NMR versus GC/MS, HPLC/GC, HCLtitration, meltingpoint test

[chantal029]

Is it true that only a NMR test is able to detect the effectiveness, quality, quantity of a product?
That it is able to detect wrong raw material, over-reaction, or isomers occurring during synthesis?
But what about the other tests like GC/MS, HPLC/GC, HCLtitration, meltingpoint test. Is one or a combination of these tests not able to do the same as a NMR, tell you the effectiveness, purity, quality of a product? How do these other tests compare
to NMR?

 

[pm35]

if i remember correctly from o-chem class 10 years ago:

GC can tell you how many components you have and the relative amounts
MS can tell you the mass of those components and some structure info

so long as you know what by-products to expect this should/could be enough

with NMR you can determine the relative amounts of products and byproducts so long as you know what you are looking for and the spectrum isn't too messy. Multidimensional NMR can further clean up a messy spectrum - for example: you can see peaks from one molecule hiding with the peak from another molecule in a 1-D spec

if you don't know what is in the mixture you'll want all 3 - with this information you could determine the composition of an unknown mixture.

 

[gravenewworld]

NMR is not sensitive. If you need something 99% pure, you won't be able to confirm that with a typical NMR run. Something like LC/MS can be used to determine purity. NMR can also be extremely complicated once your molecules start getting bigger or have all sorts of sterochemistry involved. It is good to always use both.

 

[MrSid]

NMR is not sensitive. If you need something 99% pure, you won't be able to confirm that with a typical NMR run. Something like LC/MS can be used to determine purity.

In my experience, a starting material that was involved in manufacturing an analgesic related to ibuprofen, was tested for extreme purity by melting point/freezing point. GC was available, but wasn't sensitive enough and the impurity was not completely resolved using capillary columns. It was an extremely slow analysis with freezing point determined with an extremely accurate thermocouple reading plotted on a chart.

The story was that the unwanted isomer was responsible for liver damage in early work on the compound.

 

[LudusRex]

It is not accurate to say that only NMR testing is able to detect the effectiveness, quality, and quantity of a product. Each of the tests mentioned, including GC/MS, HPLC/GC, HCL titration, and melting point testing, have their own strengths and limitations, and can provide valuable information about a product's characteristics.

NMR (Nuclear Magnetic Resonance) spectroscopy is a powerful analytical technique that can provide detailed information about the chemical structure and composition of a substance. It is particularly useful for identifying and characterizing organic compounds, as well as determining the purity of a sample. However, NMR testing can be time-consuming and expensive, and may not be suitable for all types of samples.

GC/MS (Gas Chromatography/Mass Spectrometry) is another commonly used analytical technique that combines the separation power of gas chromatography with the detection capabilities of mass spectrometry. It is often used for identifying and quantifying small molecules and volatile compounds. GC/MS can provide information about the presence of impurities or isomers in a sample, but it may not be as effective as NMR for determining the exact chemical structure of a compound.

HPLC/GC (High Performance Liquid Chromatography/Gas Chromatography) is a hybrid technique that combines the separation capabilities of both HPLC and GC. It is useful for analyzing a wide range of compounds, including small molecules, proteins, and peptides. HPLC/GC can provide information about the purity and quantity of a sample, but it may not be as effective as NMR for identifying specific functional groups or structural features.

HCl titration is a simple and cost-effective method for determining the concentration of a substance in a solution. It can be used to measure the purity of a sample, but it does not provide information about the chemical structure or composition of a compound.

Melting point testing is a physical property measurement that can be used to identify and characterize the purity of a solid substance. It can also be used to detect the presence of impurities or isomers in a sample. However, it does not provide information about the chemical structure of a compound.

In summary, each of these tests has its own unique capabilities and limitations. While NMR testing may be the most comprehensive and accurate method for determining the quality and quantity of a product, it may not always be necessary or practical. Other techniques, such as GC/MS, HPLC/G