Table 1.

Summary statistics for analyses of fluoride standard solutions

Target concentration (μmol F/ml)	Mean difference from target concentration (μmol F/ml)	SD (μmol F/ml)	Minimum fluoride recovery (%)
0.0132	0.00005	0.00157	76
0.0263	0.0005	0.00105	80
0.0526	0.0005	0.00263	94
0.2631	0.00005	0.00316	98
0.5263	0.0037	0.0053	98

n = 24 per laboratory. All nine laboratories analyzed the solutions using direct methods.