[Bidagdha_TADIR]

I was studying about Solvent UV cutoff values and came across the following link -

http://www.kayelaby.npl.co.uk/chemistry/3_8/3_8_7.html

It seems that for each solvent they list two Cutoff values - one for qualitative analysis (L₀) and another for quantitative analysis (L₁).

Before this, I've conducted some UV-Visible spectrophotometric experiments and was informed of some of the L₀ values listed. But L₁ is completely a new concept to me. The Pharmaceutical analysis books I've studied doesn't list it either.

Of course, in the experiments I've performed the analytical wavelengths were in visible range, so UV cutoff wasn't very important. But using L₁ before committing to a quantitative analysis does make very good sense to me. So, should I follow this list when performing quantitative analysis?

[marquis]

If I read it right, L0 is for quant work and L1 is for qual work.
You have it listed the other way around.


Most of the work I did was above L0.  For example, 200 nm is listed
as L0 for acetonitrile (acn).  It was very rare that we would do any
work below 210 nm.  You picked up a bunch of noise and other problems
at 200 nm. 

[Bidagdha_TADIR]

If I read it right, L0 is for quant work and L1 is for qual work.
You have it listed the other way around

Yeah, Sorry for that.

I don't understand why cutoff wavelength is defined with A_1cm>1.0. Since we want our Sample absorbance values to stay in the region of 0.3-0.9 for most purposes, shouldn't the cutoff wavelength be defined at a lower value for A_1cm? That's why the above link intrigued me.

Another problem is that these cutoff values are inconsistent from one Reference to another (e.g. the above link with Donald Pavia book). I guess before experimentation I should check for myself whether solvent is transparent or not, but seriously, why the inconsistency?

[marquis]

If you are doing spectral comparison, you can eliminate a lot of absorbance
with the reference and zeroing.  It's ok, but not great, even at these
wavelengths, for spectral comparison.  Even for spectral comparison, you
have to be careful.

I use the values given in the books as guidelines.  The minimum wavelength
can still vary, depending on a number of things (instrument, buffers if any, etc.).
Sorry, but for me, it is still best to run the method and see what you get.