SPE-01 cleanup station is designed for sample preparation in trace
analysis of food and environmental samples. By automating the tedious
cleanup procedures, SPE-01 helps to increase the sample throughput and
improves the quality of analytical results.
The instrument can handle up to 6 samples per
batch without attendance. Up to 5 solvents can be used for column
conditioning and multi step elution. Two fractions can be collected for
each sample. These features make SPE-1 an ideal tool for sample
preparation in multi residue analysis.
Applications
1. Column cleanup for analysis of pesticide residues and drugs in food
samples In trace analysis of food samples, samples are first extracted
by blending with solvents or by soaking ground sample in solvent
overnight. The extracts are filtered out and then concentrated to 1-2
mL. Sometimes solvent exchange needs to be done if the original
extraction solvent is too strong for the following column cleanup.
Traditional column cleanup uses glass columns packed with silica gel,
alumina, or Florisil. Now pre packed solid phase extraction cartridges
are getting popular.
SPE-01 can accommodate both columns of traditional
size and the small SPE cartridges. It provides elution using up to 5
solvents. A typical method of SPE-01 involves pre conditioning of column
using a strong solvent (such as acetone) followed by a weak solvent
(such as hexane). After adding the sample, columns are first eluted with
a weak solvent to remove lipids and other low polarity components from
sample matrix. The strength of elution solvents can be increased
stepwise. In handling multi residue analysis, pesticides of different
polarity may be collected into two fractions.
2. Solid phase extraction of water samples
Solid phase extraction is used for cleanup and
enrichment of water samples for analysis of semi volatile organic
pollutants. In most cases, water is drawn through the SPE cartridge by a
vacuum pump. The flow is not stable. During the extraction process, the
flow can decrease gradually or even stop due to accumulation of small
particles and natural polymers (such as humic acids) in the sorbent bed.
Frequent attendance is necessary. The unstable flow rate during sample
addition and elution also affects the reproducibility of the analytical
results.
SPE-01 uses a metering pump to deliver the sample
through the SPE cartridge. It is faster and stable. A stable flow rate
helps to improve reproducibility of the analysis.
The operation of SPE-01 is simple. Instead of
preloading sample to the loops, the inlets of sample loops are placed in
the sample container. The instrument will draw the sample to SPE
cartridge according to pre defined volume. All the necessary procedures
(preconditioning, add sample, air drying of sorbent bed prior to
elution, elution, and collection) are carried out automatically for up
to 6 water samples. There is no need of attendance during the sample
preparation.
3. Analysis of drugs in biological samples
Solid phase extraction are used to remove proteins
and lipids from biological samples (plasma and urine) prior to
determination by HPLC or LC-MS. Many available automatic SPE systems are
designed for such application. They use syringe to take an aliquot from
each sample and add it to the SPE cartridge. Here exhaustive injection
is normally not necessary. They can also handle more samples than
SPE-01.
A problem with their design is the possibility of
drying out of the sorbent bed during sample addition and elution. It may
affect recovery and the efficiency of cleanup. Although cartridges that
are tolerant to drying out are available, they are more expensive than
normal silica based cartridges.
The design of SPE-01 can overcome the drying out
problem as the liquid path is closed when there is no liquid flow.
Another advantage of SPE-01 is its lower cost compared to other
automatic SPE instruments. Several SPE-01 may be used together when
higher sample throughput is necessary.
4. Regeneration of used SPE cartridges
Sometimes used SPE cartridges are regenerated for
repeated use to reduce the cost. SPE-01 can use up to 5 elution solvents
and the flow rate can go up to 20 mL/min. It is very convenient for
fast regeneration of the cartridges.