Table T7. Techniques, standards, typical ratios of measured/expected values, and typical reproducibility for interstitial water geochemical analyses.

Analysis	Technique	Standard	Measured/expected range	Reproducibility (% rsd, 1 )
Alkalinity	AT	Sodium carbonate solutions	*	1-5
		IAPSO (low alkalinity sites)	—	—
Cl-	T	IAPSO	†	Up to 0.5
SO42-	IC	IAPSO	0.96-1.03	Up to 4
H4SiO4	S	Solution, weighed	—	1-3
HPO42-	S	Solution, weighed	—	Up to 4
NH4+	S	Solution, weighed	—	2-4
Na+	IC (1232), ICP-AES	IAPSO	0.96-1.02	Up to 3
Mg2+	IC (1232), ICP-AES	IAPSO	0.97-1.02	Up to 3
Ca2+	IC (1232), ICP-AES	IAPSO	0.95-1.02	Up to 3
K+	IC (1232), ICP-AES	IAPSO	0.95-1.04	Up to 3
Mn2+	ICP-AES	Dilutions of reference solutions in acidified NaCl matrix	0.94-1.04	Up to 4
Fe2+	ICP-AES	Dilutions of reference solutions in acidified NaCl matrix	0.97-1.11	Up to 4
B	ICP-AES	Dilutions of reference solutions in acidified NaCl matrix	0.95-1.04	Up to 4
Sr2+	ICP-AES	Dilutions of reference solutions in acidified NaCl matrix	0.99-1.04	Up to 4
Ba2+	ICP-AES	Dilutions of reference solutions in acidified NaCl matrix	0.96-1.02	Up to 4
Li+	ICP-AES	Dilutions of reference solutions in acidified NaCl matrix	0.91-1.17	Up to 4

Notes: AT = autotitration, T = titration, IC = ion chromotography, S = spectrophotometry, ICP-AES = inductively coupled plasma-atomic emission spectrophotometry. rsd = relative standard deviation. IAPSO = International Association for the Physical Sciences of the Ocean. * = range 0.88-0.96 observed; samples corrected to IAPSO and/or other standards. — = no comparison made. † = calibrated directly to IAPSO standards.