Table 2.

Regression coefficients of multiple regressions for citrate additions given with standard error (s.e.).

Analytical matrix	Mean Z slope Abs protein as f [citrate]	s.e.
PBS	−0.000266	0.000146
Soil extract in PBS	+0.000294	0.000146
HA spiked PBS (160 ppm)	+0.000052	0.000146