Chemistry Reference
In-Depth Information
To column
Traditional pump
Splitter
Mobile phase
Recycle mobile phase
Figure 10.6
The cartoon design of the homemade micro-scale analytical system. Mobile phase from traditional
LC pump may divide into two parts easily by using a commercially inexpensive splitter. Scientists can reuse the
neat mobile phase and reduce the production of organic waste.
and choose the narrower or shorter column. A splitter is demanded to achieve this green goal. One flow
direction of the splitter is to the analytical column, the other flow direction of the splitter is to the mobile
phase bottle, and then the clean mobile phase can recycle until it runs out of the mobile phase. For example,
an analyte is separated by a 15 cm column and the original flow rate and column diameter are 1 ml min
−1
and 4.0 mm respectively. If your expected column diameter is 2.0 mm and column length is 15 cm, your
desired flow rate is approximately 250
l min
−1
at the similar retention time and the same particle size of
the column. According to the experimental purpose, the user can decide on the desired column diameter
and flow rate by themselves. This is a simple and convenient method to reduce the production of organic
waste. The mobile phase can be recycled effectively and attain the goal of green chromatography easily.
However, this system is unsuitable for the gradient mode because the organic solvent percentage of the
recycled eluent is unable to be determined. The diagram of the homemade micro-scale analytical system is
showed in Figure 10.6.
μ
10.3.6
Ultra Performance Liquid Chromatography (UPLC)
HPLC has been used in separation science worldwide over 30 years. Scientists and related experts are looking
for new strategies to shorten the analytical (or separation) time and maintain the separation efficiency
simultaneously. Reducing the analytical time could also cut the cost of organic solvents and lower the
production of organic waste. Hence, ultra performance liquid chromatography (UPLC) is invented to match
the requirements. In chromatography, the separation efficiency could be evaluated by the van Deemter
equation. The smaller the particle size of the column, the better efficiency and resolution obtained. The
difference between UPLC and traditional LC is the particle size of the column. The particle size packed in the
analytical column of traditional LC is 5 or 3.5
m. By using UPLC,
the flow rates could be increased and the separation speed, resolution and sensitivity could also increase. The
net results in the chromatogram show the shortness of the analytical time, so the reduction of the organic
waste could be expected.
UPLC is similar to traditional LC except for pump pressure. 'Compared with traditional LC methods,
UPLC runs at higher pressure and can reduce 95
μ
m, the particle size of UPLC is <2.0
μ
organic solvent' says Rohit Khanna; Waters' Vice
President. Transference of the analytical method from traditional LC to UPLC is easily attainable; hence,
many application results are well documented, such as drug analysis [232-241], metabolite analysis [242-
251], protein analysis [252-261] and biomarker analysis [262-271].
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