A COMPARATIVE STUDY OF STAINS PROPOSED FOR THE DIRECT MICROSCOPIC EXAMINATION OF MILK

1951 ◽  
Vol 14 (2) ◽  
pp. 49-64 ◽  
Author(s):  
Joseph C. Olson ◽  
Luther A. Black
Keyword(s):  
Methylene Blue ◽  
Potassium Dichromate ◽  
Collaborative Study ◽  
Laboratory Procedure ◽  
Standard Methods ◽  
Weighted Averages ◽  
Counting Procedure ◽  
Direct Microscopic Examination ◽  
Blue Stain ◽  
Microscopic Counting

Five stains which have been proposed as substitutes for stains now specified in Standard Methods were compared by means of a collaborative study involving nine different laboratories. Stain I was the present Standard Methods alcohol-containing methylene blue stain; Stain II was a potassium - dichromate - sulfuric acid polychrome methylene blue stain; Stain III was an acid- and water-free methylene blue stain; Stain IV was a modification of Stain III containing hydrogen peroxide; Stain V was a methylene blue stain, the use of which was accompanied by a modification in fixation of the milk film; and Stain VI was a modified two color stain, details of which were not supplied. Examination of weighted averages of all samples from all laboratories showed that Stain III yielded the highest average count. Unfavorable comments pertaining to all stains except Stain III were received. Great variation in the results between laboratories was evident. One stain might show superior results in one laboratory and give inferior results in another laboratory. In general, Stain III showed the least variation in results among the collaborating laboratories, although it obtained the highest score in only one laboratory. The study pointed up the need for uniformity in laboratory procedure among different laboratories, particularly as regards the direct microscopic counting procedure.

Collaborative Study of a Spiral Vessel Count Method for Estimating Shell in the Chocolate Component of Cocoa and Related Products

1968 ◽  
Vol 51 (3) ◽  
pp. 725-735
Author(s):  
Manion M Jackson
Keyword(s):  
Standard Deviation ◽  
Collaborative Study ◽  
Pectic Acid ◽  
Counting Procedure ◽  
Count Method ◽  
Cocoa Products ◽  
Two Samples ◽  
Borax Solution ◽  
Vessel Count ◽  
Microscopic Counting

Abstract Part-I: The spiral vessel count method for estimating pectic acid in cocoa has been modified to replace the saturated borax solution by 4% NaOH, which gives a clearer product to count, and to include a method for preparing the sample dry fat-free and 250 mesh before analyzing, by hand grinding or grinding by two different grinders. Counts have been made on known shell in the chocolate component mixtures. A formula usable in a 1—15% range and standard curves have been prepared for the estimation of shell in the chocolate component. Counts have been taken at 100X and 200x on a 0.2 g/100 ml concentration, and at 200X on a 0.35 g/50 ml concentration; 200X counting of the higher concentration is preferred for 1—15% shell. Cocoas of known pectic acid content were analyzed by the method and per cent shell found by spiral vessel counts compared with per cent pectic acid. These cocoas were also analyzed before being made 250 mesh for comparative purposes. An intralaboratory study was made on two samples. Part-II: A collaborative study for determining per cent shell by the spiral vessel count method was made on four samples of cocoa products by six collaborators; two samples were defatted and ground to 250 mesh, the other two samples were hand-ground. Five collaborators varied less than 1 standard deviation unit from the average on the four subdivisions; one collaborator was just outside the standard deviation on one sample. The precision of the results was within a reasonable range for a microscopic counting procedure, and the method has been recommended for adoption as official, first action.

Microchemical Oxygen Flask Sulfur Determination: General Review and Collaborative Study of an Alternative Method Using Thorin-Methylene Blue Indicator

1976 ◽  
Vol 59 (5) ◽  
pp. 1135-1139
Author(s):  
Laverne H Scroggins
Keyword(s):  
Methylene Blue ◽  
Collaborative Study ◽  
Critical Factor ◽  
Potassium Sulfate ◽  
Masking Effect ◽  
Average Deviation ◽  
Collaborative Studies ◽  
Sulfur Determination ◽  
The Mean ◽  
Barium Perchlorate

Abstract Recent collaborative studies of microchemical oxygen flask sulfur determinations are summarized and compared statistically, and the 1975 collaborative study is presented. This volumetric technique, using a peroxide solution as absorbent, barium perchlorate as titrant, and a combination of thorin and methylene blue as indicator, was tested by 8 collaborators. Data from 72 determinations were reported. The samples studied were sulfanilamide, benzylisothiourea hydrochloride, cystine, potassium sulfate, and potassium sulfate with a phosphate additive. Overall statistical results for the 3 pure organic compounds gave satisfactory values: average standard deviation 0.10, overall average deviation of the mean from the theoretical value 0.13, and average bias −0.04. The overall average deviation of the mean from the theoretical value for the potassium sulfate compound was high (1.94) in this study, and that of the phosphated potassium sulfate compound was even higher (6.46). Thorin-methylene blue does not require a titration assembly (required by tetrahydroxyquinone) and has greater stability than dimethylsulfonazo III whose indicator lag-time causes troublesome pseudo end points. However, a critical factor, when using thorin-methylene blue, is the masking effect of foreign ions. All reagents must be as pure as possible, since concentrations of chloride, fluoride, nitrate, phosphate, potassium, and sodium interfere. The thorin-methylene blue method for sulfur determination has been adopted as official first action as an alternative oxygen flask microchemical method of analysis.

A COMPARISON OF SIX METHODS OF PREPARING AND USING THE METHYLENE BLUE STAIN FOR BACTERIAL COUNTS BY THE DIRECT MICROSCOPIC METHOD*

1954 ◽  
Vol 17 (6) ◽  
pp. 179-184 ◽  
Author(s):  
Nathan Mantel ◽  
A. H. Robertson
Keyword(s):  
Methylene Blue ◽  
Federal State ◽  
Cooperative Study ◽  
Microscopic Method ◽  
Bacterial Counts ◽  
Blue Stain ◽  
Microscopic Count

A cooperative study, involving 12 federal, state, local, and private laboratories throughout the country, was conducted to evaluate six methods of preparing and using the methylene blue stain for the direct microscopic count of bacteria in milk. Three of the six methods were found superior, yielding significantly higher bacteria counts, at the same time providing greater ease in counting. These three methods are: Levine and Black's acid-and-water-free stain; North's aniline oil stain; and Anderson's polychrome stain.

scholarly journals PHENOL METHYLENE BLUE STAIN

1926 ◽  
Vol 16 (10) ◽  
pp. 1049-1049
Author(s):  
Theodore C. Buck
Keyword(s):  
Methylene Blue ◽  
Blue Stain

EFFECT OF PASTEURIZATION ON THE DIRECT MICROSCOPIC COUNT OF EGGS

1971 ◽  
Vol 34 (4) ◽  
pp. 209-211 ◽  
Author(s):  
H. E. Hall ◽  
D. F. Brown ◽  
R. B. Read
Keyword(s):  
Methylene Blue ◽  
Bacterial Count ◽  
Bacterial Cells ◽  
Bacterial Counts ◽  
The North ◽  
Counting Chamber ◽  
Blue Stain ◽  
Microscopic Count ◽  
Whole Egg

When pasteurized whole eggs from breakers were examined by the Direct Microscopic Count (DMC) procedure, the bacterial count frequently appeared to be too low to correlate with the observed state of decomposition. The DMC of whole egg was found to decrease during pasteurization. To determine why, DMC's were done using the North Aniline Oil - Methylene Blue Stain and the Levowitz-Weber modification of the Newman-Lampert stain. Total bacterial counts also were made using the Petroff-Hausser counting chamber. Results indicated that the reduction in count resulted from lysis of some of the bacterial cells in egg rather than to loss of stainability. Crystalline lysozyme at the concentration found in egg and whole egg preparations produced similar reductions in the DMC of bacteria isolated from egg.

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