液相色谱/多通道电化学检测法在天然酚类化合物测定中的应用

多通道电化学检测是按照新一代电化学检测仪器的要求而设计的产品。它具有使用方便，快速准确，排除干扰等多种功能，非常适用于复杂体系中化合物的测定。本文报道了液相色谱／四通道电化学检测法在天然酚类化合物测定中的应用。此方法能快速获得待测物的流体动力学伏安图(HDV图)；色谱峰的鉴定可靠；在不同电压下同时定量测定不同的化合物。本文以测定蜂蜜中的酚酸类化合物及绿茶中的儿茶素类化合物为例对此分析方法进行了阐述。     

Simultaneous Determination of Seven Sulfonylurea-Type Oral Anti-Diabetic Agents in Adulterated Dietary Supplements and Traditional Chinese Medicines by Ultraperformance Liquid Chromatography–Tandem Mass Spectrometry

An ultraperformance liquid chromatography–tandem mass spectrometry method was developed for simultaneous determination of seven sulfonylurea-type oral anti-diabetic agents (glipizide, tolbutamide, tolazamide, gliclazide, glibenclamide, glimepiride, and glurenor) in dietary supplements and traditional Chinese medicines. The samples were extracted twice with methanol by ultrasound. The separation was achieved on a C18 column with the mobile phase consisting of acetonitrile and water (0.2% formic acid (v/v) and 5 mM ammonium acetate), at a flow rate of 0.3 mL/min with gradient elution. The analysis time was 8 min per sample. The proposed method was validated for linearity (r > 0.99), precision (relative standard deviation better than 6.0%), recoveries (83–110%), and the limit of detection in the range 0.3–2 µg kg^?1. The proposed method is rapid, reliable, sensitive, accurate, and good applicability, and it was successfully applied to analyze 20 real samples of 15 dietary supplements and five traditional Chinese medicines.     

双向电堆积与毛细管电泳联用对茶叶中咖啡酸及没食子酸的测定

采用在线双向电堆积与毛细管电泳联用技术测定茶叶中的有机酸离子。用砂芯取代盐桥隔离缓冲液与电极液,制成集成的双向电堆积装置,并用计算机程序控制分析过程。考察了电堆积时间、电堆积电压和样液体积等因素对富集倍数的影响。在优化的条件下,咖啡酸和没食子酸的富集倍数分别为24和20,检出限分别为0.4、0.2 mg/L。咖啡酸和没食子酸的线性范围分别为1.2~800 mg/L和0.8~800 mg/L。方法已应用于茶样中两种酸的测定,回收率为99%~109%。     

The Neuroprotective Effect of Tea Polyphenols on the Regulation of Intestinal Flora

Tea polyphenols (TPs) are the general compounds of natural polyhydroxyphenols extracted in tea. Although a large number of studies have shown that TPs have obvious neuroprotective and neuro repair effects, they are limited due to the low bioavailability in vivo. However, TPs can act indirectly on the central nervous system by affecting the “microflora–gut–brain axis”, in which the microbiota and its composition represent a factor that determines brain health. Bidirectional communication between the intestinal microflora and the brain (microbe–gut–brain axis) occurs through a variety of pathways, including the vagus nerve, immune system, neuroendocrine pathways, and bacteria-derived metabolites. This axis has been shown to influence neurotransmission and behavior, which is usually associated with neuropsychiatric disorders. In this review, we discuss that TPs and their metabolites may provide benefits by restoring the imbalance of intestinal microbiota and that TPs are metabolized by intestinal flora, to provide a new idea for TPs to play a neuroprotective role by regulating intestinal flora.     

Sedimentation and drying dissipative structures of green tea

Sedimentation and drying dissipative patterns formed in the course of drying green tea (Ocha) have been studied in tea cup (Ochawan), glass dish, polystyrene dish, and watch glass. The broad-ring patterns are formed within several tens of minutes in suspension state by the convectional flow of water and colloidal particles of green tea (7 μm in mean size and 5 μm in its dispersion from the mean size). Formation of the broad-ring patterns is retarded when a tea cup is covered with a watch glass, which demonstrates the important role of the convectional flow of tea particles and water induced by the evaporation of water at the air-suspension interface under the gravity. The sedimentary particles are suspended above the substrate plate and always move by the convectional flow of water. The broad-ring patterns become sharp just before the solidification occurs. The broad rings are formed even in an inclined glass dish, though the rings are transformed slightly, which demonstrates the strong convectional flow of the particles. The drying broad rings and the microscopic fine structures are formed in the solidification processes on the bases of the convectional and sedimentation patterns in suspension state.     

Simultaneous determination of six herbal components in intestinal perfusate by high‐performance liquid chromatography

An effective, accurate and reliable HPLC with UV detection method was developed and validated for quantitation of six components: baicalin, berberine hydrochloride, quercetin, kaempferol, isorhamnetin and baicalein in intestinal perfusate using rotundin as an internal standard. The chromatographic separation was performed on a Welchrom‐C₁₈ column (250 × 4.6 mm i.d. with 5.0 µm particle size) with a mobile phase consisting of acetonitrile, water, phosphoric acid and triethylamine (30:70:0.2:0.1,v/v) at a flow rate of 1.0 mL/min and a UV detection at 270 nm. The method had a chromatographic run time of 30 min and excellent linear behavior over the investigated concentration ranges observed with the values of r higher than 0.99 for all the analytes. The lower limit of quantification of the analytical method was 0.09 µg/mL for berberine hydrochloride, quercetin, kaempferol and baicalein and 0.18 µg/mL for baicalin and isorhamnetin. The intra‐ and inter‐day precisions measured at three concentration levels were all less than 10% for all analytes. The bias ranged from ?6.91 to 4.33%. The validated method has been successfully applied to investigate the rat intestine absorption profiles of baicalin, berberine hydrochloride, quercetin, kaempferol, isorhamnetin and baicalein. Copyright © 2009 John Wiley & Sons, Ltd.     

Selective square wave voltammetric determination of (+)-catechin in commercial tea samples using beta-cyclodextrin modified carbon paste electrode

Osteryoung square wave cathodic or anodic voltammetry has been used for the determination of (+)-catechin (CAT) at physiological pH in the presence of 0.05 mol · L⁻¹ phosphate/borate buffer using beta-cylcodextrin modified carbon paste electrode. A linear range up to 70.0 μg · mL⁻¹ CAT in cathodic voltammetry and up to 45.0 μg · mL⁻¹ CAT in anodic voltammetry was achieved. The method gave reproducible and reliable results with 1.35 μg · mL⁻¹ CAT as a detection limit with R.S.D. less than 2%. The proposed electrode was applied successfully for the determination of CAT in commercial tea samples with acceptable recovery range (98–102%). The extraction of CAT from commercial tea samples was rather simple, making it suitable for studies with a large number of commercial tea samples giving high accuracy of the proposed method. Correspondence: Deia El-Hady, Department of Chemistry, Faculty of Science, Assiut University, 71516 Assiut, Egypt     

顶空固相微萃取-全二维气相色谱/飞行时间质谱法分析闽南乌龙茶中的挥发性成分及其在分类中的应用

采用顶空固相微萃取(HS-SPME)结合全二维气相色谱/飞行时间质谱(GC×GC-TOF MS)分析了闽南乌龙茶中的挥发性成分。从48份不同等级和产季的乌龙茶(铁观音、黄金桂、本山、毛蟹和梅占)中获得了2000余种挥发性化合物,经筛选得到51种共有组分,并结合质谱数据库、保留指数与结构谱图等进行了初步鉴定。在此基础上采用主成分分析法(PCA)获得得分投影图,直观给出了不同样品的分类趋势。通过逐步判别获得9种对分类结果有显著影响的组分,并以此为变量通过Fisher判别法(FDA)建立了4个判别函数,对样品的分类准确率达到97.9%。本试验证实了以挥发性成分识别闽南乌龙茶的可行性。     

QuEChERS-超高效液相色谱-串联质谱法快速测定凉茶中非法添加的12种化学药物

建立了凉茶中马来酸氯苯那敏、吡罗昔康、α-细辛脑等12种非法添加的化学药物的QuEChERS结合超高效液相色谱-串联质谱(UPLC-MS/MS)的检测方法。样品经乙腈提取,应用QuEChERS技术净化,经0.22 μm微孔滤膜过滤后进行UPLC-MS/MS测定,以乙腈-0.1%(v/v)乙酸水溶液为流动相梯度洗脱,在XBridge BEH C₁₈柱(100 mm×2.1 mm, 3.5 μm)上实现12种化学药物的基线分离。该方法采用多反应监测(MRM)正离子模式扫描,标准曲线外标法定量。12种待测物在各自的质量浓度范围内线性关系良好,相关系数均大于0.997,检出限为0.1~2.1 μg/L,定量限为0.4~8.0 μg/L。在3个不同添加水平下的平均回收率为62.7%~95.2%, RSD为1.3%~10.8%。应用该方法对市面上销售的74批次凉茶进行了筛查测定,部分样品的测定结果为阳性。该方法操作简单,净化效果好,灵敏度高,适用于凉茶中12种非法添加的化学药物的快速分析。     

超高效液相色谱-四极杆-飞行时间质谱法快速筛查茶叶中的204种农药残留

利用超高效液相色谱-四极杆-飞行时间质谱(UPLC-Q-TOF/MS)技术建立了茶叶中204种农药残留的快速筛查和确证检测方法。样品采用乙腈提取,经Carb-PSA固相萃取小柱净化,用乙腈-甲苯(3:1, v/v)洗脱,采用UPLC-Q-TOF/MS检测,外标法定量。建立了204种农药的一级精确质量数据库和二级谱图库,通过化合物的精确质量数、保留时间、同位素比值等信息对检测结果进行自动检索,从而在无对照标准品的情况下完成了204种农药的定性鉴定。结果表明,该方法可以同时对茶叶中204种农药残留进行快速筛查,在10、20、50 μg/kg 3个添加水平下的平均回收率为68.1%~117.2%,相对标准偏差为3.1%~18.9%。定量限均小于10 μg/kg。采用本方法对4份阳性样品进行检测,所得结果与GB/T 23205-2008的检测结果基本一致。该方法快速、灵敏、准确,可用于茶叶中204种农药残留的快速筛查。