Suresh Ralapati, batf/National Laboratory Center

Automated Analysis by Continuous Flow Analyzer

Automated analysis using a continuous flow approach was first developed and introduced in response to the needs of the clinical chemistry laboratory and other medical facilities (27). Continuous flow systems provide a means to carry out a series of individual steps in an analytical procedure accurately, precisely and in a fully automated fashion. With such an instrument, samples can be automatically introduced into the system, diluted as appropriate, reagents added, reactions conducted at specific temperatures and for specific lengths of time, sample clean-up achieved by dialysis and reaction products of interest detected by colorimetry or other detection modes. A number of tobacco chemists have developed and refined chemistry compatible with continuous flow analysis equipment (18-20, 28-33). Continuous flow analysis is popular for the determination of nicotine because it is relatively simple and inexpensive, and it provides the capability to analyze more than one hundred samples per day.

CORESTA recommended method No. 35 describes the determination of tobacco total alkaloids by continuous flow analysis (34). Results by this method, while expressed as “nicotine”, actually represent the combined response of nicotine and other alkaloids such as nornicotine and anabasine. It should be noted that the continuous flow analyzer is calibrated specifically with nicotine and that the reaction chemistry specified by CORESTA recommended method No. 35 has not been optimized for alkaloids other than nicotine. Nicotine is, therefore, the primary response observed with the method, although studies have indicated higher response with CORESTA recommended method No. 35 than with other methods, especially for tobaccos with significant levels of alkaloids other than nicotine.

The main features of continuous flow analysis methodology can be described as follows:

Method Scope. An extract of ground tobacco is prepared and reacted with sulphanilic acid and cyanogen chloride. Total alkaloid content, expressed as nicotine, is determined based on absorbance at 460 nm. A continuous flow analyzer provides automated analysis of tobacco extracts.