HPLC DETECTORS: A BRIEF REVIEW

In an HPLC system the detector is the component responsible for turning a physical or chemical attribute into a measureable signal corresponding to concentration or identity.[ 1 Scott , R.P.W. Chromatographic Detectors. Design, Function and Operation , Marcel Dekker : New York , 1996 .[Crossref] , [Google Scholar] , 2 Snyder , L.R. ; Kirkland , J.J. ; Dolan , J.W. Introduction to Modern Liquid Chroamtography , John Wiley and Sons : New York , 2010 . [Google Scholar] ] In the early days of HPLC, detection was often carried out by collecting fractions and analyzing them off-line. It wasn't until the 1940's and 1950's that the first online detectors for HPLC were introduced.[ 3 Tiselius , A. ; Claesson , D. Arkiv. Kemi Mineral. Geol. 1942 , 15B ( 18 ), 1 . [Google Scholar] , 4 Martin , A.J.P. ; Randall , S.S. Biochem. J. 1951 , 49 , 293 .[Crossref], [PubMed], [Web of Science ®] , [Google Scholar] ] Certainly an improvement over off-line approaches, sensitivity was an issue. The search for more sensitive universal detectors for HPLC led researchers to adapt GC detectors for use in HPLC,[ 5-8 Haati , E. ; Nikkari , T. Acta Chim. Scand. 1963, 17, 2565. Scott , R.P.W. ; Lawrence , J.G.J. Chromatogr. Sci. 1970 , 11 , 65 . Julin , B.G. ; Vandenborn , H.W. ; Kirkland , J.J. J. Chromatogr. 1975 , 112 , 443 . Dolan , J.W. ; Seiber , J.N. Anal. Chem. 1977 , 49 , 326 . ] but the removal of the HPLC mobile phase originally limited applicability. However, in the 1960s the first ultraviolet detector for HPLC was introduced,[ 9 Horvath , C.G. ; Lipsky , S.R. Nature 1966 , 211 , 748 .[Crossref], [PubMed], [Web of Science ®] , [Google Scholar] ] and subsequent improvements in design led to better sensitivity[ 10 Kirkland , J.J. Anal. Chem. 1968 , 40 , 391 .[Crossref], [Web of Science ®] , [Google Scholar] ] and improvements such as variable wavelength and diode array detectors. While a truly universal HPLC detector with GC/FID levels of sensitivity is still elusive, many different types of detectors have been developed that have been very successful for a wide variety of general or specific HPLC applications. To assist in choosing the proper HPLC detector for a given application, this review describes the principles and attributes of many of the common HPLC detectors in use today, and compares and contrasts the advantages and disadvantages of the various detectors discussed where appropriate. For additional detail on the HPLC detectors addressed here, the reader is encouraged to consult the references in each section along with additional general reviews.[ 11 Parriott , D. A Practical; Guide to HPLC Detection , Academic Press : San Diego , CA , 1993 . [Google Scholar] , 12 Scott , R.P.W. Handbook of HPLC , Chapter 15; (Chromaotgraphic Science Series, Vol. 78) , Katz , E. , Eksteen , R. , Schoenmakers , P. , Miller , N. Eds.; Dekker : New York , 1998 . [Google Scholar] ]