The amount of hydrogen peroxide in biological systems can be assayed using a fluorometric assay. Raw precious metals (bullion) are assayed by an assay office. Ideally, such biomarkers can be assayed in non-invasively collected biofluids like blood or serum. Antigens, steroids and hormones are routinely assayed with heterogeneous techniques. Alternatively, granzyme activity can be assayed by virtue of their protease activity. Patulin presence can be assayed using high-performance liquid chromatography with ultraviolet detection. The enzyme can also be assayed via disproportionation of ETF semiquinone. Pollen grains can be assayed through staining techniques (carmine, lactophenol or iodine). All sites assayed were done using human tissues. Commercial samples of sugar are assayed using this parameter. Both compounds, along with THC, are assayed in blood tests. As for bacteria, only species susceptible to gentamicin can be assayed. Rask's blood samples were assayed in Copenhagen in 1984 following extensive research on AIDS. The purity of titanium ethoxide is commonly assayed by proton NMR spectroscopy. Dent claims he assayed the samples for Strangways and determined them to be ordinary rocks.