Disclosed herein are methods for chromatography, including cleaning methods for chromatography medium that make use of a linear salt gradient. The disclosed methods may be used for frontal chromatography operations and for cleaning frontal chromatography media for reuse in biologics manufacturing.

A method and apparatus for detecting mercury in air includes passing a substantial quantity of air through a concentrator column containing gold film whereby a gold-mercury amalgam is formed, purging the concentrator column with nitrogen gas for a predefined period of time to remove oxygen and other organics from the concentrator column, quickly heating the concentrator column to a substantial temperature to decompose the gold-mercury amalgam forming mercury gas, and injecting the mercury gas into a photoionization detector system. The apparatus includes a quartz housing having a quartz body defining an internal volume, a gas inlet, a gas outlet, and a heater end, and a concentrator element sealingly disposed within the quartz housing, the concentrator element having a first element portion and a second element portion, a film of gold deposited on at least a first element portion disposed in the quartz body.

In one aspect, disclosed herein is a method for determining sulfate concentration in a sample, comprising: a) providing a liquid sample comprising urea and at least one impurity; b) concentrating the liquid sample under conditions effective to reduce the liquid volume; c) forming a dilute sample solution by diluting the concentrated liquid sample of step b) in water; and d) analyzing the dilute sample solution of step c) with ion chromatography to determine if a concentration of sulfate is present in the provided liquid sample of step a); wherein the analyzing of step d) is capable of determining the presence of a sulfate concentration present in an amount less than about 1 ppm.

Methods and systems for determining relative response factors for liquid chromatography using both molar concentration-based detection and mass concentration-based detection are described herein. A method includes determining a relative response factor for a compound based on the ratio of a molar-based peak area for the compound to the logarithm of the mass-based peak area for the compound and based on the ratio of a molar-based peak area for a reference compound divided by the logarithm of the mass-based peak area for the reference compound.

HPLC-based quality control systems to perform quality control testing on a radiopharmaceutical solution shortly after synthesis. An HPLC-based quality control system makes efficient use of sample volume and is compatible with a variety of radioisotopes and radiopharmaceutical compounds. In several embodiments, the automated nature of an HPLC-based quality control system allows for quality control tests to be conducted quickly and with minimal impact on user workflow. When used as part of an integrated PET biomarker radiopharmaceutical production system, the present general inventive concept permits a manufacturer to produce product and conduct quality control tests with lower per dose costs.

A method for detecting contamination of a food sample with a target analyte by detecting whether the target analyte exceeds a maximum residue limit (MRL) of the target analyte in the food sample considering matrix effects specific to the food sample and essentially without requiring construction of a calibration curve. The method includes spiking the food sample with a stable isotope-labeled analyte analogous to the target analyte at a concentration of L.sub.eq equivalent to the MRL of the target analyte. L.sub.eq is defined by the following operation,

[00001]$L_{\mathrm{eq}}=W_N\frac{\mathrm{MW}\left(L\right)}{\mathrm{MW}\left(N\right)}\frac{\mathrm{purity}\left(N\right)}{\mathrm{purity}\left(L\right)}.$

The method further includes extracting the stable isotope-labeled analyte and the target analyte from the spiked food sample, generating an ion chromatogram including a first peak representing the stable isotope-labeled analyte and a second peak representing the target analyte, and calculating and comparing respective areas under the first peak and the second peak.

An analytical method for performing, in parallel, a first analysis step of introducing a non-derivatized first sample 132 into a first column 44 together with a first mobile phase 54, and analyzing components contained in the first sample 132; and a second analysis step of introducing a derivatized second sample 137 into the second column 84 together with a second mobile phase 94, and analyzing components contained in the second sample 137, wherein the first sample 132 contains inosinic acid and guanylic acid, and in the first analysis step, by separating components contained in the first sample 132 using the first column 44 having a length of 185 mm or more, a chromatogram is obtained in which peaks corresponding to inosinic acid and guanylic acid are separated with a separation degree of 1.5 or more.

To analytically determine concentration of dissolved gases in a water pipeline, a water sample is drawn from a source carrying water with dissolved gas, through a water source port of a four-way valve. The water sample is flowed from the water source port towards a syringe port of the valve and into a syringe fluidically coupled to the syringe port to hold the water sample. Inert gas is drawn through an inert gas port of the valve from an inert gas source and is flowed from the inert gas port towards the syringe port and into the syringe. A mixture of the water sample and the inert gas is flowed from the syringe port towards an analyzer port of the valve and into an analyzer fluidically coupled to the analyzer port.

HPLC-based quality control systems to perform quality control testing on a radiopharmaceutical solution shortly after synthesis. An HPLC-based quality control system makes efficient use of sample volume and is compatible with a variety of radioisotopes and radiopharmaceutical compounds. In several embodiments, the automated nature of an HPLC-based quality control system allows for quality control tests to be conducted quickly and with minimal impact on user workflow. When used as part of an integrated PET biomarker radiopharmaceutical production system, the present general inventive concept permits a manufacturer to produce product and conduct quality control tests with lower per dose costs.

Methods of assessing purity of cytisine using gradient chromatography at multiple wavelengths is provided herein.