Vegetation controls on channel network complexity in coastal wetlands.

Channel networks are key to coastal wetland functioning and resilience under climate change. Vegetation affects sediment and hydrodynamics in many different ways, which calls for a coherent framework to explain how vegetation shapes channel network geometry and functioning. Here, we introduce an idealized model that shows how coastal wetland vegetation creates more complexly branching networks by increasing the ratio of channel incision versus topographic diffusion rates, thereby amplifying the channelization feedback that recursively incises finer-scale side-channels.

Analysis of fat-soluble vitamins. XXIX. Liquid chromatographic determination of vitamin D in AD concentrates: collaborative study.

A simplified liquid chromatographic (LC) method for determining vitamin D in vitamin AD concentrates (greater than or equal to 5000 IU vitamin D/g) was collaboratively studied. In the simplified method, the 2 columns specified in AOAC LC method 43.101-43.

Analysis of fat-soluble vitamins. XXVIII. High performance liquid chromatographic determination of vitamin D in pet foods and feeds: collaborative study.

A high performance liquid chromatographic (HPLC) method for vitamin D in pet foods and feeds at low concentrations (2-8 IU/g = 50-200 ppb) was studied collaboratively. The procedure consists of the following purification steps: saponification, extraction of the unsaponifiable fraction, chromatography on alumina, cleanup on reverse phase HPLC, and quantitation with straight phase HPLC. The original method, developed by Knapstein, was simplified by deleting the quantitative TLC step.

Analysis of fat-soluble vitamins. XXVII. High performance liquid chromatographic and gas-liquid chromatographic determination of vitamin D in fortified milk and milk powder: collaborative study.

A collaborative study of the high performance liquid chromatographic (HPLC) method for vitamin D in fortified milkpowder (skimmed and whole milk) and a milkpowder preparation was carried out on 182 samples distributed to 26 laboratories. Thirteen laboratories submitted results. The level of vitamin D was 2-7 IU vitamin D3/g milkpowder.

Analysis of fat-soluble vitamins. XXVI. High performance liquid chromatographic determination of vitamin D in fortified milk and milk powder.

Vitamin D is determined by high performance liquid chromatography (HPLC) in samples containing other fat-soluble vitamins. The vitamin D in the unsaponifiable residue is extracted and separated from interferences by straight phase chromatography, and the fraction corresponding to vitamin D3 is collected and quantitated using the AOAC official final action HPLC method for vitamin D3. Analysis of a synthetic mixture gave reasonable recoveries.