Biomedical Engineering Reference
In-Depth Information
LC, and analyze them with ESI-MS (either positive or negative mode) without
derivatization [
10,
99
]. Similarly, corticosteroids in racing horse urine are moni-
tored by LC-ESI-MS/MS as well [
11
] .
5.3
Determination of Steroid Hormones as Environmental
Pollutants
Steroid hormones are found as pollutants in drinking water, waste water, river and
sediments. The major concerns of analytical methodologies for monitoring steroid
hormones from environmental samples are extraction techniques from aqueous or
solid matrices. Since sample volume or amount is not an issue in most cases, SPE is
the method of choice. Both LC-MS/MS and GC-MS technologies are broadly applied
for steroid analyses of environmental samples, such as LC-MS/MS analyses of steroid
hormones in effluents of wastewater treatment plants [
100
] and estrogens in water
[
101,
102
], and GC-MS analyses of steroid hormones in environmental water [
34,
45,
78,
79
]. A study by Grover and colleagues showed that GC-MS was the simplest
technique in determination of steroid hormones in environmental water samples, but
lack of sensitivity; LC-MS/MS was more sensitive than GC-MS, but susceptible to
matrix interferences; and GC-MS/MS was the recommended technique, because it
was more selective and sensitive than GC/MS and LC-MS/MS [
103
] .
6
Summary
LC-MS/MS has similar sensitivities in analysis of steroid hormones as IA, RIA, and
GC-MS/MS, but LC-MS/MS and GC-MS/MS have much higher selectivity or
specificity. The steroid hormones from different sources or matrices should be
extracted with LLE or SPE, depending on the sample volume and matrices. Isotope
(as internal standard) dilution is a standard procedure for quantitative analysis of
steroid hormone and metabolites. Deconjugation is required in order to determine
the total steroid hormones, because the very low levels of unconjugated and conju-
gated steroid hormones in biomatrices may not be feasible to be analyzed at the
same time by LC-MS/MS, GC-MS, or GC/MS/MS. Derivatization can enhance MS
detection sensitivity for many steroid hormones and metabolites, while the derivati-
zation reagents and procedures should be selected based on the techniques of
LC-MS/MS, GC-MS, or GC/MS/MS, and their ionization modes. Depending on the
objectives of the method applications, bioanalytical procedures should be devel-
oped and validated according to the scientific and regulatory guidelines, e.g., FDA,
EPA, ISO, NIST, IUPAC, and then these procedures may be standardized following
CDC/NCEH/DLS practices. LC-MS/MS is increasingly applied for steroid analysis
in research, clinical, pharmaceutical, and food industries, sports and environmental
testing, due to its selectivity, sensitivity, and versatility.
