A method of detecting gas includes determining and storing, by a controller, a zero level of a photoionization detector using ambient air inflow when an ultraviolet lamp is in a turned OFF state, wherein the stored zero level is based on an ambient temperature; sampling, by the controller, an output of a detector electrode of the photoionization detector when the ultraviolet lamp is in a turned ON state; and comparing the sampled output of the detector electrode to the stored zero level to determine if a threshold concentration of a gas is present.

A response factor that is a signal strength ratio with respect to a reference compound for various compounds is previously stored in a response factor storage (22). When an operator instructs to estimate an analysis limit value, a measurement unit (1) performs GC-MS analysis on a sample containing the reference compound a plurality of times under control of an analysis controller (3). A signal strength calculator (23) obtains a signal strength value of the reference compound based on an analysis result of the measurement unit (1), a relative strength calculator (24) calculates a relative standard deviation from the plurality of measured signal strength values, and calculates the relative standard deviation of a target compound from the response factor of the target compound read from the response factor storage (22). An analysis limit value estimator (25) estimates a limit of detection (LOD) and the like from the relative standard deviation of the target compound by a known method, and displays the LOD on a display (6). Consequently, the analysis limit value can simply be obtained without actually measuring the target compound.

A method for evaluating performance of a natural gas analysis system includes obtaining components of a natural gas analysis system as well as the maximum allowable error and the maximum allowable deviation of a calorific value of each of the components. The method includes determining components and uncertainties of a standard gas mixture; obtaining a final peak area of each of the components in each group of standard gas mixture. The method includes obtaining calibration functions of the natural gas analysis system and analytical functions of respective components. The method includes obtaining an uncertainty and a calorific value uncertainty of each of the components. The method includes judging whether the evaluation result from the natural gas analysis system to be evaluated is qualified, and providing a performance evaluation conclusion for the natural gas analysis system.

A modular gas detection system includes a primary gas chromatograph, a constant volume extractor positionable to provide a continuous fluid sample to the primary gas chromatograph, and a total hydrocarbon analyzer. The modular gas detection system also includes a processing device and a memory device including instructions executable by the processing device for causing the processing device to perform operations. The operations include adjusting a detection scheme of the primary gas chromatograph to update a detection range for the continuous fluid sample to detect different hydrocarbons within a single column. Further, the operations include controlling routing of the continuous fluid sample from the constant volume extractor to the primary gas chromatograph and the total hydrocarbon analyzer.

A chromatography system has an associated system volume and a sample dispersion volume. The chromatography system comprises a pump pumping a flow of gradient, a sample manager for introducing a sample into the flow of gradient, and a valve manager fluidically coupled to the pump and to the sample manager. The valve manager includes at least one valve. A first valve of the at least one valve has a plurality of ports including an inlet port that receives the flow of gradient from the pump and an outlet port through which the flow of gradient exits the first valve. The first valve has at least two different, automatically selectable positions. A first position of the at least two different automatically selectable positions operating to change one of the system and sample dispersion volumes of the chromatography system when the first valve is automatically switched into the first position.

An automated method of monitoring a state of an analyzer is provided including a mass spectrometer (MS) with an electrospray ionization (ESI) source coupled to a liquid chromatography (LC) stream, including monitoring an electrospray ionization current of the ESI source and identifying a condition of multiple conditions of the analyzer based on the monitored ionization current of the ESI source, one of the conditions being a presence of a dead volume in a liquid chromatography stream of the analyzer downstream of an LC column of the LC stream.

A method and kit for detecting at least two vitamin D metabolites in a biological sample is disclosed, which comprises processing the biological sample to prepare the sample for LC-MS/MS analysis, passing the prepared sample through a liquid chromatography column having an outlet connected to an inlet port of a tandem mass spectrometer to separate said two vitamin D metabolites, if present in the sample, and introduce the two vitamin D metabolites into the tandem mass spectrometer. The method further comprises generating [M+H].sup.+ ions of each of the two vitamin D metabolites in said tandem mass spectrometer, and generating two fragment ions of said [M+H].sup.+ ions associated with said vitamin D metabolites, wherein said fragment ions are not due to water losses from the [M+H].sup.+ ions; and detecting the fragment ions to identify presence of the two metabolites in the biological sample.

The present disclosure relates to methodologies, systems, apparatus, and kits for diagnosing the condition of a restrictor element in a chromatography system based on flow rate measurements, or pressure measurements, or both.

Disclosed are methods and systems for quantitation of benzene, toluene, ethyl benzene, o-xylene, m-xylene, and p-xylene. High-performance liquid chromatography using a carbon stationary phase and a gradient mobile phase is performed. The carbon stationary phase can be a porous graphitic carbon stationary phase. The mobile phase includes an organic acid in water and an alcohol. The organic acid can include formic acid, and the alcohol can include methanol. The methods and systems achieve a resolution between xylene isomer peaks of greater than 2.0.

Systems and methods are described for reducing lab-to-lab and/or instrument-to-instrument variability of Multi-Attribute Methods (MAM) analyses via run-time signal intensity calibration. In various aspects, multiple MAM-based instruments each have detectors and different instrument conditions defined by different instrument models or sets of settings. Each MAM-based instrument receives respective samples and a reference standard as a calibrant. Each MAM-based instrument detects, via its detector, sample isoforms of its respective sample and reference standard isoforms of the reference standard. The MAM-based instruments are associated with processor(s) that determine, via respective MAM iterations, correction factors and sample abundance values corresponding to the sample isoforms. The correction factors are based on the reference standard, and the sample abundance values are based on the correction factors. A variance value of the sample abundance values may be reduced based on correction factors of each of the MAM-based instruments.