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Sample Preparation Workshop

PARTICIPANT WARNING:

The following presentation may cause analyst and manager anxiety as well as potential corrective actions.

Chemists with heart conditions, tendencies to experience bad dreams or anxiety attacks should view with caution and seek expert assistance should symptoms (or cause) continue.

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How Important is Sample Prep?

• Fertilizer Blends Versus Homogeneous Granules

• AOAC Sample Prep.- 1929

• How much is the variability in your lab due to Sample Prep?

• Sample Reduction –

• What is a “Ground” Sample –

• Let’s Talk Contamination –

• Fertilizer Blends Versus Homogeneous Granules –

– AOAC Sample Prep.- Final action 1929 – No Blends/Micro’s!

• How much is the variability in your lab due to Sample Prep?

• How can you find out?

• How do you lower it?

• Sample Reduction –

• So many wrong ways, only one right way

• Equipment

• Technique

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• What is a “Ground” Sample –

• How much to grind?

• Could there be a difference between 20 (0.84mm) and 40 (0.42mm)

mesh sample analysis data? (particles/g)

• Is there an analytical difference/bias between 20 & 40 mesh

samples?

• At 100 °C, the dissociation pressure of DAP is 5 mmHg

• DAP decomposition starts as low as 70*C

To find the best suited mill for a specific application, the following

should be considered in advance: (Retch Brochure)

• Quality/characteristics of sample (e.g. dry, temperature-sensitive etc.)

• Feed size - grams to grind

• Fineness – sieve to use or - ?? mm

• Sample volume – density/weight

• Sample throughput – grams/minute

• Subsequent analysis (which type of contamination by abrasion of grinding tools

is acceptable?)

• May the sample be dried or embrittled before grinding?

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Grinding

Profiles 0.0

5.0

10.0

15.0

20.0

25.0

30.0

35.0

40.0

45.0

-.50 + .25mm -.25 + .10mm -.10mm

0.0

5.0

10.0

15.0

20.0

25.0

30.0

35.0

40.0

45.0

50.0

-.50 + .25mm -.25 + .10mm -.10mm

0.0

10.0

20.0

30.0

40.0

50.0

60.0

70.0

80.0

-.50 + .25mm -.25 + .10mm -.10mm

Nitrogen

Phosphate

Potash

A picture is worth a 1000

words – Visual segregation of ground samples

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Contamination

• Let’s Talk Contamination –

• What is it?

• Low quantities of high analysis materials

• What is CRH - Water can be a major contaminant

• Where can it occur?

• What to do to reduce it

Critical Relative

Humidity of

Materials and

Blends at 30ºC

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40

45

50

55

60

65

70

75

80

85

90

95

100Humidity in Tallahassee, FL Last Year

The Compost & Climate Connection

"Every day we ‘waste’ tons of food scraps, yard trimmings, and other organic

(carbon based) materials. How we manage these materials can have a significant

impact on climate change. Diverting them from landfills reduces the amount of

methane that is released to the atmosphere. Composting them to produce

stable soil products with nutrients provides for healthier soils that store more

carbon (another way to reduce greenhouse gas emissions) It also makes our soils

more productive and more resilient to the changes that are already occurring.

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Does Anyone Need Medical Assistance?

Questions?