Monday, September 24, 2018

Definition of Buffer Capacity of Buffer

Buffers are compounds that resist the pH modify when a small number of acids or bases adding to the buffer. The buffer is typically prepared for a weak base or weak acid and its conjugate salt.
Buffer capacity has calculated the efficiency of a buffer in opposing changes in pH. Or Buffer capacity is the number of acids that are able to absorb buffer strong acid before breaking the ability to add strong acid.
The buffer capacity is articulated as the strong acid or base quantity in gram-equivalents to change pH by an entity that should be added to 1 liter of solution. When adding strong acids, there are buffer capacities in weak base solutions and a high amount of weak acid are high levels of buffer capacity when adding a strong base. The basic behind the buffer is to remain pH in a narrow range of the solution.


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Why are Buffer Solutions used to Calibrate the pH Meter
Why is conductivity important in the water?
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Buffer Solution Preparation for pH Meter Calibration

Normally we required two different buffer solutions for calibration of pH meters. One of these solutions should have a pH of 4.00 and the other should have a pH of 7.00. You can calculate the accurate quantity of required chemicals expected to include in buffer solutions. However, it considers that your water is pure and distilled and chemicals are also considered standardized and very pure. In order to create a buffer solution for at least in ideal conditions, we should have a calibrated pH meter; this means that you should get some buffer solution from the market, but you need only once.
To prepare a buffer solution take distilled water in a beaker, add 10 g of mono-potassium phosphate per liter of solution for pH 7.00 buffer and stir the solution until it dissolves. After this, add potassium hydroxide (KOH) gradually, until your solution is reached by pH 7.00. If you go slightly above the desired pH then you can add mono-potassium phosphate to reduce it up to pH 7.00. For the 4.00 pH buffer solution, add 20 g per liter citric acid in water and add potassium hydroxide (KOH) gradually until your solution is reached by pH 4.00. Once the preparation is done, keep the buffer solutions for a few hours and measure the pH again using the pH meter to confirm that your pH remains constant. Store buffer solution in airtight containers and keep them away from the light.
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How to Calibrate a pH Meter Using Buffer Solutions
Different Types of Buffer Solutions
General Applications of Flame Photometry
Principle of Karl Fischer Titration
What are the Applications of Conductometric Titrations
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Tuesday, September 18, 2018

How to Calibrate a pH Meter Using Buffer Solutions

The pH meter is an electrical apparatus used to measure the activity of hydrogen-ion in the solution. Calibration of pH meter with a minimum two buffer solutions, but if probable three buffer solution standards are generally used each time for the calibration of a pH meter. It needs to be regularly calibrated, although modern pH meter will hold calibration for one month.
Generally, three buffer solutions are used to calibrate the pH meter one of the buffers has a neutral i.e. pH 7.00 and the second buffer solution is slightly acidic pH i.e. pH 4.00 and another is basic i.e. pH 9.20. Preferred to compare the pH range in which the measurement of pH is to be taken. Meter gain and offset settings are adjusted frequently because the probe is placed alternately in two/three calibration parameters until the solutions get accurate readings. The modern apparatus has fully automated this process and needs to be immersed in only once or twice in each solution.
Before calibrating the pH meter, clean the electrode as follows.
Immerse the pH electrode in 0.1 M HNO3 or 0.1 M HCl for 15 minutes, followed by immersing in a storage solution for 30 minutes.
The calibration procedure for a pH meter:
  • Select the buffer solutions which range the probable sample pH. The buffers should be pH 07.00, pH 04.00 and pH 09.20.
  • Make sure buffer solutions are at room temperature. If the buffers are at different temperatures, temperature compensation is suggested and the sample should be measured at 250C.
  • Rinse the electrodes with the help of distilled water and wipe with soft tissue paper.
  • Keep the electrode in pH 07.00 buffer. Wait for a stable display. Set the instrument to the pH value of the buffer at the measuring temperature.
  • Rinse the electrodes with the help of distilled water and wipe with soft tissue paper.
  • Repeat the same process to the pH 04.00 and pH 09.20 buffer solutions as followed for the pH 07.00.
  • Rinse the electrodes with the help of distilled water and wipe with soft tissue paper.
  • Keep the electrode in the sample solution. While the display is stable, read the pH.
  • Clean the electrode with distilled water and store in 3 M KCL/Saturated KCL/ pH 04.00 Buffer solution. (Do not store the pH electrode in deionized or distilled water).
Periodically check the performance of the electrode with two or three buffer standardization. If the slope is under 92 %, or if reading in the buffer drift, follow the standard cleaning procedure.


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Different Types of Buffer Solutions

In simple words, it can also be defined as a solution that resists any change in pH, while a less quantity of a strong base or a strong acid is added in it, is called a buffer or buffer solution. Often such solutions are needed, whose pH does not change in terms of merits in a remarkable way. To understand their behavior, a study of such solutions is necessary. This will assist in utilizing the buffer solutions to resist pH change for keeping product stability. A solution with constant hydrogen ion concentration and therefore generally there is no change in pH, they are almost free from little change with added some acid or base called a buffer.
Types of Buffers
Acidic buffer and basic buffer are the types of buffers.
Acidic buffer:
The acidic buffer is a mixture of a weak acid; Acidic buffer solutions have an equal amount of weak acid and its salt with a strong base.
Basic buffer:
The basic buffer is a mixture of weak Base; in a basic buffer solution, it has the equivalent amount of weak base and its salt with a strong acid.


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Monday, September 17, 2018

Helpful measurement tips for pH meter electrode

  • Electrode and RTD sensor must be used in a perpendicular position. 
  • For the standardization and calibration of pH meter, always use freshly prepared buffer solution and measure at 250C.
  • While calibrating the pH meter, Use buffer in near the expected value from the sample, this will reduce the span error 
  • The electrode should be washed between the sample measurements with deionized or distilled water. 
  • To remove excess water, never rub the electrode bulb; just dry the tip end of the electrode with a clean tissue paper. 
  • For the rapid response, stir electrodes in the sample or buffer. 
  • Reactivate or change the electrode with a new one, if variation for pH 4.00 or pH 9.20 before calibration is greater than 0.3 pH.

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pH Meter Electrode Storage Solution

For the quick response of the pH electrode throughout the measurement of sample pH, the electrode needs to be soaked into a little acidic solution and rinse with distilled water. The pH electrode should always be stored in a moist state when you keep it for a long time and between regular measurements and you can dip the pH electrode in pH 4.00 buffer solution or saturated or 3M KCL solution.
Never store the electrodes in de-ionized or distilled water, since this is the migration of the filled solution (3 M KCL) of the electrode, thus reduces the response of the hydrogen ion.
Electrode storage:
Storage between the measurements
The electrode should be left in the lab environment, Do not store in the distilled water.
Short-term storage
Immerse the pH electrode tip in electrode storage solution (3 M KCL/Saturated KCL/ pH 04.00 Buffer solution). Do not allow a solution to evaporation and crystallization on the electrode.
Long-term storage
Electrode tip covers with safety cap.


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pH Meter Electrode Maintenance

The reference electrode in one unit and combine electrode is a combination of a glass electrode.
Preparation for use
Gradually shake the electrode to make sure that the internal solution covers the entire membrane and there are no air bubbles are interrupted. Immerse the glass bulb in 4.00 pH buffer for overnight and wash the bulb with distilled water several times before use. A white base Cap is accommodated for the gel-filled joined electrode and the unbreakable electrode, which should be gradually removed. This cap is loaded up with saturated KCL to prepare the electrode for use.
Maintenance
The electrode should be washed with distilled water every time and never use ordinary tap water. Wipe the electrodes with tissue paper to remove water droplets or any other sample solution. In the long-term storage conditions, the outer surface of the bulb can be dry, to reuse, the electrode should be soaked in 4.00 pH buffer solution for 24 hours. The electrode which neglects to react to the above treatment, immerse the electrode in 10 N HCl for two hours and washed with distilled water this can be activated by the electrode and gives fast responses. For long-time storage of gel-filled electrode immerses in saturated KCL solution, So that bulb and gels cannot be dry and it can be used without soaking.
Precautions
Make use of electrodes within the pH and temperature range, Beyond the limit can cause permanent damage of electrodes.

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Tuesday, September 11, 2018

Principle of Fluorescence Spectroscopy

Fluorescence is the emission of light from a molecule, which returns from the lowest vibration level of an excited single state to its normal ground state. Excited by the molecules, it is achieved by exposing the light source of the specified wavelength. At what time the molecule/compound is fluorescent, a part of the absorbed light is converted to fluorescence light, an emission of light at a lower wavelength. The fluorescence intensity is directly proportional to the concentration of the fluorescent species. Obviously, the linear relationship among the concentration and the fluorescent, intensity falls just to the diluted solution at high concentrations, make it required to first set up a concentration to detect the concentration of fluorescent graph and unknown sample with known standards. Fluorometry use to concentration determining of fluorophores, it provides sensitive absorption more than the colorimetric method. 
Actually, there is a strong light source in a unit, a focusing system, sample compartment a primary filter to choose the suitable wavelength of the excitation source, secondary filter permits the transmission of fluorescence and absorbs the scattered excitation radiation, an electronic amplifier, a photocell, and the metering system. To reduce the interference of the primary source, fluorescence is collected at a 90-degree angle. A shutter permits the beam of the source to drop on the sample only throughout the measurement.



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Care and Maintenance of HPLC Columns

The column is packed with porous particles and it’s made of polymer and is bounded by a thin layer of silica and polystyrene. In the early years, the Chromatography work carried out by the glass column with the diameter 01 to 05 cm and length is 50 to 500 cm, now a day HPLC columns are made of stainless steel. Normally the columns are in length from 30 to 250 mm, diameter 01 to 05 mm and pore size is 03, 05 and 10 microns.
System dead volume:
Minimize the dead volume in the system by using connection tubing of small internal diameter, for the analytical columns that lengths are 0.25 mm or less. Keep the length of tubing short as much as possible between the injector, column and the detector. 
Equilibration or saturation of the column:
A new column has a storage solvent mobile phase that is used to evaluate the column unless or as specified on the chromatogram. Primarily be concerned about to do pass any material through the analytical column, which can be passed in storage solvent. Make sure the column is completely equilibrated or saturated in the mobile phase before starting the HPLC analysis. A normal phase silica column generally needs extra conditioning than the reverse phase column. The flow direction is always marked on the analytical column. 
Performance testing of the column:
It is suggested that every column performance should be tested during the arrival and periodic intervals 
HPLC solvents: 
Make use of only HPLC grade solvents and the freshly prepared buffer solution to reduce any bacterial growth in the mobile phase. To ensure the column's life maximum, keep the pH of the mobile phase between 2 to 9.5 and always filter with a 0.45-micron filter. 
Pressure on the column and system:
Exposure of analytical columns to fast change in backpressure or pressure is more than 400 bars it may reduce the column performance and life. 
Fittings - torque: 
Extreme tightening of end fittings of the column will damage the column fittings or tubing. To prolong column life and performance, it does not remove an end fitting of the column. 
Mechanical damage: 
Keep columns safe from mechanical shock, banging or Dropping of columns can spoil its performance. 
Safety:
Highest working pressure = 400 bars 
Highest working temperature = 60°C 
Storage: 
Wash out all the water and buffer from the bonded analytical columns and stores in the organic solvent, for Unbonded silica columns can be stored in the hexane or compatible organic solvent. Place the column in a cool area. To prevent drying replace the end caps.

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Monday, September 10, 2018

pH Determination by Electrometric Method

The pH value of a sample can be determined by two methods, the electrometric method, and the colorimetric method. Adequately precise values can be determined using the electrometric method, but special equipment is required. The colorimetric method is easy and desires inexpensive mechanisms, and is enough precise for common work. However, it is subject to intervention by turbidity, color, free chlorine, high saline content, and different oxidants and reducing agents.
The pH indicator of any solution can be determined using an indicator solution or indicator paper, but the obtained results are not accurate since +-1 is the built error of pH. For precise measurement, a pH meter is used.
Several indicator electrodes are available for determining pH, Glass electrodes are widely used electrodes and many types of glass are used to make sensitive glass bulbs. Lithia glass is appropriate on the whole range of pH 0.00 to 14.00. The standard buffer is recommended to calibrate the pH meter. (pH 07.00, pH 04.00 and pH 9.20). i.e., determine the asymmetric potential. Then the pH can be read directly from the panel of pH meter of the unknown solution. The pH meter includes a glass and a reference electrode, LCD/LED display and temperature compensated. 
Glass electrode: The sensor electrode is a special glass bulb in which HCL has a certain concentration and has a buffering chloride solution in contact with an inner reference electrode.


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Factors Affecting the pH of Buffer Solution

There is the use of buffer solution is essential in pharmaceutical process and analysis study. The buffer solution has base and acid. It can be a strong acid with a weak base, or a weak base with a strong acid used to keep the right pH balance.
Here are mentions some Factors influencing the pH of Buffer Solutions are as follows. 
  1. The temperature change varies the pH of a buffer solution, every buffer can influence differently. For example the pH of sodium borate- boric acid buffer solution reduces with temperature, while the pH of acetate buffer rises with temperature. 
  2. By adding neutral salts to the buffer solution, the pH of the solution can be changed due to the change in ionic strength. 
  3. Dilution of the buffer solution also modifies the pH value since as changed in ionic strength. 
  4. The activity of hydronium ion, and the activity of ionized species that changes the pH of the buffer solution. 
  5. In addition, the amount of the change compared to the basic buffer is relatively small for the acidic buffer.

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Applications of Buffer Solution in Pharmacy

The buffer is a combination of an acid-base aqueous solution adjusted to an accurate pH value. The buffer is used to maintain a specific pH of the solution, it is used in the analysis and manufacture of various manufacturing processes such as food processing, electroplating, manufacture of medicines especially injection, ear drops, eye droplets, suspension, dissolution of tablets, etc.
Here are mentioned some applications of buffer solution are as follows.
Applications of Buffer Solution
Improving Purity: 
Proteins are purified depends on the fact that amphoteric compounds are slightly soluble at their isoelectric point. For example, insulin precipitates from the aqueous solution in the pH range of 5 to 6. This technique is used for insulin purification. 
Increased Stability: 
Because of hydrolysis, many compounds are unstable in aqueous solutions. These solutions can be stabilized by regulating the pH. For example, the stability of vitamins is within a narrow range of pH only. 
Enhanced solubility: 
If the pH of the solution is not properly maintained, then the drug dissolution can precipitate. This principle applies in the dosage forms manufacturing, and some pharmaceutical ingredients and drugs dissolve only at specific pH, hence, it is necessary to maintain the right pH of the solution. 
Optimizing Biological Activity: 
Enzymes contain most activity only on certain pH values. For example, at pH 1.5, there is a maximum activity of pepsin.


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What is buffer solution and how does it work

A buffer solution is one that refuses to modify in pH after adding to the little amount of acid or base. A buffer is the mixture of an acid-base aqueous solution adjusted to an exact pH value.
Their resistance to modifying the pH makes the buffer solution most helpful for chemical manufacturing and is necessary for many processes of biochemical. In the ideal buffer for a specific pH has a pKa equivalent to the pH desired, because in this solution, the buffer has an equal quantity of base and acid and the buffering capacity is in the middle of the range. Buffer solutions are required for pH to remain right for enzymes in several organisms. Various enzymes work just under very specific conditions, If the pH is too far from the margin, the enzyme may slow down or stop working and refuse, thus eternally stop its catalytic activity. Industrially, the buffer solution is used in processes of fermentation and is used to set the right conditions for the colors used in color to fabrics. They are also used in chemical analysis, chromatographic analysis, dissolution and calibration of pH meter and some other instruments.


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What is the process of dissolution

At which rate in the solvent there is a solute change in the molecule dispersion from, powder, liquid, crystal or other states, it is known as dissolution rate. Solubility is the quantity of solute, which can be molecularly dispersed in a certain amount of the solvent. The dissolved solute in a liquid should be available only in a liquid condition because the solutions do not occupy the fixed position in relation to the ions or molecules of the solution and so, it cannot be supposed in a solid state. In a solvent, the solution involves a change in the solution of the solute along with the solvent in the transfer of soluble molecule. Molecules of Solute are separated from other molecules and make space for adjusting solute molecules. Therefore, the decomposition will occur only when the solvent and solute are mutually attracted to a degree which is sufficient to overcome the interactional attraction forces between solute-solute for solvent-solvent and solute-solvent interactions. Although these contributions force can be quite different in strength. 
Attractive forces planted between polar molecules are quite strong compared to those present between polar and non-polar molecules. Therefore, in polar solute with admirable intermolecular interactions, the transfer of solute molecules in the solution occurs only when the solvent like water is also polar since non-polar solvents such as benzene will be unable to attract adequate attraction on the molecule so that the separation from the other solute molecules. 
As opposed to this, the intermolecular attraction of non-polar substances such as paraffin wax is relatively weak, therefore, dissolution of such substances occurs when solvent-solute integration is stronger than solvent-solvent interaction. Between polar solvent molecules, a marked intermolecular association such as water is used to prevent the dissolution of a non-polar solute and therefore, solute tends to be controlled to the non-polar liquids such as benzene. 
The above thought can be summarized as if a non-polar solvent dissolves a non-polar solute and polar solvent dissolves a polar solute. Though, this overview should be used with concern as the intermolecular interaction concerned with the dissolution process is influenced by factors that are not responsible for the polarity of the molecule. 


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Wednesday, September 5, 2018

Karl Fischer Titration Methods

The reaction of Karl Fischer titration uses volumetric or coulometric titration to determine the amount of water present in a sample based on the oxidation of sulfur dioxide by iodine, in which water is consumed in a buffer solution.

This technique was discovered by Karl Fischer. Karl Fisher Titration is a method to determine the content of moisture in different types of substances. It depends to a reagent that reacts with water content and changes water content into the non-conductive chemical. Volumetric KF titration and Coulometric KF titration are two techniques available for determination of water by the Karl Fischer: 
Volumetric Karl Fischer Titration:
With this technique, the moisture content determines on the base of volume or amount of reagent used to convert the water. The volumetric determination is appropriate for water content determination of down to 1% of the water. In these types of KF technique, samples are dissolved in a solvent before the starting the titration, until the water has removed a reagent is added and the endpoint is determined potentiometrically.
In this method, the Karl Fischer reagent contains a buffer base, alcohol, sulfur dioxide, and a recognized amount of iodine, which is necessary to achieve the titration endpoint. 
Coulometric Karl Fischer Titration:
The benefit of the coulometric Karl Fisher technique is the capability to precisely calculate the quantity of moisture content. Generally, this method is used if the moisture content is less than the 1 %. In this method, the solvents and reagent mixed in the titration cell and have need of just one iodide-containing solution. Iodine required for the KF reaction produced by the anodic oxidation of the iodide from solution and the endpoint is determined by electrochemically.
The quantity of iodine added in the sample is calculated by measuring the present current requirement for the electrochemical generation of iodine. When reacting with water, the brown iodine solution is reduced to the colorless iodide. In this method, sulfur dioxide, iodide ions, base, and solvent (alcohol) are used to complete the reaction.
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Applications of Karl Fischer titration

KF titration is a precise method for determining the quantity of water content in the substance. This method can also be used in the determination of moisture, particularly for water content in various manufacturing processes. In this method Iodine, Pyridine as an organic base, (Dry Methanol) alcohol, sulfur dioxide, and iodine are used, now these days less toxic Karl Fisher Reagent is available, which is pyridine free. 
Karl Fischer titration is generally used for the analysis of the water content in different manufacturing as well as to check the quality control in about all manufacturing processes that required measuring the water/ moisture content in the sample/materials. Karl Fischer titration is used as a robust and reliable method. In the food industry, it is used for the determination of water content in cocoa powder, chips, honey, noodles, fruit juices, and flour, etc. in petroleum manufacturing for all types of kerosene, gasoline, oils, and petroleum, etc. In the cosmetic industry for water determination in the shampoos, toothpaste, lipstick creams, etc, in pharmaceutical manufacturing for active materials, raw substances, tablets, oils, ointments, etc. It is used for the purpose of water determination in the paper, wood wool, silk, and even in construction materials.
In this blog, we also cover the point related to the principle of Karl Fischer titration, applications of Karl Fischer titration, Karl Fischer titration methods, what are the 4 types of titration advantages and disadvantages of Karl Fischer titration.


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pH Meter Principle and Applications

The pH measurement is the most common requirement of today's laboratory which is engaged in soil analysis, water, and wastewater analysis, industrial water, environmental analysis, food processing, agrochemical manufacturing, electroplating, pharmaceutical manufacturing and in bulk drug manufacturing necessitate to check the pH at different level of processes in different aspects like quality control, process monitoring, pollution control and finalize the product etc. Generally, on the scale of 0 to 14 pH units, pH is measured, but with the growth of technology and increasing needs of different industries and study, the pH measurement range is increased from pH 2.0 to pH 20.00.
The measurement of the pH of every aqueous solution provides the degree of alkalinity or acidity of the solution. Generally, pH is defined as the logarithm of the hydrogen ion concentration. The pH electrode measures a solution potentiometrically as the pH electrode is deep in the solution, the electrical signal develops in the sensing membrane of the electrode. The output of the electrode fluctuates with the change in pH value with the linear relationship of 59.16 mV / pH unit value. Electrode slope varies in temperature, therefore the requirement of temperature compensation; this slope can be compensated automatically or manually with modern pH meter. For accurate pH measurement, automatic temperature compensation with the different sensor is required. pH calibrates auto with measurement buffers, detection with ATC to read the PH value at 25 degrees. It scans, stores, prints and preserves data as per the GLP concept.
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