Salt in medium - (Feb/26/2014 )

Can you please help me.  I am trying to find an assay or other method for measuring salt concentration in a medium that we used for growing microalgae. I was thinking there must be some kind  of biochemical assay that might do the trick.

Regards,

JC

you can determine salt concentration with a refractometer or electronically.

there are tables of refractive index for various salt concentrations or you can construct your own by taking readings with standard salt solutions. there are also digital refractometers like this one.

electronically, you can use a conductivity probe (you can attach to a pH meter or dedicated conductivity meter like these) and calibrate with standard salt solutions.

or

depending on the precision required, you can use a cheap (less than $12) salt probe like this one.

Thanks for that. Ill certainly look into them. I suppose the challenge is that there are many other components in there so if i find the method that wont suffer so much interference, that would be a great help. 

see my response to your question in the chemistry forum

For Chloride assay modified TPTZ method

Principle

Chloride ions in serum react with a Hg-TPTZ complex. This reaction liberates TPTZ which then reacts with a ferrous ion to form a blue Fe-TPTZ complex. The absorbance of this blue complex is proporzional to the chloride concentration.

Reagents

TPTZ-reagent: dissolve in 600 ml dH2O, 0.55 g (1.76 mM) of 2,4,6-tri-(2-pyridyl)-1,3,5-triazine (TPTZ – Sigma cod. T1253 - Molecular Weight: 312.33), 0.86 mM mercuric nitrate monohydrate, 0.42 mM ferrous sulfate anhydrous, and 0.24 M manganese sulfate monohydrate. Bring solution to pH 1.6 using 1 N sulfuric acid (final 10 mM) and then adjusted to an absorbance of 0.05 at 600 nm using a 0.2 molar mercuric nitrate solution before bringing the final volume to one liter with deionized water. Store at R.T. protected from light, resulting stable for 1 year.

Chloride standard (70, 100, and 125 mM): dissolve, weighing exactly 4.092, 5.845 and 7.306 g of NaCl, pre-dry overnight to 110 °C and cool at room temperature in exicater, for each ones in 1 liter dH2O. 

Procedure

Combining 5.0 µl of serum or urine dilute 1:1 in dH2O or other biological fluid, standard, and distilled water (blank) and 1.0 ml of TPTZ-reagent, mix and incubate for 5 min. at 25 to 37 °C. Within 10 min. from start reaction read Abs at 610 nm (593-630) against blank. Calculate again standard chloride 75 and 100 mM, and for urine multiplied result by 2. Normal value: serum: 98 - 108 mM; urine: 110 - 250 mM