Microporous Filter Membranes Introduction

 In the lab filtration process, a filter membrane is required. The material and type of filter membrane sometimes have a great influence on the sample, and different filter membranes need to be screened. The following briefly introduces the microporous filter membrane.

Microporous Filter Membranes Introduction:

 

Definition of microporous membrane filter:

• The membrane separation process is a method of separating mixtures using a thin film.
• As a selective pass-through phase between two phases, the membrane can allow one or more components in the two phases to pass through the membrane and retain other components, so as to realize the separation between different components and achieve separation, concentration, and purification.
• It mainly uses the fluid pressure difference as the driving force for the screening and separation process. Microfiltration, reverse osmosis, nanofiltration, and ultrafiltration are all pressure-driven membrane separation technologies.

Microporous filter membrane material：

• Microporous membranes filter material mainly include cellulose acetate membranes, mixed cellulose ester microporous membranes, nylon membranes
• And polytetrafluoroethylene membranes, polyvinylidene fluoride membranes (PVDF), polyethersulfone membranes, and PP filter membranes.

Microporous Filter Membranes Pore Sizes:

1. What are the differences in the pore size of the microporous membrane?

• Nominal microporous membrane pore size ratings are provided as a general indicator of membrane retention.
• It is understood that some particles larger than or equal to the nominal pore size will pass through the filter membrane and enter the filtrate.
• Some manufacturers may relate a nominal pore size rating to a percent filtration efficiency.
• Nominal pore size grades vary by manufacturer and therefore are not necessarily the same.
• Filters from manufacturers with similar nominal pore size ratings may not exhibit similar retention characteristics.
• Pore size ratings are often based on retention studies using standard microbial cultures or challenging suspended particles of known size.
• The pore size rating indicates the size of the small microorganisms or particles retained in these studies. Pore ​​size ratings are almost always related to bubble point specifications used for quality control during membrane manufacturing. Most pore size grades, especially those based on microbial retention, are comparable between manufacturers.
• There is more uncertainty in pore size classes based on particle retention studies, especially for pore size classes < 0.2 µm, as there are no standard methods for these studies.
• And regardless of pore size, it is important to understand that conditions of use do affect particle retention. Even a filter with a nominal pore size can operate at the condition of allowing particles larger than the expected size to pass through.

2.Common pore sizes are 0.22μm, 0.45μm, 0.8μm, 1.0μm

a.0.22μm:

• It can remove the requirements of extremely fine particles in samples and mobile phases; meet the requirements of GMP or Pharmacopoeia, and the sterilization rate reaches 99.99%.
• It is suitable for the treatment of solvents and samples with high requirements such as ion-pair reagents and ultra-pure chromatography. Filtered water, mass spec solvent samples, etc. Applicable to packing chromatography systems smaller than 3μm, 3μm, or larger.

b.0.45μm:

• It can filter out most bacteria and microorganisms, is suitable for routine sample and mobile phase filtration, and can meet general chromatographic requirements

c.0.8μm, 1.0μm

• And can remove most insoluble particles, suitable for analysis and detection of relatively low sample content

Brief Introductions of PH Test Papers

 PH test papers are a “ruler” to test the pH of a solution, also called litmus paper. And have many kinds, such as pH health test strips.

 

What is pH test paper:

• There are three indicators of methyl red, bromocresol green, and thymol blue on the PH test papers, and they will change color according to certain rules in solutions of different pH values.
• PH test papers are popular. When testing the pH of the solution, use a clean and dry glass rod to test the liquid
• And drop it in the middle of the test paper, observe the color after the change is stable, and compare it with the standard color chart to judge the properties of the solution.
• When testing the pH of the gas, first wet the test paper with distilled water, stick it to one end of the glass rod
• And then send it to the mouth of the container containing the gas to be tested, observe the change of color, and judge the nature of the gas.

 What do ph test papers for:

Method 1: Detect the pH of the liquid

Preparation tools: test paper glass rod

1. When you need to test the pH of the solution, take a small piece of test paper on the watch glass or glass, and be sure to use a clean glass.

2. Then use a clean and dry glass rod to dip a little of the liquid you need to test on the middle part of the test paper.

3. It does not take a long time to observe his changes. After the color is stable, you can compare it with the standard colorimetric card
4. And then judge whether the solution is acidic or alkaline, that is, the nature of the solution.

How to use ph test papers:

Method 2: Detect the pH of the gas

Preparation tools: test paper distilled water glass rod

1. First, you need to use distilled water to soak your PH test paper strips, and then stick it to one end of your glass rod.

2. Send it near the mouth of the gas container you need to test.

3. After a while, you can observe his changes, and judge the nature of the gas according to his changes. The editor here reminds us that the test paper should not touch the edge of the container’s mouth.

What is the principle of pH test paper:

• The prototype of pH test paper, litmus paper, was discovered by Boyle by chance:
• During a tense experiment, splashed the violets in the laboratory with concentrated hydrochloric acid.
• Boyle, who loves flowers, hurriedly rinsed the smoking violets with water and put them in a vase.
• After a while, Boyle noticed that the deep purple violets had turned red. This strange phenomenon prompted him to conduct many experiments on the interaction of flowers and trees with acids and bases.
• From this, he found that most flowers and plants can change their color under the action of acid or alkali.
• Among them, the purple infusion extracted from litmus lichen is the most obvious.
• It turns red when it encounters acid, and blue when it encounters alkali.
• Taking advantage of this feature, Boyle soaked the paper with litmus infusion, and then baked it, which made the acid-base test paper commonly used in experiments – litmus paper.
• And there are three indicators on the ph test strips: methyl red, bromocresol green, and thymol blue. Methyl red, bromocresol green, thymol blue.
• And phenolphthalein will change color according to certain rules in solutions of different pH values.

There are more introduces about other products, like the material of centrifuge tubes, type of centrifuge tubes, etc.

Brief Introductions of Pasteur Pipettes

 Pasteur pipettes are made from selected medical grade LDPE raw materials and are suitable for small volume pipetting. Optimized surface tension for more fluid flow and easier handling.

Brief introductions of Pasteur Pipettes:

 

What is a Pasteur pipette:

It is a glass tube with two open ends (usually about 5 mm inside diameter). The tube is thinner at one end and has a smaller inner diameter (less than 1mm and has a glue tip at the other end). It is mainly for non-steady-state transfer of liquids, however, often “corrected” by calculating the number of droplets transferred per ml of fluorine, e.g. the ratio of droplets/mL is about Q.U2 ml/decreased.

How to use pasteur pipette:

Pasteur pipette uses by inserting the docking end of Pasteur pipettes with a cotton plug before use and then sterilizing the pipettes so plugged, that the transferred liquid can avoid microbial contamination. In microbiology research, graduated tampons can also block (analytical) pipettes for the same reason.

Features:

1. Good transparency, with tick marks, easy to observe;
2. It has certain elasticity and plasticity and should bend at a certain angle, which is conducive to entering the micro-container for liquid extraction or liquid addition;
3. Good elasticity, not easy to break, suitable for quick pipetting. Easy to use, accurate and reliable, good repeatability of drop volume;
4. Disposable Pasteur pipette ends are heat sealable for conveying small quantities of liquids;
5. Light weight, compact structure, easy to use, low consumption of consumables, one-time reduction of raw material pollution during use;
6. Smooth and transparent, reducing liquid adhesion, good elasticity, easy pipetting, accurate scale;
7. Small tips ensure repeatability of drops; tube ends can be heat-sealed to easily carry liquids;
8. The infusion tube body is translucent and bright white, with the ideal liquid flow on the tube wall and strong controllability;
9. Disposable sterile straws are slender, flexible, and bendable for easy access to micro or special containers;
10. Often used for operations such as absorbing, transferring, or carrying small amounts of liquids;
11. The tube body is translucent and bright white, the wall fluidity is ideal, and the controllability is strong;
12. The tube body is slender and soft, bendable, and easy to enter and exit traces or special containers;
13.  Sterilization method: ethylene oxide EO disinfection and sterilization.

Notice about Pasteur Pipettes:

• In addition to the cost, various conditions should be considered when using plastic as a reaction vessel, similar to heating and refluxing strong corrosive solvents, whether the plastic can accommodate it
• And should affect the process no matter if there are residual additives, then it will dissolve in the solvent, etc.

There are more introduces about other products: adjustable pipettes use, how to disinfect a pipette, etc.

Brief Introductions of Pipettes

What are pipettes– A pipette is a measuring instrument with a certain range, which can quantitatively pipette or add liquid reagents, and has the characteristics of fast and accurate!

 

The predecessor of the pipette:

• More than a hundred years ago, the pipette use to transfer liquids. The so-called pipette is a hollow glass tube marked with some scales.
• Insert this glass tube into the liquid, and use the mouth on the other end of the tube or the ear ball to draw the liquid into the tube, the scale at the top tells us how much liquid there is.
• After filling the amount we need, plug the end of the straw with your thumb, then place the tube into another container, release the handle, and let the liquid in the tube flow into the second container.
• This completes our task of transferring the liquid!

The birth of the pipette:

• However, with the progress of society, the elites found that the pipette was really difficult to use, tired and slow, and it was not easy to clean.
• As a result, loose thoughts accumulate, accumulate, and explode in the brain – and the gorgeous pipette is born!

How A pipette work:

• Generally speaking, there are two types of pipettes, one is the exhaust type (the official name, which is the pipette we usually use);
• The other is the external piston-type often as a pipette, it is often for transferring special liquids, and the application range is relatively narrow.
• The so-called exhaust type means that the piston is pressed down and the air inside the lower end of the pipette is pressed out.
• Then, when the piston moves upward, the air pressure inside the lower end of the pipette is smaller than the external air pressure
• The so-called outer piston type is actually the same as the principle of the syringe.
• And if you have seen the working process of the syringe, you can probably understand the principle of the outer piston type.

Pipettes volume range:

• The original pipette cannot adjust the volume, which fixed volume pipette on the market now.
• Over time, this pipette has struggled to meet the needs of the modern researcher.
• Later, a pipette with an adjustable range appeared, but there are fewer optional ranges, which is indeed much more convenient than the previous one.
• However, this kind of pipette is limited in range selection and gradually eliminated. We also classify this type of pipette as a fixed volume pipette.
• Freely adjusted within a certain range in the mainstream pipettes on the market, which are adjustable volume pipettes.
• Generally speaking, the volume adjustment range of the pipette is 10%-100% of its marked larger volume.

The number of pipettes channels:

• From the first pipette to the mainstream of the pipette market, only one transferred liquid sample at a time, which we call a single-channel pipette.
• But with the rapid development of the life science field, many times single-channel pipette means inefficiency.
• Thus, multi-channel pipettes have emerged, that is, a single pipetting operation can transfer multiple liquid samples.
• There are many types of multi-channel pipettes on the market today, including 6 channels, 8 channels,  12 channel multichannel pipettes, 16 channels, 24 channels, and even 36 channels, 48 ​​channels, 64 channels, etc.
• For a long time since accomplished the introduction of pipettes, aspiration, and discharge by the movement of a thumb-driven piston.
• In short, an electric pipette uses a tiny motor to drive the piston movement, allowing people to aspirate and dispense liquid with the push of a button.
• In this way, the thumb does not have to complain every day. We believe that the replacement of manual pipettes with electric pipettes is an irreversible trend in the future.

There are more introduces about what is adjustable pipettes, how to disinfect a pipette, etc.