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 at 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 discuss 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.

                      Nataša Gros
                      University of Ljubljana
                      Faculty of Chemistry and Chemical Technology