N tris hydroxymethyl methyl 3 aminopropanesulfonic acid taps

A nickel standard solution (1000 mg/L) was purchased from Kanto Chemical Co. (Tokyo, Japan). The reagent, α-furil dioxime (α-FD), was obtained from Tokyo Chemical Industry Co., Ltd. (Tokyo, Japan) and dissolved in ethanol to make a 0.1 wt% solution. The pH buffer agent, N-tris(hydroxymethyl)methyl-3-aminopropanesulfonic acid (TAPS), was obtained from Dojindo Laboratories (Kumamoto, Japan) and dissolved it in a NaOH aqueous solution to make a 0.1 M buffer solution (pH 8.2). All other reagents used were of guaranteed reagent grade. All solutions were prepared using 18 MΩ cm deionized water, which was obtained with a water-purification system (Milli-Q ® Gradient A10, Millipore). A disposable syringe filter unit integrated with a membrane filter made of cellulose acetate (03CP045AN, an effective filtration area: 0.06 cm 2 , pore size: 0.45 μm) was purchased from ADVANTEC (Tokyo, Japan).

Glucose oxidase (GOx) from Aspergillus niger was purchased from Toyobo (Tokyo, Japan). The concentration of GOx was determined spectrophotometrically using the absorption coefficient of 18240 M -1 cm -1 at 460 nm. 24 PHMB and catalase were purchased from Nacalai Tesque (Kyoto, Japan). Ethylenediamine-N,N,N,′N′,-tetraacetic acid, disodium salt, dehydrate (EDTA), 2-morpholinoethanesulfonic acid (MES), 3-morpholinopropanesulfonic acid (MOPS) and N-tris(hydroxymethyl)methyl-3-aminopropanesulfonic acid (TAPS) were purchased from Dojindo Laboratories (Mashiki, Japan). Poloxamer 407 was purchased from Sigma-Aldrich (St. Louis, MO). They were used without further purification. Other chemicals were of reagent grade and were used as received.