--- Ian Barlow <[log in to unmask]>
wrote: > Calcium phosphate will re-dissolve readily
after
> acidification. However
> calcium oxalate is very difficult to re-dissolve -
> it requires urine pH to
> be well below 2 and the sample should then be boiled
> for about 30 mins for
> maximum recovery. But please note that calcium
> oxalate is very much the
> minor constituent (< 0.5 mmol/L) in comparison to
> calcium phosphate
> therefore even if it was not fully recovered, post
> acidification, the
> effects on the result for 24 hour calcium excretion
> would be relatively
> small.
>
Is it not the case that 24 hour urine calcium is of
limited use anyway, because it is so dependant on diet
(amongst other things)?
Urinary oxalate, on the other hand, is useful in
investigation of stone formers, so it is important to
ensure complete dissolution before analysis.
Stuart Robertson
Hull Royal Infirmary
Hull
HU3 2JZ
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