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Laser ablation inductively coupled plasma mass spectrometry (laser ablation-ICP-MS) has been applied to the spatially resolved determination of the elements Mg, Ca, Cu, Ni, Ba, Al, Pb, Sr and Mn in green leaves of oak trees. Instrument operating parameters such as the laser wavelength and the pulse energy have been optimized to provide the sensitivity and reproducibility required for the analysis. The method provides spatial resolution down to 300 microm with the use of the 355 nm wavelength (3rd harmonic of the 1,064 nm Nd:YAG laser wavelength) and the pulse energy of 50 mJ. Plant standards and cellulose, doped with multi element solution standards, dried and pressed to pellets were used as calibration samples. To compensate for signal fluctuations caused by the variation of the ablated sample mass 13C was used as a "natural" internal standard. The accuracy of the calibration was verified with selected samples analyzed by ICP-MS (high pressure digestion, 170 degrees C, 10(7) Pa, HNO3, 2 h) and by laser ablation-ICP-MS. Recovery rates between 93% (Cu) and 108% (Mn) were obtained. Leaves taken from oak trees (Quercus robur) were analyzed.

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Splitless sample injection plays an important role in kinetic studies and sometimes also in trace analysis since this technique enables one to avoid the withdrawal of large amounts of substances from the sample, a quantity perhaps 10-50 times more than that needed for the investigation.Perkin Elmer instruments (F 42, F 45, H S 6) are widely used with capillary columns and splitting for headspace analysis. The electropneumatic dosing system of these instruments [5] works in such a way that the amount of samples administered to the column depends linearly on injection time; this is indeed the case with packed columns and capillary columns if injection with splitting is used. However, if splitless injection is applied for capillary columns at the usual carrier gas velocities, i. e.0.5-3 cm3/ min, a maximum curve is obtained (Figure l., curves 1 and 2) which indicates the system to be unstable. With the increase of carrier gas velocity in the control system the dependence approaches linearity (Figure 1 ., curves 3 und 4).The instability can be understood in terms of "swinging" oscillation of the system, a process triggered by opening and closing of the electromagnetic valve. This "swinging" renders the amount of sample introduced susceptible to the parameters of injection, i. e. duration of pressure balance, input pressure, free gas volume of the sample vessel, etc.The assumption of instability of the pneumatic injector if carrier gas flow rates are low is supported by the appearance of double or multiple peaks with one-component samples; the effect depends upon injection time (Figure 2). This indicates pulsing injection.Splitless injection requires the stabilization of the electropneumatic dosing system. This is effected by the insertion of a damping component (pneumatic resistor) (Figure 3) between the pressure regulator and the electromagnetic valve.On use of this modification of an electropneumatic dosing system, no double or multiple peaks were observed and a linear relationship is obtained between injection time and sample volume (Figure 4.). Sample amount versus Injection t h e as Influenced by carrier gas flow rate.Average of ten detetminations, relatlve empirical mean deviatlon 3.6%, substance: n-propyl alcohol 12 mg/cm3].