scholarly journals INTERFERENCE WITH THE COLORIMETRIC DETERMINATION OF LACTIC ACID (BARKER-SUMMERSON METHOD) BY NITRATE AND NITRITE IONS

1944 ◽  
Vol 156 (2) ◽  
pp. 463-465
Author(s):  
Jane A. Russell
Keyword(s):  
Lactic Acid ◽  
Colorimetric Determination ◽  
Nitrate And Nitrite

Collaborative Study of the Colorimetric Determination of Nitrate and Nitrite in Cheese

1976 ◽  
Vol 59 (2) ◽  
pp. 284-288
Author(s):  
James E Hamilton
Keyword(s):  
Azo Dye ◽  
Collaborative Study ◽  
Colorimetric Method ◽  
Sulfanilic Acid ◽  
Zinc Hydroxide ◽  
Colorimetric Determination ◽  
Standard Curve ◽  
Nitrite Nitrate ◽  
Nitrate And Nitrite

Abstract A quantitative colorimetric method for the determination of nitrate and nitrite in cheese has been subjected to collaborative study. The method includes clarification of an aqueous extract of cheese with zinc hydroxide, reduction of nitrate to nitrite via a spongy cadmium column (the nitrite originally present is unaltered), diazotization of sulfanilic acid with the nitrite, and coupling with 1-naphthylamine hydrochloride to form a pink azo dye whose absorbance is measured at 522 nm. The spectrophotometric responses are compared to a standard curve. In samples containing both nitrate and nitrite, nitrate is determined by difference. A standard deviation of 5.5 was obtained (5 of 6 collaborators) when a cheese sample spiked with 276 ppm sodium nitrate was analyzed by the method. The method has been adopted as official first action.

scholarly journals The colorimetric determination of lactic acid in silage

1951 ◽  
Vol 49 (4) ◽  
pp. 527-529 ◽  
Author(s):  
A. J. G. Barnett
Keyword(s):  
Lactic Acid ◽  
Colorimetric Determination

388. The colorimetric determination of lactic acid in milk and milk products

1949 ◽  
Vol 16 (2) ◽  
pp. 209-216 ◽  
Author(s):  
J. Davidson
Keyword(s):  
Lactic Acid ◽  
Calcium Hydroxide ◽  
Copper Sulphate ◽  
Colorimetric Determination ◽  
Colour Intensity ◽  
Purple Colour ◽  
Milk Products ◽  
Fresh Milk ◽  
Large Numbers

A method is described for the colorimetric determination of lactic acid in milk and unsweetened milk products. The protein and lactose is removed after precipitation with copper sulphate and calcium hydroxide at 45° C, the lactic acid in an aliquot of the filtrate is oxidized to acetaldehyde in sulphuric acid in the presence of copper sulphate, a purple colour is developed with p–hydroxydiphenyl, and the colour intensity is measured in a photoelectric absorptiometer or other suitable instrument.Recoveries of from 96 to 103%, averaging 100%, were obtained when 20–400 mg. lactic acid/100 ml. were added to fresh milk.The proposed method has an advantage over existing methods in the ease and speed with which large numbers of determinations can be carried out simultaneously whilst retaining the essential accuracy.

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