pK

[Bill Tindall]

Brian Evans,
It seemed to me that you hijacked this thread for the purpose of promoting a business. If I am incorrect, then I welcome the correction. But if not, promotional hijacking does not leave this potential customer with a favorable impression.

[sunht]

[quote="Bill Tindall"]sunht, why don't you publish in Journal of Chromatography?[/quote]

Because for company's protection, I can't publish any data. So, I want people to practice it. If people success in their experiment, I'll be very happy. If people need help or want to cooperate with me, all I'll like to as long as my condition allowed.

[HW Mueller]

sunht,
what´s proprietary about that (especially now that you spilled the beans)?

Maybe Bryan can rehabilitate himself and explain this sunht math?

[Bryan Evans]

Bill,

Sunht's data is very interesting and is very helpfull for adjusting
analyte selectivity. I'm sure we would all like to see his work get
published. I felt it was pertinent to the topic to add
that increasing the efficiency of the column is another tool he can
use to increase the resolution. It was not my intention to
"hijack" this conversation topic.

Victor, please email me at bevans@silvertonesciences.com
and I can forward you some data concerning our columns.
Thank you.

[anilray1155]

If you don't mind, I would appreciate if you send your spreadsheet to my e-mail address.

Thanks
Uwe[/quote]


my email add. given below

anilray1155@indiatimes.com

[anilray1155]

thanks for spreadsheet

i have some problems regarding spreadsheet
if i tried mobile phase for different ph, the buffer
is not actual buffer because the buffer is working with buffer properties in fixed ph range so how i can try a wide range of ph in same component of mobile phase
and the other side if i try different component how i can find the PKa value

[sunht]

thanks for spreadsheet

i have some problems regarding spreadsheet
if i tried mobile phase for different ph, the buffer
is not actual buffer because the buffer is working with buffer properties in fixed ph range so how i can try a wide range of ph in same component of mobile phase
and the other side if i try different component how i can find the PKa value

I’ll suggest using buffer pair K2HPO4:NaH2PO4 from 1:10 to 10:1 that spans about 2 pH units(~pH 6 to pH 8). The advantages are they are very soluble in water, they have no UV absorbance, many organic bases’ pK are in this range (pH 6 to 8) and the buffer pH is stable. Then, you can prepare mobile phases in the same organic percentage and with buffer, for example, 1:9, 3:7, 5:5, 7:3, and 9:1. Don’t forget to keep buffer in the same concentration, 20mM, 30mM, or 50mM, whatever and you have to measure the pH reading of each mobile phase with pH meter.

Then, you can try different compounds with these 5 mobile phases to figure out their pKs.

If you want to set pH beyond above range, you can find a lot. I don’t have any specific suggestion but the principle is the same.

[anilray1155]

if i prepare a mobile phase with mixing of buffer and organic how i measure the ph of that solution with the help of ph meter .
because the ph of organic solvent could not mesured with the help of glass electrode so if i mesure the ph of M.P.
i get worng ph of mobile phase because the glass electrode is work with aqueous solution only

so how i can measure the actual ph of mobile phase

[sunht]

if i prepare a mobile phase with mixing of buffer and organic how i measure the ph of that solution with the help of ph meter .
because the ph of organic solvent could not mesured with the help of glass electrode so if i mesure the ph of M.P.
i get worng ph of mobile phase because the glass electrode is work with aqueous solution only

so how i can measure the actual ph of mobile phase

1. Are you using reverse phase HPLC? All I talked only for reverse phase HPLC.

2. Definitely the pH measured by pH meter is an apparent pH. As long as it works, just use it. Do you think it's a real pH when measured in 100%water solution? No, it's an apparent pH, too. Only maybe it's a little bit closer to real pH. Most practice only care about so called "apparent" pH because "apparent pH" shows the real practical activity. So, I like to call them "practical pH".

Above only for my personal opinion, just as your reference.

[sunht]

In case more people need the spreadsheet, I publish my email address for 3 days, from now through 3-15-06:

[ntruong]

Hi,
Please further explain these:
1. using buffer pair K2HPO4:NaH2PO4 from 1:10 to 10:1 that spans about 2 pH units(~pH 6 to pH . What does it mean by "2 pH unit span"?
2. prepare mobile phases in the same organic percentage and with buffer, for example, 1:9, 3:7, 5:5, 7:3, and 9:1. Is this going to be isocratic?
Since I'm new to method development, any tips would be very helpful.
Thanks,
[/quote]

[sunht]

[quote="ntruong"]Hi,
Please further explain these:
1. using buffer pair K2HPO4:NaH2PO4 from 1:10 to 10:1 that spans about 2 pH units(~pH 6 to pH 8). What does it mean by "2 pH unit span"?
2. prepare mobile phases in the same organic percentage and with buffer, for example, 1:9, 3:7, 5:5, 7:3, and 9:1. Is this going to be isocratic?
Since I'm new to method development, any tips would be very helpful.
Thanks,
[/quote]

1."2 pH unit span" means if K2HPO4:NaH2PO4 is 1:10, pH about 6, if 10:1, pH about 8.
2. Yes, isocratic.