Assessment of ENI Gemeni microprocessor-controlled centrifugal analyser

II for each step of the analysis cycle. At the end of each step the external clock is reset as is the 8 bit control pattern for the next function. The final step is to activate the AA analysis cycle and to wait for the furnace to cool before injection of the next sample. We have found that programming a waiting time longer than the cooling time extends the life of the graphite cuvettes. The program for operation in the pulsed mode is given in Table 1. The second injection is a critical part of the analysis cycle for non-metals such as selenium and arsenic. The addition of a co-analyte such as Ni2+ has been shown to increase the sensitivity for these elements and reduces loss due to the volatility of these elements 1, 5]. The syringe pump used for the second injection delivers 11.0 + 0.1 /.tl/sec of co-analyte. The same syringe pump is used for the total consumption analysis mode. In the total consumption mode, however, the analyte is pumped out of the holding tube into the sampling valve and the dispensing of the sample then proceeds in the same fashion as in the pulsed mode of operation. The software modification for total consumption analysis involves only increasing the second injection time to 4-8 seconds and performing the second injection prior to the sample injection. The graphite cuvette volume in the currently employed AA system is approximately 50 /al and the standard pulsed mode experiment employs 37/al + 1.7 ktl analyte from the sampling loop and 1.0/al + 0.1 /al of co-analyte from the syringe pump. The total consumption mode pumps 100 of eluent into the sampling loop and 37/.tl are then dispensed into the graphite furnace. This 'overrun' ensures the complete filling of the sample loop and causes no problem in subsequent interpretation of data. Conclusion The use of an inexpensive microprocessor system adds a great deal of versatility to a previously "hard wired" LCAA sampling system [1]. Both pulsed and total consumption analyses are possible with only minor plumbing and software changes. The use of other microprocessor systems would require only a change in machine language. The system has the advantage of being inexpensive. The interface sampling system can be assembled for a component cost of approximately $500 (depending on the availability of surplus equipment). With the many advantages of performing LCAA analysis on trace level …