[Application progress of on-line sample preparation techniques coupled with liquid chromatography-mass spectrometry system in the detection of food hazards].

Food safety has received increased attention, and food detection is of great significance. The food matrix is complex, and diverse food hazards have been identified. Thus, the detection methods and sample preparation techniques for food matrices must be continuously optimized and updated. Several steps are usually required when a chromatographic system is used to determine food hazards: sample preparation, that is, the separation of targets from different substrates using a suitable preprocessing method and target-substance separation and purification, which is usually achieved using chromatographic separation. The selection of an appropriate detector for qualitative and quantitative analyses is usually based on the properties of the target compound. The sample preparation procedure is considered the most time-consuming aspect of the entire food-analysis process. It is also prone to analytical errors. Therefore, optimization of the sample preparation process is a key issue in the field of chemical analysis. Researchers have developed a series of new, efficient, and accurate sample preprocessing methods, and an on-line sample-preparation system has been found to be a feasible approach. On-line sample preparation coupled with liquid chromatography-mass spectrometry (LC-MS) presents many advantages. First, manual operation could reduce analytical errors to ensure good accuracy and repeatability. It could also reduce the consumption of chemical reagents and avoid cross-contamination between samples. Furthermore, an on-line sample-preparation system could shorten the sample-preparation time and improve the detection efficiency. On-line sample preparation coupled with LC-MS has been widely applied in the fields of environment, biology, and food. On-line sample preparation systems coupled with LC-MS are divided into two modules: the first modules involves sample preparation and the second module involves the LC system. The first module remove impurities and isolates the target compounds in preparation for their qualitative and quantitative detection. The coupling of these two modules depends mainly on valve switching. In this paper, we introduce the most frequently used on-line sample-preparation techniques, including on-line solid phase extraction (on-line SPE), in-tube solid phase microextraction (in-tube SPME), and turbulent chromatography (TFC). We then describe the basic principles and coupling equipment of these three on-line analytical technologies in detail. The coupling equipment establishes a physical connection between the two modules. Next, we discuss the properties of different purification fillers in an on-line sample-preparation column. The applications and research progress of on-line systems for pesticide residues, veterinary drug residues, and biotoxins are also discussed. Compared with offline sample preparation, on-line analytical systems present several advantages. On-line analytical systems can not only greatly reduce the analysis time and solvent consumption but also improve the detection sensitivity and accuracy. Such systems can be used to determine food hazards to ensure food safety. Finally, the existing problems and development trends of on-line analytical systems are discussed and prospected. To promote the applications of on-line analytical technology in food-safety detection, we suggest that the following three aspects be considered. First, more on-line purification columns with novel fillers, in addition to C18 or polymer fillers, should be developed. Second, compared with ordinary detectors, high-resolution MS detectors have better precision and accuracy. Coupling on-line analytical technologies with a high-resolution mass spectrometer may be beneficial for the further development of on-line analyses. Third, different food matrices should be compared and evaluated to continuously optimize the detection process and improve the efficiency of on-line analytical systems. As concerns regarding food safety issues have increased, the applications of on-line analytical technologies for food detection can be expected to become increasingly important.

Determination of Deoxynivalenol and Its Derivative in Corn Flour and Wheat Flour Using Automated On-line Solid-Phase Extraction Combined with LC-MS/MS.

An automated on-line solid-phase extraction (SPE) combined with LC-MS/MS method was developed for determination of deoxynivalenol (DON), 3-acetyl-DON and 15-acetyl-DON in corn flour and wheat flour samples. The extraction solvent of the samples was injected into the automated on-line SPE system to remove matrix interference. After washing step, the targets were eluted from the SPE cartridge into liquid chromatography (LC) column. Several SPE parameters including injection volume, elution volume and eluting flow rate were assessed and optimized. Method validation was evaluated and good linearity was obtained (R2 > 99%) with the limit of detection of 0.1-0.2 µg/kg. Recoveries were evaluated in spiked corn flour and wheat flour samples at three concentrations and the values ranged from 86.5% to 99.7%. The benefit of the present method with automated on-line SPE system is the ability to inject directly pure extracts into LC-MS/MS, offering faster analyses and improving analysis efficiency.

[Determination of ten alkaloids in cosmetics by high performance liquid chromatography-tandem mass spectrometry].

A high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) method was established for the determination of ten alkaloids in cosmetics. Extraction conditions, purification methods and instrumental parameters were optimized. The samples were ultrasonically extracted with 80% (v/v) methanol aqueous solution. The extracts were separated and filtered after centrifugation. The analytes were separated on a Waters BEH C18 column, and detected in the selected reaction monitoring mode. Ten alkaloids were quantified by the external standard method. The ten alkaloids showed good linearity with correlation coefficients (R2) greater than 0.9900. The limits of detection (LODs) and the limits of quantification (LOQs) of the ten alkaloids were in range of 5.0-12.5 µg/kg and 12.5-50.0 µg/kg, respectively. The average spiked recoveries in the cosmetics ranged from 70.91% to 116.75%, and the relative standard deviations (RSDs) ranged from 0.49% to 9.98%. The method can be used for the rapid screening and quantitative analysis of ten alkaloids in cosmetics.

Natural zwitterionic l-Carnitine as efficient cryoprotectant for solvent-free cell cryopreservation.

Organic solvents, such as dimethyl sulfoxide (DMSO) and glycerol, have been commonly used as cryoprotectants (CPAs) in cell cryopreservation. However, their cytotoxicity and need of complex freezing protocols have impeded their applications especially in clinical cell therapy and regenerative medicine. Trehalose has been explored as a natural CPA to cryopreserve cells, but its poor cell permeability frequently results in low cryopreservation efficacy. In this work, we presented that a natural zwitterionic molecule-l-carnitine-could serve as a promising CPA for solvent-free cryopreservation. We demonstrated that l-carnitine possessed strong ability to depress water freezing point, and with ultrarapid freezing protocol, we studied the post-thaw survival efficiency of four cell lines (GLC-82 cells, MCF-7 cells, NIH-3T3 cells and Sheep Red Blood Cells) using l-carnitine without addition of any organic solvents. At the optimum l-carnitine concentration, all four cell lines could achieve above 80% survival efficiency, compared with the significantly lower efficiency using organic CPAs and trehalose. After cryopreservation, the recovered cell behaviors including cell attachment and proliferation were found to be similar to the normal cells, indicating that the cell functionalities were not affected. Moreover, l-carnitine showed no observable cytotoxicity, which was superior to the organic CPAs. This work offered an attractive alternative to traditional CPAs and held great promise to revolutionize current cryopreservation technologies, to benefit the patients in various cell-based clinical applications.

Natural zwitterionic betaine enables cells to survive ultrarapid cryopreservation.

Cryoprotectants (CPAs) play a critical role in cryopreservation because they can resist the cell damage caused by the freezing process. Current state-of-the-art CPAs are mainly based on an organic solvent dimethyl sulfoxide (DMSO), and several DMSO-cryopreserved cell products have been brought to market. However, the intrinsic toxicity and complex freezing protocol of DMSO still remain as the bottleneck of the wide use for clinical applications. Herein, we reported that betaine, a natural zwitterionic molecule, could serve as a nontoxic and high efficient CPA. At optimum concentration of betaine, different cell types exhibited exceptional post-thaw survival efficiency with ultrarapid freezing protocol, which was straightforward, cost efficient but difficult to succeed using DMSO. Moreover, betaine showed negligible cytotoxicity even after long-term exposure of cells. Mechanistically, we hypothesized that betaine could be ultra-rapidly taken up by cells for intracellular protection during the freezing process. This technology unlocks the possibility of alternating the traditional toxic CPAs and is applicable to a variety of clinical applications.