Determination of benzo(a)pyrene in fried and baked foods by HPLC combined with vesicular coacervative supramolecular solvent extraction.

A simple, rapid and low-cost determination method of benzo(a)pyrene in fried and baked foods was proposed by high performance liquid chromatography combined with vesicular coacervative supramolecular solvent (SUPRAS) extraction. The vesicular coacervate was composed of 1-octanol and tetrabutylammonium bromide. 200 mg of dried samples with 600 µL SUPRAS could be mixed to extract benzo(a)pyrene. Neither evaporation nor further clean-up steps for the extracts were needed. The overall sample treatment took approximately 30 min, and several samples could be simultaneously treated using conventional lab equipment. Then, benzo(a)pyrene was analyzed via liquid chromatography-fluorescence detection. Parameters affecting the extraction efficiency were investigated and optimized. The results showed good linearity of benzo(a)pyrene with the coefficients of determination (R 2) of more than 0.9999 in the range of 0.1-50.0 µg/kg. The limit of detection of the method was 0.11 µg/kg. Recoveries for spiked samples in the range of 1-10 µg/kg were between 89.86 and 100.01%, with relative standard deviations from 1.20 to 3.20%. Benzo(a)pyrene was present in food samples (including instant noodles, biscuits, rice crust and fried bread stick) at concentrations in the range of 0.08-0.39 µg/kg according to the proposed method. The proposed pretreatment method significantly reduces the analysis time. Furthermore, the solventless approach is in accordance with the green chemistry development trend and has significant application prospects.

[Research advances in nano liquid chromatography instrumentation].

The miniaturization of liquid chromatography equipment is among the most important focus areas in chromatographic technology. It involves the miniaturization of the physical dimensions of the instrument, size of the separation material, and inner diameter of the column. The advantages of a reduced inner diameter of the column have been investigated for several decades, and can be summarized as follows. First, the sample consumption is lower, which is particularly beneficial when a limited amount of sample is available, as is the case with natural products, and in biochemistry and biomedicine. Second, the consumption of the mobile phase is reduced, making the process environmentally friendly and facilitating green chemistry. This allows the addition of more expensive solvent additives, such as chiral additives or isotopic reagents, while maintaining a low analysis cost. Moreover, the degree of band dilution in the column is lower than that with conventional liquid chromatography under the same sample injection conditions. Thus, enhanced mass sensitivity is achieved. Other benefits of a reduced inner diameter of the column include temperature control due to effective heat transfer through the columns and easier coupling to mass detectors, which is particularly advantageous for analyzing complex samples. Typically, the term “nano liquid chromatography” is associated with liquid chromatography, which employs capillary columns of inner diameters less than 100 μm and flow rates in the range of tens to hundreds of nanoliters per minute. Because of the extremely low flow rates and small column volume, the extra-column effect becomes more prominent. Thus, the requirements for every component of liquid chromatographs are augmented toward improving their performance and optimizing the extra-column band broadening of the entire system. The solvent delivery equipment should be able to pump mobile phases accurately and steadily at nanoliter-level flow rates. A gradient mode is required to achieve this, which implies that the lowest flow rate for a single pump unit should reach a few nanoliters per minute. A certain operating pressure is also necessary to employ columns with different inner diameters and particle sizes. A precise and repeatable sample injection procedure is essential for nano liquid chromatography. The injection volume and mode should be suitable for capillary columns, without inducing a significant extra-column effect. A higher-sensitivity detector should be employed, and sample dispersion should be limited. The improved tubing and connection method in nano liquid chromatography should offer stability, reliability, and ease of operation. The extra-column volume should also be restricted to suit nanoliter-level flow rates. Considering that most nano liquid chromatographic instruments have been coupled with a mass detector, this review mainly focused on nanoliter solvent delivery modules, sample injection modules, and tubing and connection modules. By searching and summarizing research articles, technical patents, and brochures of instrument manufacturers, technical routes and research progress on these modules were described in detail. The pump designs can be classified into four types. Pneumatic amplifying pumps have been used in ultra-high-pressure applications. The flow-splitting delivery system, though easy to realize, may lead to a large amount of solvent wastage. Splitless pumps, which are classified based on two main principles, are widely used. Some pumps based on other physical phenomena have been suggested; however, they lacked stability and robustness. Two types of injection modes have been utilized in nano liquid chromatography. The direct nanoliter injection mode typically takes advantage of the groove on the rotor of a switching valve. The trapping injection mode uses trap columns to enable the introduction of large sample volumes. As for the tubing and connection, a few appropriate designs can be acquired from commercial suppliers. The robustness has been improved using some patented technologies. The optimization principles and research progress on optical absorption detection are briefly introduced. Finally, commercial nano liquid chromatographic systems are compared by considering the pumps and injectors.

[Integrated multi-column two-dimensional liquid chromatographic system for determination of amisulpride in serum].

Amisulpride is a clinically effective antipsychotic drug. It has been recommended for therapeutic drug monitoring in Consensus Guidelines for Therapeutic Drug Monitoring in Neuropsychopharmacology. An integrated multicolumn two-dimensional liquid chromatography system was constructed. Two reversed-phase columns, Supersil ODS2 (150 mm×4.6 mm, 5 µm) and SinoChrom ODS-BP (150 mm×4.6 mm, 5 µm), with different hydrophobicities were employed in the first and second separation dimensions, respectively. A strong cation-exchange short column, Supersil SCX (10 mm×4.6 mm, 5 µm) was used to trap samples after the first dimensional separation. A two-position six-port valve was applied to change the flow path for transferring the samples. An auxiliary pump was used to change the mobile phase between the first dimensional column and the trapping column. An intact method for analyzing amisulpride in serum was developed using an integrated multicolumn two-dimensional liquid chromatography system. Serum samples were pretreated only by protein precipitation and centrifugation. In the protein precipitation step, a mixture of perchloric acid (6%, v/v) and methanol was used as the precipitation reagent, whose volume was three times that of the serum sample. The use of this reagent helped eliminate the obvious solvent effects resulting from the large injection volume (300 µL). Then, the samples were vortexed for 2 min and centrifuged for 5 min at a velocity of 10000 r/min. The supernatant was injected into the system directly. Acetonitrile/phosphate buffer (25 mmol/L, pH 3.0; 20∶80, v/v) and acetonitrile/phosphate buffer (25 mmol/L, pH 7.0; 25∶75, v/v) were used as mobile phases for the first and second dimensions, respectively, at a flow rate of 1 mL/min. The solvent strength and pH of the first dimensional eluent were adjusted at the two-dimensional chromatographic interface. Phosphate buffer (25 mmol/L, pH 3.0) was supplied at a rate of 1 mL/min by the auxiliary pump for adjustment. The adjustment process allowed amisulpride to remain cationic, thus leading to improved transfer and trapping efficiencies in strong cation-exchange columns, in the heart-cutting mode. The trapping time was determined to be between 4 and 5 min by a confirmation experiment. The use of a short trapping column and the appropriate mobile phase conditions allowed us to complete the analysis within 12 min. The established method was validated in detail by investigating the linearity, limit of detection (LOD), limit of quantification (LOQ), and recovery. A good linear relationship was observed between 10 and 200 ng/mL (r=0.9998). The LOD and LOQ were 7.28 ng/mL and 24.27 ng/mL, respectively. The high sensitivity of the validated method met the requirements of the therapeutic reference range of the Consensus Guidelines for Therapeutic Drug Monitoring in Neuropsychopharmacology. The recovery of amisulpride spiked in a serum sample at 50 and 100 ng/mL were stabilized between 73.7% and 76.8%, which revealed the good stability of the established method. As opposed to the complicated traditional analytical methods, our method based on the automated integrated system is cost-effective and low-maintenance, thus being appropriate for routine therapeutic drug monitoring in clinical research. Moreover, our method is highly promising as the system cost is much lower than that of the popular LC-MS, while the capacity is sufficient for the determination of drugs in serum.

[Development and evaluation of a single stroke direct-driven ultrahigh pressure nano pump].

With the development of life science, nano liquid chromatography systems are being involved in various applications in the field of biochemical analysis. Being one of the key components in the system, the nano flow rate pump directly affected the accuracy and repeatability of the analysis. Based on two high precision direct-driven motors and a ten-port switch valve, a single stroke direct-driven ultrahigh pressure nano pump was developed. The results show that the accuracy of the flow rate and stability were better than 1% and 0.7%, respectively, at 500 nL/min. The maximum operating pressure was more than 100 MPa, and the gradient deviation was lower than 1%. The nano pump was used to construct a nano liquid chromatography-mass spectrometry system. A bovine serum albumin (BSA) digest (1 µg) was analyzed by the system, and a sequence coverage of 45% was achieved. Furthermore, 2809 proteins were identified from a 1.25 µg Hela cell digest. All these results demonstrated that the single stroke direct-driven ultrahigh pressure nano pump could be a useful tool in the biochemical analyses, especially for proteome research.

[Analysis of traditional Chinese medicine components by high performance liquid chromatography with diode array detection based on double qualitative principles].

The double qualitative principle is a new composite qualitative method based on retention time and the characteristic peaks of the absorption spectra. Using a self-designed and assembled diode array detector (DAD), a high performance liquid chromatography (HPLC) system was constructed. The illegal additive auramine O in six kinds of herbal slices and the active ingredient schisandrin in Jujube kernel Tianma capsules were separated and qualitative analyzed using the HPLC-DAD system. The results showed that there were similar peaks in the chromatograms of pollen typhae and Jujube kernel Tianma capsules when comparing the target analytes. However, the probabilities of the targets were excluded by comparing the absorption spectra. The application results indicated that, based on the double qualitative principle of retention time/absorption spectrum, the interference of impurities in the samples could be well eliminated and the false positives could be avoided. This provides a reference method for the study of traditional Chinese medicine components.

[Supramolecular solvent-based direct extraction for the determination of polycyclic aromatic hydrocarbons in water].

Supramolecular solvent (SUPRAS) is a nano-structured liquid generated from amphiphiles through a sequential self-assembly process. It is an efficient and excellent solvent for the sample extraction. In this paper, a method to directly extract and rapidly analyze polycyclic aromatic hydrocarbons (PAHs) in water samples by high performance liquid chromatography-fluorescence detection (HPLC-FLD) was developed. The composition and amount of SUPRAS were optimized and practical samples were tested. It indicated that the combination of tetrahydrofuran and 1-octanol was a suitable SUPRAS for the extraction of four PAHs with recoveries between 89.08% and 102.47% and relative standard deviations (RSDs) from 1.38% to 3.92% (n=5). Results showed a good linearity of four PAHs with the correlation coefficients (R2) more than 0.999. The limits of detection (LODs) ranged from 1.26 to 9.23 ng/L. The proposed pretreatment method greatly reduces the analysis time. And the solvent-less approach is in accordance with the development trend of green chemistry and of great application prospects.

Research development of designing flow cells for optical absorption detectors.

The optical absorption detector is one of the most commonly used detectors for high performance liquid chromatography (HPLC). As a core part of this kind of detector, the designs of flow cells, where light passes through samples for acquiring samples information, will affect the performance of a detector. In order to enhance the signal to noise ratio of detectors and reduce the bands broadening that come from flow cells, it is necessary to design a flow cell with a longer optical path length and a less cell volume while maintaining the luminous flux. However the limitations of the machining capacity make it difficult to increase the optical path length, reduce the cell volume and keep or increase the luminous flux simultaneously. It is a challenge to optimize the designing and machining of flow cells so as to improve the performance of detectors. This review discusses the development of designing flow cells based on the detection principle in some aspects of increasing the optical path length, reducing the cell volume, taking the advantages of total reflection and so on. At the same time, some of the designs are illustrated in detail. These various ideas and structures are significant references for designing flow cells and developing optical absorption detectors.