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Gavriel Levin (levin)
Intermediate Member
Username: levin

Post Number: 19
Registered: 1-2006
Posted on Monday, October 16, 2006 - 1:42 pm:   

Hi,

My comments were made to address the question of mineral salts in solution that was raised in relation to dialysis, not the salts you mentioned that were naturally organic. In the course of doing so I though it may be useful to emphasize the differences between the organic and mineral salts.
The point I was trying to make is primarily addressed to people who may not have previous experience and may make a typical error of creating beautiful calibrations that don't hold water in the real world.

Gabi
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Dr.K.Balasubramanian (drkbala)
Intermediate Member
Username: drkbala

Post Number: 18
Registered: 9-2006
Posted on Monday, October 16, 2006 - 10:59 am:   

Dear Mr.Gavirel Lavin,
We do know that the cataions and inorganic & Organic anions.
This is evident of your statement The usual anions (Cl, SO4, NO3, etc)do not provide much of a spectrum by themselves, therefore it is difficult to calibrate. In general, calibration for salts is based on the impact they have on the spectrum of the water. The electrostatic interaction between the ions and the negative and positive poles of the water dipole affect the vibrational frequencies, and cause measureable spectrum change that can be correlated to concentration.
We have used this in measuring HF concnetrations for semi-conductor company many years ago.

The major problem with this method - the effect on the water spectrum is not unique to any specific cation/anion or combinations of them. Therefore, in a solution which has several cations/anions involved, the same effect on the spectrum can be caused by more than one combination of concentrations of ions. There is a possibility of ambiguity - thus a method is only vaild within the narrow boundaries where it is proven to be yielding unambiguous results.
Organic anions do give good results.I have already told you that we have worked in Ascorbates,acetates,citrates and tartarates.
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Gavriel Levin (levin)
Intermediate Member
Username: levin

Post Number: 17
Registered: 1-2006
Posted on Monday, October 16, 2006 - 5:44 am:   

Thanks to Venkat, I feel obliged to respond. I must admit that I am truly perplexed now -

Initially we were asked about pellets of mineral salts. Mineral salts to me mean:
1. A cation of a metal, such as Ca, Na, K, etc.
2. An anion such as Cl, SO4, PO4, NO3, etc.

All salts that contain an anion such as Acetate, Citrate, ascorbate etc are organic salts, not mineral salts. This is the basics in chemistry I went through years ago and I don't think it changed.
All salts that contain a cation such as NH3,
R-NH2, (where R is any organic based group) are oranic salts as well.

The measurement of the organic salts in either solid form or solution can be successfully done through the absorptions associated with the organic part. That's why Magnesium stearate can be measured, and if the only magnesium present is associated with the stearic anion than you shall be able to determine the magnesium through the stearic group. However, should we have magnesium that is not associated with the stearate - then your calibration will go heywire.

If you have two salts of different organic acids both containing magnesium as a cation, you may have huge difficulties calibrating for Mg.

Back to minerals - the solid minerals are of least interst, and usually the interest is in their solutions in water.

The usual anions (Cl, SO4, NO3, etc)do not provide much of a spectrum by themselves, therefore it is difficult to calibrate. In general, calibration for salts is based on the impact they have on the spectrum of the water. The electrostatic interaction between the ions and the negative and positive poles of the water dipole affect the vibrational frequencies, and cause measureable spectrum change that can be correlated to concentration.
We have used this in measuring HF concnetrations for semi-conductor company many years ago.

The major problem with this method - the effect on the water spectrum is not unique to any specific cation/anion or combinations of them. Therefore, in a solution which has several cations/anions involved, the same effect on the spectrum can be caused by more than one combination of concentrations of ions. There is a possibility of ambiguity - thus a method is only vaild within the narrow boundaries where it is proven to be yielding unambiguous results.
Unfortunately, a simplified set of samples prepared in the lab where there is most likely a nice "order" in which concentrations vary up and down can provide excellent regressions that will be worthless once "things" start to behave randomly.
Thus, to the question if it is possible to use NIR for dialysis solutions - it might, but it needs to be based on very carefully crafted set of samples, so that there will be true randomness in the way concentrations change, and that it will be possible to validate that the same spectra can not be produced by several combinations of concentrations that may occur within the normal product range.

If it can be proven with satisfactory chanllenges that there is no ambiguity - then wellcome. And remember, if you step out of the boundaries for which the non-ambiguity was proven - you need to prove it again for the new realm.

I hope I don't disappoint people who wish that NIR was a magic medicine for all analytical problems.

Gabi Levin
Brimrose
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venkatarman (venkynir)
Member
Username: venkynir

Post Number: 15
Registered: 3-2004
Posted on Monday, October 16, 2006 - 2:13 am:   

As per my opinon ,the dervaitive of spectra would not specify the wave length. More over to build good Caliberations much work should be done .Wave selection differ method should be applied . Regarding quantification with NIRS , I am sure my friend Gabi Levin and Tony davies is right person to answer Dr. Bala
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Dr.K.Balasubramanian (drkbala)
Member
Username: drkbala

Post Number: 14
Registered: 9-2006
Posted on Friday, October 13, 2006 - 8:22 pm:   

Dear Dr.Miguel A. Suarez M. ,
It does work.Caliberations and derivatisation of spectra would give you specific wavelength and quantification for each item.Pl send the NIR spectra to [email protected]
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Miguel A. Suarez M. (engendro63)
New member
Username: engendro63

Post Number: 3
Registered: 10-2006
Posted on Thursday, October 12, 2006 - 9:31 am:   

Dr. K. Balasubramanian:

This aqueous solutions are dilute with concentration of sodium, calcium, magnesium chloride, dextrose and sodium lactate (5260 ppm, 240 ppm, 49 ppm, 1.42% and 4210 ppm respectively). We measuring this solutions in the NIR module transmision witn quartz cells. the pathleght of this cells is 1 cm.
What is your opinion?
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Dr.K.Balasubramanian (drkbala)
Junior Member
Username: drkbala

Post Number: 10
Registered: 9-2006
Posted on Wednesday, October 11, 2006 - 7:43 pm:   

We do have worked on Chlorides of metals.But the salt form would not yield the results.Dilute solutions on specific wavelengths do give quantitative correlations.
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Miguel A. Suarez M. (engendro63)
New member
Username: engendro63

Post Number: 2
Registered: 10-2006
Posted on Wednesday, October 11, 2006 - 9:26 am:   

Thanks Dr. K. Balasubramanian:

We working with sodium, calcium and magnesium chloride, dextrose and sodium lactate. We know what in the NIR the inorganics salts not present bands. These aqueous solutions are named dialysis and want to know the factibility of analysis with NIR.
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Dr.K.Balasubramanian (drkbala)
Junior Member
Username: drkbala

Post Number: 9
Registered: 9-2006
Posted on Wednesday, October 11, 2006 - 6:00 am:   

We are working with Sodium,Potassium,and calcium salts of Citric,Asxcorbic and tartaric acids.
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Gavriel Levin (levin)
Member
Username: levin

Post Number: 15
Registered: 1-2006
Posted on Thursday, October 05, 2006 - 8:56 am:   

Word of caution - the synthetic sets of samples may mislead you big time - you might get excellent regressions and if you can't assign specific spectral features that will truly be unequivocally related to the salt, than it will fall apart once you step into the real world.

I would strongly recommend to someone who is not really apt in NIR to stay away from minerals.

Magnesium stearate is a salt, but of an organic acid - thus it is measureable through the C-H stretches at 1724 and has nothing to do with the fact that it is a salt. All organic acids or amino based salts can be measured through C-H or N-H absorptions.

Gabi Levin
Brimrose
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James Malone (jmalone)
New member
Username: jmalone

Post Number: 2
Registered: 8-2006
Posted on Thursday, October 05, 2006 - 6:56 am:   

Miguel:

I think you can find some measurments of salts in solid dosage forms in the literature; a classic is magnesium stearate by NIR. The elements themselves are not going to be measureable but many salts either have NIR spectra or cause perturbations in NIR bands that can be measured. This last technique is a little "tricky", since NIR bands, especially water, can be perturbed by many things and sorting them out may not be easy.

A simple test might be to prepare a few formulations with known variations in mineral salt concentrations, then collect NIR spectra. If, for example, the concentration of a potassium salt could vary from 5 - 50 mg/g; then perhaps 5 preparations of say 0, 5, 15, 30, and 50 mg of that potassium salt could be made. With all other components held to the same concentrations, any observed differences in the NIR spectra would probably relate to the potassium salt concentration.

This is only a "quick and dirty" test but it should indicate if NIR can be useful for your measurements.

Good luck
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Miguel A. Suarez M. (engendro63)
New member
Username: engendro63

Post Number: 1
Registered: 10-2006
Posted on Wednesday, October 04, 2006 - 4:21 pm:   

Hi,

Is there any experience in the NIR community,
for mineral salts quantitative analysis
(Calcium, Potasssium, Sodium, Magnesium, Chloride) ?

Application : Pellets of mineral salts used for dialysis ?

Thanks

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