酸-碱滴定法测定海洋浮游植物细胞表面积

1995年改进了浮游植物表面积的酸碱滴定测定法，其中应用改进BET方程对酸滴定曲线拟合求最大表面酸量，由此测定了18种海洋浮游植物（包括8种绿藻，7种硅藻，2种甲藻，1种红藻）的细胞表面积。结果表明，该方法精密度为15．2％，所测定的18种海洋浮游植物的表面积为2．78×10-8—6．9×10-6m2，变异系数为0．9％—31．3％，较传统的用光／电子显微镜粗略估算的方法，更为精确，并且设备简单，操作方便。

DETERMINING SURFACE AREAS OF MARINE PHYTOPLANKTON CELLS BY ACID-BASE TITRATION METHOD

In 1995, the acid-base titration method for determining the surface area of marine phytoplankton cells was improved, in which the modified BET equation was used to estimate the maximum surface acid amount {M⁺}_T by fitting the surface acid amount {MOH₂⁺}_T to H⁺]. Estimate of {M⁺}_T with the modified BET equation is more feasible and reliable than measurement by the back-titration technique liable to under or overestimate of {M⁺}_T. The acid-base titration technique to measure {MOH₂⁺} of phytoplankton cells is based on the assumption that the hydrous cell walls have carbohydrates or other structural compounds which can behave as surface Bronsted acid-base sites due to coordination of environmental H₂O molecules. The improved method was applied to 18 diverse phytoplankton species (including 7 diatoms, 2 ?agellates, 8 green phytoplankton and l red phytoplankton) maintained in seawater cultures. For the species examined, the surface area of individual cell (A) ranged from 2.78×10^-8 m² for Nannochloropsis oculata to 690×10^-8 m² for Dunaliella viridis. Measurement accuracy was l5.2% (n = 6). A values of marine phytoplankton may relate to, but is not dominated by, the cell size. Furthermore, A values were approximately 2 to 4 orders of magnitude more than the geometric surface area of the cell, assuming that the phytoplankton cell is a smooth ball. This suggested that marine phytoplankton A determined by the acid-base titration method may reveal the actual surface area of marine phytoplankton cells in seawater. Preliminary study showed that the improved method may be more promising and accurate than light / electron microscopic measurements for coarse estimation of the surface areas of phytoplankton only if the cell walls behave like a Bronsted acid-base site due to the coordination of environmental H₂O molecules. In addition, the method has merits, such as use of simple equipment, convenient operation, and easy dissemination. It is useful for study on the quantitative relationship between bioconcentration of HOC in marine phytoplankton and their surface areas.