18 sept. 2017

Diagnostics : Peak to Peak (P2P)

Is the way we can see if we have extreme peaks on the noise spectra (like in this case due to encoder noise).
It is the absolute value between the absorbance in the highest peak and the absorbance in the lowest peak.
The manufacturers fix this value according to the  quality of the instrument components.

7 sept. 2017

PUZZLE: Spectra Reconstruction




I use to explain the concept of the spectra reconstruction as trying to fix a puzzle. We have the pieces ( loadings) which once are multiplied by the scores have difference sizes, but the same pattern.





We fit all the pieces, but it can be that the puzzle does not fit correctly, that we have some gaps or spaces not filled,...., etc. is the concept of spectra reconstruction whe we have a error matrix which is the part of the puzzle not completed. It can be small, large,...

One application of this concept is used to define if the spectra belongs to a certain category.

In this blog you will find post about the spectra reconstruction.

6 sept. 2017

Sub-sample and sub-scan concept

When we analyzed heterogeneous samples, it is normal to use large cups. The cups rotate and stops in certain places called sub-samples (suppose eight). At each sub-sample several sub-scans (normally  four) are acquired.
So we have eight sub-samples spectra composed of the average of four sub-scans each. In total we have thirty two scans.
We can get a prediction of each of the sub-samples to get the eight predictions and calculate the standard deviation for every constituent in order to see the heterogeneity of the sample composition.
We can export the average spectrum of all the sub-samples,  the eight spectra of the eight sub-samples or the thirty two total sub-scans for further study.



5 sept. 2017

Thanks a lot (more than 250.000 visits to this blog)

Thanks to all of you who read and follow this blog. We have pass the 250.000 visits in this Blog Life and I really happy about that.
 
Of course these are the main countries who visit the Blog, but I appreciate visits from many other places.

                  thanks so much



Maximum Distance (Discriminate Method)

I wrote in other posts, about the Maximum Distance algorithm, in order to discriminate products. In resume is the spectra of a set of samples for training, where we apply a math treatment, and calculate the standard deviation at each wavelength (s), in order to fit some limits to the spectra (will be added to the average spectrum). Therefore, the new samples should come into the defined limits in order to be classify as a sample of this group.

Therefore, in the areas of the spectra where there are more variability, the limits will be higher than in the area of lower variability.

We can see first the spectra (gray ones) with the mat treatment applied and draw the average spectrum (red one):
 

 and to over plot  the standard deviation spectra at each wavelength (green one) with the average spectrum (red one), in order to imagine how the limit will fit.
 

I will try to work on it exporting in Excel the spectra to show you better in a new post.


 

4 sept. 2017

How to load the Check Sample product in MOSAIC

On the DSs or DAs, the check sample comes with a USB pen with some files (DA1650, DS2500 and DS2500F) with the extension  "mcf". If we import a this files into Mosaic we will install the parameter, prediction model and check cell product at the same time, so it is not necessary to go step by step, so it is more quick to have the instrument ready to analyze the Check Sample.

 
Go  to your Network, right clic with the mouse and choose "Import instrument group configuration". Open in Explorer the adequate "msc" file on the USB pen drive and the configuration will be loaded and ready to work in NOVA if we use  Mosaic Solo, or after synchronization, if we use Mosaic Network. 

7 ago. 2017

Certified Reference Materials for Spectroscopy

A catalogue of “Starna” (www.starna.com) Certified Reference Materials for spectrometers came with the last issue of Spectroscopy Europe.
The materials have a function and a range. The function is:  The purpose of the filter (check Absorbance, check accuracy, check stray light or check the resolution. 
The range can cover the UV, Visible, NIR and FTIR zone of the electromagnetic zones.

In the case of NIR there are some filters like:

NIR Neutral Density Glass References (800 - 3200nm): To check the Absorbance accuracy and linearity pf NIR spectrometers.

Metal on Quartz filters (250 – 3200 nm): With Absorbance and Transmittance values certified at different wavelengths.

NIR Solution References (900 – 2600 nm): With 14 certified peaks for wavelength qualification purposes.

Chloroform Stray Light Cell (at approx. 2365 nm): To check Stray Light.

Polystyrene NIR References (NIR and MIR range): With 14 certified peaks in the MIR spectrum. In addition, eight peaks in the NIR spectrum. These calibration values are traceable to NIST SRM 2065.

Didymium Glass Filter (430 – 890 nm): This filter has 11 peaks covering this range (four peaks over 700 nm).

Wide Range Wavelength Reference (335 – 1945 nm): This filter 20 peaks in this range (nine of them over 700 nm). It is equivalent to NIST SRM 2065.


You can download the catalog from:
http://www.starna.com/images/reference_material_catalogue2017.pdf

1 ago. 2017

Checking Wavelength Accuracy (XDS)

It is important to check the accuracy of the wavelength peaks using if posible a NIST Standard like in this case.

Manufacturer send a file showing the accuracy of the instrument against this standard and we have to verify periodically to see if it shifts.

The verification tell us if the deviation is more than recommend, even if the diagnostics pass. In this case, we perform an Instrument Calibration and the values come closer to the values from which the instrument leaves the factory.
 
Delta value is the difference between the nominal value and the found value.

11 jul. 2017

Dror Sharon: This Tiny Molecular Sensor can Identify a Viagra Pill | WIR...


I am a reader of the Wired Magazine, and is nice to see how NIR technology is becoming a part of this digitalized world, so it will be amazing what this technology can bring to the future.

3 jul. 2017

Lid Adjustment - NIRS™ DS2500


The firsts DS2500 (Generation 1) don´t have this system to adjust the gap for the door, and the way to do it is more dificult. If your instrument does not have the 2 screws to remove the cover showed in the video is becouse is a "Generation 1" instrument .
The instrument showed in the video is a "Generation 2".