QUANTITATIVE ASSAYS WITH MICROTRACERS F

(The Counting of Demagnetized Particles)

Microtracers (tm) F (colored uniformly sized iron particles) are easily retrievable "harmless markers" used to code the presence of vitamins, minerals and drugs in animal and poultry feeds. They are also used to measure the quality of mix of feeds and to locate and quantify "feed carryover" in feed manufacturing equipment. They are described in detail in Micro-Tracers' literature Item L.

While many times, clients need only qualitative information from Microtracers, quantitative information is required especially to evaluate mixing. This literature item describes our current method for obtaining good quantitative information from Microtracer F. analyses.

4) A coffeemill (burrmill type preferred) to grind pellets to a  mash.

1) Pour a weighed sample of feed through the "Rotary Detector" To assure complete tracer recovery, the sample may be passed through the unit twice. Approx. 98% of all tracer will be retrieved on the first pass and nearly 100% will be retrieved in two passes.

The weight of the sample to be analyzed is determined in advance to yield a desired number of tracer particles. If one wants to find aprox. 100 particles of Microtracer and one formulated the tracer at 50 grams per 2,000-lbs. of feed, one would analyze 75 grams of feed (25,000 particles per gram of tracer multiplied by 50 grams of tracer divided by 2,000 and divided again by 75/455 grams = 103).

Pellets must be ground to mash prior to analysis. Refer to Literature Item N for proper operation of the "Rotary Detector"

2) Take the magnetic material isolated from the feed sample by the "Rotary Detector" and transfer it to the 30 ml analytical scoop. Do not develop the tracer on the "Rotary Detector"

3) "Demagnetize" this material by holding the weigh scoop directly over the bulk tape eraser, turning the bulk tape "on" and slowly raising the scoop to a distance 2 or 3 feet removed from the eraser. Turn the eraser "off" The magnetic material separated by the "Rotary Detector" will now be "demagnetized" and free flowing.

4) Wet a 15 or 24 cm Whatman #1 circle with the desired tracer developer. For most feeds this will be a 60% ethanol solution. For mash feeds, the paper must be uniformly wetted but not too wet, Certainly, no beads of moisture should be present. For pelleted feeds, the paper should be wetter than for mash feeds but still no beads of moisture should be present.

5) Sprinkle the magnetic material (Including the Microtracers F) from the scoop onto the wetted paper so the material is evenly distributed on the paper. This the most difficult part of the analysis. Even distribution of the material may be achieved by moving the scoop in a circular pattern over the filter paper, slowly increasing the angle of incline of the spout of the scoop until tracer falls from the scoop to the paper. It is also helpful to tap the scoop. This may assist in"bouncing" the magnetic material from the scoop to the paper.

6) As soon as any color is visually apparent, transfer the wetted filter paper to a hot plate pre-heated to 300 degrees F or to again disregard the initial result and re-run the analysis.

7) When the paper is dry, mark it for identification. When time is available, count the colored spots by circling all the paper and the third color on the opposite side.

8) Employ Poisson statistics and chi-squared calculations to interpret the results of the test. P