Creatinine electrolytic separation

The first report demonstrating the feasibility of indirect detection in CE was published in 1987 by Hjerten et al.45 who employed indirect UV absorbance detection for the analysis of both inorganic ions and organic acids. The UV-background-providing electrolyte was 25 mM sodium veronal, pH 8.6, and detection was monitored on-column at 225 nm. In 1990, the first separation of alkali, alkaline earth, and lanthanide metals was reported by Foret et al46 Indirect UV detection at 220 nm was employed to detect 14 metals in 5 min, with baseline resolution achieved between all but two of the components. The baseline showed a reproducible upward drift between 1 and 3 min. The UV-absorbing component of the electrolyte was creatinine, with a-hydroxyisobutyric acid introduced to complex with the lanthanides and improve resolution. 

Tensides based on derivatives of PEGs can also be separated by CE [31 ]. They may already contain charged groups, so that their migration is not problematic, only their detection. Here, indirect detection techniques with creatinine as background electrolyte have also been applied for samples up to molecular masses of 4000. 

In safety pharmacology, a number of renal functional tests, such as creatinine and electrolyte measurements, can be supported by most clinical chemistry laboratories (Kinter, Gossett, and Kerns 1994 Seuter 1996 ICH 2000). In some of the later chapters discussing assessments of hepatotoxicity and renal toxicity, a few functional tests are mentioned. Although it may be desirable to include function tests in repeated-dose toxicity studies, given the additional and sometimes invasive procedures, these tests may be better performed by incorporation into single-dose toxicity studies or separate additional studies (Matsuzawa et al. 1997). 

Fig. 11. Separation of a model mixture of putrescine (PU), cadaverine (CD), sodium (Na), spermidine (SPD) and spermine (SP), containing ca. 2 nmol of each substance. 0.01 M KOH -H citric acid at pH = 4.40 served as the leading electrolyte (L) and creatinine as the terminator (T)...

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