報告者 : 黃俊強 2010/11/17

INTRODUCTION

MATERIALS AND METHODS

RESULTS AND DISCUSSION

CONCLUSIONS

3

INTRODUCTION

N-Methylcarbamates (NMCs) first introduction into the agrochemi

cal market in the1950s. They are used world-wide as insecticides,acari

cides, nematocides and molluscicides on a large number of crops.

NMCs currently constitute a class of chemicals widely used in agriculture

to combat a large number of pests in a great variety of crops, and their re

sidues may be encountered in fruits and vegetables.

INTRODUCTION

High solubility and low sorption causes aldicarb and carbofuran t

o be mobile in groundwater, and their toxic degradation products

aldicarb sulfoxide and aldicarb sulfone and 3-hydroxy-carbofuran

are also soluble in water.

Gas chromatography (GC) has provided good results, but proble

ms sometimes arise because of the thermal lability of the analytes.

INTRODUCTION

Since the 1970s, high-performance liquid chromatography (HPLC) has be

come the preferred choice for the determination of NMCs, because, in thi

s case, the thermal lability problem is obviated.

Although normal-phase separations have been implemented successfully

in many cases, reversed-phase HPLC (RP-HPLC) has been much more po

pular, due mainly to its operational simplicity and better performance.

INTRODUCTION

Capillary electrophoresis (CE) has achieved recognition as a sepa

ration technique for use in the separation of inorganic and organi

c compounds,and has also been reported as a novel approach for

the determination of pesticides

INTRODUCTION 2.1 Chemicals and samples

MATERIALS AND METHODS

RESULTS AND DISCUSSION

CONCLUSIONS

2.2 Instrumental set-up

2.3 Solid-phase extraction

Chemicals and samples

Chemicals and samples

Acetonitrile and ethyl acetate were obtained from Scharlau

Sodium dodecyl sulfate (SDS) was obtained from Riedel–de Ha¨en

The solid-phase extraction (SPE) cartridges were 500mg of graphi

te carbon obtained from Supelco

The pesticide standards were obtained from Riedel–de Ha¨en

Instrumental set-up

All CE experiments were performed with P/ACE model 5500 (Beckman In

struments) equipped with a Beckman diode-array detector.

Beckman System Gold Software was used for system control, and for dat

a collection and processing.

A fused-silica capillary with 75-μm internal diameter (ID) and total length

(LT) of 57cm (50 cm to the detector, (LD)), 375 μm outer diameter (OD) we

re chosen.

P/ACE 5500

Instrumental set-up

Sodium hydroxide (0.1M)for 5 min

1min with Milli-Q water

Background electrolyte solution for 4 min

sample injection

Instrumental set-up

20.0 psi presure for each run

Sodium hydroxide(0.1M) for 1min

Milli-Q water for 1min

Solid-phase extraction

1.Ethyl acetate 10ml

2.Acetonitrile 15ml

3. Milli-Q water 10ml

4.water sample 250ml (flow rate of 5mlmin−1)

5.Dried 10min

6.Elute with ACN (2ml)

7.Dry

8.250ml buffer

INTRODUCTION

MATERIALS AND METHODS

RESULTS AND DISCUSSION

CONCLUSIONS

3.1 Development of the CE separation

3.2 Application to environmental samples

Development of the CE separation

The pH of the buffer systems tested

pH: 7~11 pH:8

(1)Phosphate(2)Carbonate(3)Borate

Borate

Development of the CE separation

Different voltages tests:

Different injection time tests:

20~27kv 23 kv

4~12s 12s

Development of the CE separation

Figure 1. Migration time versus concentration of SDS. Conditions:20mM borax/HCl

running buffer, pH 8; separation voltage: 23 kV;detection: 210 nm.

Development of the CE separation

Figure 2. Electropherogram of the five compounds (30 ng ml−1)under optimal c

onditions. Experimental and instrumental conditionsas in Fig 1. SDS: 140mM.

Development of the CE separation

Separation were made using a sodoum borate/Hcl

(20mM;pH:8)buffer solution and140mM sodium dodecy

l sulfate at 23 kv.

Th sample were injected for 12 S and detector was con

duced by UV diode-array absorption at 210nm in less t

han 17min.

Application to environmental samples

77~97%

CONCLUSIONS

The present data confirm the viability of MEKC in the d

etection and quantification of a family of well-known p

esticides

These results demonstrated that the analysis are more

economical than current methods due to the low solve

nt consumption , analysis times and resolutions.

Summery

2004 年 Carretero 團隊以 MEKC-DAD 偵測得滅克、得滅克亞風、得滅克風、加保扶、 3- 羥基加保扶等五種農藥，並藉由 MEKC 的方法可在20 分鐘內將這些農藥分離出來。所探討的最佳條件為 20 mM 硼酸鈉 /

鹽酸 緩衝溶液 (pH8) 並添加 140 mM SDS 。 LOD 分別為 2.3 、 3.8 、2.01 、 7.47 、 5.11 (μg litre−1) 其中以 3- 羥基加保扶的偵測極限可達最低 2.01 (μg litre−1) 。 MEKC 的方法應用在真實樣品上以簡單的固相萃取處理方式減少干擾並加以淨化、濃縮達到分析的效果，得到平均回收率為 77~97% (n=5) RSD 值為 2~7%