Mikio Chiba

Development of an automated high-performance liquid chromatographic method for the on-line pre-concentration and determination of trace concentrations of pesticides in drinking water.

An automated reversed-phase high-performance liquid chromatographic (HPLC) method has been developed for the determination of trace concentrations of propoxur, carbofuran, carbaryl, propham, captan, chloropropham, barban and butylate in drinking water. A 100-ml of sample water is passed through a 3-cm precolumn, packed with 5-microns ODS sorbent, at a flow-rate of 5 ml/min. The HPLC system is then switched to an acetonitrile-water gradient elution program. The analytes, which are concentrated on the precolumn, are eluted and separated on a 25-cm C8 analytical column and determined by measuring the UV absorption at 220 nm. The resolution of analytes is excellent regardless of whether the elution from the precolumn is done unidirectionally or with backflushing. The precolumn can be used repeatedly for at least 30 samples without a significant decrease in efficiency. The total analytical time is 60 min. Tap, distilled, deionized, commercial spring and HPLC-grade waters were analyzed. The lowest detectable concentrations are in the range of 10.10(-12)-460.10(-12) g/ml for the eight pesticides with 100 ml of sample.

Simultaneous determination of trace concentrations of benomyl, carbendazim (MBC) and nine other pesticides in water using an automated on-line pre-concentration high-performance liquid chromatographic method

Methyl I-(butylcarbamoyl)-2-benzimidazolecarbamate (benomyl) is used worldwide as a systemic fungicide for disease control in crops. The analysis of benomy1 residues in water is made difficult by the varying instability of the compound in different organic solvents [l-3] and its low solubility in water [4]. Benomyl also decomposes in water, but at a rate slower than that in organic solvent [5,6]. High-performance liquid chromatographic (HPLC) methods are most popular for the analysis of benomyl but most employ the determination of the degradation product methyl 2-benzimidazolecarbamate (carbendazim or MBC) after quantitative conversion of the parent compound [7-91. These techniques are lacking in that the MBC that is produced from the parent benomyl during the sample preparation procedure cannot be distinguished from MBC that was present in the sample as a natural degradation product of benomyl. This methodology, which is not acceptable in principle, has been widely used in the past, however, for the following two reasons. The main reason is that the determination of intact benomyl residues is exceptionally difficult. Another reason is that MBC is also fungitoxic, and the fungitoxicity of benomyl is, in fact, thought to be due to the presence of MBC [lo]. An HPLC method for the simultaneous determination of benomyl and MBC in aqueous media has been described [ 111. Benomyl is quantitatively converted by treatment with base to 3-butyl-2,4-dioxo-s-triazino[l,2-ulbenzimidazole (STB), while

Determination of benomyl and its degradation products by chromatographic methods in water, wettable powder formulations, and crops

Abstract Chromatographic methods, used for the determination of methyl [1-(butylcarbamoyl)-1H-benzimidazol-2-yl]carbamate (benomyl) and methyl 1H-benzimidazol-2-ylcarbamate (carbendazim or MBC) in water, wettable powder (WP) formulations, and crops have been discussed. Because of the instability of benomyl in water and common organic solvents, most methods reported for the analytical determination of benomyl use an indirect approach. Since the kinetics of degradation of benomyl in water and common organic solvents is important in the development of analytical methods of benomyl, kinetic rates of various degradation reactions of benomyl are also discussed. The methods, based on the conversion of benomyl into MBC, and stabilization of benomyl in the presence of excess butyl isocyanate (BIC), will over-estimate benomyl with wide range of errors. Since MBC is a natural degradation product of benomyl and is present in different media at varying concentrations with benomyl, it should be determined individually with the intact concentrations of benomyl.

Rapid on-line precolumn high-performance liquid chromatographic method for the determination of benomyl, carbendazim and aldicarb species in drinking water.

A reversed-phase high-performance liquid chromatographic (HPLC) method has been developed for the determination of trace concentrations of benomyl, carbendazim, aldicarb, aldicarb sulphoxide and aldicarb sulphone in drinking water. A 10-ml sample of water is passed through a 3-cm precolumn, packed with 5-microns C8 sorbent, at a flow-rate of 5 ml/min. The HPLC system is then switched to an acetonitrile-water gradient elution program. The preconcentrated analytes are eluted from, and separated by, the 3-cm C8 precolumn and determined by UV absorption. The total analytical time is 25 min. The lowest detectable concentrations are in the range of 2.5 x 10(-9)-11.0 x 10(-9) g/ml for the five analytes investigated with 10 ml of sample.

Determination of polycyclic aromatic hydrocarbons by high-performance liquid chromatography-particle beam-mass spectrometry

In this article, we report a high-performance liquid chromatography-particle beam-mass spectrometric (HPLC-PB-MS) method for the determination of polycyclic aromatic hydrocarbons (PAHs). The PB interface consists of a concentric ultrasonic nebulizer with temperature-controlled desolvation chamber and a three-stage momentum separator. The HPLCPB-MS method showed greater sensitivity for PAHs with molecular weights above 178 than for those PAHs with molecular weights below 178. The percent relative standard deviations for the determination of 0.5 ng chrysene, 1.0 ng dibenzo[a,h]anthracene, 1.0 ng benzo[g,h,i]perylene, and 2.5 ng coronene were 20%, 2.5%, 13.7%, and 6%, respectively. The detection limits at signal/noise = 3 were 0.2 ng for chrysene, 1.0 ng for dibenzo[a,h]anthracene, 0.5 ng for benzo[g,h,i]perylene, and 1.5 ng for coronene.

Fast atom bombardment mass spectrometry of sodium and potassium oxalates—mass spectrometric evidence for the existence of (sodium–oxalate)– and (potassium–oxalate)– ion pairs in aqueous solutions

Mass spectrometric evidence for the formation of (sodium-oxalate)–(NaC2O4–) and (potassium-oxalate)–(KC2O4–) ion pairs in aqueous solutions of potassium oxalate and sodium oxalate was obtained by analysing different concentrations of sodium and potassium oxalates in water containing 10% glycerol. The results suggest that fast atom bombardment mass spectrometry can be used to reveal the behaviour of ionic species in aqueous solutions. The KC2O4– and NaC2O4– ion pairs form clusters with neutral molecules of potassium oxalate and sodium oxalate and glycerol. No ion pair or cluster formation was observed when dry salts (without glycerol) were analysed. This behaviour differs from what has been observed for alkali halides under similar experimental conditions.

Systemic Movement in Herbaceous Plants of Benomyl and Its Methyl Isocyanate Homologue

14C-labeled Azindoyle (MBC-MIC), the methyl isocyanate homologue of benomyl, was found to exhibit more systemic movement than benomyl in herbaceous plants. Of the total radioactivity applied to the leaf surface, the movement was mainly toward the growing tips, with some sign of downward movement. On broad beans the percentage of translocated activities were 31.5 and 12.0% of that applied for Azindoyle and benomyl, respectively. Both Azindoyle and benomyl were relatively stable at the site of application, and after 48 h, the percentages of intact parent compound were 47.5 and 52.2% for Azindoyle and benomyl, respectively. However, after 48 h, the percentage of parent compound at the translocated site was lower than that at the site of application, at 6.8 and 3.8% for Azindoyle and benomyl, respectively. Keywords: Azindoyle; benomyl; benomyl homologues; systemic movement; radioautographs