Chromatography tailing peaks

The reader should be aware that these definitions are different from those normally used in chromatography, where peak tailing leads to values larger than unity and peak fronting to values smaller than unity. The ISO/EN/DIN definitions (22,23) are just reciprocal. 

The origin of tailing peaks of basic compounds in reversed-phase chromatography has been an issue in the chromatographic literature for many years. Erom the foregoing discussion, it follows... 

Tertiary amines can also be selectively derivatized with citric acid on acetic acid anhydride, a mixture that is mixed with the eluent after chromatography and then heated to 393 K to develop a violet-red color (237). Absorbance is measure at 550 nm but some compounds can show strongly tailing peaks. 

Clearly, the difference between eqns.(4.31) and (4.31a) is small. If we assume that genuine chromatography columns have a minimum of2500 theoretical plates, then the difference between the two equations is always less than 4%. Even for non-symmetrical ( tailing ) peaks eqn.(4.31) will almost always be an adequate approximation of eqn.(4.31a). 

High Pressure Liquid Chromatography. System HA—k 2.8 (tailing peak). 

Gas Chromatography. Decomposition occurs giving a single, broad and severely tailing peak. 

Gas Chromatography. System GA—RI695 (tailing peak) system GI—retention time 12.5 min (tailing peak). 

High Pressure Liquid Chromatography. System HA—cocaine k 2.8, benzoylecgonine k 0.9 (tailing peak), ecgonine k 1.1 system HQ—cocaine k 2.68, benzoylecgonine k 5.68. 

High Pressure Liquid Chromatography. System HA—codeine k 4.8 (tailing peak), morphine k 3.8 (tailing peak), norcodeine k 3.1 (tailing peak) system HC—codeine k 1.21, morphine k 1.30, norcodeine k 3.51 system HS—codeine k 1.90, morphine k 5.16. 

High Pressure Liquid Chromatography. System HA—dothiepin k 3.2, dothiepin sulphoxide k 4.6 (tailing peak), monodes-methyldothiepin k 2.2 system HF—k 3.60. 

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