Books
in black and white
Main menu
Share a book About us Home
Books
Biology Business Chemistry Computers Culture Economics Fiction Games Guide History Management Mathematical Medicine Mental Fitnes Physics Psychology Scince Sport Technics
Ads

Cromatography Handbook of HPLC - Rizzi A.

Rizzi A. Cromatography Handbook of HPLC - John Wiley & Sons, 2005. - 14 p.
Download (direct link): chromatographyhandbook2005.pdf
Previous << 1 .. 286 287 288 289 290 291 < 292 > 293 294 295 296 297 298 .. 604 >> Next

1_L J 1 30
0 11 1 20 ' citric acid cycle acids by ion exclusion chromatography. Analytes: (1)
Figure 21 S Tim* (ft lint
eparat ion 0
ds-aconitic (30 ppm); (2) a-ketoglutaric (190 ppm); (3) oxaloacetic (260 ppm); (4) citric (1220
nnmV isocitric (1770V malic (16^0 nnrnV (\ furnaric 9 nnrtiV ^8^
UUlllj ^ V, mJ J lOvv 111 Iv 1 / / \JJ yv J lililllv 1 v/Jv UUillJ ) \ ' / ^ Ulllfll 1 v J UU111J \^\J J i)Uvvllllv 1 J I \J L/L/lllJ,
Eluent: 1.0 mM HC1 at 1.0 mL min-1. Column: BioRad Aminex 50W-X4. (From Ref. 143.)

boxy lie acids on a strong cation exchanger using a 10-mM methanesulfonic acid eluent and
UV detection at 210 nm.
Weak acids, which also provide a low-conductivity background, such as carbonic acid,
phosphoric acid, fluorinated aliphatic carboxylic acids, aliphatic carboxylic acids, and benzoic
acids, have also been used. Often the suppression step can be omitted when the lower-
conducting background eluents are employed in IEC. Including organic solvent in the IEC
plnpnt will inflnptirp rpfpntinn of* it9 pffiprt on thp ^ hpfwppn thp ^tl^lvfp
vlUvlll W 111 lllllUvllvv 1 vlvllllUll UvVtlUdL U1 Hj vllVvl Ull 11IV/ llllWlClvllUllj UUlWV/Ull lliv^ Ullul Y Iv
and the polymer matrix of the ion exchanger and its effect on analyte ionization. The effect
of carboxylic acid retention on cation exchangers also depends on the cation form of the
exchanger [149] and decreases in the order
K+ cv > NH^ > Na+ > I i+ > H+ (7)
which also indicates the complex nature of the exclusion process in IEC.
452
Pietrzyk
Table 8 Retention of Organic Acids on an Ion Exclusion Column3
Organic acid k'
Ketoglutaric acid 0.23
Maleic acid 0.34
Pyruvic acid 0.38
Isocitric acid 0.39
Citric acid 0.42
Tartaric acid 0.47
Glyoxylic acid 0.65
Malic acid 0.68
Malonic acid 0.71
Ascorbic acid 0.86
Fumaric acid 1.21
Succinic acid 1.24
Lactic acid 1.26
Glycolic acid 1.30
Formic acid 1.45
Acetic acid 1.72
Glutaric acid 1.78
Adipic acid 2.39
aA Benson polymeric OA850 strong acid cation exchange column and a 0.5 mM H2S04 eluent.
Source: Ref. 136.
Suppression in IEC is not limited to membrane-type suppression devices. For example, an HC1 eluent can be suppressed with a column packed with a Ag+ form cation exchanger (see Sec. II.F). The H+ in the eluent replaces Ag+, which precipitates as AgCl, and the weak acid analytes are converted to Ag+ salts, thereby enhancing the conductivity detection. The conductivity detection of HCO3, which is separated by IEC, is enhanced with two ion-
Previous << 1 .. 286 287 288 289 290 291 < 292 > 293 294 295 296 297 298 .. 604 >> Next