Table 2.

Limit of detection (LOD) of the Cu-ion selective electrode (Cu-ISE) (indicative of free Cu ions) and Pseudomonas fluorescens OS8::KnCueRPcopAlux Cu-biosensor (indicative of bioavailable Cu) for CuSO₄ in selected ecotoxicological and microbiological media. Average of three replicates ± standard deviation is shown. Data calculated from Figure 1.

Designation of the mediuma	Cu-ISELOD, mg/L	Free Cu2+(mg/L) at Cu-ISELODb	Cu-biosensorLOD, mg/L	Free Cu2+(mg/L) at Cu-biosensorLODa
Deionized (DI) water c	0.021 ± 0.005	0.021 c	n.a	n.a.
Osterhout’s medium	0.015 ± 0.005	0.017	0.000065 ± 0.000003	0.00006
AFW1	0.008 ± 0.002	0.0016	0.00002 ± 0.000005	0.000005
AFW2	0.03 ± 0.01	0.0054	0.0001 ± 0.000006	0.000012
Algal medium	0.035 ± 0.014	0.003	0.00012 ± 0.000009	0.000003
Malt extraxt (ME)	0.4 ± 0.07	n.a.	0.03 ± 0.013	n.a.
YPD	2.0 ± 0.07	n.a.	2 ± 0.37	n.a.
M9 + 0.5%AA	1.5 ± 1.09	n.a.	0.35 ± 0.041	n.a.
M9	0.05	0.0018	n.a.	n.a.
LB	2.7 ± 0.17	n.a.	3.1 ± 0.21	n.a.
HMM + 0.5%AA	0.45 ± 0.2	n.a.	0.02 ± 0.0036	n.a.
HMM	0.015	0.0053	n.a.	n.a.
2% NaCl	0.012	0.0086	0.006 ± 0.00025	0.0043
0.9% NaCl	0.008 ± 0.001	0.006	0.0003 ± 0.00005	0.0046
0.9% NaCl + 0.01%AA	0.03 ± 0.02	n.a	0.015 ± 0.0036	n.a
0.9% NaCl + 0.05%AA	0.05 ± 0.01	n.a	0.05 ± 0.012	n.a
0.9% NaCl + 0.1%AA	0.14 ± 0.001	n.a	0.15 ± 0.066	n.a
0.9% NaCl + 0.5%AA	0.71 ± 0.3	n.a	0.6 ± 0.12	n.a

^achemical composition is shown in Table 1;

^bFree Cu at Cu-ISE LOD in test media was calculated using the Visual MINTEQ chemical equilibrium model (see also Figure S3);

^c100% free ions were assumed in deionized water;

n.a.—not analysed.