UPLC-ESI-MS/MS for determining trans- and cis-vitamin K1 in infant formulas: method and applications

A simple and sensitive method of determining vitamin K₁ isomers (cis-and trans-forms) was developed for routine monitoring of supplemented infant formulas. The proposed method involves the applications of the lipase hydrolysis and the liquid-to-liquid extraction. After the hydrolysis and extraction procedures, the vitamin K₁-enriched extract was directly injected into the ultra-performance liquid chromatography–tandem mass spectrometry system (UPLC-MS/MS). The components were detected using electrospray ionization (ESI) in positive-ion and quantified by multiple-reaction monitoring (MRM) mode. trans-vitamin K₁ was separated from the biologically inactive cis-isomer through a C₃₀ column (4.6?×?150?mm, 3?μm), and vitamin K₁-d₇ was used as an internal standard. Calibration curves were linear over the range of 9.3–464.75?ng?ml^?1 for trans-vitamin K₁ (r ²?>?0.999) and 1.71–85.25?ng?ml^?1 for cis-vitamin K₁ (r ²?>?0.999). The limit of detection for trans- and cis-vitamin K₁ was 0.011?μg 100?g^?1 and 0.01?μg 100?g^?1. The limit of quantification was 0.037?μg 100?g^?1 and 0.031?μg 100?g^?1, respectively. The intra- and inter-batch variations (RSD%) were less than 5?%. The proposed method was applied to determine vitamin K₁ isomers in milk-based, soy-based and rice-based infant formulas, and the cis-vitamin K₁ isomer contributes to 7.05–17.21?% of the total vitamin K₁ in certain infant formulas.     

Enhancement of flavour development in ras cheese made by direct acidification

An attempt has been made to enhance flavour development in Ras cheese made from directly acidified milk. Addition of a ripened cheese slurry, yoghurt culture (Streptococcus thermophilus + Lactobacillus bulgaricus) or cheese starter (S. lactis + L. casei + Leuconostoc citrovorum) to the chemically acidified curd enhanced flavour intensity, body characteristics, the formation of both soluble nitrogen compounds and Free Fatty Acids and stimulated bacterial growth. Sensory properties (or characteristics) of cheese from chemically acidified curd incorporating the above additives approached those of control cheese.     

响应面试验优化QuEChERS法提取鸡蛋中杂色曲霉毒素工艺及方法学验证

使用乙腈溶液对鸡蛋中杂色曲霉毒素进行提取,后加入无水Na_2SO_4、NaCl和无水CH_3COONa进行盐析,取出上层乙腈后加入C_(18)吸附剂和无水Na2SO4进行净化浓缩后上机检测。采用Plackett-Burman试验、单因素试验和响应面法优化,最大限度地提高杂色曲霉毒素的提取率。使用基质匹配曲线外标法定量,所有阳性样品均使用免疫亲和柱法复测。结果表明,杂色曲霉毒素在0.125~1 000 ng/mL质量浓度范围内线性良好,相关系数达0.999 6,检出限为0.1μg/kg,定量限为0.5μg/kg。在空白鸡蛋基质中进行三水平加标实验,测得提取率在86.8%~90.4%范围内,日间重复性在1.5%~6.2%范围内。最终,将建立的方法用于45份样品检测,其中10份鸡蛋样品检测结果呈阳性,含量为0.5~3 608μg/kg。     

加速溶剂萃取结合亲水液相色谱柱分离测定坚果中的8种生育酚异构体

目的建立加速溶剂萃取(ASE)结合亲水液相色谱(HILIC)柱分离测定坚果中8种生育酚异构体的方法。方法 2 g坚果样品经ASE提取富集后,用BEH Amide色谱柱(150 mm×3.0 mm,1.7μm)分离,以90%正己烷,10%叔丁基甲基醚-四氢呋喃-甲醇(20∶1∶0.1,V/V)作为流动相等度洗脱,荧光检测器激发波长294 nm,发射波长328 nm检测,外标法定量。结果 4种生育酚在0.5~80.0μg/ml、4种生育三烯酚在0.5~30.0μg/ml之间具有良好的线性(r~20.998),方法检出限在0.032~0.070 mg/kg之间,方法定量限范围0.096~0.210 mg/kg,三个水平加标回收率在87.5%~114.2%之间,6次重复测定相对标准偏差(RSD)均≤12%。结论本方法具有良好的灵敏度、回收率和重复性,适用于坚果中8种生育酚异构体的含量分布的测定。     

China belting up or down? Seat belt wearing trends in Nanjing and Zhoushan

National seat belt wearing legislation became effective in China May 2004 and associated provincial and city regulations followed. Despite rapid motorisation seat belt studies in China have been scarce. Patterns and trends in urban seat belt wearing were observed for all driver, front and rear seating positions over the years 2005–2007 in two eastern cities Nanjing (Jiangsu Province) and Zhoushan (Zhejiang Province). There were 35,256 vehicles observed in Nanjing, 20,939 in Zhoushan and 95,933 occupants overall. Males dominated all seating positions, especially drivers. Seat belt wearing overall was significantly higher for drivers (49.9% Nanjing, 47.4% Zhoushan) than for front seat passengers (9.1% Nanjing, 1.0% Zhoushan) and virtually nonexistent for rear passengers (0.5% Nanjing, 0.2% Zhoushan). Generally levels declined significantly from year to year (drivers Nanjing 66.7%, 47.7%, 38.6%; Zhoushan 57.4%, 57.9%, 30.6%; front passengers Nanjing 19.2%, 6.6%, 3.2%). Zhoushan wearing did not initially decline, 2006 observations coinciding with anticipation of provincial regulations (July 2006). Observations revealed an absence of child restraints. Pretend wearing/belt tampering was observed almost exclusively in taxi drivers (14.2% of Nanjing taxi drivers, 11.3% of Zhoushan’s). Awareness of and attitudes to urban seat belt laws should be investigated, appropriate countermeasures developed and enforcement reassessed.     

Behaviour of alkylphenol polyethoxylate surfactants in the aquatic environment—III. Occurrence and elimination of their persistent metabolites during infiltration of river water to groundwater

The behaviour of various persistent metabolites derived from nonylphenol polyethoxylate (NPnEO) surfactants was studied during infiltration of river water to groundwater at two field sites situated in the northern part of Switzerland (Glatt River and Sitter River). Nonylphenol (NP), nonylphenol monoethoxylate (NP1EO), nonylphenol diethoxylate (NP2EO), nonylphenoxy acetic acid (NP1EC) and nonylphenoxy(ethoxy) acetic acid (NP2EC) were observed in the two investigated rivers at relatively high concentrations with average values of the individual types of nonylphenolic compounds ranging from 1.8 to 25 μg/l. The average concentrations of NP, NP1EO and NP2EO in groundwater were significantly lower (range <0.1–1 μg/l) suggesting an efficient elimination of these compounds during infiltration. In contrast, the elimination of nonylphenoxy carboxylic acids was less efficient. Most of the observed elimination occurred in the first 2.5 m of the aquifer, while further decrease in concentration was rather slow. In one sampling period, residual concentrations of nonylphenolic compounds up to 7.2 μg/l were detected in a pumping station used for drinking water supply which is situated 130 m from the Glatt River bed. Concentrations of NP, NP1EO and NP2EO in both river water and groundwater showed a pronounced seasonal variability with higher values observed during winter. The data suggest that low temperatures, which prevail in winter, significantly reduce the elimination efficiency of NP and to a lesser extent of NP1EO, while the behaviour of NP2EO was not affected. Such a behaviour indicates biogical transformation as the responsible elimination process. A comparison of average elimination efficiences of nonylphenolic compounds with those of pentachlorphenol (PCP) and nitrilotriacetate (NTA) gives the following sequence: NTA ≧ NP2EO > NP1EO > NP > PCP > NP1EC = NP2EC.     

Prevalence and fluoroquinolones resistance of Campylobacter and Salmonella isolates from poultry carcasses in Rio de Janeiro,Brazil

To investigate the prevalence of Campylobacter and Salmonella in poultry carcasses in state of Rio de Janeiro, Brazil, 60 samples from 6 slaughterhouses were collected over a period of 6 months. A total of 82 Campylobacter isolates were obtained from twenty seven (45%) positive chicken carcasses, including 44 isolates (53.66%) of Campylobacter jejuni and 38 (46.34%) of Campylobacter coli. The identification of all strains was confirmed by PCR. Salmonella was isolated from 4 (6.67%) carcasses by conventional method and was detected in 5 (8.33%) of 60 chicken carcasses by PCR. Two Salmonella Albany and two Salmonella Typhimurium were identified. Antimicrobial susceptibility testing was primarily done by the disk diffusion method and later by assessing minimum inhibitory concentrations (MICs) against all the isolates. All the Campylobacter isolates were resistant to ciprofloxacin and enrofloxacin. It was observed high MIC values for enrofloxacin (64 μg/mL) in one C. jejuni and two C. coli strains, and for ciprofloxacin (≥128 μg/mL) in one C. jejuni and three C. coli strains. No Salmonella isolate was resistant to these antibiotics by both methods. These findings reveal a broad extent of fluoroquinolone resistance in Campylobacter isolates from chicken carcasses in Brazil and underline the need for prudent use of these antibiotics in poultry production to minimize the spread of fluoroquinolone resistant Campylobacter.     

液质联用法检测掺罂栗壳食物中生物碱的残留

采用液相色谱-电喷雾串联四极杆质谱法定量检测掺罂粟壳食物中生物碱的残留。文中对食物中生物碱的提取、样品预处理及液质联用分析方法进行了研究。吗啡、可待因、罂粟碱、那可丁最低检出限（LOD）分别为0．073、0．024、0．003、0．0009μg/L（进样量10μL），最低定量限LOQ分别为0．24、0．08、0.01、0.003μg/L。回收率在95％～110％。该方法灵敏度高、操作简单、定量准确，为食物中罂粟壳残留物检测的理想方法。     

婴幼儿配方奶粉中酪蛋白磷酸肽2种检测方法的比较

目的比较婴幼儿配方奶粉中酪蛋白磷酸肽(casein phosphopeptides,CPPs)的2种主要检测方法。方法分别采用高效液相色谱法(high performance liquid chromatography,HPLC)和高效液相色谱-串联质谱法(high performance liquid chromatography-tandem mass spectrometry, HPLC-MS/MS)检测婴幼儿配方奶粉中酪蛋白磷酸肽的含量。结果 HPLC操作简便,检出限为7.5mg/100g,日内精密度≤2.7%,满足婴幼儿配方奶粉中酪蛋白磷酸肽的检测要求;而HPLC-MS/MS检出限为1mg/100 g,日内精密度≤8.8%,较HPLC具有更好的灵敏度。结论 HPLC高效准确,实验操作简单,适合于CPPs含量较高样品的检测分析;HPLC-MS/MS灵敏度高、特异性强,适用于CPPs含量较低样品的检测。