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首页> 外文期刊>Marine Chemistry >The effect of pressure on meta-Cresol Purple protonation and absorbance characteristics for spectrophotometric pH measurements in seawater
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The effect of pressure on meta-Cresol Purple protonation and absorbance characteristics for spectrophotometric pH measurements in seawater

机译：压力对分光光度法测定海水中间甲酚紫质子化和吸光度特性的影响

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The sulfonephthalein indicator meta-Cresol Purple (mCP) is well suited to direct spectrophotometric pH measurements throughout the oceanic water column. In prior work the molar absorbance and proton exchange characteristics of purified mCP were characterized over a wide range of salinities and temperatures, allowing use of the indicator over a broad range of oceanic conditions in the surface ocean. Modern spectrophotometric instrumentation allows direct in situ measurements of seawater pH at depths that create substantial pressure-dependent changes in the physical chemical behavior of mCP. In order to allow use of purified mCP for quantitative pH measurements over essentially the full range of ocean depths, prior calibrations of mCP for measurements of seawater pH were extended to include pressures up to 827 bar. Using purified mCP, seawater pH is measured using the equation pH_T= -log(K_2e_2) + log((R-e_1)/91-R·(e_3)/(e_2)) where e_1 = {-0.007762+ 4.5174 × 10~(-5)T} + (l.7 × 10~(-6))P e_3/e_2 = {-0.020813 + 2.60262 × 10~(-4) T+1.0436 × 10~(-4)(S-35)}+ (4.6 × 10~(-6))P -log(K_2e_2) = {a + (b/T) + c lnT - dT) - (0.05645/T) × P and a = 246.64209 + 0.315971S + 2.8855 × 10~(-4)S~2 b = 722923864 - 7.098137S - 0.057034S~2 c =44.493382 - 0.052711S d = 0.0781344. P and Tare gauge pressure (bar) and Kelvin temperature, and the coefficients a, b and c are salinity dependent coefficients determined in previous work. The influence of pressure on the properties of mCP is sufficient to cause easily measureable effects at depths less than 100 m.
机译：磺酞指示剂间甲酚紫（mCP）非常适合直接分光光度法测量整个海洋水柱的pH。在先前的工作中，纯化的mCP的摩尔吸光度和质子交换特性在广泛的盐度和温度范围内进行了表征，从而可以在表层海洋的广泛海洋条件下使用该指示剂。现代分光光度仪可以在深度直接进行海水pH值的原位测量，从而在mCP的物理化学行为中产生与压力有关的显着变化。为了允许使用纯化的mCP基本上在整个海洋深度范围内进行定量pH测量，将用于测量海水pH的mCP的先前校准扩展到包括高达827 bar的压力。使用纯化的mCP，使用公式pH_T = -log（K_2e_2）+ log（（R-e_1）/ 91-R·（e_3）/（e_2））来测量海水pH，其中e_1 = {-0.007762+ 4.5174×10〜 （-5）T} +（l.7×10〜（-6））P e_3 / e_2 = {-0.020813 + 2.60262×10〜（-4）T + 1.0436×10〜（-4）（S-35 ）} +（4.6×10〜（-6））P -log（K_2e_2）= {a +（b / T）+ c lnT-dT）-（0.05645 / T）×P和a = 246.64209 + 0.315971S + 2.8855×10〜（-4）S〜2 b = 722923864-7.098137S-0.057034S〜2 c = 44.493382-0.052711S d = 0.0781344。 P和皮重表压（bar）和开尔文温度，系数a，b和c是在先前工作中确定的与盐度有关的系数。压力对mCP特性的影响足以在小于100 m的深度处引起易于测量的影响。

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