Columns, Septa, Filaments, and Unplanned Repair Work

3 Columns, Septa, Filaments, and Unplanned Repair Work 

The costs of chromatographic columns and septa depend directly on the number of measurements. The costs of unplanned repairs depend on the age of the equipment and its extent of utilization. 

If the proportional costs of procurement are added to the costs of the carrier gas, electricity, inserts and maintenance, and if the GC/MS is always kept switched on and ready for use, the fixed costs per year are ca. 19 000 DM, using the example of the calculation given above. This represents very low variable costs for columns, septa, filaments and repairs, namely 2.16 DM for each measurement carried out. 

The machine cost per measurement as a function of the extent of use of the equipment is shown in Table 12-3. In this calculation, it is assumed that the machine is operated on 250 days of the year. The calculations are as shown in Table 12-2. A medium work rate of 1000-5000 measurements per year was assumed. For a very high or a very low extent of utilization of the GC/MS, a modification of the fundamental basis of the calculation is necessary. As can be seen from Table 12-3, the machine costs per measurement result are 21.20 DM if there are only four measurements per working day. This amount decreases considerably with a small increase in the equipment work rate, becoming 7.00 DM per measurement result for 16 measurements per working day. A graph of the GC/MS machine costs of a measurement result plotted against the number of urine samples analyzed per year is shown in Fig. 12-1. 

If the equipment is provided with an automatic sample injector (Autosampler), the use of the method described in Chapter 9 for drug screening enables considerably more than the 20 measurements per working day shown in Table 12-3. 

---