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INTRODUCTION
Water analysis
using the SpektraTM spectrometer
is a three-hour activity that was introduced
into a thirty-hour laboratory module on
analytical chemistry for students of the
Faculty of Education of the University of
Ljubljana a few years ago. Students who
take the module are those in their first
year of chemical and biological or chemical
and physics education. The module consists
of three main parts: qualitative analysis
on blisters with minimal quantities of chemicals;
gravimetric and volumetric analysis; and
the analysis of natural waters. The analysis
of several water samples in only three hours
was made possible by the introduction of
simplified and miniaturised titrations and
rapid spectrometric determinations on blisters.
The analysis of each water sample involves
determinations of the following: hydrogen
carbonate, total water hardness, calcium,
chloride, hydrogen phosphate, ammonium,
nitrite, pH, conductivity and TDS. Two students
of chemical education, Mojca Vrtič and Metka
Srebotnik, participated in the optimisation
of the analytical procedures for the module
during their diploma work in 2001 and 2002.
The analysis
of natural waters is organised as follows.
Each student selects a natural water, which
he or she knows well and would like to examine.
The student then justifies the selection,
states the hypothesis, collects the sample
and brings it to the laboratory, where he/she
analyses the sample, evaluates and compares
his/her results with those of the whole
group. In the final stage the student writes
a report.
The objective
of this activity is to demonstrate to students
that an analytical approach is much more
than just an analysis performed in the laboratory
under the supervision of staff that know
all the answers, and even the correct result,
in advance. A student’s experience is often
limited to determining a single parameter
in a synthetic sample. The procedure for
students usually starts with the sample
on the laboratory bench and ends with the
numerical results, which can be a better
or a worse match to the result they are
expected to obtain, but otherwise mostly
has no meaning for them. Students
thus lack the experience that analytical
work starts with a real question or problem
and ends with new information, which tries
to answer the question or contribute to
solving the real problem. This activity
is designed to give students this kind of
experience.
The laboratory
work for the students starts with the registration
of all the water samples. Each sample is
given a serial number. The data on the water
source, the sampling location, the sampling
date and time, and the name of the person
who collected the sample are entered in
the table entitled “Basic
data on water samples”. Later, the
table is completed with the data on the
waters’ pH, conductivity and TDS. The first
laboratory determination is a spectrometric
determination of calcium, which is performed
as a group task. The determination is based
on a five-point calibration, and a micropipette
is used for measuring all the volumes. All
the other spectrometric procedures are performed
with a simplified drop-based approach and
a one-point calibration. Students continue
their work and rotate to different working
positions. All the measurements are collected
in a table called “Working
sheet”. The results are inserted
into the tables “Results
– Major components” and “Results
– Contaminants”. At the end of the
laboratory activity, each student is given
photocopies of all four tables. These tables
are the contexts within which they discus
their results while writing the report.
As part of
the project we would like to exchange and
share experiences with other project partners.
We are especially interested in a kit for
water analysis that was developed by a Portuguese
partner and in possibilities to combine
or compliment the two approaches. We would
also like to test the module in Slovene
vocational schools for agriculture and food
processing or any other Slovene secondary
school and obtain their response.
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