Carrageenan is that the carrageenan is first dissolved and filtered to remove cell wall debris. The carrageenan is then precipitated from the clear solution either by isopropanol or by potassium chloride. A hybrid technology in which seaweed is treated heterogeneously as in the semirefined process exists, but alcohol or high salt levels are used to inhibit dissolution. This process is often used on South American seaweeds and gives some of the cost benefits of semirefined processing, while allowing a wider range of seaweeds to be processed, however, the naturally low cellulose levels in some South American seaweeds allow them to be
Simultaneously extracted metals and Acid-volatile sulfide initially unbound to AVS (due to insufficient AVS in the sediment to "mop up" all the metal ions). The concentrations of metals in the acid solution can be measured by a number of analytical chemistry methods, including atomic emission spectrometry, atomic absorption spectrometry (AAS), or mass spectrometry. These are known as "simultaneously extracted metals" because they are the metals liberated from the sediment "while the volatilization of sulfide is occurring". Metals extracted from sediment by digestion, or with a different acid than HCl are "not" simultaneously extracted metals. By correcting appropriately for dilution, the SEM concentration in the sediment can