# My brain hurts...(help needed)

Duncan Young dsy21 at cam.ac.uk
Mon May 7 05:46:15 EST 2001

```i'm just a lowly phd student, but here goes...

The amount of lactate in the cuvette is completely derived from the agar? In
that case, can you just say that you have 1.18 umol lactate, that came from
the agar .
agar volume 137 mm3 =0.137 cm3 = 0.137 ml = 0.000137 l L
this volume had 1.18 umol lactate
therefore lactate concentration of agar is 1.18/0.000137 = 8613 umol/l

ie roughly 8.5 mmol/L

does this make sense?

"Rich H" <richh6109 at remove-this.yahoo.co.uk> wrote in message
news:0UjJ6.6142\$EI.1268257 at news2-win.server.ntlworld.com...
> OK, I'll start by apologising for going a bit OT but.....
>
> I wonder if someone can help me with this simple problem (I think I know
the
> answer, but I would like someone to confirm this).
>
> I'm currently doing a lactate assay, which normally wouldn't be a problem,
I
> just get the readings from a spectrophotometer, compare them against a
> standard and get the reading in mg/dL (or mmol/L by multiplying by 0.111).
> The problem is I'm helping a microbiologist calculate the amount of
lactate
> in an agar core (which is dissolved in 1ml deionised water)and I'm
> struggling to work out the answer.
>
> I've got the lactate reading of the solution (1.18 mmol/L), but this is
the
> reading for the dissolved core + water, so I thought I'd better work out
the
> volume of the core.  To work this out I need to find the volume of the
> cylinder, yes? This was 2.5mm radius by 7mm height. Using pi x radius
(2.5mm
> sq) x height (7mm) gave me a volume of 137mm cubed.  So I divided the
> lactate reading by the volume and then multiplied by the dilution factor
> (1000).  Is this correct?  Do I need to include the mass of the cylinder
in
> there somewhere?
>
> Apologies to newsgroup regulars who don't want to read this simplistic
> drivel, but I'm a middle-aged molecular biologist who remembers little of
> his chemistry calculations all those years ago!
>
> R.
>
>
>
>

```