The present invention relates to novel phalloidin derivatives and their fluorescent dye conjugates. Also provided are methods for comparing two or more radiographic images including standardizing the images against at least one reference value of at least one image characteristic obtained from a digital radiographic image of a variable attenuation plate. The inlet compartment is interposed between a sample inlet port and a sample outlet port and includes a gas permeable, liquid impermeable filter element for separating liquid from a gas sample, the liquid separated from the gas sample passing to a collection chamber.