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Picoplankton is characterized by large fractions of cells with less than 1 um diameter. This implies that currently used glass-fibre filters, such as the WHATMAN GF/F with 0.7 um retention efficiency, may be inadequate for accurate quantitative analyses. In particular GF/F filtering negatively affects the 'in vivo' particle absorption spectrum, yielded by light-transmission measurements carried out on the particles retained in glass-fibre filters, in two ways: the absorption spectrum of the particle fraction that passes through the filter remains undetermined; and the global particle absorption is underestimated. This study shows that the above limitation can be removed by performing the light-transmission measurements on particles retained in 0.22 um Millipore cellulose membranes, provided that the sample depigmentation is carried by a bleaching procedure recently set up by the same authors. Results proved that the performance of the Millipore membrane is comparable (for some aspects superior) to that of the standard GF/F glass-fibre filter. A double measurement, carried out first on the particles retained in the GF/F filter, and then on the sample obtained passing the GF/F filtrate through a Millipore membrane, permits selective determination of the absorption spectrum of the particle fraction with equivalent diameter in the range of 0.22 to 0.7 um.

Additional information

Authors: FERRARI G M, JRC Ispra (IT);TASSAN S, JRC Ispra (IT)
Bibliographic Reference: Paper presented: XII Congresso Associazione Italiana di Oceanologia e Limnologia, Isola di Vulcano (IT), September 19-21, 1996
Availability: Available from (1) as Paper EN 40051 ORA
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