Report No xxxx - Instytut Fizyki JÄ drowej PAN

DETERMINATION OF AMINO ACIDS IN BODY FLUIDS WITH THE
US E OF 19 F NMR SPECTROSCOPY
Przemysław Szczeciński, Dorota Bartusik
Warsaw University of Technology, Faculty of Chemistry, ul. Noakowskiego 3,
00-664 Warsaw, Poland
It is commonly known that amino acids play a very important role in living organisms.
They are reactants as well as products of many biological processes and therefore their
qualitative and quantitative determination in body fluids, e.g. urine or blood, is essential for
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the diagnosis of numerous metabolic diseases. The usefulness of the H and C NMR
spectroscopy for such determinations is well documented. However, body fluids, being multicomponent
mixtures, give complex spectra, in which identification of the interesting signals
may be often difficult. To avoid this problem the method of determination of amino acids
with the use of 19 F NMR spectroscopy has been developed. Investigated compounds are
transformed into fluoro derivatives (see Scheme 1) and then identified on the basis of their 19 F
chemical shifts.
HOOC CH R
Cl
N O 2
NH
CF H 3
2 O
NaHCO 3 O N
CF
+ R CH COOH 2 3
EtOH
NO 2
NH 2
Scheme1
NO 2
Because marker used is insoluble in water the reaction has to be performed in water-ethanol
mixture. It was found that the presence of alcohol in measured sample noticeably influenced
the fluorine signal positions. Therefore, to obtain reproducible results, ethanol has to be
effectively removed prior to resonance measurement. It undesirably complicates the
procedure of sample preparation. To overcome this problem we decided to use a marker
soluble in water. We assumed that 4-chloro-3-nitro-5-trifluoromethylbenzenesufonic acid
should fulfil this demand. Its synthesis is shown in Scheme 2.
Cl
Cl
Cl
CF
3
65 %
fuming
H 2
SO 4
CF 3
fuming
HNO 3
O
2
N
CF 3
Scheme 2
SO 3
H
30 %
fuming
H SO
2 4
SO 3
H
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