Number

117-EN

Section

General Section

Use

Abstract

In analysis of pesticide residues cyclohexane, ethylacetate, tert. butyl methyl ether, diethylether and light petroleum are tried as alternatives to dichloromethane. Conclusively cyclohexane, light petroleum or tert. butyl methyl ether is recommended in the article . Of these three recommended substances, light petroleum and tert. butyl methyl ether is included in the database of hazardous substances according to SUBSPORTplusS screening criteria (SDSC).

Substituted substances

Alternative Substances

Reason substitution

ecotoxicity
physical hazards

Hazard Assessment

Substances to be substituted: There is limited evidence of carcinogenic effect of dichloromethane . Dichloromethane is included in the database of hazardous substances according to SUBSPORTplusS screening criteria (SDSC). It is on the list of IARC as a 2B carcinogen , a 1A or 1B carcinogen according to CLP Regulation and it is also on the list of edlists.org: as Substances identified as endocrine disruptors at EU. Alternative substance: The alternative, cyclohexane, may be fatal if swallowed and enters airways, is very toxic to aquatic life, is very toxic to aquatic life with long lasting effects, is a highly flammable liquid and vapour, causes skin irritation and may cause drowsiness or dizziness. Light petroleum (CAS No. 64741-84-0) and tert. butyl methyl ether (CAS No. 1634-04-4) are also recommended as alternatives in the article. They are both hazardous according to SUBSPORTplusS screening criteria (SDSC). Light petroleum may cause cancer and tert. butyl methyl ether is an endocrine disruptor.

Description of Substitution

In pesticide multiresidue analysis the most common applied method (S19) involves liquid/liquid extraction using dichloromethane. Dichloromethane is used because of its ability to transfer both non-polar and polar substances from the aqueous into the organic phase. This document reports the investigation of substituting dichloromethane by several non-chlorinated solvents (ethyl acetate, tert. butyl methyl ether, diethyl ether, light petroleum, cyclohexane/ethyl acetate (1:1), cyclohexane). S19 is used as a reference method. In S19 the following solvents are used in different parts of the analysis: acetone, water, dichloromethane, ethylacetate and cyclohexane/ethylacetate (1:1). With the aim of reducing the amount of chlorinated solvent in waste water a substitute for dichloromethane was investigated while the rest of the method was kept the same. Replacing the extraction procedure with so-called “on-line” methods was also tried out in order to omit the liquid/liquid partition with dichloromethane. One methodology consists of an application of ethyl acetate for the extraction step in combination with sodium sulphate as drying agent. In another "on-line" method an extraction with a hexane/acetone mixture (8:2) directly includes a transfer of pesticides into the non-polar organic phase. The results show comparable high recoveries for each methodical approach. Only the ethyl acetate yields a lower recovery both in the liquid/liquid partition and in the “on-line” method. Cyclohexane showed to be a suitable substitute because it is used as a solvent in the following procedures. Repeatability is also an important parameter of an analytical method. Especially the “on-line” methods lead to comparable results. The other variants show higher relative standard deviations up to 27% for light petroleum. The final conclusion of this study is “it is recommended to replace this chlorinated solvent with cyclohexane, light petroleum or tertiary butyl methyl ether. For special applications, “on-line” methods are possible alternatives”.

Case/substitution evaluation

This article does not contain any CAS- numbers. Light petroleum can have many CAS -numbers, but the one listed in this SUBSPORTplus description fits the boiling point of the described solvent. The risk of flammability has to be taken into account in organising the working procedures. Only three of the tested alternatives can be recommended. Two of these recommended alternatives - light petroleum and tert. butyl methyl ether - are included in the database of hazardous substances according to SUBSPORTplusS screening criteria (SDSC). Of the recommended alternatives only cyclohexane is not included in SDSC. This substance is on several others lists of objectionable substances, and the resulting risks have to be taken into account in organising the working procedures.

Type of information supplier

Research

Further information

A. Koinecke, R. Kreuzig, M. Bahadir, J. Siebers, H.G.Nolting: Investigation on the substitution of dichloromethane in pesticide residue analysis of plant materials. Fresenius J Anal Chem (1994) 349:301-305

Type of publication and availability

Scientific publication

Publication source: author, company, institute, year

A. Koinecke, R. Kreuzig, M. Bahadir, J. Siebers, H.G.Nolting: Investigation on the substitution of dichloromethane in pesticide residue analysis of plant materials. Fresenius J Anal Chem (1994) 349:301-305

Publication source

Type of publication and availability

https://link.springer.com/article/10.1007/BF00323208

Date, reviewed

December 11, 2020