The measurement of glutaraldehyde-based biocides in seawater without the use of a derivatization agent. The measurement of glutaraldehyde-based biocides in seawater may be performed without additional components to reduce background interferences. The concentration of a glutaraldehyde-based biocides in a seawater sample is determined using reversed phase liquid chromatography and a gradient mobile phase of acetonitrile and deionized water. Systems for determining the concentration of glutaraldehyde-based biocide in a seawater injection system are also provided.

The invention relates to a method for the determination of crocetin and its derivative amounts and the derivative composition from gardenia yellow. The method mainly comprises of following steps: the absorbance measurement of a gardenia yellow aqueous solution at known concentration by UV-VIS, the absorption coefficient measurement of total crocetin derivative, the total crocetin derivative amount calculation according to Lambert-Beer law, the relative amount calculation of each crocetin derivative from its absorption coefficient and peak area on HPLC, the amount calculation of each crocetin derivative from the total amount of crocetin derivative and the relative amount of each crocetin derivative, and finally total crocetin amount calculation. In practice, the absorption coefficient of each crocetin derivative is calculated from that of its root structure, crocetin, based on the negative correlation-ship of absorbance with molecular mass of the molecule while the molecular mass of each crocetin derivative is substituted by the m/z value of its parent ion.

The invention provides methods and formulations comprising a protein comprising solvent accessible amino acid residues susceptible to oxidation wherein N-acetyl tryptophan (NAT) is used to prevent oxidation of the protein. The invention also provides methods for making such formulations and methods of using such formulations. Methods to measure degradation of NAT in protein formulations are also provided.

Disclosed herein is a method for selectively reducing, using electrical energy, CO.sub.2 to formic acid, a catalyst for use in the method, and an electrochemical reduction system. The method for producing formic acid by electrochemically reducing carbon dioxide of the present invention includes (a) reacting carbon dioxide with a metal complex represented by formula (1), and (b) applying a voltage to a reaction product of the carbon dioxide and the metal complex represented by formula (1):

##STR00001##

A pre-analysis treatment device usable for an amino acid, organic acid, and glucide includes an ion-exchange unit configured to load a test sample on a solid-phase cartridge S having a strong ion-exchange resin phase, to allow the strong ion-exchange resin phase to adsorb a predetermined organic compound, then supply a dehydration solvent to dehydrate the strong ion-exchange resin phase, and a derivatization unit configured to feed a predetermined amount of the derivatization reagent to the dehydrated strong ion-exchange resin phase to allow the derivatization reagent to retain for a predetermined time period, thereby trimethylsilylating the organic compound adsorbed on the strong ion-exchange resin phase, and simultaneously desorbing the trimethylsilylated organic compound from the strong ion-exchange resin phase, and then supply a push-out solvent to push the trimethylsilylated organic compound desorbed, out of the solid-phase cartridge S. The device enables at least one organic compound selected from amino acids, organic acids and glucides contained in a test sample to be derivatized and collected easily in a short period of time, and automation of the pre-analysis treatment.

The disclosure relates to a gradient twin column recycling chromatography method that is used to separate a mixture containing closely eluting compounds. In one embodiment, a sample includes a primary organic compound and one or more impurities that closely elute with the primary organic compound. A gradient mobile phase is initially used to remove unwanted early eluting and late eluting impurities from the sample. After the gradient removal of some of the impurities is complete, the remaining mixture of the primary organic compound and the closely eluting impurities are separated using recycle chromatography methodology with an isocratic mobile phase.

There are only two ways to increase the amount of sample that can be purified by preparative reversed phase high performance liquid chromatography (Prep-RP-HPLC) in a single run: (1) The traditional approach is to use a bigger column (greater amount of stationary phase); and (2) Use displacement chromatography which uses the stationary phase more effectively. This invention describes a unique Prep-RP-HPLC technique that uses a C-18/C-8 derivatized silica coated with a hydrophobic quaternary ammonium salt or quaternary phosphonium salt to result in 7 to 12 fold increase in sample loading (of the crude mixture of organic compounds including synthetic crude peptides) in contrast to the conventional Prep-RP-HPLC technique. This increase in sample loading capacity and output is due to the additional surrogate stationary phase characteristic of the C-18/C8 bound quaternary salt. The quaternary surfactant is bound to the C-18/C-8 chains and silanols of the stationary phase.

A gas chromatographic (GC) column using a zwitterionic compound and methods of use thereof are disclosed herein. The volatile free acids were observed to strongly retain on these zwitterionic compounds-based columns with excellent peak symmetry. By carefully tuning the structures of these zwitterionic compounds, different selectivity toward volatile free acids was demonstrated. These stationary phases possess a wide working range with thermal stabilities at higher temperatures.

An automated dispersive liquid-liquid microextraction method of detecting and quanta N-nitrosamines in an aqueous sample. The method includes (a) extracting an aqueous solution containing the N-nitrosamines by mixing an extraction solvent and a dispersive solvent with the aqueous solution, such that the N-nitrosamines, or a portion thereof, re-distribute from the aqueous solution to the extraction solvent, (b) permitting the resulting mixture in (a) to form a two-phase mixture containing an aqueous phase comprising containing the aqueous solution with reduced amounts of the N-nitrosamines and an organic phase containing the extraction solvent with the N-nitrosamines extracted from the aqueous solution, (c) injecting the organic phase, or a portion thereof, into an injection port of a gas chromatograph coupled with at least one mass spectrometer, and (d) analyzing the N-nitrosamines by gas chromatography and mass spectrometry to detect and quantify the concentration of the N-nitrosamines in the aqueous solution.

A catalyst-free electrochemical deuteration method using deuterium oxide as a deuterium source, adding an electrolyte, an organic compound containing an ethylenic bond or acetylenic bond, deuterium oxide, and an organic solvent into a reactor, applying a direct current voltage of 4-8 V between electrodes of a carbon felt in an atmosphere of an inert gas for an electrolytic reaction, to obtain a product, and purifying the product to obtain a deuterated product. In the method provided by the present disclosure, with the organic compound containing an ethylenic bond or acetylenic bond as a raw material, deuterium oxide as a deuterium source, cheap and readily available carbon electrode materials as cathodes and anodes, it is possible to obtain deuterated products by a direct current electrolysis in an organic solvent, without any transition metal catalysts.