Fisons Elemental

Table 5.3 sets out the advantages and disadvantages of the batch and continuous flow techniques. The introduction of continuous-flow hydride/vapour-generation has substantially advanced the value and acceptance of the technique for trace elemental analysis. Appfied Research Laboratories (now part of Fisons Elemental), P.S. Analytical and Varian have all introduced continuous-flow hydride/vapour-generation systems, whilst Perkin Ehner has used the flow injection modification to automate the techniques with their instrumentation. 

For solution-based analyses, it is normal to make up a set of synthetic standards from commercial calibration solutions (normally supplied as 1000 ppm stock solutions, e.g., from Aldrich, BDH, Fisons, or ROMIL). These are available to different degrees of purity, and it is necessary to use the level of purity commensurate with the sensitivity of the analytical technique to be used it is, however, better not to use the highest purity in all circumstances, since these are very expensive. Ideally each element to be determined in the sample should be calibrated against a standard solution containing that element, although interpolation is sometimes possible between adjacent elements in the periodic table, if some elements are missing. For most techniques, it is better to mix up a single standard solution... 

Fisons Instruments (incorporating VG Elemental and Applied Research Laboratories), Ion Path Road Three, Winsford, Cheshire CW7 3BX, UK. 

TMS) was used as a reference. Frequencies of proton measurements were 250 MHz, 300 MHz or 400 MHz and frequencies of carbon measurements were 50.3 MHz, 62.9 MHz, 75.5 MHz or 100.6 MHz. MS spectra were measured on a Fisons MALDI-time-of-flight (TOF) spectrometer or a Fisons Platform II ESI spectrometer. CNH elemental analyses were done on a Foss Heraeus CHN-O-Rapid device. 

Cell concentration in the medium was estimated as diy cell weight. The harvested cells were collected by centrifugation (12,000 x g, 4 C for 15 min) and washed with distilled water. The cells dried under reduced pressure were subjected to chemical analysis. The calorific value of the cells was measured using an automatic bomb calorimeter (CA-3, Shimadzu, Japan). Elemental composition of the cells was measuredusing an automatic elemental analyzer (EA1108, Fisons Instruments Co., Italy). 

BET surface areas of the porous films were measured by nitrogen adsorption at -196 °C after the BET method by using a Fisons Sorptomatic 1900. The surface of the catalysts and the pore structure were examined by scanning electron microscopy (SEM) in a Hitachi S-570 scanning electron microscope. The concentration profile of the chemical elements along the oxide film was determined by energy-dispersive X-ray spectroscopy (EDX). 

Immediately prior to analysis, 100 jiL of a 10 ppm In solution were added to a 10 mL aliquot of each sample as an internal spike to correct for instrument drift. Analyses were performed on a Fisons PQ 2 Plus quadmpole ICP mass spectrometer. Rather than produce calibration curves for each of the 41 elements analyzed, simple blank subtraction was used and the results for the artifacts were compared directly against geological source samples prepared and analyzed in the same way (55). 

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