10 Step Near IR Calibration Procedure

Calibration Procedure for New Products

MCT Moisture Analyzer

 

This procedure is outlined for snack foods that may or may not be ground in the lab for analysis or powder and bulk solid or similar applications.  Double-Blind Samples are recommended for calibration and validation.  This allows the sensitivity or span (linear regression slope) to be accurately determined in the laboratory to speed up the calibration of on-line transmitter when it’s difficult to create a range of process moisture samples on-line.

 

 

Step 1: Collect sufficient product for about four or five samples of 200 grams each.

 

Step 2: Measure 100 grams +/- 2 grams and place into a sealed Bag or container.

This will be sample 1.

 

Step 3: Measure 100 grams and spray about 2 grams of water on the sample. Mix

the sample and place into a sealed bag or container. This will be sample 2.

 

Step 4: Measure 100 grams and spray about 4 grams of water on the sample. Mix

the sample and place into a sealed bag or container. This will be sample 3.

 

Step 5: Measure 100 grams and place in an oven with a temperature of 100 degrees C.

Leave this sample in the oven for 10 minutes*. Remove from the oven and

Place into a sealed Bag or Container. This will be Sample 4.

 

Note:   If a fifth sample is used repeat Step 5, but keep in oven for 20 minutes*.

 

Step 6: Leave these samples in the Sealed Bag or Container for at least four hours to equlibrate.

 

Step 7: Take Sample 1 and place under the MCT. Record the moisture measurement.

 

Step 8: Do the Normal Lab analysis for this sample. A Confection Oven or

Vacuum Oven is recommended.

 

Step 9: Repeat Steps 7 and 8 for the remaining samples. When all the samples are

Analyzed, we can begin the MCT Calibration Routine. This can either be performed

via the MCT Operator Interface panel or by using the PSC Viewer Suite software. Entering the    Lab vs. MCT Near Infrared Transmitter Data allows for a linear regression to be performed and    the new Span/Sensitivity (Linear Regression Slope) and Zero/Offset (Linear Regression Y-    Intercept) to automatically be generated for correct calibration.

 

Step 10:  Confirm calibration by collecting sample on-line within target set point values and only make a zero or offset adjustment based on double-blind lab sample.  Congratulations!

 

MCT466-SF on Chips 021615

 

 

*          Theseare variable.

Some products may need more or less water. Some products may take more or less time.               Please contact PSC to discuss any questions or to request our assistance.

Sample Collection Procedure for Calibration and Validation

Most companies outline sample collection procedures in a Best Practices write up.  Consistency in sample collection and sample processing is the most important variable for good sample analysis. 

Samples should be collected and immediately taken to the laboratory or packaged for shipment to an outside lab in a sealed moisture barrier container or bag.  If sending samples to an outside lab an additional moisture barrier tape should be applied around container lid.  If samples are delivered to an in-house lab the procedure must outline for lab personnel the time to grind or process sample prior to measurement.

Calibration samples should be done individually meaning that sample one is ground, weighed, placed in oven for specified time interval at specified temperature for that product and weighed again for moisture determination.  At that point the next sample is processed.  Grinding all samples initially introduces an opportunity for increased variation while they await analysis unless all samples can be placed in the same oven immediately.

Consistency is the key to this process.  If the first shift collects samples and the lab analyzes these samples when received, results are good.  If another shift or operator collects the samples in a different manner or lets them sit for a while before bringing to the lab, or the lab lets samples accumulate before processing, variations can occur.  Consistency is important for successful calibration.

Alternatively, samples can be created in the lab and allowed to equilibrate.  These samples can be used for calibration.  A final double- blind target set point sample should be analyzed and averaged to determine any offset (zero) adjustment on-line.

Other parameters such as fat and oil are subject to stratification and a well-mixed double-blind sample analysis is even more important for these constituents during calibration.

 

chemistry-labratory tech

What is a Double-Blind Sample and Why Do I Care?

Double-blind refers to the same collected sample being divided into two samples and analyzed “blind” meaning that lab technician or off site lab does not know that within the samples being analyzed that several are duplicate samples.

When calibrating an analyzer the results can never exceed the laboratory accuracy and sample collection method.  Variances can be due to sample collection, head space in sample container, temperature and duration and type of lab method and other variables.  All can be minimized in a simple specific procedure outline for the product.

Moisture samples should be collected in a polypropylene or other suitable container with a moisture barrier lid.  Container should be full with minimal air head space.  Crush samples if possible to increase sample density.

Determine the appropriate sample size 200 – 450g, temperature and duration for weigh dry weigh lab determination of control samples.  Many labs feature automated weigh dry weigh analyzers that predict sample moisture.  The higher the temperature of the convection oven the quicker the extrapolate result, and usually a less accurate result.  While this speeds sample turn around and increases throughput its contribution to variance must be considered.  Hence, double-blind sample averaging minimizes this variation and improve calibration.

For example, using a weigh-dry-weigh gravimetric procedure with an oven temperature of 115?C for 6 minutes will yield a different result than running the sample at 80?C two or three hours.  There also may appear to be “crisping” or “sample browning” at the higher temperature that adversely impacts accuracy.  Again, this is in regards to calibration samples and not necessarily day to day production lab tests that require rapid turn around and high throughput.

Let’s view results for samples tested at 80?C, 115?C and those sent to an outside sample as double-blinds.  Outside labs can be subject to the same variation as in-house labs and double-blind samples reveal the accuracy of their results too.  The chart below shows the benefit of using double-blind samples for calibration and any subsequent validation to improve accuracy.

 

Double Blind Chart for Word 051116 D

Calibration Check Standard

cal check

Calibration Check Standard

The check standard is a stability check and validation that analyzer performance hasn’t changed.  After the unit has been calibrated, you go to a pre-selected “Cal Check” product channel and record the high value and low value.  The high and low value for the check standard should always be between +/- 0.1 to 0.2 of original cal check values.

There are three immediate benefits for the standards.  First is that they are stable and don’t change.  Samples of known moisture, oil, coat weight or other parameter are required for calibration.  Typically 3-5 samples throughout the range of interest.  Calibration is easy.  To check calibration after start up, you can’t use retained samples because they aren’t stable and degrade.  The Cal Check standards are stable to check analyzer stability.

Secondly, most customers want to routinely validate all of their analyzers performance.  The Cal Check standards allow for periodic validation.  Most customers who have used our analyzers for a long time check every 3 months.  Newer users usually check once a week, then once a month etc.  It’s a confidence booster.

Thirdly, if you get an usually high or low measurement you can quickly check whether the analyzer has changed or sample or process.  And make necessary adjustments.  Calibration Check Standards are a valuable tool in diagnostics.