BRUINS INSTRUMENTS 10 / 07

Training Near Infrared Transmission Whole Grain Analyzer

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Targets: 

History and Basics of NIR

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Calibration development

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Toubleshooting & Maintainance

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History of NIR 

First detected by William Herschel beginning of 19th century

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First instrument built by W.W. Coblentz about 1900

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First practical use in the 1930s

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First agriculture usage by Karl Norris 1968

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First commercial scanning instruments 1978

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First BRUINS NIR spectrophotometer 1979

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First BRUINS NIT spectrophotometer 1982

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Basics of NIR

NIR = Near InfraRed Spectroscopy Wavelength of Light UV nm > VIS 380 Energy of Light > NIR 750 / 1100 (NIT / NIR)

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>(M)IR 2500

4

Basics of NIR

Typical properties analysed by NIR are organic compounds like Oil Protein Starch And Water Useful concentration are in % range, ppm or ppb level are normally impossible .

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Basics of NIR  NIR active groups

O-H Water, Alcohol C-H Carbohydrates (Starch, Sugar, Cellulose) Fat / Oil N-H Protein

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Basics of NIR

Molekular Vibrations O

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H H

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Basics of NIR

Molekular Vibrations

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Basics of NIR

Molekular Vibrations

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Calibration 

Reference Analysis

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Sample selection

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Sampling

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Sample Preparation / Homogenisation

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Sample Presentation

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Calibration: Reference Analysis 

NIR calibration will be dependend from reference analysis, so

 

Select best possible method Investigate „real“ method error

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Make sure that the same sample material will be analysed

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Use at least double analysis

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Comment all specialities of actual sample

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Calibration: Lab Error Influence 10 / 07 BRUINS INSTRUMENTS 12

Calibration: Lab Error Influence 10 / 07 BRUINS INSTRUMENTS 13

Calibration: Sample Selection 

The complete interesting concentration range must be covered by calibration samples.

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The calibration set must also include samples with changes from other constituents, eg. low protein with high moisture, low protein with low moisture etc.

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Further samples must be included which are representing influences from climate, soil, cultivars etc.

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Due to the effect of temperature to NIR also cold and warm samples should be added.

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Calibration: Sampling 

The sample must be representative for the total amount.

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Take subsamples from different locations.

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Thoroughly mix these to get a homogene sample.

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Calibration: Sample Preparation      

No extra preparation needed for most grain and oil seeds.

Samples with thick shell must be ground (e.g. sunflower seeds).

The same sample preparation must be used for calibration and routine analysis.

By grinding a sample the moisture content will decrease.

Select the best grinder to reduce this moisture loss.

If a grinder with a sieve will be used, control the size of the mesh.

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Calibration: Sample Presentation 

OmegAnalyzer and AgriCheck uses the NIR transmission, so for such meal the MultiCheck will be the better choice

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As an alternative, but less efficient, a micro sample cup for meal or powders can be used

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Calibration: Sample Presentation

In all cases, if fine powder or ground sample:

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Thoroughly mix the sample before filling

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In cases of components with different density make sure, that no material separate If a micro sample cup is used:

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Make sure that the sample is filled without wholes

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Knock a bit, that the sample will slide together, but not to often because different components may separate

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Calibration: Standardisation

Before using the instrument in routine, it must be compared against the reference method with a set of samples. These samples should cover the range of concentrations and normal variations in moisture, area and genotypes.

In order to get a good adjustment, the sample must be well mixed that the same material will be analysed with both methods.

The data for the reference analysis need to be well controlled, at least a double analysis must be performed.

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Calibration: Standardisation

The easiest comparison of accuracy and necessary adjustment can be made with Excel.

Just two columns need to filled , one with reference analysis the second with predicted NIR data.

Using the Excel functions for mean, standard error xy and correlation will calculate all necessary information.

Additional the Excel graph can be used to show how good the predicted values fit to the reference analysis.

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Calibration: Bias 10 / 07

Actual 8 9 10 11 12 13 14 15 16 17 18

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Predicted 7.5

8.5

9.7

10.6

11.7

12.4

13.7

14.4

15.5

16.6

17.7

21

Calibration: Bias 10 / 07

Actual 8 9 10 11 12 13 14 15 16 17 18 Predicted 7.5

8.5

9.7

10.6

11.7

12.4

13.7

14.4

15.5

16.6

17.7

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Mean SEP R² Bias Slope Actual Predicted 13.00

0.121

0.999

- 0.43

1.001

12.57

22

Calibration: Bias 10 / 07 BRUINS INSTRUMENTS 23

Calibration: Bias, 0.43 added 10 / 07

Actual 8 9 10 11 12 13 14 15 16 17 18

BRUINS INSTRUMENTS

Predicted

7.93

8.93

10.13

11.03

12.13

12.83

14.13

14.83

15.93

17.03

18.08

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Calibration: Bias 10 / 07 BRUINS INSTRUMENTS 25

Calibration: Slope

While the bias will move all data parallel, the slope will change the extreme values more than the values around the middle.

So adjusting the slope will much more influence the predicted result.

For the slope adjustment the sample set must really cover the full calibration range.

Normally this adjustment should not be used. If it seems to be necessary, look for the reason. It might be better to select or built another calibration.

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Calibration: Slope 10 / 07

Actual 8 9 10 11 12 13 14 15 16 17 18

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Predicted 7.5

8.3

9.8

10.5

12.1

12.9

14.5

15.0

16.6

17.2

18.5

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Calibration: Slope 10 / 07 BRUINS INSTRUMENTS 28

Calibration: corrected Slope 10 / 07

Actual 8 9 10 11 12 13 14 15 16 17 18

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Predicted

8.14

8.86

10.21

10.83

12.27

12.99

14.43

14.88

16.31

16.85

18.02

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Calibration: corrected Slope 10 / 07 BRUINS INSTRUMENTS 30

Calibration: Slope

Actual 11 12 13 14 Predicted 10.5

12.1

12.9

14.5

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Calibration: Slope 10 / 07 BRUINS INSTRUMENTS 32

Calibration: Slope 10 / 07 BRUINS INSTRUMENTS 33

Calibration: corrected Slope?

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Actual 8 9 10 11 12 13 14 15 16 17 18

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Predicted 8.59

9.21

10.39

10.93

12.18

12.81

14.06

14.45

15.70

16.17

17.18

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Calibration: corrected Slope?

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