液相色谱-串联质谱法同时测定大黄鱼中20种磺胺类药物残留

建立了一种液相色谱-电喷雾串联质谱同时测定大黄鱼中20种磺胺类药物残留的方法.均质样品先后用乙腈、二氯甲烷提取,合并提取液,取部分提取液经氮吹浓缩.残渣用1 mL流动相溶解,饱和正己烷脱脂净化.采用ZORBAX Eclipse XDB-C8色谱柱,以含0.2%乙酸的水溶液和甲醇(7: 3)为流动相,梯度洗脱,在电喷雾-多反应监测离子模式下,进行定量定性分析.方法的定量限为5 μg/kg;以标准加入法计算回收率,在10～40 μg/kg添加范围内,平均回收率为79.6%～109%;相对标准偏差为3.55%～16.5%.     

GC-MS测定水产品中氯霉素的残留量

报道了利用气相色谱-质谱联用技术分析水产品中氯霉素的残留量。试样中的氯霉素用乙酸乙酯提取,经正己烷去脂,及硅烷化试剂衍生后,用配有负化学电离源的气-质联用仪测定,选择离子的质量数为466、468、470、376。衍生物的峰面积与样品质量浓度在0.5~250μg/L范围内呈良好的线性,相关系数为0.9996。当添加水平为0.5~10.0μg/kg时,回收率为74.8%~84.8%,相对标准偏差为4.90%~8.99%。     

First chemical study of anaspidean Syphonota geographica: structure of degraded sterols aplykurodinone-1 and -2

Two unprecedented degraded sterols, aplykurodinone-1 (1) and -2 (2), have been isolated from the skin of the marine anaspidean Syphonota geographica, collected along the coasts of Greece. The structures and the relative stereochemistry were established by spectroscopic analysis and confirmed by chemical correlation with related known compounds.     

Development and validation of a stability-indicating HPLC method for the determination of degradation products in dipyridamole injection

Summary The development and subsequent validation of an isocratic high-performance liquid chromatographic (HPLC) procedure employing ultraviolet (UV) detection for the determination of degradation products in Dipyridamole Injection is reported. The development of this assay involved the evaluation of several factors including buffer type, ionic strength, pH, organic composition, and column type. The described method is simple, reproducible, accurate, and selective. The precision, relative standard deviation (RSD), amongst five sample preparations for total degradation products was not more than (NMT) 10.2 %, while the individual degradation products were NMT 12.1%. Intermediate precision, as determined from fifteen sample preparations, generated by two Analysts on different HPLC systems over three days, exhibited an RSD for total and individual degradation products of 8.2 % and NMT 27.5 %, respectively. The mean absolute recovery of dipyridamole using the described method is 102.1±1. 9%, (mean±SD, n=12) over the concentration range of 0.03 % to 5.0 % of its label claim of 5 mg mL⁻¹. The limit of detection and limit of quantitation were 0.1 and 0.3 μg mL⁻¹, respectively. The linearity of the peak response was verified with respect to dipyridamole concentration over a range of 0.3 and 50 μg mL⁻¹ (0.03 % to 5.0 % label claim). The Standard and Assay Preparations are stable for up to 48 hours at room temperature. The selectivity was evaluated by subjecting the finished product (Dipyridamole Injection) to thermal, acidic, basic, oxidative and fluorescent radiation stress conditions. No interference in the analysis of degradation products was observed, showing the method is stability-indicating.     

衍生-气相色谱法测定水产品中的游离甲醛

建立了水产品中游离甲醛残留量的衍生-气相色谱快速检测方法,对衍生剂、抗干扰剂、萃取剂、色谱条件进行了研究.用HP-5 (30 m×0.32 mm i.d.,0.25 μm)毛细管色谱柱,程序升温,γ-ECD检测器,外标法定量.甲醛的检出限为0.05 mg/kg,在0.1～20.0 mg/L范围内,其线性相关系数R2=0.9994,标准偏差为0.041,在0.5、 1.5、 5.0 mg/kg 3个添加水平下回收率为89.6%～102.6%.3个实验室间的RSD为2.7%～4.4%.     

Synthesis of (+)-goniothalesdiol and (+)-7-epi-goniothalesdiol

A total synthesis of (+)-goniothalesdiol, a 3,4-dihydroxy-2,5-disubstituted tetrahydrofuran isolated from Goniothalamus borneensis (Annonaceae), and its 7-epimer is reported using oxycarbonylation methodology for construction of polyhydroxylated substituted heterocycles. Diastereoselectivity of addition of organometallic reagents to 2,3-O-isopropylidene-d-threose derivatives using theoretical calculations based on the semiempirical PM5 was studied.     

QuEChERS/超高效液相色谱-串联质谱法同时测定水产品中四溴双酚A与六溴环十二烷

建立了同时测定水产品中四溴双酚A(TBBPA)和六溴环十二烷(HBCD)的超高效液相色谱-串联质谱方法。样品前处理采用QuEChERS方法,均质生物样品用水分散后加乙腈提取,经C_(18)分散固相萃取净化。采用CORTECS~?C_(18)色谱柱(4.6 mm×100 mm×2.7μm)分离,以甲醇-水为流动相进行梯度洗脱,流速为0.7 mL/min。采用电喷雾离子源,在负离子模式下以多反应监测(MRM)方式检测。结果表明,TBBPA和3种HBCD单体在0.5～500μg/L范围内线性良好,相关系数(r)大于0.998,检出限(LOD,S/N=3)和定量下限(LOQ,S/N=10)分别为0.04～0.16μg/kg和0.12～0.55μg/kg。在5、20、50μg/kg加标水平下的平均回收率为74.0%～121%,相对标准偏差(RSD)为0.20%～23%。该方法操作简单、快速、重现性好,适用于水产品中TBBPA和HBCD的快速检测。     

Assigning the C-15 configuration of 15-hydroxy-, 15-methoxy-, 15-ethoxy-hexahydrofurofuran neoclerodane diterpenoids

Examination of ¹H and ¹³C NMR spectra allows the establishment of rules for assigning the correct configuration at C-15 of 15-hydroxy-, 15-methoxy-, 15-ethoxy-hexahydrofurofuran neoclerodane diterpenoids. The structure of several diterpenoids has been assigned or ammended.     

Glass and polymeric membrane electrodes for the measurement of pH in milk and cheese

While there is a considerable interest in the food industry in determining various analytes using ion-selective electrodes (ISEs), only few reports describe their use for direct measurements in food. In this study, the suitability of glass electrodes and ionophore-based solvent polymeric ISEs for the determination of pH in Process cheese, Cheddar cheese and milk was investigated. The liquid junction potential between a 3 M KCl bridge electrolyte and diluted as well as undiluted Process cheese was found to be negligible. Reference electrodes with ceramic plug and sleeve-type junctions performed well, although precautions needed to be taken to prevent plugging at the junctions. While the protein rennet casein posed no problems in pH measurements, the extraction of neutral lipophilic compounds or hydrophobic peptides into solvent polymeric membranes was evident, resulting in some loss of selectivity for monovalent cations upon exposure to cheese. However, it was found that ISEs based on tridodecylamine (R₃N) as ionophore and o-nitrophenyl octyl ether (oNPOE) as plasticizer can be used to accurately measure the pH of milk and, after desensitization of the electrodes in a cheese emulsion, of diluted Process cheese. Since pH measurements with a glass electrode showed that emulsions of cheese moderately diluted to a cheese content of 70% have the same pH as undiluted cheeses, it is possible to determine the pH in cheese with ionophore-based ISEs. R₃N membranes also performed well in undiluted milk.     

Separation of phytosterol oxidation products by combination of different polarity gas chromatography capillary columns

The number of characterized phytosterol oxidation products (POPs) from both ring- and side-chain structures has increased during recent decades, resulting in difficulties in the separation of POPs on different gas chromatography (GC) capillary columns. The main objective of this study was to separate a mixture of 29 purified and characterized oxidation products from sito-, campe- and stigmasterol using GC capillary columns with different polarity. For the first time in the area of POPs analysis, the separation efficiency of the combination of two capillary GC columns with different polarities was investigated. A non-polar 5% phenyl coated (DB5-MS) and a mid-polar 35% phenyl coated (DB35-MS) column was combined with a pressfit connector. The main improvement was enhanced base line separation for many of the analyzed POPs, compared with the separations achieved using the individual columns. However, three pairs of POPs co-eluted: 24-hydroxysitosterol/campesterol-5beta,6beta-epoxide, stigmasterol-5beta,6beta-epoxide/campesterol-5alpha,6alpha-epoxide and stigmasterol-5alpha,6alpha-epoxide/campestanetriol.