Liren Chen

Simultaneous determination of sex hormones in egg products by ZnCl2 depositing lipid, solid-phase extraction and ultra performance liquid chromatography/electrospray ionization tandem mass spectrometry

A method was developed for simultaneous determination of residues of 17 sex hormones in egg products. Target compounds were extracted from samples with methanol in an ultrasonic bath, effectively separated from lipids in the extracts by ZnCl(2) depositing filtration and purified using a C(18) solid-phase extraction (SPE) and followed by NH(2) SPE cartridge. The analytes were quantified by liquid chromatography using a BEH C(18) column coupled to an electrospray ionization tandem mass spectrometer (LC-ESI-MS/MS) operating in negative mode for estrogens and in positive multiple reaction monitoring mode for androgens. The parameters of the mass spectrometer and the composition of mobile phase and additives were also optimized to enhance detection sensitivity. Average recoveries of the target compounds varied from 70.0% to 121.0% with relative standard deviations ranging from 2.3% to 11.2% at two fortification levels. The limits of detection (LOD) of the method were from 0.002 μg kg(-1) to 0.23 μg kg(-1) and the limits of quantification (LOQ) were in the range of 0.007-0.76 μg kg(-1).

Determination of inorganic ions in oil field waters by single-column ion chromatography

Abstract A new method to determine inorganic ions in oil field water by single-column ion chromatography is presented. On an anion-bonded column, using a mixture of sodium benzoate (1.5 m M ) and sodium citrate (0.1 m M ) as eluent, the Cl − , NO 3 − and SO 4 2 − in oil field water can be determined. On a cation-bonded column, using 1.5 m M HNO 3 as eluent, the Na + and K + in oil field water can be determined. If a mixture of oxalic acid and ethylene diamine (both at 1.5 m M ) is used as the eluent, then Mg 2 + , Ca 2 + , Sr 2 + and Ba 2 + can be determined. If the content of Cl − and Na + is much higher than that of other inorganic ions, the sample may be diluted to allow the determination of these ions. The proposed method is characterized by its simplicity, rapidity and accuracy. The results match those obtained with the current procedures used in oil fields.

Enantioseparation of novel chiral heterometal tetrahedral clusters by high-performance liquid chromatography.

A series of novel chiral heterometal tetrahedral clusters have firstly been separated on cellulose tris-(3,5-dimethylphenylcarbamate) stationary phase by high-performance liquid chromatography using n-hexane as the mobile phase containing different alcohols as modifiers. The effects of concentration and structures of alcohols in the mobile phases and structures of chiral heterometal tetrahedral clusters on enantioseparation were investigated. The results showed that the concentration and structures of alcohols had large effects on enantioseparation. It also was found that both the metal in the tetrahedral core and the ligand coordinated to the atom in tetrahedral core had significant effects on their chromatographic behavior.

[Simultaneous determination of seven sex hormones in fish products using ultra performance liquid chromatography-tandem mass spectrometry].

A rapid, specific and highly sensitive method for the determination of seven sex hormones (norgestrel, methyltestosterone, testosterone propionate, medroxyprogesterone acetate, megestrol acetate, chlormadinone acetate, and nandrolone) residues in fish products was developed using ultra performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) with electrospray ionization (ESI) in positive mode. The target compounds were extracted with methanol after the enzyme hydrolysis of the fish products. ZnCl2 was added to the extract solution to remove lipids. Then target compounds were purified by an LC-C18 and an LC-NH2 solid phase extraction cartridges. The target compounds were separated on a Waters ACQUITY UPLC BEH-C18 column (100 mm x 2.1 mm, 1.7 microm) and detected qualitatively and quantitatively in multi reaction monitoring (MRM) mode. For the seven sex hormones, the limits of detection (LOD) of the method were from 0.08 to 0.17 microg/kg and the limits of quantification (LOQ) were in the range of 0.24 -0.58 microg/kg. At the spiked levels of 1 and 4 microg/kg, the average recoveries ranged from 76% to 118% with the relative standard deviations between 5.0% and 11.3% for the seven sex hormones using internal standard method; and the average recoveries ranged from 66% to 94% with the relative standard deviations between 4.5% and 10.7% using matrix matched external standard method. The results showed that both methods are able to meet the multi-residue detection of the seven sex hormone residues in fish products. The degreased large yellow croaker and roast fish fillet real samples from a local market were detected by the developed method, and the seven targets were not found.

Ion chromatographic separation of metallic ions on a bonded poly-β-diketone-type non-cyclic crown ether stationary phase

Tetra(oxydimethyl) poly-β-diketone-type non-cyclic crown ether ion chromatographic stationary phase was prepared by grafting non-cyclic crown ether on silica gel modified previously with γ-aminopropyltriethoxysilane. The chromatographic behavior of this stationary phase was studied. Very good separation was obtained for alkali, alkaline earth and transition metals on this stationary phase using methanol and water of various proportions as mobile phase.