Analysis of Plant Protection Agents in Air with Active Personal Sampling and Micro HPLC

Particularly in spring time one frequently can observe farmers driving over their fields to distribute more or less noxious plant protection agents by sprinkling or spraying operations. Regarding the finely dispersed spray fogs it may be asked, to what extent the farmer or his employee himself is charged by inhalation of these chemicals, which are certainly referred to as hazardous working substances. In contrast to this there are not at all many data available to answer this question. The reason may be either the fact, that the subject itself is rather sensitive: Crop protection and pest control is regarded as indispensable; however, reporting on disadvantages involved is undesirable and shall be omitted as far as possible. The other reason might be that air monitoring itself is by far not a trivial analytical problem. The procedure looks easy: The farmer bears a portable battery powered air pump with a sampling tube, through which a defined air volume from the inhalation region is drawn. The sampling tube is transported to the lab for analysis. The problem is, that, even though there are numerous analytical methods at choice, most of them are designed for one active substance only. Farmers, however, disperse a great number of active substances, depending on type of crops cultivated, climatic conditions, geographic region and the just prevailing pest attack. This means, that the analytical method for monitoring must be changed each time, which makes the analysis complex and hence expensive. Users tend to avoid these costs. The subject of this research project is therefore to design and develop a true multiclass/multiresidue method, which allows to measure reliably from one sampling in one single run a number of plant protection agents sensitively and, even if they are very diverse in chemical and physicochemical behavior. This has the advantage, that any routine lab is forced to implement just one general method, which is able to measure all these various substances without modification. A very important aspect was to make measurable just those compounds, which are "up to date" right now and are actually brought out regularly and in great amounts. Information on this topic is not at all found in literature, but is rather obtained by direct communication with plant protection experts and the farmers themselves. It was just this procedure which led to "priority lists" of substances with very differing in chemical nature, but nevertheless are to be measured simultaneously. However, despite of these preconditions we managed to keep the mode of operation simple and to implement a modern separation technique using so called microcolumns. Thereby we proved, that these microcolumns, which are regarded by the analytical community still with some reluctance, are indeed capable to process a number of different substances, not only in dilute solutions, but also in chemically complex sample eluates, and are stable even under severe practical conditions. Field measurements with actual spraying actions were performed to assess the general applicability of our method. It turned out, that the air concentrations actually measured did not exceed several micrograms per cubic meter air. This means, that the frequently cited excessive exposure could not be confirmed. However, this result is valid for the scope of grain- and fruit growing in the foothills of the alps and cannot be transferred to other cultures or other climatic zones. It also should be noted, that all farmers, who have taken part voluntarily in these tests, were well trained in crop protection and pest control, and that is why the results may be subject to some bias.