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<h2>TECHNICAL SUMMARY REPORT</h2>

<h2>EPA METHOD 505:  VALIDATION FOR DETERMINATION OF ACETOCHLOR</h2>

<h3>Summary</h3>

<p>EPA method 505, Analysis of Organohalide Pesticides and Commercial Polychlorinated  Biphenyl (PCB) Products in Water by Microextraction and Gas Chromatography, has been  applied to the analysis of acetochlor in distilled, tap and ground water.</p>

<p>Using the exact procedures described in EPA method 505, with final analysis performed  using the primary GC column (DB-1 equivalent, 30m x 0.32mm id, 1.0µm film) with  electron capture detection, acetochlor was quantitatively recovered from all three water  types to levels of between 0.2 and 1.0 µg litre<sup>-1</sup>, depending on the  temperature programme used for gas chromatographic analysis.</p>

<p>Recoveries from all types of water ranged from 73-125% with an overall mean recovery  of 98% and a cv of 12% (n = 36).  In all cases laboratory reagent blanks and control  samples were free from interferences at the retention time of acetochlor.</p>

<p>Using the above conditions, baseline separation was observed between acetochlor and  other closely related acetanilides alachlor and metolachlor.</p>

<h3>Experimental Details</h3>

<h4>Sample Extraction</h4>

<p>For all water types 35 ml of water was measured into precleaned 40 ml screw capped  glass vials.  Samples were fortified with acetochlor at levels between 0.5 and 5.0  µg litre<sup>-1</sup> by addition of a standard solution in methanol via a glass  syringe.  Sodium chloride (6g) was added to each sample and the vials were shaken until  the sodium chloride dissolved.  Hexane (2mL) was added to each sample and the vials were  shaken vigorously for approximately 1 minute.  Samples were centrifuged at 2000 rpm for 2  minutes to aid separation.  The upper hexane layers were transferred to an autosampler  vial for analysis by GC/ECD.</p>

<h4>GC Analysis</h4>

<table class="table zebra">
<tr><th scope="row">Instrument</th>
<td>Varian 3400 GC fitted with an electron capture detector.</td></tr>
<tr><th scope="row">Autosampler</th><td>Varian 8000.</td></tr>
<tr><th scope="row">Column</th>
<td>Rtx1 (DB-1 equivalent) 30m x 0.32mm id x 1.0µm df </td></tr>
<tr><th scope="row">Injection volume</th><td>1µL</td></tr>
</table>

<p>Two temperature programmes were used.  Programme 1 is exactly as described in EPA  method 505.  Programme 2 was developed in-house in order to improve chromatography and to  optimize sensitivity.</p>

<p>Temp. Programme 1: 180°C (1 min) => 260°C @ 4°C min-1 => hold for 10  mins.   Acetochlor retention time = 16.5 minutes</p>

<p>Temp. Programme 2: 50°C (1 min) => 250°C @ 40°C min-1 => hold for 10  mins.  Acetochlor retention time = 8.1 minutes</p>

<p>Prior to analysis of the recovery samples a mixed standard solution of acetochlor and  two similar acetanilide herbicides, alachlor and metolachlor, were injected in order to  assess the resolution of these compounds from one another under the stated conditions  using both temperature programmes.</p>

<p>Results were assessed in terms of recovery value, cv of recovery values and resolution  of acetochlor from two similar acetanilide herbicides alachlor and metolachlor.</p>

<h3>Experimental Results</h3>

<h4>Recovery Data</h4>

<p>Results obtained from the analysis of acetochlor in distilled, tap and ground water  are detailed in Table 1.</p>

<table class="table zebra">
<caption>Table 1 :  Recovery Data From the Analysis of Acetochlor in Distilled, Tap and  Ground Water</caption>
<thead><tr>
<th rowspan="2" scope="col">MATRIX</th>
<th rowspan="2" scope="col">LEVEL<br />(µg litre<sup>-1</sup>)</th>
<th colspan="2" scope="colgroup">RECOVERY (%)</th></tr>
<tr><th scope="col">Temperature<br />Programme 1</th>
<th scope="col">Temperature<br />Programme 2</th>
</tr></thead>
<tbody style="vertical-align:top;">
<tr><th rowspan="4" scope="rowgroup">DISTILLED WATER</th>
<td>5.0</td><td rowspan="4" scope="rowgroup">85, 89</td><td>88</td></tr>
<tr><td>1.0</td><td>100</td></tr>
<tr><td>0.5</td><td>91, 107</td></tr>
<tr><td>0.2</td><td>96, 93</td></tr>
<tr><th rowspan="4" scope="rowgroup">TAP WATER</th>
<td>5.0</td><td>106, 105</td><td>82</td></tr>
<tr><td>1.0</td><td rowspan="3">91</td><td>80</td></tr>
<tr><td>0.5</td><td>108, 103, 111</td></tr>
<tr><td>0.2</td><td> 119, 101</td></tr>
<tr><th rowspan="4" scope="rowgroup">GROUND WATER</th>
<td>5.0</td><td>91, 110, 99</td><td>106, 73</td></tr>
<tr><td>1.0</td><td rowspan="3">86, 125</td><td>106, 109, 87, 89, 86, 80</td></tr>
<tr><td>0.5</td><td>106, 114</td></tr>
<tr><td>0.2</td><td>92, 100, 97</td></tr>
</tbody>
</table>

<p>n = 36<br />cv = 12%<br />mean = 98%</p>

<h4>Resolution</h4>

<p>Both temperature programmes were found to give baseline resolution between acetochlor  and the two other acetanilides of similar structure, alachlor and metolachlor.</p>

<h4>Minimum Detectable Level (MDL)</h4>

<p>The MDL of the method was defined as the sample concentration which gave an instrumental response equivalent to 5x background noise.  Using temperature programme 1,  the MDL for acetochlor was approximately 1.0 µg litre<sup>-1</sup>. Using programme  2 the MDL was approximately 0.2 µg litre<sup>-1</sup>.</p>

<h4>Conclusions</h4>

<p>Using the procedures described in EPA method 505 acetochlor can be quantitatively,  accurately and precisely recovered from distilled, tap and ground water to levels of  between 0.2 - 1.0 µg litre <sup>-1</sup>, depending on the GC temperature programme  used.  The method has been shown to provide adequate separation of acetochlor from other  similar acetanilides, and is therefore suitable for use as a multi-residue method for the  analysis of acetochlor and other organohalide pesticides in water.</p>

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