Abstract: Raman spectroscopy probe assemblies are disclosed for use with portable and/or handheld analyzers. The probes are also adaptable to sample liquids, and/or powders, tablets and/or other solids and are capable of withstanding harsh environmental conditions. The probes include an optical head assembly, associated optical fibers and replaceable sampling tubes. In one aspect of the invention, a simple orthogonal optical head assembly is disclosed that does not require collinear optical paths. The orthogonal arrangement of input and captured light paths also reduces the need for precise alignment of the optical components. The orthogonal optical head assemblies of the present invention are well suited to accommodate the shutoff mechanisms of the present invention. In another aspect of the invention, sampling tubes, and replaceable end caps for such tubes, are disclosed that facilitate hand measurements of substances.