10.4 Sensitivity

25ppt in routine CGC/MS analysis. 30ppt in routine HPLC analysis.

10.5 Detailed Procedures

10.5.1 Procedure 1: Solid phase extraction/HPLC/DAD

or CGC/MS after methylation

Materials

• Chemicals

• acetone, p.a.

• acetonitrile, p.a.

• ethyl acetate, p.a.

• methanol, p.a.

• phosphoric acid

• phenoxy acid reference compounds

• sodium chloride, p.a.

• water, HPLC-grade

• reagents for diazomethane preparation :

• diazald (N-methyl-N-nitroso-4-toluene-sulfonamide)

• potassium hydroxide

• diethyl ether, p.a.

• ethanol, p.a.

210 10 Phenoxy acid herbicides and bentazone

Phenylurea herbicides and pyrazon

11.1 Introduction

Substituted phenylureas and pyrazon are widely used selective herbicides and therefore potential water pollutants. The EC list of priority pollutants includes two phenylurea herbicides, linuron and monolinuron and the methods described in this chapter permit a precise analysis of these compounds, together with other pesticides. Pyrazon (chloridazon), which is also included on the EC priority pollutants list has a different chemical structure, but may also be analysed using the same techniques.

11.2 Compounds

CH,

1. Fenuron

2. Chloridazon

3. Metoxuron

4. Chlortoluron

5. Monolinuron

6. Diuron

7. Isoproturon

8. Metobromuron

9. Dimcfuron

10. Linuron

ll.Chloroxuron

HC<H,O,

N1ICONICH,),

оси,

Phenylurea herbicides and pyrazon 11

225

11.3 General Procedure

Water samples are extracted by solid phase extraction (SPE) or by liquid-liquid extraction. The extracts are analysed by reverse phase liquid chromatography (RP-HPLC) with diode-array detection (DAD).

11.4 Sensitivity

0.25 ppb in routine analysis.

11.5 Detailed Procedures

11.5.1 Procedure 1: Solid phase extraction/HPLC/DAD

Materials

• Chemicals

• phenylurea herbicide reference compounds

• acetone, p.a.

• acetonitrile, p.a.

• sodium acetate

• methanol, p.a.

• water, HPLC grade

• RP-C18 bulk material

• florisil

• Solutions

• 0.002 M acetate buffer (pH6.5) : 28.5g sodium acetate are dissolved in 100ml water. This solution is diluted 1:1000 in water (lml/1). After adjusting to pH6.5 with acetic acid the buffer is filtered through a 0.2 urn membrane filter.

• standard solution of phenylurea standards in acetone (400 ug/ml) : 20 mg of each substance is dissolved in 50 ml of acetone.

• working standards : the standard solution is diluted in a buffer/acetonitrile mixture (7:3) to yield concentrations of 0.05 ug/ml, 0.10 ug/ml and 0.25|ig/ml.

• Tools

• membrane filter, pore size 0.2 um

• glass fibre filter paper

• empty SPE-columns with polyethylene frits

226 11 Phenylurea herbicides and pyrazon

Triazine herbicides

12.1 Introduction

Triazine herbicides are among the most common agricultural pesticides in use today, their high water solubility leading to fast accumulation in ground water. To help minimize toxic hazards, the legal maximum allowable concentration of triazines in drinking water is limited to less than 100ng/l per individual compound.

In order to determine the two triazines, simazine and atrazine included in the EC priority pollutants list, adequate analytical procedures are required. The following methods may be used to monitor these compounds together with other triazines and some metabolites. By using HPLC with UV detection, other pesticides may be monitored simultaneously.