By Anonymous on Monday, April 2, 2001 - 11:40 am:
In a reported method for indirect chiral analysis of NSAID as L-leucinamide dr. the mobile phase recipe is: Acetonitrile:pot. dihyrogen phosphate: Triethylamine(36:64:.01). There is no mention about the pH. Clarify the following points:
a. Should this be treated as a buffered mobile phase or simply a salt solution.
b) what is the role of triethylamine? is it only a peak shape modifier or has it any other role?
By Anonymous on Thursday, April 5, 2001 - 08:50 am:
The above recipe is indeed buffered, the phoshpate will buffer at about pH 4.5 or so, this is not simply a salt solution. The low level of TEA added would seem to be a peak shape modifier as you put it, since there is not enough to really alter the pH of the solution.
Regards,
Mark
By Anonymous on Wednesday, April 11, 2001 - 12:34 pm:
Taking the rule of thumb that a buffer is only effective within about 1 to 1.5 pH units of its own pKa, phoshphate isn't a buffer (or at least not a good one) at pH 4.5 -- it's a salt.
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