Chapter 15
Detection Limits for Amino Acids in Environmental Samples 1
2
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P. E. Hare and P. A. St. John 1
Geophysical Laboratory, 2801 Upton Street, N.W., Washington, DC 20008 St. John Associates, Inc., 4805 Prince Georges Avenue, Beltsville, MD 20705 2
Liquid chromatography techniques using fluorescent derivatives and laser-induced fluorescence can separate and detect sub-femtomole levels of amino acids. The widespread distribution of amino acids and proteins from living organisms produces nanomolar and higher levels of amino acid material in most environments of the earth's surface. Contamination usually occurs to some extent during sample collecting and processing and must be recognized and addressed before meaningful amino acid concentrations and distributions can be obtained from environmental samples. Amino acids are distributed ubiquitously throughout much of the earth's crust, including the atmosphere Their occurrence and important r o l e i n l i v i n g organisms are well known, but amino acids have also been found i n f o s s i l s and rocks hundreds of m i l l i o n s of years and even b i l l i o n s of years old (2). Amino acids have been reported at p a r t s - p e r - b i l l i o n l e v e l s i n e x t r a - t e r r e s t r i a l samples such as the Apollo moon rocks as well as i n several meteorites (3,4). Even d i s t i l l e d water, reagent-grade HC1 and other chemicals f r e quently contain trace amounts of amino acids. Figure 1 summarizes the l e v e l s of amino acids found i n several samples of environmental interest. Current a n a l y t i c a l techniques for the analysis of the common amino acids are able to detect less than femtomole (10~15) amounts using l i q u i d chromatographic methods with fluorescent derivatives. However, t h i s l e v e l of s e n s i t i v i t y may be extremely d i f f i c u l t to u t i l i z e because of the widespread presence of amino acids from l i v i n g organisms. For example, the r e l a t i v e l y high l e v e l s of amino acids i n human body tissues and f l u i d s make human f i n g e r p r i n t s or even a person's breath a potential serious contaminant i n detecting amino acids i n s p e c i f i c environmental samples (5). Sample c o l l e c t i n g and preparation are major concerns to amino acid trace analysis. Even with c a r e f u l handling during sample c o l l e c t i o n and preparation i t i s always possible that the sample may have been contaminated i n s i t u before i t s c o l l e c t i o n . 0097-6156/88/0361-0275$06.00/0 © 1988 American Chemical Society
Currie; Detection in Analytical Chemistry ACS Symposium Series; American Chemical Society: Washington, DC, 1987.
DETECTION IN ANALYTICAL CHEMISTRY
276
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Downloaded by NANYANG TECHNOLOGICAL UNIV on June 1, 2016 | http://pubs.acs.org Publication Date: December 9, 1987 | doi: 10.1021/bk-1988-0361.ch015
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F i g u r e 1. D i s t r i b u t i o n o f amino a c i d s i n s e l e c t e d components o f t h e E a r t h ' s c r u s t . R a t i o o f w e i g h t o f r e c o v e r e d amino a c i d s t o w e i g h t o f s a m p l e . P u r e p r o t e i n s p l o t a s 1 gram p e r gram.
Currie; Detection in Analytical Chemistry ACS Symposium Series; American Chemical Society: Washington, DC, 1987.
Downloaded by NANYANG TECHNOLOGICAL UNIV on June 1, 2016 | http://pubs.acs.org Publication Date: December 9, 1987 | doi: 10.1021/bk-1988-0361.ch015
15.
H A R E & ST. J O H N
Detection Limits for Amino Acids
277
Because of the widespread d i s t r i b u t i o n of l i v i n g organisms i t i s often d i f f i c u l t to interpret the significance of finding amino acids at trace l e v e l s (
