Combination of online hollow fiber liquid phase microextraction with smartphone-based sensing for in situ formaldehyde assay in fabric and wastewater samples.

A miniaturized analytical methodology was introduced based on the combination of a direct and online hollow fiber microextraction method with smartphone color detection. The method was used for the determination of formaldehyde (target analyte) in fabric and wastewater samples. In this regard, two reagents including ammonium acetate buffer and acetylacetone were added to the formaldehyde samples to create a colored compound. The colored compound was extracted from the sample by using the hollow fiber liquid-phase microextraction method, the extracted phase was not taken out of the extraction box and was directly transferred into a specially designed detection cell, and a smartphone was applied for in-situ color sensing and data readout. This combination gathered the advantages of both state-of-the-art microextraction techniques and smartphone sensing. Formaldehyde, as a carcinogenic compound widely used in paint and clothing industries, was selected as a model test. Factors affecting extraction efficiency were investigated and optimized, including the type of organic solvents, reagent concentration, salt, pH, stirring speed, reaction temperature, and extraction time. The linear region of the method under optimal conditions was 40-1500 µg L-1 for wastewater samples and 0.3-11.2 mg kg-1 for fabrics. The limit of detection and limit of qualification were 13 and 40 µg L-1, respectively. The relative standard deviations for concentrations of 100 and 1000 µg L-1 were 6% and 4%, respectively. To evaluate the application of the method for real samples, types of fabric and two samples of oil refinery wastewater were selected. The relative recovery in real samples was 84-98%. The results of the analytical parameters of the method show that the developed method can be used as an efficient method to determine formaldehyde in real samples.

Single-drop microextraction combined with gas chromatography-electron capture detection for the determination of acrylamide in food samples.

A single-drop microextraction method followed by gas chromatography-electron capture detection was developed to determine acrylamide in food samples. Acrylamide was extracted by water and derivatized by hydrobromic acid in the presence of ammonium peroxydisulfate. The derivatization was carried out at 45 °C in 15 min using 46 µL of hydrobromic acid and 98 mg of ammonium peroxydisulfate. A 3.0-mL volume of the derivatized analyte was extracted using a 1.0-µL n-octanol droplet hanging from the needle tip of a GC microsyringe. After extraction, the extract was injected into the gas chromatograph. The influence of experimental parameters effective on derivatization reaction yield and extraction performance was studied. The limit of detection and quantification, relative standard deviation and linearity of the method were 0.60 µg/L, 2.0 µg/L, <6.0%, and 2.0-100.0 µg/L, respectively. The method was utilized to determine acrylamide in three food samples (i.e., bread, potato chips and cookie).