| With the MICRO DIST®
system from Lachat Instruments, you can now
distill up to 21 samples for cyanides, sulfide and
ammonia in 30 minutes; and phenolics and tritium
in 90 minutes.
|
USEPA-approved QuikChem® methods
for the determination of several chemical
species in environmental samples have been
used for several years with the QuikChem®
Automated Ion Analyzer. Based on the
techniques of flow injection analysis (FIA),
these methods provide rapid, accurate and
precise determinations. However, for some
analytes samples must be taken through a
complicated and time-consuming distillation
process to remove the analyte from a
potentially interfering matrix prior to
automated analysis. As a result, the analyst
is required to use a low-throughput,
large-volume manual distillation method
involving classical vaporization,
condensation, and collection with expensive
and fragile |
|
|
macro-scale glassware. This is incompatible
with the productivity features of
high-throughput automated analyzers. |
In response, Lachat has developed the MICRO
DIST® system. This system distills 21
samples simultaneously in convenient, disposable
or recyclable polypropylene tubes. The most
popular applications are the distillation of
cyanides and total recoverable phenolics. Both
solid and liquid samples can be digested and
distilled.
The MICRO DIST® system
quantitatively scales down the sample and reagent
volumes such as those required by
macro-distillations in USEPA methods 335.2 for
cyanides, 420.1 for phenolics and Standard Methods
(20th Ed.) method 4500-CN-N. MICRO DIST®
is a batch micro-distillation system which uses
sample volumes of less than 10mL. The key to the
system is a disposable, distillation tube assembly
(US Patents 5,022,967 and 5,304,287).
The sample is dispensed into a sample tube
which is then attached to a collector tube
containing a hydrophobic membrane. This assembly
is then inserted into a heating block where the
sample is boiled. The resulting vapor passes
through the membrane, condenses, and collects
above the membrane in a trapping solution specific
to the analyte.
Upon completion of the distillations, the
collector tube is snapped in half and the
distillate is brought up to volume. With MICRO
DIST®, the sample is distilled under
conditions that are significantly more
reproducible than those of a macro-distillation
procedure.
|
Macro-distillation Glassware |
MICRO DIST® |
| There are many fragile
pieces to disassemble, clean and reassemble
between each distillation |
The MICRO DIST®
tube consists of only two pieces which are
disposed of after use |
| Leaks at glass joints are
a major cause of low recoveries |
The tube has one plastic
press-fit joint that will never leak |
| The flow rate of the purge
gas stream is critical |
The in situ steam
is self-purging so no external gas stream is
required |
| Irregular contact with the
heating mantle causes variable heating for
each sample |
The high contact block
heater is temperature controlled for high
precision across all samples |
| About 10 samples per day
can be distilled in a typical lab |
Over 100 samples per day
can be distilled |
|
Track up to 10 items on this computer in 
)
