this is very difficult to assess.  in general, you should run a spiked blank (performing batch sorption but omitting the solid phase) to see how much of a problem you might have (depends on the metal).  If sorption to the container is negligible, then you can ignore the problem.  If sorption to the container is high, you can acknowledge this problem, but, I have not seen any accurate method to quantitatively account for this.  You may want to try different container materials (teflon, polycarbonate, polysulfone, etc.) to see if you can minimize the problem.  However, you will have to live with some uncertainty....

Dear Srinu,

Generally the sorption of heavy metals onto the walls of containers is negligible since these heavy metals are already dissolved in water. If you have any doubt of any sorption, you should empty the container from the water content, let the container be dried, add sufficient amount of fresh water to ensure that the water covered all the container walls, shake well for few minutes and finally analyze the content of the fresh. 

In our group, we have carried many batch experiments to investigate the removal of heavy metals by a variety of adsorbents and we never noticed (according to the analysis results) that heavy metals were sorped onto the walls of the containers used.

Hoping this will be helpful,

Rafik

The adsorption of metal ions onto the walls of the experimental vessels is negligible; however, if you want to measure it, you may put the solution containing metal ions in your working vessel without adding your adsorbent. Set the parameter at which you would like to carry the experiment out. Measure the change in metal concentration. The result will indicate towards the adsorption of metals by the vessel's walls.  

Dear Srinu.... I was stuck in this limbo for a while too. Here's what I did to circumvent this problem...

At higher concentrations, this won't be an issue. However, you will tend to get some deviations at lower concentrations around 0.5 PPM to 5 PPM levels (Atleast for the metal ions, Cu, Cr, Pb, Zn, As, Hg which I have encountered). Simply run a batch adsorption series for your targeted metal ions at lower concentration range (by the way go to both extreme possible acidic and alkaline range levels) and check whether you are deviating any results. If the range of deviation is less than 0.1 percent (allowable as per ASTM standards) you are just doing fine. Remember, reviewer's may grill you on Mass Balance Approach when you quote this statement, but you can handle them. 

Further, remember that if you are using old teflon bottles whose internal linings are almost rough, you may get hazy results. This often happens if your seniors have run their tests on them at aggressive pH levels for extended time periods. Just to be on the safer side, use new teflon bottles. Rinse them gently after each use and you will do just fine. 

As Mavrik stated, running a blank experiment will let you know if you can neglect the amount of metal that is adsorbing to the container, generally it is low even for >100 ppm metal solutions (at least for glass beakers). In addition, if you know how much metal remains in your solution and how much was loaded onto your adsorbent (microwave digestion), you can get a good idea as to how much metal could have been adsorbed to the container. Keep a good eye for precipitation though, because if you have metal as a solid in the solution, then it probably wont show in your metal mass balance, since you would need a powerful material characterization tecnique to quantify it. In any case, you should be fine by running a blank, and determining the metal-loading on the adsorbent with a simple digestion, then just work your balances with known initial and final concentrations.  

1. Along with all the above useful suggestions, you can also look at existing literature on the pH edge of that  specific metal-adsorbent and perform experiments at a pH of higher adsorption so that the losses to container walls are kept minimal.

2. In any case, if you had to quantify the amount of adsorption to container walls, even if its negligible, then, at the end of the experiment, you can do a dilute acid leach and recover the losses to container walls and close the mass balance. Best.

Thank you, everyone, for your valuable suggestions