CHU-10 concentrate | Canadian Phycological Culture Centre

*This formulation has been modified by J. Acreman (CPCC) from the original.

Reference: Stein, J (ED.) 1973. Handbook of Phycological methods. Culture methods and growth measurements. Cambridge University Press. 448 pp.

This concentrate is used for most freshwater diatoms plus some chrysophytes and cryptophytes.

Stock	Substance	Primary stock (g/L)	Volume used to prepare 90 mL concentrate	Concentrated stock (g/L)	Final concentration in medium (mg/L) (adding 9 mL/L)
	Purified H₂O	–	15 mL	–	–
1.	Na2SiO3•9H2O^a	5.8	–^a	–^a	58^a
2.	Ca(NO₃)2•4H₂O	57.56	10 mL	6.396	57.56
3.	K₂HPO₄	10	10 mL	1.11	10
4.	MgSO₄•7H₂O	25	10 mL	2.78	25
5.	Na₂CO₃^a	20	–^a	–^a	20^a
6.	f/2 vitamin solution	See below for concentrations	10 mL	See below for concentrations	See below for concentrations
7.	Na₂EDTA•2H₂O	1	10 mL	0.11	1
8.	Trace metal solution	See below for concentrations	10 mL	See below for concentrations	See below for concentrations
9.	Citric acid	6	10 mL	0.67	6
9.	Ferric Citrate	6	10 mL	0.67	6
10	H₂SeO₃	0.163	5 mL	0.018	0.163

^aNOTE: CHU-10 Stock 1 that is normally added to CHU-10 medium is excluded from the concentrate since it might need to be pH adjusted to neutral prior to addition to the medium and may also cause precipitation. CHU-10 Stock 5 that is normally added to CHU-10 medium is excluded from the concentrate as it causes precipitation. Therefore, these two stock solutions are added separately during preparation of the medium.

Trace metal solution

Substock	Substance	Primary stock (g/L)	Concentration (g/L)	Final concentration in medium (mg/L)
1.	H₃BO₃	2.86	0.318	2.86
2.	FeCl₃•6H₂O	1.81	0.201	1.81
3.	ZnSO₄•7H₂O	0.222	0.0247	0.222
4.	Na₂MoO₄•2H₂O	0.390	0.043	0.390
5.	CuSO₄•5H₂O	0.079	0.0088	0.079
6.	Co(NO₃)₂•6H₂O	0.049	0.00549	0.0494

f/2 vitamin solution

Substock	Substance	Primary stock (g/L)	Concentration (g/L)	Final concentration in medium (mg/L)
1.	Vitamin B12 (Cyanocobalamin)	0.001	0.00011	0.001
2.	Biotin	0.001	0.00011	0.001
3.	Thiamine	0.200	0.022	0.200

To prepare concentrate:

The concentrate is prepared by adding stock solutions 2-4 and 6-10 to 15 mL of purified water (e.g., Milli-Q, Nanopure, distilled), in the order listed above, to make 90 mL total volume. This volume will then prepare 10L of CHU-10 medium. Concentrate may be stored in the fridge in the dark until needed.

To prepare medium:

The final concentrations shown above are to prepare a 100% CHU-10 medium by adding 10 mL of Stock 1 (may need to adjust to pH neutral first), 1 mL of Stock 5, plus 9 mL of the concentrate to 980 mL of purified water (e.g., Milli-Q, Nanopure, distilled). Stir, pH adjust to 6.4 if necessary with 1N HCl or 1N NaOH. If sterile medium is needed, then the final medium may be filter-sterilized through a 0.22 um filter and dispensed aseptically into sterile vessels or autoclaved directly in the vessels. Prepared medium may be stored in the fridge in the dark until needed.