Table 1. Alkalinity Attained by Our Method and through Manual Titration.

	initial pH		alkalinity (mM HCO3–)
	pH meter	PANI sensor	new methoda	titrationb	difference (%)
1	7.3	7.3	1.57 ± 0.04	1.50	4.7
2	7.5	7.4	1.55 ± 0.05	1.48	4.7
3	7.3	7.6	1.63 ± 0.05	1.63	0
4	7.3	7.4	1.40 ± 0.09	1.54	9.1
5	7.3	7.5	1.40 ± 0.21	1.53	8.5
6	7.4	7.5	1.66 ± 0.05	1.46	12.0
7	7.2	7.4	1.49 ± 0.18	1.46	2.1
8c	7.6	7.7	2.75 ± 0.03	2.73	0.8
9d	7.8	7.9	3.30 ± 0.12	3.23	2.5

^aAverage ± standard deviation of n = 3 measurements.

^bAverage of n = 3 measurements, with a standard deviation always lower than 0.04 mM.

^cSynthetic seawater.

^dSpiked synthetic seawater (+0.5 mM NaHCO₃^–).