The Knowledge Of HPLC Column Packing

The common packing materials we use in HPLC columns are silica, hydroxyapatite media and polymeric resins, as many of types of packing used for gravity or low-pressure chromatography cannot stand the high pressures which are used in an HPLC separating system.

Due to the increased surface area, smaller-diameter beads can improve the sensitivity of separation. For an analytical HPLC column, media bead diameters are usually in the range of 1.8–5 μm. We should set the lower limit of bead size, as column pressure increases and bead diameter is reduced for a given flow rate, at the same time.

In the early time, we pack early HPLC columns with irregularly shaped silica particles to increase surface area. When scientists found that the spherical shape could provide increased efficiency and the porosity of the surface area, irregular silica was replaced by spherical porous silica.

The Knowledge Of HPLC Column Packing

What Are The Applications Of Ion-Exchange Solid Phase Extraction?

Ion-exchange solid phase extraction is widely used in biological samples and environmental monitoring.

During the extraction process, the pH of the sample is adjusted so that the solute is easily ionized. The solute is exchanged from the resin by changing the pH or increasing the strength of the competing ions during elution.

The pH of the organic base or acid is 50% protonated or ionized near the pKa. If the pH of the two units is lowered or increased, respectively, 99% of the base or acid is ionized, so the elution should also be increased or Lower the pH of the two units.

The sensitivity of ion exchange solid phase extraction is affected by pH, interionic force, flow rate and buffer ionic strength. The higher the competitive ionic strength in the sample matrix, the lower the extraction efficiency. For example, citric acid can compete for anion exchange sites.

In addition, some adsorbents can chelate with certain metal ions, such as iminodiacetic acid and Na+, which can effectively separate certain metal ions. Hawach offers you ion-exchange solid phase extraction cartridges.

What Are The Applications Of Ion-Exchange Solid Phase Extraction?

Six Major Operational Misunderstandings Using Pipettes

Pipettes are widely used in the laboratory. Proper operation and use of pipettes can improve work efficiency. What are the six common operational misunderstandings of pipettes? Pipettes are widely used in laboratories. The correct operation and the use of pipettes can improve work efficiency. What are the common 6 operating mistakes of using pipettes:

Misunderstanding 1. When assembling the tip, the force is too strong. The result is that the tip is difficult to be detached correctly: no need to use excessive force, select the tip that matches the pipette.

Misunderstanding 2. When pipetting, the pipette itself tilts: The pipetting is inaccurate and correct: vertical pipetting, slow suction and slow release.

Misunderstanding 3. Lay the pipette with a residual liquid tip. Consequence: The liquid reverses corrosion. The piston spring is correct: the pipette should be hung on the pipette holder.

Misunderstanding 4. Use a large-scale pipette to remove small volume samples. Consequences: Inaccurate pipetting. Correct: Pipettes with appropriate range should be selected.

Misunderstanding 5. directly press the second file to the correct absorption: it should be operated according to standard methods.

Misunderstanding 6. Cleaning the pipette with acetone or highly corrosive liquids: Damage to the pipette. The correct method: look at the instructions in detail, do not use corrosive liquids for cleaning. In the process of operating the pipette, be sure to avoid similar problems, bearing in mind the above six major misunderstandings.

Six Major Operational Misunderstandings Using Pipettes

Overview of QuEChERS Technology

QuEChERS, composed with Quick, Easy, Cheap, Effective, Rugged and Safe, is a latest developed sample pretreatment technology of detecting agricultural products, which was developed by one professor from the United States Department of Agriculture in 2003.

Principle

Its principle is similar to that of High-Performance Liquid Chromatography (HPLC) and Solid Phase Extraction (SPE). Both of them utilize the interaction between adsorbents and impurities of the matrix adsorbing impurities to remove impurities and realize purification.

General Steps

The steps of QuEChERS technology can be simply summarized as follows.

1. Crush samples
2. Extract and separate of acetonitrile of the single solvent
3. Add MgSO4 and other salts to remove water
4. Add ethylenediamine-N-propyl silane (PSA) or other adsorbents to remove impurities
5. Detect the supernatant

Advantages

The QuEChERS also has the following advantages. (three of the all are listed only)

1.High Recovery Rate
The recovery rate of a large number of polar and volatile pesticides is more than 85%;
2.High Accuracy and Precision
This can be modified by the internal standard method.
3.A Wide Range of Analyzable Pesticides
Including polar and non-polar pesticides, experts can apply this technology to acquire a higher recovery rate.

Overview of QuEChERS Technology

Testing Report Of Glass Fiber Extraction Thimble

The thimble is utilized in extraction, so the dissolution rate of impurities is a comparatively deductive target. For the deficient data of cellulose extraction thimbles, the mental content in glass fiber ones has to be tested, and respective results of different sizes are listed.

Even though they have similar characteristics in maximum temperature, DOP retention, weight loss and composition, which separately are 600C(usually 500C for big brands), higher than 99.99% (with the condition of at least 0.3um, oil mist method GB6165-85), lower than 0.2m(m ranges from m1 to m2, and m1 means the weight after dried at use-temperature for 60 min with similar m2 – the weight after dried at use-temperature of 120 minutes.), and super-fine glass micro-fiber.

Hence, the differences between products indicate in the background response and flow pressure.

SLGET32120 Glass Fiber Extraction Thimbles
57.22 % silicon dioxide(SiO2), 0.3% iron dioxide(Fe2O3) and 14.63% aluminium oxide(Al2O3) are deducted. The flow pressure is 14 to 16 mmHg.

SLGET2590 Glass Fiber Extraction Thimbles
It has been figured out in the samplings that 16.12% calcium oxide(CaO) and 3.66% magnesium oxide(MgO). 16 to 18 mmHg of flow pressure is checked.

SLGET2870 Glass Fiber Extraction Thimbles
0.16% calcium oxide(CaO) and 0.38% sodium oxide(Na2O) exist with 18-20 mmHg flow pressure.

Testing Report Of Glass Fiber Extraction Thimble

How To Use The Bottle-Top Dispensers

This article will focus on the methods of using the bottle-top dispensers.

1. Put the intake pipe into the dispenser and then tighten the nut.
2. Put the drain pipe into the dispenser and then tighten it.
3. Take off the cap of the drain pipe and put it under the drain pipe
4. Adjust the volume from zero to numerical value by rotating scale
5. Start the exhaust process. First, we should ensure the cap of the drain pipe open. Second, we lift the piston for a certain distance and then press it down. At last, we repeat the previous steps for several times until we see the bubbles are completely eliminated through the observation window.
6. Prepare the separation after the exhaust process. And pay attention that if we always can see the bubbles, we should check whether the suction pipe or other valves are installed correctly.
7. Adjust the volume from zero to numerical value from an arbitrary direction.
8. Press the piston to the bottom, and then adjust the knob to zero scales. Lock the dispenser.
9. Transfer the liquid. The piston is lifted stably to the top and then pressed equally stable to the bottom. There is a complete separation process. In this process, we should care that if the piston is lifted too fast, there may be excessive drops dripping into the piston which will cause errors.

Lock the dispensers after separating the liquid. That’s all for using the bottle-top dispensers.

How To Use The Bottle-Top Dispensers

Learn About Quantitative Filter Papers

Quantitative filter papers are widely used for quantitative and gravimetric analysis in the lab. To make them ash-less and achieve high purity, a special production process with acid is required in production, washing with HF or HCl acids, cleaning with demineralized water followed. The specific processes make the quantitative filter papers achieve two characters: high resistance to wet state and low ash content.

Called as ash-free filter paper as well, the quantitative filter papers can be divided into three formats, ashless, hardened low ash and hardened ashless.

With 0.007% ash maximum for grades 40 to 44, ashless quantitative filter papers are ideals for a wide range of critical analytical filtration procedures.

Treated with a strong acid to remove trace metals and produce high wet strength and chemical resistance, hardened low ash quantitative filter papers have 0.015% ash maximum. These filters are particularly used for vacuum filtration, as the tough smooth surface of the filter can recover precipitates easily. Its high wet strength and chemical resistance are similar to the acid hardened ashless filter papers.

And hardened ashless quantitative filter papers, with 0.006% ash maximum, are hardened by acid. The process gives high wet strength and chemical resistance with extremely low ash content.

Learn About Quantitative Filter Papers