Method To Obtain Optimum Internal Ratio & Right Dosage Of Two Component Emulsifiers  

Our Technical Service Department are eager to do the necessary laboratory work of screening, if a representative blank solution (i.e. without emulsifiers) is submitted. The optimization and the dosage ascertainment through simple ‘Titration Method’ is also detailed below which can be applied to any two component emulsifier not only for the MAC emulsifier but also for any two component emulsifier offered by any other emulsifier supplier or manufacturer.

Apparatus required:-

Two 50ml capacity Burettes with stand (Step-4,5,6)

  1. Two 250ml capacity beakers (Step-2)

  2. Two 100ml capacity beakers (Step-5)

  3. Test tube stand (Step-5, Picture-1)

  4. Adequate quantity of Test tubes for 34.2, 342, 800 ppm hard water (Step-5)

  5. Glass rods

 

First of all we need to prepare 34.2ppm, 342ppm & 800ppm. Although all the formulation chemists are aware of method of preparation of above mentioned standard hard waters, we feel our duty to mention here as follows.

Method of Preparation of Hard Waters:-

    1. 342ppm Hard Water:-

      Take CaCl2– 0.304 gms, MgCl2-0.139 gms dilute up to 1 litre using distilled water.

    2. 34.2ppm Hard Water:-

      Take 100ml of 342ppm water dilute up to 1 litre using distilled water.

    3. 800ppm Hard Water:-

      Take CaCl2– 0.7111 gms, MgCl2-0.3252 gms dilute up to 1 litre using distilled water.

Please note use dehydrated CaCl2 and MgCl2 (GR Grade)

SPONTANEITY:  Spontaneity is the criteria for testing self-emulsifiability and dispersibility of the emulsifiable concentrate without external aid, such as stirring etc.

When a drop of emulsifiable concentrate (sp. Gr > 1) eg.Chlorpyrifos 50% + Cypermethrin 5% EC is added in 3 different test tubes each containing 34.2, 342, 800 ppm, hard water respectively, it should show immediate bloom or it should flourish in the form of white emulsion forming cloud made of very small emulsified particles where it bloomed. Click Here for the video

When a drop of emulsifiable concentrate (Sp. Gr<1)eg. Cypermethrin 25% EC is added to aforesaid range of hard waters, it should immediately emulsify on the surface of water without showing aggregation of emulsified particles or part emulsification. Click Here for the video

The above test also gives the judgement for the optimisation of the Anionic & Non-ionic combinations and to ascertain the dosage of Emulsifier required for any formulation. At the same time it is an effective method to judge the quality of Emulsifier supplied by any supplier.

WHITENESS: When one drop of EC is added in 3 different test tubes, first test tube containing 34.2 ppm, Second test tube containing 342ppm and third test tube containing 800ppm hard water respectively, it should show good and almost equal whiteness in all the three aforesaid range of hard water. More whiteness will enhance thickness of emulsion(See Picture-4).

If the subjected sample of formulation satisfy the above mentioned test (showing dense emulsion in all the hard waters or show bluish emulsion in 342ppm hard water) then you can be confident that the subjected formulation can withstand against all the found probable water hardness and temperatures.

Figure 1
Picture 1

Step 1: Since here we are considering our premium grade emulsifier as an example, being a formulation chemist you will have to refer the recommendation chart for our premium grade emulsifier and find out the recommended pair and its dosage recommended for your formulation. Eg. If desired formulation is Cypermethrin 25% EC then in the recommendation chart our recommendation is combination of MAC-A & MAC-B and the dosage is 3.6% to 3.8% then the average dosage is 3.7%.

Step 2: Prepare a stock solution (also called ‘blank solution’) leaving a gap of 3.7% as arrived from the Step-1. The stock solution will contain the toxicant(s), solvent(s) and all additives representative of the ingredients to be used in bulk formulation.

Step 3: Weigh 96.3 grams i.e. (100-3.7) of the stock solution and add 3.7 grams of the emulsifier ‘A’ Stir well. Label this as ‘3.7% A’. This is really an EC with 3.7% of the emulsifier ‘A’ similarly; mix another 96.3 grams of stock solution and 3.7 grams of the emulsifier ‘B’. Label it as ‘3.7% B’. Now this is really an EC with 3.7% of the emulsifier ‘B’.

Step 4: Take two 50 ml capacity burette; fill the both EC in the burette respectively. Label it as A solution & B solution respectively.

Step 5: Please note that the goal of right emulsifier, right dosage and right optimization ratio is considered to be achieved only if the subjected formulation gives equal & dense whiteness in all the hard waters in other words the search for right emulsifier, right dosage and right optimization ratio is completed when the subjected formulation gives equal & dense whiteness in all the hard waters(See Picture-4).

In the correlation with the optimization guide table if the subjected emulsifier doesn’t reach to match the above mentioned goal even after trying two cycles of trials (titration of solution A with solution B, See Picture-2 and solution B with solution A, See Picture-3) then only a formulation chemist is advised to switch to another emulsifier.

Since the pair of emulsifiers offered by us are binary mixtures it is also possible that one of the two either Emulsifier-A alone or Emulsifier-B alone may work directly at the prescribed dosage if the technical content or it’s impurities is too high or too low and/or the solvent used in the formulation having aromatic contents either too high or too low.

Picture 2
Picture 3

In the view of the above you have to initiate optimization trials by adding single drop in 3 test tubes each containing 34.2ppm, 342ppm & 800ppm hard water respectively from ‘A’ solution, Check the spontaneity and whiteness in all the three hard waters, if doesn’t show any response then try with another set of hard waters with ‘B’ solution in a same manner.

If you observe slightest positive response in any of the solution then initiate the trial by taking 25ml of that solution e.g. ‘3.7% A’ in 100ml capacity beaker next add 0.5ml of the second solution ‘3.7% B’ by using the burette (See Fig.2). Stir it well. Check the spontaneity and whiteness in all the three hard waters

Observe the optimization Guide table below and if you found ‘3.7% B’ is less in the mix solution then add 0.5ml of ‘B’ solution in the mix solution and check again for the spontaneity and whiteness. Keep doing this till whiteness of all the hard water found to be good and approx. same (See Fig.4).

Please do not worry if you have added more by mistake you can re-correct the same by adding solution drop wise from the other burette because we are going to calculate the ratio from burette readings only.

In case even after adding 26ml of solution B in solution A if you do not see any positive response in any of the hard waters then refill both the burettes with the stock solutions and restart the trial by taking 25ml of solution B in the beaker and then titrate in same way as mentioned above. (See Fig.3).

Picture 4

As seen in Fig.4, where whiteness of the 342ppm is more than rest of the hard waters so now, increasing dosage from 3.7% to 3.8% maintaining the same ratio we will get accurately same whiteness in all the hard waters therefore the actual dosage shall be 3.8% not 3.7%. Please do not worry if you have added more by mistake you can re-correct the same by adding solution slowly from other burette because we are going to calculate the ratio from burette readings only.

Criteria Observed Reason Suggestion
No whiteness in any of test tube in all the trials
1) A.I. level or its impurity level is too high or too low. 2) Problem with solvent system.
1) Take a trial using only ‘A’ solution and optimise with ‘B’ solution increasing ‘B’ solution drop wise. 2) Take a trial using only ‘B’ solution and optimise with ‘A’ solution increasing ‘A’ solution drop wise.
Only good in 342ppm & bad in 34.2ppm & 800ppm
Emulsifier Dosage is less.
Increase the total dosage of emulsifiers till you get good and equal whiteness in all three.
Better whiteness in 34.2ppm than other two
The added quantity of solution A is more
Add solution B drop wise.
Better whiteness in 800ppm than other two
The added quantity of solution B is more
Add solution A drop wise.
Same but less whiteness in all three
Emulsifier Dosage is less.
Increase the dosage
Bad in 342 & good in other two or not improving in either 34.2ppm or 800ppm or both inspite of dosage increase & proper ratio optimisation
Problem may lies in hard waters
1). Check distilled water used to make hard water. 2). Check water hardness with water hardness meter. 3). Check pH of all the waters 4).CaCl2 & MgCl2 might be either contaminated or very old.

Step 6: To derive the ratio use following formula

M = Burette Reading of A + Burette reading of B

% of A in total dosage = Burette Reading of A x 100  =  N
                                                            M

% of B in total dosage = 100 – N

Example:

If Total B.R. of ‘A’ Burette = 25 ml and Total B.R. of ‘B’ Burette = 25.4 ml

M = 25 + 25.4 = 50.4 ml

N =  25  x 100  =  49.60 % of A
          50.4

% of B = 100 – 49.60  = 50.40 % of  B

On the above basis in the total dosage A : B ratio is 49.60 : 50.40

After the ascertainment of optimization ratio and the dosages formulation chemists are requested to take the blank solution and add the emulsifiers w/w in blank solution accordingly and check again in all hard waters and if found ok then take 2 ml or 5ml of the same formulated solution and check the same in all the hardness as per the method prescribed by BIS, CIPAC, WHO standard specifications in 100ml capacity emulsion tubes and keep it for 1 hr. for observation. If observed no creaming/oil separation at the top or no sediment/oil separation at the bottom in all the hard waters then formulation chemist can forward the batch recipe to the production department.

It is very obvious that as mentioned above, two cycles of titrations is only required when you come across development of new formulation or when solvent system is changed drastically, otherwise during regular production you will be starting titration either with solution A to solution B or with solution B to solution A and initiate with +10% or -10% proportion for eg. If the previous batch ratio was 50:50 then either you can start optimization with 55:45 or with 45:55 or even from +5% or -5%.

In testing the emulsion performance of the above the test criteria followed by most of the formulators are as per Indian standards, WHO standards or a variant of these according to their policy.

Here, we have depicted the test methods, on following the same, any technologist can reach most closely to the optimum combination and perfect level of dosage of MAC Emulsifier.

Furthermore ….

PARTICLE SIZE: Smaller particle size enhances emulsion stability. However, since BIS and WHO standards specify manual stirring, particle size less than 0.1 μm can not be achieved, as it requires higher agitation. When draining it from a side of a jar produces a thin emulsion film, particle size of an emulsion can be judged roughly by observing colour appearance of the thin emulsion film is showed in the following table.

Picture 5
Picture 6
Appearance
Particle Size
Two phases may be distinguished easily
macroglobules
Milky-white emulsion
greater than 1 μm
Blue-white emulsion
1-0.1 μm
Grey semitransparent emulsion
0.1-0.05 μm
Transparent emulsion
0.05 μm and smaller

From the above table it is clear that if emulsion film is giving blue-white appearance, the particle size of the emulsion would about 1 to 0.1 μm. If this particle size is achieved, then this can be considered as best available emulsion with manual stirring.

The said emulsion will give no separation (creaming/sediment) for a long time. However, it is difficult to observe this criteria in case of product like Quinalphos EC colour of which is dark. In other words, the colour appearance created by particle size will be masked if the colour of the product itself is dark. Observation of colour appearance in this product could be misguiding.

Based on optimization method and optimization tips you will automatically derive the ratio and dosage, required to formulate your excellent quality emulsifier which will perform in all the hardness and at the temperature right from 4°C to 42°C though your material is optimize at room temperature of 30°C.How ever please check for its emulsion stability test in all 3 hard waters if after 1 hour all 3 gives no sediment or no creaming then that particular dosage should be considered as the right dosage of Emulsifier for the pesticides formulation.

NOTE: The proportions of the Emulsifier suggested are for general guidance only. The optimum quantity to be used should be worked out after testing the recommended Emulsifiers in the proposed formulation made with procured materials in relation to the desired emulsion performance.

This information is based on our general experience, which is believed to be accurate & reliable.

However, there may be other factors beyond our knowledge, experience & control, which could affect the final product. Hence we cannot assume any responsibility other than for the uniform quality of the product.