No abstract

A method for the determination of Boron in steels by Fl-lCP-MS is described. It is shown that flow injection (Fl) can alleviate problems arising from high amounts of dissolved solids in Inductively Coupled Plasma MassSpectrometry (lCP-MS) due to the capability to operate with microliter amounts of sample with a rapid sample rate. Samp]edissolution was carried out in a microwave oven using diluted aqua regia (HC[ + H NO., 3+ I ) and high pressure digestion vessels, which gave notable advantages over conventional dissolution techniques, such as lower costs, greater volatile retention, reduced contamination and faster dissolution rates. The operating parameters in flow injection ICP-MS, such as carrier flow rate, nebu]izer flow rate, and i njection volu mewere establ ished. Thedetection I imit obta ined when di rect samplenebu] ization was used, with a O.05"/o m/v Fe concentration, wasI .2 pg ' g ~I B, comparedto a detection limit of 0.2 ,lg ' g ~1 when the Fl system was used with samples containing a higher concentration of dissolved solids (0,5"/m/v Fe), The influence of the internal standard on precision and accuracy was studied and Beryllium was selected as the internal standard. The RSDS Obtained for four peak area determinations of 200pl injection volumes of a solution of I OO ng ' m/-1 B in the presence of 0.5•/• m/v Fe were below I .5'/•. The accuracy of the method proposed was verified by analyzing Reference Materials (EURONORM-CRM 097-1 ; BCS 456, 457 and 460; NBS 361 , 363 and 365), using an external calibration system with calibration samples, prepared from a standard Boron solution, in the same acid mediumas the test sample solutions.

Spark ablation coupled with excitation in an argon inductively coupled plasma is applied to the analysis of remelted ferrovanadium. A medium-voltage spark at a high-repetition rate was used as the sampling technique for samples prepared using a high-frequency remelting system. Problems of sample fracturing were avoided by dilution of the ferroalloy with pure iron. Calibration graphs were obtained with samples prepared from a commercial ferrovanadium alloy, previously analysed using standard wet chemical methods and diluted with pure iron at two different dilution ratios. The two FeV to Fe dilution ratios were selected in order to cover the desired range of concentrations. When using an Fe line as the internal standard, the relative standard deviations for the major element (V) are below 0.3% (V content, 35-80°/0). The limits of determination for the minor elements (Mn, Cu, Al and Si) are below the required IS0 specifications. The accuracy of the developed method was tested by the analysis of three reference materials.

Methods were developed for the determination of As, Sb, Sn, Bi, Se and Te in leads and refined coppers using both direct sample solutions and the hydride generation technique. For hydride generation in coppers, prior separation of the matrix was necessary owing to the inhibiting effect of copper on hydride formation. For leads, it is possible to generate hydrides for As, Sb, Bi and Se directly from test solutions. Tin and Te require prior separation of the matrix in order to avoid lead precipitation in the hydrochloric medium suitable for the generation of the tin hydride in the former instance and the inhibition produced by lead in the latter. The dissolution of samples, separation processes, sample treatment, choice of analytical lines and measurable concentration levels were investigated.

The use of microwave ovens for the dissolution of samples is widespread and has made it possible to obtain results very rapidly giving precision and accuracy identical with, or better than, than that obtained by classical procedures. Technical publications and instruction manuals, however, rarely give information on the dissolution of insoluble compounds in acids such as, for example, compounds of aluminium the determination of which in iron and steel is important in iron and steel industrial laboratories. Procedures are proposed for the dissolution of aluminium in iron ores and steels; the procedures were tested using certified reference materials. For steels, dissolution is accomplished far faster than with classical procedures. Preliminary dissolution tests on pure alumina, under controlled temperature and pressure conditions, were necessary in order to determine the optimum conditions for the dissolution of iron ores. Complete dissolution of an iron ore sample takes approximately 90 min.