A greener and highly sensitive flow-based procedure for carbaryl determination exploiting long pathlength spectrophotometry and photochemical waste degradation

Abstract

An environmentally friendly analytical procedure with high sensitivity for determination of carbaryl pesticide in natural waters was developed. The flow system was designed with solenoid micro-pumps in order to improve mixing conditions and minimize reagent consumption as well as waste generation. A long pathlength (100 cm) flow cell based on a liquid core waveguide (LCW) was employed to increase the sensitivity in detection of the indophenol formed from the reaction between carbaryl and p-aminophenol (PAP). A clean-up step based on cloud-point extraction was explored to remove the interfering organic matter, avoiding the use of toxic organic solvents. A linear response was observed within the range 5-200 microg L(-1) and the detection limit, coefficient of variation and sampling rate were estimated as 1.7 microg L(-1) (99.7% confidence level), 0.7% (n=20) and 55 determinations per hour, respectively. The reagents consumption was 1.9 microg of PAP and 5.7 microg of potassium metaperiodate, with volume of 2.6 mL of effluent per determination. The proposed procedure was selective for the determination of carbaryl, without interference from other carbamate pesticides. Recoveries within 84% and 104% were estimated for carbaryl spiked to water samples and the results obtained were also in agreement with those found by a batch spectrophotometric procedure at the 95% confidence level. The waste of the analytical procedure was treated with potassium persulphate and ultraviolet irradiation, yielding a colorless residue and a decrease of 94% of total organic carbon. In addition, the residue after treatment was not toxic for Vibrio fischeri bacteria.

Photoinduced chemiluminescence determination of carbamate pesticides

“…Spectrophotometry determination is often based on diazotization reaction (several reagents have been proposed) to obtain azo-dye compounds. 4,5 Fluorescence has also been applied, often employing compounds such as cyclodextrins 6 to enhance the emission since most carbamates have poor fluorescence.…”

A critical review on photochemical conversions in flow analysis

“…With Table 8). Most of them have exploited heterogeneous photocatalysis by continuously adding a TiO 2 slurry to the effluent of the measurement cell [60,193,194], but photo-Fenton (H 2 O 2 + Fe 2+ ) [195] and persulfate + UV [196] also provided efficient mineralization. Generation of additional wastes was avoided by reutilization of the TiO 2 catalyst or conversion of persulfate to sulfate ions.…”

“…Generation of additional wastes was avoided by reutilization of the TiO 2 catalyst or conversion of persulfate to sulfate ions. On the other hand, it was demonstrated that wastes containing H 2 O 2 can be highly toxic [196].…”

“…Bioassays, such as that based on the Vibrio Fisheri bacteria [196], can be exploited to this end. In-line coupling of waste treatment and toxicity evaluation by a bioassay would then be very interesting.…”

An Environmental Friendly Procedure for Photometric Determination of Hypochlorite in Tap Water Employing a Miniaturized Multicommuted Flow Analysis Setup

“…Reduction of reagent consumption and waste generation are among the requisites necessary to attain the GAC recommendation [18, 19]. Multicommuted flow analysis (MCFA) [20–22] and multisyringe flow injection analysis (MSFIA) [18, 23] are efficient tools for handling low volumes of sample and reagent solutions, thus providing facilities to save them.…”