QC by color

Quality control (QC) by color? Isn’t that rather subjective? What if you are a male (or a rare female) with color blindness? We know that when Cu(I)NA2 oxidizes to Cu(II)NA2 the color appears turquoise. Why is that? The reason it appears to our eyes to be turquoise is because the material is absorbing in the red region of the visible (to our eyes) spectrum and reflecting other wavelengths of light that are absorbed by blue and green rhodopsin containing cone cells in our retinas. Blue and Green in the RGB color scheme is turquoise, or as it is more technically called cyan.

Figure 1 The basis of Quality Conrol by visual inspection A. An absorbance spectrum of Cu(II)NA2 (arrow from reference [1]. B. Reference guide to perceived color of the 400-700nm range of visible light. C. Three types of cone cells in the human retina are responsible for color vision. D. Range of light absorbed by human cone cells.

Stability under the time of the trial

Three color spectral imaging

The “True Chelation” patented method of C LAB Pharma has an advantage over previous methods of production in that Cu(I)NA2 remains in the +1 oxidation state (as judged by the “new penny” color) for years.  Upon addition of water the product will quickly oxidize to a cyan/turquoise color. 

Figure 2 Top Cu(I)NA2 from Obitor and Regis Technologies 30% v/v H2O2 was added to the Regis Cu(I)NA2. Cu(I)Cl Bottom: same as the top after the Regis Cu(I)NA2 was fully oxidized. .

Addition of H2O2 will accelerate this oxidation to a turquoise/cyan color.  The color appears to be cyan to our eyes because the substance absorbs in the red region of the spectrum and reflects light in regions of the spectrum that are detected by blue and green cone cells of our retina.  Likewise, the Cu(I)Cl appears green to our eyes because regions of the blue and red spectrum are absorbed leaving only green light to activate green cone cells of our retina.  To make Mr Barker’s quality control method more quantitative, we will take black and white color photos of the investigational substance under red  (626 nm), green (525 nm), and blue (440 nm) light.  A compound that absorbs in the green region will appear dark or black under green LED light.   The first prototype was constructed with a black bucket and a string of LED lights from SuperbrightLEDS.com


Figure 3. Cable ties were used to secure the string of LED lights to the interior of the bucket.  Each “square” contains an element with about three red and green LED lights and only one blue.  A minor issue is that the blue light source is much weaker than the red and green light sources.  A hole in the top of the bucket allows for placement of a cell phone camera.  A production model would have the same basic design only LED lights would come from Thor Laboratories because they sell a more quantified product.

This image from the bottom panel of Fig. 2 was taken with green LED light.  Note that oxidized Cu(I)NA2 is almost white and Cu(I)Cl is light gray.  The other two samples appear much darker because they absorb light of this wavelength.. 

Figre 4 B&W image photographed under 525 nm green LED light.

Two more images of this sample were taken with red and blue LED light without moving the cell phone camera.  “Stacks” of these images were created in ImageJ with the red light image on the top of the stack.  Note the presumably two lots of Cu(I)NA2 on the left now appear much lighter in color under red light.  The oxidized product, third from left, and Cu(I)Cl are darker.

Figure 5 The same sample photographed in B&W mode under 626 nm red LED light.
Figure 7. This B&W photograph was taken 440 nm blue LED light
Figure 8. The three images were assembled into a stack. The bar at the bottom of the GUI was set to the top image of the stack. A region of interest (ROI) was drawn around the pile of Obitor Cu(I)NA2. The program was instructed to measure the intensity of particles in the ROI

This stack contains red, green, and blue light images, in this order.  A region of interest is drawn around the Obitor Cu(I)NA2 in the first dish.  The bar at the bottom and the density is measured for the green channel, then the blue.    ImageJ software measures the pixel intensity within each ROI in all three layers of the stack.  These data may be exported into a spreadsheet for additional analysis.     When the Obitor Cu(I)NA2 was photographed looking down into an open bag, the red, green, and blue channels were 100%, 100%, 35%.  The RGB ratios looking down into a bag of Regis Cu(I)NA2 were 100%, 66%, and 24% of the red channel.  We do not know if being right next to a sample bubbling with H2O2 had any influence on the results.  It is noteworthy that the RGB ratios of an open bag of Cu(II) glycinate were 100%, 158%, and 68%.

sampleLED  areameanminmax %red
Obitorred1199510052151100%
 green21995993818599%
 blue3199535107835%
Regisred4326710867147100%
 green53267792417173%
 blue6326728138226%
Regis Oxred727048952255100%
 green8270417076185191%
 blue9270456020463%
Cu(I)Clred1033419648120100%
 green11334114667167152%
 blue1233413134732%
Table of pixel intensity within the chosen ROI. Note that pixel intensity increases going from black to white.

The dark “old penny” color that caused the Obitor batch to be rejected makes sense when viewed with tri-spectral imaging.

  • The green channel is almost twice the red channel in the oxidized Regis Cu(II)NA2 while green is only 73% of the red in the presumably fully reduced Regis Cu(I)NA2.
  • The red and green ratios of the rejected Obitor Cu(I)NA2 is somewhere inbetweenthese two values suggesting that the Obitor is partially oxidized.
  • Note that the blue channel is 63% of the red in the oxidized Regis Cu(II)NA2 but only 26% in the presumably fully reduced “new penny” colored Regis Cu(I)NA2. The Obitor blue channel is 35% of the red, somewhere inbetween fully oxidized and reduced Regis Cu(I)NA2.

We still need to think about more powerful blue LED lights in this prototype. We need a more defined power output and distribution spectra. Thor Laboratories sells more characterized LED lights. The conclusions of this post are (1) Quality Control by visual inspection has a strong rationale in science. (2) There are inexpensive means to make this quality control more quantitative and less subjective due to individual variations in color perception.

Figure 9 Thor Laboratory LED light characteristics.
  1. Rajhi, A.Y., Ju, YH., Angkawijaya, A.E. et al. Complex Formation Equilibria and Molecular Structure of Divalent Metal Ions–Vitamin B3–Glycine Oligopeptides Systems. J Solution Chem 42, 2409–2442 (2013). https://doi.org/10.1007/s10953-013-0116-5

Published by BL

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