A simple fluorescence pyrocatechol-polyethyleneimine detection method for 3-MCPD.

A rapid fluorescence detection method was established for 3-monochloropropane-1,2-diol (3-MCPD). The detection system works based on the fluorescence quenching of pyrocatechol-polyethyleneimine (PCh-PEI) polymer by 3-MCPD. The fluorescence quenching ability of 3-MCPD for PCh-PEI polymer was measured at different pH and temperatures. Indeed, in the presence of 3-MCPD, the fluorescence intensity of PCh-PEI polymer solution was quenched best at 100 °C and pH 8.5. Also, the effect of different concentrations of 3-MCPD on the optical properties of the PCh-PEI polymer was examined. Under optimal experimental conditions, fluorescence detection was linear in a range of 0.08-2.0 mg per L 3-MCPD, with a calculated detection limit of 0.06 mg L-1 and a correlation coefficient of 0.9974. Concisely, the reported method has good sensitivity and can be used for the rapid detection of 3-MCPD contamination in food products.

Fabrication of a Disposable Amperometric Sensor for the Determination of Nitrite in Food.

Silver nanoparticles (AgNPs) were synthesized through an environmentally friendly method with tea extract as a reduction agent. By immobilizing them on the surface of a low-cost pencil graphite electrode (PGE) with the aid of a simple and well-controlled in-situ electropolymerization method, a novel nanosensing interface for nitrite was constructed. The film-modified PGE showed good electrocatalytic effects on the oxidation of nitrite and was characterized through scanning electron microscopy, X-ray photoelectron spectroscopy, and electrochemical techniques. Characterization results clearly show that the successful modification of AgNPs improved the surface area and conductivity of PGEs, which is beneficial to the high sensitivity and short response time of the nitrite sensor. Under the optimal detection conditions, the oxidation peak current of nitrite had a good linear relationship with its concentration in the range of 0.02-1160 µmol/L with a detection limit of 4 nmol/L and a response time of 2 s. Moreover, the sensor had high sensitivity, a wide linear range, a good anti-interference capability, and stability and reproducibility. Additionally, it can be used for the determination of nitrite in food.

[Screening and quantitative analysis of nine illicit antiallergics in emulsion cosmetics by ultra-high performance liquid chromatography-quadrupole-time-of-flight high-resolution mass spectrometry].

A rapid and accurate analysis method based on ultra-high performance liquid chromatography coupled with quadrupole-time-of-flight high-resolution mass spectrometry (UPLC-Q-TOF-HRMS) was developed to screen and determine nine antiallergy drugs in emulsion cosmetics. First, a standard library of the target compounds was established. The library contained the TOF-MS information and secondary MS information such as retention time, ion addition mode, mass error, isotope distribution, mass-to-charge ratio of the parent ion, and fragment ion distribution. According to the European Union regulation (SANTE/11945/2015), the standard for the qualitative determination by HRMS was determined; that is, each compound was confirmed by two ions with a mass error below 5%, and the abundance ratio of the two ions was less than 30%. Second, the instrument conditions and sample pretreatment conditions for the determination of different compounds were optimized, and the influence of different levels of quantitative ions on the matrix effect was compared. The following observations were made:(1) the addition of 0.1% formic acid to the water phase improved the response of the chromatographic peaks; (2) among the various solvent amounts tested (4, 5, 6, 8 mL acetonitrile and 4, 5, 6, 8 mL methanol), 4 mL acetonitrile showed the best extraction efficiency; (3) PRiME HLB had a better purification effect than the other two purification columns (C18 and HLB solid-phase extraction cartridges), thus reducing the interference of impurities and ensuring good recovery of the target compounds; (4) the use of two pairs of secondary product ion quantification could significantly reduce the matrix effect of anti-allergic compounds and improve the quantification accuracy. Finally, based on the above findings, the experimental procedure was established. The lotion samples were first ultrasonically extracted with acetonitrile and purified on the PRiME HLB column. Chromatographic separation was performed on a Waters XBridge C18 column with gradient elution using 0.1% (v/v) formic acid in water and acetonitrile. Finally, the sequential window acquisition of all theoretical mass spectra (SWATH), which shows obvious advantages in continuous and high-throughput acquisition, was selected for MS data acquisition. The retention time, mass accuracy, isotope distribution, and fragment ion matching ratio were used for fast qualitative screening, while the peak areas of characteristic product ions were used for precise quantification. All the calibration curves showed good linearity (r2>0.99) within the tested ranges (5-100 µg/L) under the optimum conditions. The limits of quantification (LOQs) were in the range of 0.05-0.10 mg/kg. The recoveries were in the range of 65.3%-107% at three spiked levels (0.10, 0.20, and 0.60 mg/kg), with relative standard deviations (RSDs, n=6) below 20%. Compared with the existing ion exchange column methods, the proposed "one-step" purification method based on PRiME HLB is simpler and more rapid, where the extraction solution is filtered directly after allowing it to pass through the column, without any subsequent washing and elution procedures. In addition, the LOQs of this method are lower than those of other LC-MS/MS methods, indicating that the proposed method has higher sensitivity. The application of SWATH data acquisition makes it possible to achieve quantification with two pairs of product ions, thus reducing the matrix effect and ensuring accuracy of the quantitative results. Therefore, the proposed method is less time-consuming and operationally convenient, and it can be used for the rapid screening and accurate quantification of antiallergics in lotion samples.

[Determination of two non-phthalates plasticizers in edible oil by gas chromatography-tandem mass spectrometry].

A gas chromatography-tandem mass spectrometry (GC-MS/MS) method was developed for the simultaneous determination of di (2-ethylhexyl) terephthalate and tris (2-ethylhexyl) trimellitate in edible oils. The plasticizers in the samples were extracted with acetonitrile. The extract was purified by freezing at -20 ℃, and determined by GC-MS/MS in selective reaction monitoring mode. For the two compounds, the limit of detection and limit of quantification were 0.03 mg/kg and 0.1 mg/kg, respectively, and the linear range was 0.1-10 mg/kg. The recoveries of the two compounds ranged from 81.04% to 108.31% at three spiked levels (0.1, 0.3, and 1.0 mg/kg), and the relative standard deviation ranged from 0.70% to 9.91%. The method is simple, accurate, and suitable for the determination of di (2-ethylhexyl) terephthalate and tris (2-ethylhexyl) trimellitate in edible oils.

[Determination of sodium cyclamate in liquor by high performance liquid chromatography-tandem mass spectrometry with linear trap technology].

An accurate determination of quantitative and confirmative method for sodium cyclamate in liquor by high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) with linear trap technology has been established. Without pretreatment, the sample was directly injected after filtering through a 0.2 microm micro filter. The HPLC separation was performed on an Atlantis dC18 column (150 mm x 2.1 mm, 3 microm) by gradient elution with methanol and water containing 0.1% (v/v) formic acid. The eluent was determined and confirmed in multiple reaction monitoring-enhanced product ion (MRM-EPI) scan mode. The acquired data from MRM for the quantitative determination, and the product ion spectra were used for library search for qualitative confirmatory analysis. External standard was used for the quantitative determination of sodium cyclamate in liquor, and good linearity (r = 0.9991) was obtained over the range of 1.320 - 132.0 microg/L. The limit of detection (LOD, S/N = 3) for sodium cyclamate was 0.1 microg/L. The average recoveries ranged from 96.38% to 107.2% at the spiked levels of 2.640, 26.40 and 100.0 microg/L with the relative standard deviations (RSDs) less than 9%. The matching degrees of the spectra for all positive samples were higher than 92%. The method is simple, accurate and efficient for the determination of sodium cyclamate in liquor and particularly suitable for confirmatory analysis of positive samples.