I don’t have a definite evidence for your inquiry but I would recommend the maximum solubility option, in other words; choose maximum calcium and phosphate based on dextrose or Amino acid used whichever is higher. Below is my interpretation: –
1- Solubility of Calcium phosphate depends on the availability of soluble form of phosphate (monobasic phosphate) which tends to be available with increased acidity of TPN solution.
2- Referring to the equation of PH calculation in typical situation (excluding other factors such as inherent buffering capacity and dissociation constants): –
A) PH= – log [H+]
B) Assuming PH of (X) with the said volume (1000 ml) of the chosen solution (AA, D5W, D20W or D50W)
C) Assuming total volume of (3000ml), i.e (3) times the volume of the chosen acidic solution; then the PH would increase by the value of [- log (1/3) = 0.477].
3- The increase in PH would be lower than assumed in (C) as a part of the added solutions is usually acidic considering either amino acid or dextrose as additive with referral to their role as main determinants of the final PH as well as inherent buffering capacity.
Attached is a theoretical numerical example for the recommended allowed amounts of glycophos and calcium based on the final concentration of the said used components. Referring to the said example, kindly observe that using higher dextrose concentration would allow higher amounts of phosphate and calcium to be incorporated as well as lower volumes to be used.
Generally speaking, risk of precipitation with organic phosphate is lower than that with inorganic phosphate.
Again, this is a theoretical interpretation which I hope to be reviewed and assured as appropriate.