A method for preparing thin layers from liquid samples is disclosed. Such thin layers can be useful when analyzing samples with probes whose penetration length in these samples is short The method consists of squeezing a certain amount of a liquid sample between two approximately flat and parallel surfaces separated by a small distance then cooling down the liquid sample until it freezes in a way that the frozen sample adheres only to one of these two flat surfaces. Removing the non-adhered flat surface leaves the frozen sample layer with the thickness approximately equal to the initial distance between the two parallel surfaces.

A calibration device and a method of calibrating a mass spectrometer are described where two or more immiscible mass spectrometry calibration compounds in close proximity to each other share a common headspace volume above their liquid surfaces. This arrangement allows each calibrant to evaporate at differing rates while allowing the headspace concentrations to remain relatively unchanged over time (forming a quasi-equilibrium calibrant mixture). The mixture is either delivered to an ion source of a mass spectrometer or to a vacuum pump via a flow restrictor from a calibration vial. The calibrant gas mixture in the headspace volume may be used to calibrate a mass spectrometer.

The invention generally relates to methods of analyzing crude oil. In certain embodiments, methods of the invention involve obtaining a crude oil sample, and subjecting the crude oil sample to mass spectrometry analysis. In certain embodiments, the method is performed without any sample pre-purification steps.

An ionizer includes an ionization probe (21) provided with a capillary (211), a metallic slender tube (212), and a nebulizing gas pipe (213). The ionization probe (21) is equipped to perform ESI-based ionization of components in a liquid sample. An electroconductive capillary (22) is disposed at a position forward in a flow direction of a nebulized flow of the liquid sample from the ionization probe (21). A high voltage from a high voltage power supply (23) is applied to the electroconductive capillary (22) to induce corona discharge so that the components in the liquid sample are ionized by the APCI as well. At the time of tuning the ionizer, a standard sample solution is provided through the electroconductive capillary (22), and a high voltage from the high voltage power supply (23) is applied to the electroconductive capillary (22) so that components in the standard sample solution are ionized by the ESI or due to an ion molecular reaction with solvent molecular ions produced in the ionization probe (21). Thus, components in a standard sample can be ionized and subjected to mass spectrometry without pipe rearranging operations or without switch to and from different flow paths using a valve.

The invention relates to the detection of DHA and EPA. In a particular aspect, the invention relates to methods for detecting DHA and EPA by mass spectrometry and kits for carrying out such methods.

Provided herein are systems and methods for sampling analytes into an atmospheric pressure inlet mass spectrometer using ultrasonic nebulization-assisted atmospheric pressure chemical ionization. The systems can include a mass spectrometer having an input and an ultrasonic nebulizer chip. The ultrasonic nebulizer chip can be operatively coupled to the mass spectrometer, such that when the ultrasonic nebulizer chip nebulizes the analyte to provide a nebulized analyte, at least some of the nebulized analyte enters the input of the mass spectrometer.

The invention generally relates to ion generation using modified wetted porous materials. In certain aspects, the invention generally relates to systems and methods for ion generation using a wetted porous substrate that substantially prevents diffusion of sample into the substrate. In other aspects, the invention generally relate to ion generation using a wetted porous material and a drying agent. In other aspects, the invention generally relates to ion generation using a modified wetted porous substrate in which at least a portion of the porous substrate includes a material that modifies an interaction between a sample and the substrate.

An apparatus and method for detecting an analyte of interest using paper spray mass spectrometry includes a spray material; a sample on the spray material including an enzyme of interest; a solvent to hydrate the sample, promote enzymatic activity, and extract analytes of interest from the sample; a substrate specific to the enzyme of interest, wherein any of the spray material and the solvent includes the substrate; a voltage source to apply a voltage to the spray material to create charged droplets of a mixture containing the sample; and a mass spectrometer to perform spectrometry on the droplets to perform any of: identify the analytes of interest in the sample; and measure a level of inhibition in any enzymes contained in the sample.

Method for producing ions for mass spectrometry analysis, including introducing vaporized sample compounds behind a supersonic nozzle and expanding the sample compounds with a carrier gas from the supersonic nozzle into a supersonic nozzle vacuum chamber proximate thereto for vibrationally cooling the sample compounds prior to their ionization. Sample compounds are ionized by either illumination with vacuum ultra-violet photons produced by a continuously operated vacuum ultra-violet photon source or by electrons produced in a fly-through electron ionization ion source; and the ions are transferred to a mass analyzer mounted in a mass analyzer vacuum chamber to obtain mass spectra from vibrationally cold molecules. A quadrupole mass analyzer mounted may be used to obtain mass spectra with dominant molecular ions and fragment ion intensities below 3% of the molecular ion for hydrocarbons. Carrier gas flow rate may exceed 20 ml/min for vibrationally cooling the sample compounds prior to their ionization.

An ionizer includes a probe having multiple coaxially aligned conduits. The conduits may carry liquids, and nebulizing and heating gases at various flow rates and temperatures, for generation of ions from a liquid source. An outermost conduit defines an entrainment region that transports and entrains ions in a gas for a defined distance along the length of the conduits. In embodiments, various voltages may be applied to the multiple conduits to aid in ionization and to guide ions. Depending on the voltages applied to the multiple conduits and electrodes, the ionizer can act as an electrospray, APCI, or APPI source. Further, the ionizer may include a source of photons or a source of corona ionization. Formed ions may be provided to a downstream mass analyser.