Provided are methods for determining the amount of estrone in a sample using mass spectrometry. The methods generally involve ionizing estrone in a sample and detecting and quantifying the amount of the ion to determine the amount of estrone in the sample.

A plug for a container for storing liquid includes a housing and an input end at an end of the housing, the input end having a liquid-impermeable membrane that allows gas flow to pass through. A first sensor is in a first sensor chamber inside the housing, the first sensor being configured to detect a smoke taint compound. A first filter is between the input end and the first sensor, where the first filter selectively allows phenols to pass through. A second sensor is in a second sensor chamber inside the housing, the second sensor being configured to detect a second substance different from the smoke taint compound. A second filter is between the input end and the second sensor, wherein the second filter selectively allows the second substance to pass through.

Provided are methods for determining the amount of estrone in a sample using mass spectrometry. The methods generally involve ionizing estrone in a sample and detecting and quantifying the amount of the ion to determine the amount of estrone in the sample.

Systems and methods of in vivo and in vitro radical protein foot-printing using an opto-fluidic array are presented. These teachings may be used to, for example, study three-dimensional protein structure or bio-kinetics. Radical dosimetry including an optional intrinsic standard is used. Real-time feedback based on an internal standard provides comparability between different experiments and in vivo and in vitro analysis results in data that is representative of actual biological conditions.

A plug for a container for storing liquid includes a housing and an input end at an end of the housing, the input end having a liquid-impermeable membrane that allows gas flow to pass through. A first sensor is in a first sensor chamber inside the housing, the first sensor being configured to detect a smoke taint compound. A first filter is between the input end and the first sensor, where the first filter selectively allows phenols to pass through. A second sensor is in a second sensor chamber inside the housing, the second sensor being configured to detect a second substance different from the smoke taint compound. A second filter is between the input end and the second sensor, wherein the second filter selectively allows the second substance to pass through.

The three-dimensional structural analysis of pharmaceutical and/or biological molecules is performed by the reaction of OH radicals on the surfaces of the molecules of interest. Quantitation and/or completeness of the OH radicals are optionally measured using buffers intrinsic to the sample solutions as internal standards. Measurements of the reactions of these buffers with OH radicals provide an internal standard while avoiding the use of prior art internal standards that can have unwanted effects on the three-dimensional structures of interest.

The invention relates to the detection of vitamin D metabolites. In a particular aspect, the invention relates to methods for detecting derivatized vitamin D metabolites by mass spectrometry.

Provided are methods of detecting the presence or amount of a vitamin D metabolite in a sample using mass spectrometry. The methods generally directed to ionizing a vitamin D metabolite in a sample and detecting the amount of the ion to determine the presence or amount of the vitamin D metabolite in the sample. Also provided are methods to detect the presence or amount of two or more vitamin D metabolites in a single assay.

The three-dimensional structural analysis of pharmaceutical and/or biological molecules is performed by the reaction of OH radicals on the surfaces of the molecules of interest. Quantitation and/or completeness of the OH radicals are optionally measured using buffers intrinsic to the sample solutions as internal standards. Measurements of the reactions of these buffers with OH radicals provide an internal standard while avoiding the use of prior art internal standards that can have unwanted effects on the three-dimensional structures of interest.

Provided are methods of detecting the presence or amount of a vitamin D metabolite in a sample using mass spectrometry. The methods generally directed to ionizing a vitamin D metabolite in a sample and detecting the amount of the ion to determine the presence or amount of the vitamin D metabolite in the sample. Also provided are methods to detect the presence or amount of two or more vitamin D metabolites in a single assay.