Archive for June, 2014

Photostability Chamber Testing The Stability Of Drugs

June 23rd, 2014

Light-related adverse side-effects of drugs are now an important source of concern. In order that the mechanism underlying to such effects is recognized, an in-depth photochemical study must be carried out. ICH Q1B (The ICH rule Q1B defines the Irradiation dose for UV and white light) guideline is the harmonized effort to standardize photostability testing on new pharmaceutical drug substances and drug products. For companies developing or manufacturing pharmaceutical drugs, a robust photostability testing process is essential to ensure product quality and regulatory compliance.

Stability tests are an important step in the course of the development of new drugs and pharmaceutical substances. Photostability chambers are designed to carry out stability and shelf life studies on drug and drugs substances. These chambers are also known as Pharmaceutical Photostability Chamber. These chambers allow the photostability test in accordance with ICH guidelines. (The ICH rule Q1B defines the Irradiation dose for UV and white light). Photostability chambers are characterized by an ideal light, UV, temperature and humidity distribution.
Note: ICH stands for International Conference on Harmonization

Photostability Test

At first the actual substance without any modification is tested, after that the final product without any wrapping is tested. If the final product remains photostable, that is the changes caused by the light are negligible or acceptable or can be disregarded; the test is finished at this point.

If unacceptable changes occur those modify the chemical structure of the test product, actions can be taken for the light protection of the specimens. The examinations are carried out once again e.g. in the first step the specimens are tested in a direct wrapping (like blister wrapping or glass), for further steps in sales packaging.

If the light stability is achieved with the taken action, normally this is seen in the storage tips, e.g. store only in the dark.

With such photostability examinations it is tested, how far the mentioned products change their chemical characteristics by light irradiation

One of the most important requirements in Photostability Tests is the homogeneous irradiation of the specimens. For this reason, all the specimens have to be positioned at the same distance from the light source.


June 17th, 2014

What is pH?

pH is a unit of measurement which is used to express the degree of acidity of a product or it can also be defined as negative logarithm of Hydrogen ion concentration i.e

pH= -log[H+]

The pH scale runs from 0 which means very acidic to 14 which means very basic.

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The scale is actually referring to the concentration of hydrogen (H+) ions in the product being tested. The more H+ ions that are present, the more acidic the product will be. The scale is logarithmic, meaning that each pH unit has 10 times more H+ ions than the one above it.pH can be measured using either pH indicators (like phenolphthalein) in form of solution or pH strips or using potentiometric method. Strips are very useful when all you need is 0.2-0.5 pH unit accuracy.

Tool for measuring pH with higher precision is the pH meter. Its working depends on the voltage that is caused by the H+ ions present in the product. A typical pH meter consists of a glass electrode connected to an electronic meter that measures and displays the pH value.


Parts of a pH meter:

pH meter consists of two or three parts that depends on the model(purchased)

  • Main Body Component; it houses the microchip used to process the measurements made by meter and the meter’s display.
  • A Probe commonly called an Electrode; it is the part where the measurement actually takes place, this part is consumable, sensitive and most expensive part of meter and should be handled with care.
  • Automatic Temperature Compensation (not present in all pH meters); some pH meters are equipped with the ability to measure the temperature of the solution being measured .This feature is called “Automatic Temperature Compensation.”Some ATC pH meters have the temperature sensor built into the electrode, and some have an independent thermometer probe which plugs into its own port on the back of the body of the meter.

How pH Meter works?

A pH meter is a precise voltmeter that measures the potential difference, in thousandths of a volt (mV), between the reference electrode and the measuring pH electrode. It’s scaled in such a way that it displays not the measured potential, but converts it to a display of pH. The pH meter calculates a value by measuring the voltage differences between the pH electrode (responsive to hydronium ion concentration) and the reference electrode (which provides a constant voltage). The meter must be calibrated in order to compensate for the difference in voltage output from different electrodes. It is recommended that at least two buffer solutions are used to calibrate the machine.(pH values 4,7 and 10).

According to Nernst equation (Nernst equation is a mathematical description of an ideal pH electrode behavior) a standard pH electrode generates a voltage of about 59 mV per pH, and at pH 7 (neutral pH) the electrode produces 0 volts. Acids produce positive and bases produce negative voltages.

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Calibration of a pH meter

This is required to calibrate the pH meter against a known set of values (e.g. pH= 4, 7 &10) so that it can yield accurate readings. For best results, calibrate pH with a buffer that is within 3 pH units of the test sample. Procedure:

1. Rinse the pH electrode in tap water.

2. Insert pH electrode in a fresh pH buffer solution.

3. Measure the temperature of the buffer solution.

4. Adjust the TEMP screw to the corresponding temperature value.

5. Observe the pH reading and adjust the “Cal” screw to pH 7 if required.

6. Remove pH electrode and rinse in distilled water.

7. Insert in a pH 4 if measuring an acid solution, or pH 10 bufsfer if measuring an alkaline solution.

8. Adjust the slope screw until the measurement value corresponds with the pH 4 or pH 10 buffer

What are the Types of pH meter?  

There are three different types of pH meters:

  • portable,
  • bench and
  • in-line.

    Portable devices are useful when there is a need to perform measurements outside the laboratory. Portable pH tester should be ergonomic, rugged and versatile.

    Bench tester is usually more precise and has more options. They are typically used in a laboratory where an interface for data communication and advance measurement features are         important.

    • In-line pH transmitters for process control are designed to with stand harsh environments.

Safety guidelines for pH meter

i) When it is not in use, it should be turned off and the electrode tip should be covered with the plastic cap.

ii) If the meter has not been used for some time, it should be soaked for several days in distilled water prior to use, with the power off. For effective soaking, the protective cap must be removed.

iii) The meter should ever not be placed in water deep enough to submerge any part of the upper body of the meter. this will ruin the electronics.

iv) After soaking, remove the pH meter from the water, dry the probe tip, and cap the probe until one is ready to use the meter again.

v) The meter may be laid on a paper towel on the bench top when not in use. However, under any circumstances the meter should not be inverted (turned probe-up); this may cause water inside the probe tip to run up into the meter electronics.

vi) Before using the meter to determine the pH of your analyte, it may be        necessary to standardize/caliberate it–that is, to immerse it in a buffer of known pH and adjust the meter to display the correct pH.

Pest Insects Control Air Curtains

June 12th, 2014

Air curtain is a device that is used for cooling, drying and cleaning within various manufacturing lines and other processes. By using compressed air as their power source, a balanced sheet of airflow stretches across the full length of the Air Curtain. The Air Curtain is used extensively in many industrial as well as commercial application areas to keep dust, contamination or even flying insects/pests out by creating forceful turbulence.

Pest/insect control Air Curtains, sometimes called “Fly Fans” are used in

  • Food processing plants
  • Dairies and bakeries
  • Bottling plants
  • Restaurants and school cafeterias
  • Supermarkets
  • Hospitals and Pharma industries

And other areas where the control of flying insects is required. The powerful stream of air that is produced by Air Curtain/Fly Fan is an excellent deterrent to insects. Sanitation maintenance applications require these Air curtains/Fly fans that prevent airborne insects from entering. For fly and insect control, the Air curtain projects the high velocity air jets across the opening, deflecting and prohibiting the entrance on unsanitary insects, thereby maintaining sanitary conditions. The Air Curtain is equally effective either mounted horizontally or vertically.

For the pest/insect control the Air Curtains can be mounted on either inside or outside of the doorways. It is very important that the entire doorway be covered so that there are no gaps for the insects/pests to enter.

  • Inside of the doorway; inside mounted unit helps to control the building’s climate in the winter by stopping the influx of cold outside air and preventing airborne insects.
  • Outside of the doorway; when the building contains odors which are attractive to flying insects it is recommended that the Air curtain be mounted on the outside.

The most effective Air Curtain design for insect control has a nozzle that can angle the air stream away from the area to be protected. An angle of about 20 degree from the vertical is usually optimal.

For this application i.e. Pest/insect control which requires maximum protection, it is common and widely accepted to use a more powerful Air curtain in order to achieve the necessary level of protection.