Millipore Sigma Vibrant Logo
 

hi-flow


90 Results Advanced Search  
Showing
Products (71)
Documents (10)
Site Content (9)

Narrow Your Results Use the filters below to refine your search

Document Type

  • (4)
  • (2)
  • (2)
  • (1)
  • (1)
Can't Find What You're Looking For?
Contact Customer Service

 
  • «
  • <
  • 1
  • >
  • »

  • Determining estrogenic steroids in Taipei waters and removal in drinking water treatment using high-flow solid-phase extraction and liquid chromatography/tandem mass spec ... 17428520

    River water and wastewater treatment plant (WWTP) effluents from metropolitan Taipei, Taiwan were tested for the presence of the pollutants estrone (E1), estriol (E3), 17β-estradiol (E2), and 17α-ethinylestradiol (EE2) using a new methodology that involves high-flow solid-phase extraction and liquid chromatography/tandem mass spectrometry. The method was also used to investigate the removal of the analytes by conventional drinking water treatment processes. Without adjusting the pH, we extracted 1-L samples with PolarPlus C18 Speedisks under a flow rate exceeding 100 mL/min, in which six samples could be done simultaneously using an extraction station. The adsorbent was washed with 40% methanol/60% water and then eluted by 50% methanol/50% dichloromethane. The eluate was concentrated until almost dry and was reconstituted by 20 μL of methanol. Quantitation was done by LC-MS/MS-negative electrospray ionization in the selected reaction monitoring mode with isotope-dilution techniques. The mobile phase was 10 mM N-methylmorpholine aqueous solution/acetonitrile with gradient elution. Mean recoveries of spiked Milli-Q water were 65–79% and precisions were within 2–20% of the tested concentrations (5.0–200 ng/L). The method was validated with spiked upstream river water; precisions were most within 10% of the tested concentrations (10–100 ng/L) with most RSDs < 10%. LODs of the environmental matrixes were 0.78–7.65 ng/L. A pre-filtration step before solid-phase extraction may significantly influence the measurement of E1 and EE2 concentrations; disk overloading by water matrix may also impact analyte recoveries along with ion suppression. In the Taipei water study, the four steroid estrogens were detected in river samples (ca. 15 ng/L for E2 and EE2 and 35−45 ng/L for E1 and E3). Average levels of 19–26 ng/L for E1, E2, and EE2 were detected in most wastewater effluents, while only a single effluent sample contained E3. The higher level in the river was likely caused by the discharge of untreated human and farming waste into the water. In the drinking water treatment simulations, coagulation removed 20–50% of the estrogens. An increased dose of aluminum sulfate did not improve the performance. Despite the reactive phenolic moiety in the analytes, the steroids were decreased only 20–44% of the initial concentrations in pre- or post-chlorination. Rapid filtration, with crushed anthracite playing a major role, took out more than 84% of the estrogens. Except for E3, the whole procedure successfully removed most of the estrogens even if the initial concentration reached levels as high as 500 ng/L.
    Document Type:
    Reference
    Product Catalog Number:
    Multiple

  • Novel HY peptide antigens presented by HLA-B27. 9300696

    We have identified two peptides corresponding to the male-specific HY minor histocompatibility Ags presented by HLA-B27 in transgenic rodents, isolated from whole cell extracts and from immunoprecipitated B27 molecules of male B27 rat spleen cells. HPLC peptide fractions that sensitized female B27 targets for lysis by B27-restricted anti-HY CTL were analyzed by electrospray tandem mass spectrometry using a new highly sensitive quadrupole/time-of-flight instrument. Two peptide sequences were obtained, KQYQKSTER and AVLNKSNREVR. Synthetic peptides corresponding to these sequences bound B27 in vitro and were recognized by distinct B27-restricted anti-HY CTL populations. Neither peptide sequence entirely matches known protein sequences or shows a resemblance to known Y chromosome genes, but both show homology to known autosomally encoded proteins. Both peptides were shown to be controlled by the Sxr(b) segment of the short arm of the mouse Y chromosome, a segment known to contain all previously identified HY Ags. Taken together, these findings suggest that the two peptides arise as a result of Y chromosome-regulated control of one or more autosomal gene products. Although arginine at position 2 is a dominant anchor residue for peptides bound to B27, neither B27-presented HY sequence contains this residue. These studies, employing sensitive new methodology for identification of MHC-bound peptides, significantly extend the complexity of the genetic basis of HY Ags and expand the repertoire of antigenically active peptides bound to B27.
    Document Type:
    Reference
    Product Catalog Number:
    2750
    Product Catalog Name:
    BrdU Cell Proliferation Kit
  • «
  • <
  • 1
  • >
  • »