title: Amperometric and spectrophotometric determination of carbaryl in natural waters and commercial formulations.
abstract: The work presented describes the development and evaluation of two flow-injection analysis (FIA) systems for the automated determination of carbaryl in spiked natural waters and commercial formulations. Samples are injected directly into the system where they are subjected to alkaline hydrolysis thus forming 1-naphthol. This product is readily oxidised at a glassy carbon electrode. The electrochemical behaviour of 1-naphthol allows the development of an FIA system with an amperometric detector in which 1-naphthol determination, and thus measurement of carbaryl concentration, can be performed. Linear response over the range 1.0 x 10(-7) to 1.0 x 10(-5) mol L(-1), with a sampling rate of 80 samples h(-1), was recorded. The detection limit was 1.0 x 10(-8) mol L(-1). Another FIA manifold was constructed but this used a colorimetric detector. The methodology was based on the coupling of 1-naphthol with phenylhydrazine hydrochloride to produce a red complex which has maximum absorbance at 495 nm. The response was linear from 1.0 x 10(-5) to 1.5 x 10(-3) mol L(-1) with a detection limit of 1.0 x 10(-6) mol L(-1). Sample-throughput was about 60 samples h(-1). Validation of the results provided by the two FIA methodologies was performed by comparing them with results from a standard HPLC-UV technique. The relative deviation was <5%. Recovery trials were also carried out and the values obtained ranged from 97.0 to 102.0% for both methods. The repeatability ( RSD, %) of 12 consecutive injections of one sample was 0.8% and 1.6% for the amperometric and colorimetric systems, respectively.
authors.affiliation: CEQUP/Departamento de Engenharia Química, Instituto Superior de Engenharia do Porto, Instituto Politécnico do Porto, Rua António Bernardino 431, 4200-072 Porto, Portugal.
authors.forename: Dionísia C
authors.initials: DC
authors.lastname: Portela
authors.forename: Isabel M F
authors.initials: IM
authors.lastname: Pereira
authors.forename: Paula
authors.initials: P
authors.lastname: Paíga
authors.forename: Cristina
authors.initials: C
authors.lastname: Delerue-Matos
authors.forename: M Carmo V F
authors.initials: MC
authors.lastname: Vaz
mesh_terms: D012721:Carbaryl / Q000032:analysis*; D002851:Chromatography, High Pressure Liquid; D004563:Electrochemistry / Q000379:methods*; D017022:Flow Injection Analysis; D007306:Insecticides / Q000032:analysis*; D013053:Spectrophotometry / Q000379:methods*; D014874:Water Pollutants, Chemical / Q000032:analysis*
chemical_list: D007306:Insecticides; D014874:Water Pollutants, Chemical; D012721:Carbaryl