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With a view to enhance the sensitivity of analytical instruments used in the measurement of trace elements contained in a single cell, we have now equipped the previously reported micro-droplet injection system (M-DIS) with a desolvation system. This modified M-DIS was coupled to inductively coupled plasma atomic emission spectroscopy (ICP-AES) and evaluated for its ability to measure trace elements. A flow rate of 100 mL/min for the additional gas and a measurement point -7.5 mm above the load coil (ALC) have been determined to be the optimal parameters for recording the emission intensity of the Ca(II) spectral lines. To evaluate the influence of the desolvation system, we recorded the emission intensities of the Ca(I), Ca(II), and H-β spectral lines with and without inclusion of the desolvation system. The emission intensity of the H-β spectral line reduces and the magnitude of the Ca(II)/Ca(I) emission intensity ratio increases four-fold with inclusion of the desolvation system. Finally, the elements Ca, Mg, and Fe present in a single cell of Pseudococcomyxa simplex are simultaneously determined by coupling the M-DIS equipped with the desolvation system to ICP-AES.

Antibiotics containing a quinone group show characteristic reduced pseudo-molecular ions (M+2)+ and (M+3)+ during the measurements of secondary ion mass spectra using glycerol as a matrix. The ratios of peak intensities (M+2)+ and (M+3)+ over (M+l)+ increase with time. As this phenomenonis not found using sulfolane as a matrix, the quinone group seems to be hydrogenated to a hydroquinone by active hydrogen which is produced from a free hydroxyl group of the glycerol by bombardment with the Xe+ beam. This hydrogenation reaction is specific for the quinone group.Secondary ion (SI)-MS is an excellent ionization method for unstable natural compounds.Amongthe antibiotics, there are manycompoundscontaining a quinone group, such as mitomycins A, B, C, rifamycin S, kidamycin, doxorubicin, daunorubicin, herbimycin and geldanamycin. The quinone groups are thought to play an important role in their biological activities.1>2) During the SI-MS measurement of these compounds, it was found that the quinone group was hydrogenated to form (M+3)+ions. This hydrogenation reaction was found in all the compoundsso far examined and is believed to occur generally in all compounds having a quinone group. Similar hydrogenation of quinones in mass spectrometry has been reported in the fast atom bombardment (FAB)-MSof saframycms,3'4) the field desorption (FD) and FAB-MSof fredericamycin A,5) and the electron impact (EI)-MS of plastoquinones.65Experiment al SI-MSwere recorded on a Hitachi M-80Bdouble focusing mass spectrometer fitted with a high field magnet. The standard Hitachi M-8082SI-MSion source was employed to generate an 8 kV xenon ion beam. All mass spectrometric analyses were performed with a 3-kV accelerating voltage. Samples (25 jug) were dissolved in 1 ju\ of the following solvents: Methanol for mitomycins A, B, kidamycin and herbimycin; a 4 : 1 mixture of methanol and dimethyl sulfoxide for mitomycin C and a 1 : 1 mixture of methanol and dimethyl sulfoxide for rifamycin S, doxorubicin and daunorubicin. The solutions were mixed with glycerol (1~2 jul) on a silver target plate (2 mmwide). Whensulfolane was used as a matrix, samples (50^g) were dissolved in sulfolane (5^1) alone on a broad silver target plate (4 mmwide). For the purpose of examing the time-course under the operating conditions of the mass spectrometer and data processor, the data acquisition was started simultaneously with xenon ion acceleration.Results and Discussion SI-MS of mitomycin B (1) using glycerol as a matrix are shown in Figs. 1A~1C. At the early stage of Xe+ beam bombardment, the (M+l)+ ion (m/z 350) was observed as the most intense of the pseudo-molecular ion peaks (Fig. 1A). The relative intensity of (M+2)+ (m/z 351) and (M+3)+ (m/z 352) increased gradually with time (Fig. IB), and finally (M+3)+ became the most intense peak

An optimal signal acquisition and processing method for use with intermittent small-sized sample introduction techniques, such as the micro-droplet injection system (M-DIS), was investigated.