An innovative arrangement for in-vial membrane-assisted liquid-liquid microextraction: application to the determination of esters of phthalic acid in alcoholic beverages by gas chromatography-mass spectrometry.

A new arrangement for membrane-assisted liquid-liquid microextraction is presented. The extracting organic solvent was placed into a chromatographic microvial, compatible with the chromatograph autosampler, whose septum was replaced by a disc of porous hydrophobic membrane. This extraction device was completely immersed into the analytical sample contained in a cylindrical container subjected to rotary and basculant movement.

Development of a new three-phase membrane-assisted liquid-phase microextraction method: determination of nitrite in tap water samples as model analytical application.

A novel and simple device for membrane-assisted liquid-phase microextraction is used for the first time in a three-phase system. The device consists of a glass vial containing the aqueous acceptor phase, whose septum of its screw stopper has been replaced by a sized piece of polytetrafluoroethylene membrane impregnated with n-decane. The vial is assembled to a volumetric flask containing the aqueous donor phase, and the membrane comes in contact alternatively with both donor and acceptor aqueous phases by orbital agitation.

A sensitive extracto-photometric method for determination of residual chlorine in greywater.

A new photometric method for chlorine determination based on the oxidative transformation of iodide to iodine and subsequent extraction in ethyl acetate has been developed. The effects of several chemical variables (pH, ionic strength, and iodide concentration) have been studied. Characteristics of the method were linear range 0-0.

Enzymatic determination of pyrophosphate in urine by flow methods.

Two flow methods for the enzymatic determination of pyrophosphate are described that are used to diminish the consumption of reagents. One method is based on the use of an open-close circuit with manual injection using a syringe. The other is a sequential injection method.