Samples for sulfate and chloride are collected together with a peristaltic pump and tubing and in-line filtered (through a 0.40 micron polycarbonate filter) into new, 20 ml HDPE plastic containers with conical caps. They are refrigerated at 4 degrees Celsius until analysis, which should occur within 6 months. The samples are analyzed for sulfate (and chloride) simultaneously by Ion Chromatography, using a hydroxide eluent.
The detection limit for sulfate is approximately 0.01 ppm and the analytical range for the method extends to 60 ppm.
Method Log: Prior to January 1998 samples, sulfate was determined on a Dionex DX10 Ion Chromatograph, using a chemical fiber suppressor. From 1998 to 2011, sulfate was determined by a Dionex model DX500, using an electro-chemical suppressor. From January 2011 until present, sulfate is determined by a Dionex model ICS2100, using an elctro-chemical suppressor.
field & laboratory