Hydrogel particles and their use in cytometric applications are described. The hydrogel particles described herein are selectively tunable to have at least one optical property substantially similar to at least one optical property of a target cell. In this regard, the hydrogel particles provided herein, in one aspect, are used as a calibration reagent for the detection of a target cell in a sample.

The invention relates to a microbial test standard for use in infrared spectrometry which has at least two resealable vessels which are liquid-tight when closed, each of which contains a predefined amount of dried biomass of a microorganism. The microorganisms in the different vessels differ in at least one characteristic, which is selected in particular from the group comprising species, subspecies, strain, serovar, pathovar, toxivar and variety, and the difference manifests itself in a predefined intermicrobial spectral distance. The disclosure furthermore comprises a method of using the microbial test standard.

A method and a system for creating a reference standard for hydrogen sulfide concentrations in crude oil are described. The method includes receiving a volume of crude oil in a vessel. A hydrogen sulfide gas is flowed from a pressurized gas cylinder to the vessel to form a hydrogen sulfide gas-crude oil mixture. The hydrogen sulfide gas continues to flow from the pressurized gas cylinder to the vessel at a set pressure for a predetermined time to adjust the hydrogen sulfide concentration in the hydrogen sulfide gas-crude oil mixture to a hydrogen sulfide threshold concentration. The flow of the hydrogen sulfide gas into the vessel is stopped.

The present disclosure provides a filtration system for collecting Black Carbon (BC) samples present in snow samples and similar matrices which comprises the collection of BC in polycarbonate filters. It also discloses a method of determination of (BC) in snow samples and similar matrices using real soot from the gases of a diesel vehicle as calibration standards.

An embodiment provides a method for measuring zinc and copper in an aqueous sample, including: reducing an aqueous sample containing an amount of zinc and an amount of copper with a reducing agent; buffering the reduced aqueous sample; chelating the amount of copper in the buffered aqueous sample with a copper(I) chelating agent; measuring the amount of copper in the aqueous sample by measuring a first change in intensity of the absorbance of the copper chelated aqueous sample; chelating the amount of zinc in the buffered aqueous sample with a zinc(II) chelating agent; and measuring the amount of zinc in the aqueous sample by measuring a second change in intensity of the absorbance of the zinc chelated aqueous sample. Other aspects are described and claimed.

Hydrogel particles and their use in cytometric applications are described. The hydrogel particles described herein are selectively tunable to have at least one optical property substantially similar to at least one optical property of a target cell. In this regard, the hydrogel particles provided herein, in one aspect, are used as a calibration reagent for the detection of a target cell in a sample.

Systems and methods for measuring analytes in fluid samples are disclosed. The systems and methods employ test strips which are generally comprised of a substrate, at least one electrical connection, at least one sensing chemistry and at least one additional layer. The test strips can be batch calibrated.

Methods and apparatuses for rapid detection and quantification of analytes are disclosed. The analytes may be opioids such as fentanyl. The method includes the use of an internal standard. The internal standard is introduced into the unknown sample. The method may involve a separation step prior to an electrochemical detection step. In some embodiments, the separation step is omitted. The analyte may be selectively adsorbed onto a surface of an electrode by maintaining a potential on the electrode during which a solution containing the dissolved analyte flows through the electrode. Performing electroanalysis on the analyte-adsorbed electrode detects and quantifies only the adsorbed analyte. In some embodiments, the internal standard is methyl vanillate.

A composition of a bilimbin stock and a method of preparation are provided. In one aspect of the invention, the composition includes a base solution. The composition further includes a carbonate salt. Additionally, the composition includes bilimbin. Furthermore, the composition includes human serum albumin.

A molecular spectrophotometric method of high precision and accuracy for determining concentration of oil-derived hydrocarbons in water is described. The method allows to obtain direct measurements of oil mass concentration in a water sample and uses environmentally friendly solvents.