani says

      January 23, 2018 at 12:19 am

      Due to the weakly acidic nature of Barfoed’s reagent, it is reduced only by monosaccharides

      Reply
  7. Tina says

    April 16, 2016 at 1:49 pm

    Do u know about christen barfoed and how he find this way to find reducing monosaccharides and disaccharides?it’s necessary for me to know the answer pls help me.

    Reply
    • Admin says

      April 16, 2016 at 5:36 pm

      sorry don’t know about the history of this test. Google it. Or ask in yahoo answers or in quora.

      Reply
  8. Shani saxena says

    May 1, 2016 at 5:05 pm

    Why barfoed reagent react fast with mono saccharide not with di saccharide

    Reply
    • Admin says

      May 2, 2016 at 1:49 pm

      Don’t know the exact answer but probably due to need of less energy for reaction because of short chain molecules.

      Reply
  9. ashla says

    July 2, 2016 at 2:12 pm

    What will happen if we add more original solution than barfoed’s reagent?

    Reply
    • Admin says

      July 3, 2016 at 9:26 am

      i think it will not give results….but do it yourself and then let us know here.

      Reply
  10. marceline abadeer says

    July 14, 2016 at 1:34 pm

    When you test starch with Barfoed’s reagent, what would be the answer, positive or negative? Explain your answer by giving reasons and structures.

    Reply
    • Admin says

      July 18, 2016 at 5:36 pm

      it would be negative. because barfoed’s reagent react with monosacchardies very fast while with disaccharide slow…that means that when CHO chains length increases it would react slow with barfoard reagent. And as starch is a polysaccharide, it would react very slow and we say that barfoed reaction is negative for starch.
      Sorry can’t draw structures etc and there is not any image of reactions for your question in google.

      Reply
  11. princess says

    September 11, 2016 at 5:00 am

    What would be the result if we combined the glucose to barfoed’s reagent ? same as to control(distilled water) with barfoed’s reagent? same as fructose with barfoeds and lactose with barfoed’s reagent? Explain why ??

    Reply
    • Admin says

      September 14, 2016 at 6:13 pm

      if you use glucose solution then ppt should form in less then 7 minutes as glucose is a monosaccharide.

      Reply
  12. gloria says

    October 19, 2016 at 12:53 am

    what test is used 4 monosaccharide

    Reply
    • Admin says

      October 26, 2016 at 2:31 pm

      this one.

      Reply
  13. Noni says

    November 16, 2016 at 10:19 pm

    What is the difference between the precipitate of Barfoed and Benedict test?

    Reply
  14. moon says

    November 27, 2016 at 5:03 pm

    Hi …What is the carbohydrates that give negative barfoed test???

    Reply
    • Admin says

      December 3, 2016 at 8:12 am

      polysaccharides.

      Reply
  15. Trina says

    December 3, 2016 at 7:26 am

    What is the equation involved in Barfoed’s test using Galactose?

    Reply
    • Admin says

      December 3, 2016 at 8:04 am

      sorry

      Reply
  16. ab says

    January 27, 2017 at 4:54 am

    sir plz i nid precautions taken in barfoed’s test……right nw sir

    Reply
    • Admin says

      February 11, 2017 at 2:59 pm

      precautions are mentioned above in post.

      Reply
  17. Zoe says

    February 1, 2018 at 5:30 am

    1. Barfoed’s test when does it give blue – green colour
    in a laboratory experiment a student was giving an unknown compound . After performing the test for carbohydrates analysis the student reported the unknown as a reducing aldol pentose. Please describe the experimental procedure that makes the student to infer the result or conclude

    Reply
    • Admin says

      February 6, 2018 at 4:07 am

      as i have mentioned in some of the posts that you will do different tests starting for molisch’s test and if positive going towards others. this way you can find which sugar it is…as there are separate tests for different sugars.

      Reply

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Hamza is the writer and owner of this blog. He is a hobby blogger and student of MBBS in BMC (Bannu Medical college). He blogs to help others and share his knowledge with others.

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