Trace Determination of Pesticides and their Degradation Products in Water (BOOK REPRINT) (eBook)

Damia Barcelo (Autor)

M.-C. Hennion (Herausgeber)

eBook Download: PDF

1997 | 1. Auflage
556 Seiten
Elsevier Science (Verlag)
978-0-08-054312-3 (ISBN)

Infos

The book covers a critical compilation of analytical methods used for the monitoring of pesticides and their degradation products in water. It contains up-to-date material and is the direct result of the authors' experience in the field of pesticide analysis. The book is structured in six chapters, starting from general aspects of pesticides like usage, physicochemical parameters and occurrence in the environment. A second chapter is devoted to sampling from water matrices, stability methods of pesticides in water and quality assurance issues. The general chromatographic methods for pesticides are reported, including the newly developed electrophoresis methods and GC-MS and LC-MS confirmatory analytical methods. Sample preparation methodologies, including off-line and on-line techniques are described in the next two chapters, with a comprehensive list of examples of pesticides and many metabolites, including the use of different GC-methods and LC-methods. The final chapter is devoted to the development of biological techniques, immunoassays and biosensors, for the trace determination of pesticides in water samples.

The book answers one of the key problems in pesticide analysis: the diversity of chemical functional groups, with varying polarity and physicochemical properties. Pesticides and their metabolites have received particular attention during the last few years in environmental trace-organic analysis. For instance, in the case of groundwater, the use of pesticides has become a cause for concern. Under the right conditions, pesticides, such as fertilizer nitrogen, can move through the soil into groundwater, a phenomenon once thought improbable. The movement of agrochemicals in surface water flow can be, in some instances, a major problem, specially in the case of water soluble pesticides that are generally transported to estuarine and coastal waters. Estuarine waters feature gradients of both pollutant concentrations and physicochemical characteristics such as salinity, turbidity and pH, and all these parameters must be carefully considered when developing methods of analysis for trace organics in estuarine waters.

One of the key parameters in analytical determination is the environmental sampling. Different protocols and devices are needed for sampling sea-water samples - usually using large sample volumes of more than 50 litres either with LLE or SPE, with the problems encountered due to dissolved and particulate matter - which is different from drinking water and well water sampling. The representativeness of the sampling is also of concern.

The sample preparation of organic compounds from water matrices has been recognized to be a bottleneck and it has been traditionally neglected in the literature. We should comment following R.W. Frie's ideas - that the most sophisticated hardware is useless if the chemistry in the protocol does not work. During the last few years new adsorbents have appeared - carbon type, polymeric sorbents with high capacity and immunosorbents - which can more efficiently trap the more polar compounds.

The development of advanced automation methods based, usually on solid phase extraction techniques - PROSPEKT, OSP-2 and ASPEC XL - are examples of commercially available equipment that are of growing importance. These systems are generally coupled to LC and GC techniques.

Sampling and sample handling can not be regarded as separate techniques in the analytical process and both should be integrated into the whole analytical determination. For this reason, validation and confirmation methods, such as mass spectrometry, either GC-MS and/or LC-MS, are needed. These serve to check the quality assurance of the developed method. The discussion between multiscreening versus specific methods of analysis and the influence of the matrix (ground-, surface- and estuarine-water), is also a point of concern due to the diversity of chemical classes within the compounds of study.

Finally the use of rapid methods of analysis, which refer basically to biological techniques, biosensors and immunoassays are also of growing interest for the determination of pesticides in environmental matrices. The rapid development of these techniques, being more sensitive and that can work at different pH and drastic environmental conditions, like very different pH and salinity values, makes that these methods are very useful and complementary to conventional GC and/or LC techniques for the determination of pesticides.

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Trace Determination of Pesticides and their Degradation Products in Water is a critical compilation of analytical methods for the monitoring of pesticides and their degradation products in water. It contains up-to-date material and is the result of the authors' experience in the pesticide analysis field. The book is structured in six chapters, starting from general aspects of pesticides like usage, physicochemical parameters and occurrence in the environment. A second chapter is devoted to sampling from water matrices, stability methods of pesticides in water and quality assurance issues. The general chromatographic methods for pesticides are reported, including the newly developed electrophoresis methods and GC-MS and LC-MS confirmatory analytical methods. Sample preparation methodologies, including off-line and on-line techniques are described in the next two chapters, with a comprehensive list of examples of pesticides and many metabolites, including the use of different GC-methods and LC-methods. The final chapter is devoted to the development of biological techniques, immunoassays and biosensors, for the trace determination of pesticides in water samples.

Inhalt

Front Cover 1
Trace Determination of Pesticides and Their Degradation Products in Water 4
Copyright Page 5
Contents 8
Preface 6
Chapter 1. Pesticides and their Degradation Products: Characteristics, Usage and Environmental Behaviour 16
1.1. Introduction 16
1.2. Chemical classes and physico-chemical properties of pesticides 30
1.3. Environmental relevance in the aquatic environment 55
1.4. Degradation of pesticides in the aquatic environment 91
1.5.Toxicity and ecotoxicity 100
1.6. Conclusions 104
1.7. References 104
Chapter 2. Quality Assurance Issues: Sampling, Storage and Interlaboratory Studies 110
2.1. Sampling 110
2.2. Storage 131
2.3. Interlaboratory performance studies 144
2.4. References 167
Chapter 3. Chromatographic and Related Techniques for the Analysis and Detection of Pesticides 172
3.1. Introduction 172
3.2. Gas chromatography 174
3.3 Liquid chromatography 189
3.4. Thin layer chromatography 212
3.5. Capillary electrophoresis 217
3.6. Mass spectrometric methods 226
3.7. Conclusions 253
3.8 References 255
Chapter 4. Sample Handling Techniques (Extraction and Clean-up of Samples) 264
4.1. Introduction 264
4.2. Extraction and concentration procedures 266
4.3. Clean-up procedures 351
4.4. Conclusion and further developments 363
4.5. References 364
Chapter 5. On-Line Sample Handling Strategies 372
5.1. Introduction 372
5.2. On-line techniques with separation by liquid chromatography 373
5.3. On-line techniques with separation by gas chromatography 423
5.4. On-line solid-phase extraction, supercritical fluid extraction, and super-critical chromatography 436
5.5 Conclusion and further trends 437
5.6. References 438
Chapter 6. Immunochemical Methods and Biosensors 444
6.1. Introduction 444
6.2. Immunoassays 446
6.3. Immunochemical sample preparation methods 502
6.4. Biosensors 511
6.5. Conclusions and perspectives 522
6.6. References 524
Subject Index 534

Textauszug

1.3.3 Pesticides in river and estuarine waters

The current generation of pesticides is not as fat soluble as the organochlorinated pesticides, such as DDT. They are transported in aquatic systems primarily in the dissolved phase, generally exhibit much shorter half-lives than the organochlorinated pesticides, and have only a minor bioaccumulation potential. This is true for the agricultural use of herbicides, which are being used in increasingly larger amounts than insecticides. In the last few years, the monitoring programmes have started to consider the new generation of pesticides and their transport through rivers and estuarine areas.

Agrochemicals are applied annually to agricultural soils throughout the world. Many of these organic chemicals are transported to surface waters by a variety of mechanisms such as non-point source pollution, ground water discharge, or atmospheric deposition. Millions of pounds weight of relatively water-soluble pesticides, such as atrazine, simazine, alachlor and metolachlor, are applied each year in the USA and in Europe as pre- and post-emergence weed control agents on crops such as corn and soybean [2,100]. It is reasonable to assume that substantial amounts of these compounds may be present in the surface waters which drain agricultural areas of each country. Also, highways and railroads close to rivers may receive the impact of non-agricultural applications of pesticides, such as triazines, chlorinated acids, and phenylureas.

Following considerations based on usage information, physic-chemical properties, and persistency, a priority list of herbicides was established for the Mediterranean countries France, Italy, Greece and Spain. The list, shown in Table 1.14, considers selected herbicides and fungicides that can cause contamination of estuarine and coastal environments. The selection of pollutants has been based on the availability of usage data and the consideration of half-lives, so pesticides that do not exceed a total of 10 tonnes after 90 days of application have been excluded. Fungicides such as carbendazim, ethirimol, metalaxyl, captan, folpet, captafol, vinclozolin and chlorothalonil, which are each used in amounts varying from 20 to 300 tonnes per year in the cited Mediterranean countries are also included. Other fungicides such as mancozeb, maneb, ziram and thiram, which are also used in the same countries but in larger amounts, between 300 and 700 tonnes per year, were not included in a pilot monitoring study because of the need to develop specific methods for analysis at the low μg/l level in water samples [101].

Table 1.14

Herbcidies and Fungicides of Potential Concern in the Mediterranean Region

1.3.3.1 Organonitrogen pesticides in river waters

Some of the most relevant information on the environmental behaviour of pesticides in aquatic systems is the extent to which, after application, they can reach surface and river waters and, at a later stage, estuarine waters, with the potential of contaminating coastal sea waters.

The fate of chlorotriazine herbicides in aquatic systems has occasioned several investigations in recent years. The modelling approach, under laboratory conditions, has established that around 92% of the herbicide will be in the dissolved phase whereas about 1% is in the particulate matter [68,100].

Field studies have agreed with the modelling approach, giving values of 99.5% and 0.5% of atrazine in the dissolved and particulate matter, respectively. Atrazine has been transported in a number of river basins with an estimated loss of the applied herbicide varying between 0.4 and 1.8% [48,100,102]. These values have been reported from monitoring in the Camargue region, on the Rhone estuary [103] where the concentration values from the different stations are the same order and agree with the concentration range expected from other rivers such as the Mississippi in Minnesota and others. The concentrations in the dissolved phase were ca. 95–97% whereas in the particulate matter they vary between 3 and 5%. This behaviour can be explained by the Koc (soil adsorption coefficients) which are low, thus giving the pesticide a tendency to leach instead of remaining adsorbed on the particulate matter. The losses of atrazine after application have been estimated to be comparable to other world rivers, with a value of ca. 0.4% of the load.

A number of approaches can be used to estimate fluvial loadings of contaminants to the sea. The approaches used to estimate fluvial loads of atrazine from the Ebro river to the Mediterranean sea [104] were averaging estimators, ratio estimators, and regression-based estimators.

Collective mode (method 1):

=∑i=112CiQi

where Ci is the pesticide concentration in the month i and Qi is the total water amount which outflows in the month i.

Averaging method (method 2):

=36512∑i=112CiQi

where Ci is the concentration on the ith day and Qi is the discharge on the ith day.

Ratio method (method 3):

=l¯q¯Q

where ¯ is the average daily load, ¯ is the average daily discharge and Q is the total flow.

Regression method (method 4):

=∑n=1365qnexpB0+B1lnqn

where qn is the daily discharge, B0 and B1 are the regression coefficients from

c=B0+B1lnq

where c is the concentration and q is the discharge.

In order to apply such expressions, it is necessary to know the discharge for the Ebro river during a period of at least 1 year. Figure 1.13 shows the discharge (m3 s− 1) for the Ebro river in the extended Julian day period, 1 June 1994 to 30 May 1995. Table 1.15 presents the annual usage and loads of various pesticides, applying the four methods mentioned above. The four methods can be seen to give very similar results.

Fig. 1.13 Discharge (m3/s) for the Ebro river in the extended Julian day period 1 June 1994 to 30 May 1995.

Table 1.15

Annual Usage (Tonnes) and Loads (Kg) of Organonitrogen Pesticides Applying Four Methods of Estimating Fluvial Loads

Atrazine

130

970

817

819

666

Simazine

13

485

503

504

435

de-ethylatrazine

–

496

414

415

337

Alachlor

58

112

92

92

51

Metolachlor

37

236

194

194

144

The annual usages of the pesticides in the Ebro river basin, 130, 13, 58 and 37 tons/year, respectively, of atrazine, simazine, alachlor and metolachlor [93], make it possible to calculate ratios of loss/usage of these pesticides as 0.63, 3.85, 0.17 and 0.54%, respectively. However, it is necessary to keep in mind the fact that de-ethylatrazine is a direct metabolite from atrazine; therefore, if the two values are summed, the ratio of loss/usage of 0.97% is obtained (the recovery of de-ethylatrazine, 76%, was not applied). The atrazine ratio is within the expected range.

If we consider the usage of the herbicides studied above we can observe a parallelism between the pesticide detection, and the loads and usage for atrazine and metolachlor. In addition, the loads varied between 0.54 and 0.97% and are similar to values observed in other areas for alachlor, of which much more is applied than metolachlor, but only approximately half as much as atrazine, the pesticide loss is only 0.17%, which is much less than for all the other pesticides. This also occurred in Chesapeake Bay and can be attributed to the much larger Henry’s Law constant of this pesticide as compared to the other herbicides. In this respect, more air–soil volatilization of alachlor occurs compared to the other major organonitrogen herbicides. Along with its degradative process, this is responsible for the smaller relative percentage of the application...

Produkt-Details

• Erscheint lt. Verlag: 15.12.1997
• Sprache: englisch
• Themenwelt: Medizin / Pharmazie ► Gesundheitsfachberufe
• Themenwelt: Studium ► 2. Studienabschnitt (Klinik) ► Pharmakologie / Toxikologie
• Themenwelt: Naturwissenschaften ► Biologie ► Ökologie / Naturschutz
• Themenwelt: Naturwissenschaften ► Chemie ► Analytische Chemie
• Themenwelt: Naturwissenschaften ► Chemie ► Technische Chemie
• Themenwelt: Naturwissenschaften ► Physik / Astronomie
• Themenwelt: Technik ► Umwelttechnik / Biotechnologie
• ISBN-10: 0-08-054312-X / 008054312X
• ISBN-13: 978-0-08-054312-3 / 9780080543123