Quantitative LAMMA analysis of biological specimens I. Standards. II. Isotope labeling

Summary Besides a remarkably high sensitivity for light elements, laser microprobe mass spectroscopy offers two main advantages for microprobe analysis: 1) the possibility to obtain data of relatively high precision and 2) the ability to discriminate isotopes. This opens the possibility to use cold isotopes as atomic labels to study cellular or subcellular kinetics of ions or labelled organic compounds. In this study photoreceptor cells were labelled with ⁴⁴Ca²⁺ prior to LAMMA analysis to monitor Ca²⁺ uptake and/or Ca²⁺ accumulation from extracellular sources into intracellular compartments such as the various pigment granula present in these photoreceptors.As in other microprobe techniques also LAMMA analysis requires internal standards for quantitative work. For this purpose thin films of inorganic material were shown to be useful standards when deposited (in vacuum) directly onto the specimen to be analyzed. Some metals and dielectrica have been tested for their possible suitability for standardisation procedures. Even though metals like Pt, Ag, Au, Al are excellent for thin film production, they seem to be less useful for the present purpose because their threshold for laser induced perforation and ion production is rather different from that of the specimen material. However, thin film deposits of some dielectric materials such as MgF₂ turned out to be more suitable to serve as an internal standard for plastic embedded biological material in LAMMA analysis.

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Quantitative LAMMA-Analyse biologischer Proben. I. Standards. II. Isotopenmarkierung