One-step displacement dispersive liquid-liquid microextraction coupled with graphite furnace atomic absorption spectrometry for the selective determination of methylmercury in environmental samples.

A novel method for the selective determination of methylmercury (MeHg) was developed by one-step displacement dispersive liquid-liquid microextraction (D-DLLME) coupled with graphite furnace atomic absorption spectrometry. In the proposed method, Cu(II) reacted with diethyldithiocarbamate (DDTC) to form Cu-DDTC complex, which was used as the chelating agent instead of DDTC for the dispersive liquid-liquid microextraction (DLLME) of MeHg. Because the stability of MeHg-DDTC is higher than that of Cu-DDTC, MeHg can displace Cu from the Cu-DDTC complex and be preconcentrated in a single DLLME procedure. MeHg could be extracted into the extraction solvent phase at pH 6 while Hg(II) remained in the sample solution. Potential interference from co-existing metal ions with lower DDTC complex stability was largely eliminated without the need of any masking reagent. Under the optimal conditions, the limit of detection of this method was 13.6ngL(-1) (as Hg), and an enhancement factor of 81 was achieved with a sample volume of 5.0mL. The proposed method was successfully applied for the determination of trace MeHg in some environmental samples with satisfactory results.

Electrochemical assay of α-glucosidase activity and the inhibitor screening in cell medium.

An electrochemical method is established in this work for the assay of α-glucosidase activity and the inhibitor screening through one-step displacement reaction, which can be directly used in cell medium. The displacement reaction can be achieved via strong binding of 4-aminophenyl-α-D-glucopyranoside (pAPG)/magnetic nanoparticles (MNPs) to pyrene boric acid (PBA) immobilized on the surface of graphite electrode (GE), compared to that of dopamine (DA)/sliver nanoparticles (AgNPs). Since α-glucosidase can specifically catalyze MNPs/pAPG into MNPs/pAP which has no binding capacity with PBA, the activity of both isolated and membrane bound enzyme can be well evaluated by using this proposed method. Meanwhile, signal amplification can be accomplished via the immobilization of DA at the outer layer of AgNPs, and the accuracy can be strengthened through magnetic separation. Moreover, this method can also be utilized for inhibitor screening not only in the medium containing the enzyme but also in cell medium. With good precision and accuracy, it may be extended to other proteases and their inhibitors as well.

Assessment of articular fragment displacement in acetabular fractures: a comparison between computerized tomography and plain radiographs / 中华创伤骨科杂志

Objectives To evaluate plain radiographs and computed tomography (CT) scans in respect of assessment of articular fragment displacements (step and gap) in displaced acetabular fractures. Methods A retrospective evaluation was done to analyze the CT scans and plain radiographs of 64 patients who had been treated for displaced acetabular fractures in our hospital from January 1998 to May 2003. Of them, 20 met the inclusion criteria. In a blind method, 3 independent reviewers measured step and gap deformities on plain radiographs and CT scans utilizing a standardized measurement technique. The sensitivity and specificity of plain radiographs in detecting step and gap displacements (2 mm and 4 mm) in comparison of those of CT scans were determined. Moreover, intraclass correlation coefficient and intraobserver reliability were also calculated. Results Compared with CT, plain radiographs showed poor sensitivity in detecting step deformity (sensitivity = 44.3%). As far as fracture type was concerned, plain radiographs were particularly poor at detecting step deformity in fractures involving a single column of the acetabulum (sensitivity = 0%). Excellent intraobserver and intraclass reliability existed among the 3 reviewers. Conclusions Compared with CT scans, plain radiographs are poorly sensitive in detection of step and gap deformities in patients with acetabular fractures, and particularly poor at detecting step deformities. Therefore, in treatment of displaced acetabular fractures, CT scans are essential and should not only be used together with plain radiographs in the preoperative evaluation but also be considered in the postoperative assessment of fracture reduction and predicting future outcomes.