薄层色谱-紫外可见分光光度法同时测定食品中的苏丹红Ⅰ～Ⅳ

建立了测定食品中苏丹红色素含量的新方法——薄层色谱-紫外可见分光光度法,对影响测定的因素如样品预处理方式、展开剂等进行了讨论,检测苏丹红Ⅰ~Ⅳ的线性范围分别为0.5~14μg/mL,0.5~10μg/mL,0.5~15μg/mL,0.5~15μg/mL,线性相关系数均为0.999,检出限均为0.05μg/mL。该方法测定结果与国家标准方法测定结果基本一致。     

紫外可见分光光度法测定水中六价铬的线性范围

探讨紫外可见分光光度法测定水中六价铬的最佳线性范围。GB 7467–1987规定以二苯碳酰二肼为显色剂,用紫外可见分光光度法测定水中的六价铬,实践表明,在标准规定的浓度区间内,测量精密度和准确度不能达到标准要求。大量的实验数据表明此法测定水中六价铬的最佳线性范围为0.05～0.4μg/mL。     

硫酸钠盐析对萃取微量铜的增敏作用及其应用

建立了以二乙基二硫代氨基甲酸钠(DDTC)为络合剂,硫酸钠-氯仿-水盐析萃取,紫外可见分光光度法测定痕量铜(Ⅱ)的新方法.研究了萃取的条件,共存离子的干扰.结果表明本法灵敏度高,选择性好,在最佳实验条件下,铜的线性范围为0.002～0.08μg/mL,0.002μg/mL铜标准液测定的RSD=1.9%(n=7),检出限...     

茜素红荷移分光光度法测定头孢克洛

以茜素红(ARS)为荷移试剂,采用分光光度法直接测定了头孢克洛(CFC),并研究了ARS-CFC络合物的可见光谱性质及最佳反应条件.CFC浓度在1.157～38.58μg/mL范围内遵循比尔定律,回归方程为A=0.1312683 p+0.01064(ρ:μg/mL),检出限0.56μg/mL,表观摩尔吸光系数5.77×...     

原子吸收分光光度法测定钢铁中的铬

在稀硝酸介质中,不需分离其它干扰杂质,用原子吸收分光光度法直接测定中、低合金钢中的铬。该法测定铬的特征浓度(灵敏度)为0.08μg/mL,铬含量在0~6μg/mL内与吸光度线性相关,检出限为0.003μg/mL。该法测定速度快,与标准法测定结果的相对误差在±4.6%以内,回收率为97%~115%。     

气体扩散耦合顺序注射分光光度法测定葡萄酒中的二氧化硫

依据在微碱性条件下,亚硫酸根离子可与孔雀绿溶液发生加成反应并使其褪色的原理,建立了气体扩散耦合顺序注射分光光度法测定葡萄酒中二氧化硫的新方法。当接收液流速为1.2mL/min和4.2mL/min时,方法的线性响应范围分别为1.0~5.0μg/mL和5.0~50.0μg/mL,方法的检出限为0.33μg/mL,相对标准偏差(RSD)≤0.43%,对葡萄酒样中二氧化硫测定的加标回收率为98.7%~104.7%。     

流动注射-分光光度法测定痕量过氧化氢

在NaOH-Na_2CO_3介质(pH=12.0)中,Cu~(2+)对过氧化氢氧化钙试剂羧酸钠褪色的反应有催化作用,据此建立了测定痕量过氧化氢的流动注射分光光度法.该方法的线性范围为0.1~2.4μg/mL,进样频率为120次/h,应用本法测定雨水中痕量过氧化氢,获得了满意的结果.     

微波消解/干灰化-分光光度法测定面制食品中的铝

采用微波消解法和干灰化法对面制品进行前处理,用分光光度法测定面制品中的铝含量,建立了微波消解/干灰化-分光光度法测定铝的方法.实验结果表明,本方法前处理简单,检测结果准确度高,精密度好,在0～10μg/25 mL线性范围内:相关系数r=0.999 5,方法检出限为0.2 μg/25 mL,样品的加标回收率在92.0 %...     

气体扩散耦合顺序注射光度分析法测定葡萄酒中的二氧化硫*

依据在微碱性条件下,亚硫酸根离子可与孔雀绿溶液发生加成反应并使其褪色的原理,建立了气体扩散耦合顺序注射分光光度法测定葡萄酒中二氧化硫的新方法。当接收液流速为1.2mL/min和4.2mL/min时,方法的线性响应范围分别为1.0-5.0μg/mL和5.0-50.0μg/mL,方法的检出限为0.33μg/mL,相对标准偏差（RSD）≤0.43%,对葡萄酒样中二氧化硫测定的加标回收率为98.7%-104.7%。     

单纯形最优化法确定硅存在时钙的测定条件

应用改进单纯形最优化法研究了利用锶-镧-十六烷基三甲基溴化铵（CTMAB）-盐酸、锶-镧-四乙基氯化铵-盐酸、锶-TritonX-100-盐酸3种混合试剂体系消除原子吸收分光光度法测定钙时共存硅干扰的方法。最佳条件分别为：1000μg/mL锶 1238μg/mL镧 108μg/mL CTMAB 4.05%盐酸，700μg/mL锶 1187μg/mL镧 150μg/mL四乙基氯化铵 4.63%盐酸，300μg/mL CTMAB 4.05%盐酸，700μg/mL锶 1187μg/mL镧 150μg/mL四乙基氯化铵 4.63%盐酸，300μg/mL锶 0.97% TrionX-100 4%盐酸。在以上3种条件下，100μg/mL硅不干扰钙的测定，钙的回收率为92.3%-106.0%。     

Determination of uric acid in human urine by capillary zone electrophoresis with indirect laser-induced fluorescence detection

A CZE with indirect LIF detection method was used for the determination of uric acid (UA) in human urine. UA and its coexisting analytes (i.e. hypoxanthine, xanthine and ascorbic acid) could be well separated within 4.5?min at a voltage of 25?kV with 25°C cartridge temperature in a running buffer composed of 5?mM sodium borate, 10% methanol (v/v) and 0.3?μM fluorescein sodium (apparent pH of the final mixed hydro-organic solution of sodium borate, methanol and fluorescein is 9.5). Under the optimum condition, the method has good linearity relationships (correlation coefficients: 0.9973-0.9987) with ranges of 25-500, 25-350, 25-250 and 25-300?μg/mL for hypoxanthine, ascorbic acid, xanthine and UA, respectively. The detection limits for the analytes were in the range of 0.29-0.90?μg/mL. The intra-day RSD values for migration times and peak areas were less than 0.43 and 3.27%, respectively. This method was applied to the quantitation of UA in human urine with recoveries in the range of 93.1-107.3%.     

Amperometric Determination of Cholesterol-Reducing Drug,Ezetimibe, Using Glassy Carbon Electrode Modified with Multiwalled Carbon Nanotubes and Sodium Dodecylsulfate

A simple and sensitive electrochemical method is described for the determination of the cholesterol-reducing drug ezetimibe in aqueous solution. A glassy carbon electrode, modified with multiwalled carbon nanotubes and sodium dodecylsulphate was used as the working electrode. Ezetimibe yields a well-defined anodic peak at the surface of the electrode in an aqueous solution of pH 13. A linear amperometric calibration curve was obtained in the range of 1.2–78 μM (0.5–32.0 μg/mL) of ezetimibe, with a sensitivity of 88.6 nA/μM and a detection limit of 300 nM (0.12 μg/mL). The sensor was applied successfully to the determination of ezetimibe in pharmaceutical preparations.     

Separation and determination of six catechins in tea by pressurized capillary electrochromatography

An efficient pressurized capillary electrochromatography (pCEC) method has been successfully developed for the determination of six catechins in tea. The separation was performed on a reversed-phase EP-100-20/45-3-C18 capillary column (total length of 45?cm, effective length of 20?cm, diameter of 100?μm, ODS packing inside for 3?μm). The mobile phase ratio of organic phase, the concentration of phosphate buffer and sodium heptanesulfonate, separation voltage, and other experimental conditions were investigated and optimized. The mobile phase was 15?mM NaH₂PO₄ and 12?mM sodium heptanesulfonate (pH 3.0)/methanol (64:36) at a flow rate of 0.04?mL/min. Under optimal conditions including applied voltage of ?4?kV and a UV detection wavelength of 230?nm, the six catechins in the tea were well separated. The calibration curves for the analytes had good linearity in the range of 8.02?μg/mL–202.13?μg/mL with a correlation coefficient of 0.9928–0.9997. The limits of detection (LOD) for the six catechins were 4.62?μg/mL–11.63?μg/mL (S/N?=?3). The recoveries of the six catechins were 96.2%–108.4% with a relative standard deviation (RSD) between 0.78% and 4.51%. The method has been used for the determination of six catechins in tea samples with good results.     

On-Line Flow-Injection Chemiluminescence Determination of Bovine Serum Albumin Using Surfactant-Enhanced Dichlorofluorescein-Hypochlorite System

A flow injection technique combined with a chemiluminescence method was established for the determination of bovine serum albumin (BSA). Strong chemiluminescence was observed when BSA-dichlorofluoresce (DCF) complex was oxidized by sodium hypochlorite (NaClO) in an alkaline medium and in the presence of cetyltrimethylammonium bromide (CTAB). The reaction conditions of the chemiluminescence were carefully optimized. Under the optimal conditions, the method had a linear range of 0.01–20.0 μg/mL, with a detection limit of 0.007 μg/mL for BSA (3σ). The relative standard deviation of 1.0 μg/mL BSA (n = 8) is 1.4%. The method was applied to determine BSA in milk samples and it worked well.     

Simultaneous determination of nitrite and nitrate in dew, rain, snow and lake water samples by ion-pair high-performance liquid chromatography

A simple, fast, sensitive and accurate reversed-phase ion-pair HPLC method for simultaneous determination of nitrite and nitrate in atmospheric liquids and lake waters has been developed. Separations were accomplished in less than 10 min using a reversed-phase C₁₈ column (150 mm × 2.00 mm i.d., 5 μm particle size) with a mobile phase containing 83% 3.0 mM ion-interaction reagent tetrabutylammonium hydroxide (TBA-OH) and 2.0 mM sodium phosphate buffer at pH 3.9 and 17% acetonitrile (flow rate, 0.4 mL/min). UV light absorption responses at 205 nm were linear over a wide concentration range from 100 μg/mL to the detection limits of 10 μg/L for nitrite and 5 μg/L nitrate. Quantitation was carried out by the peak area method. The relative standard deviation for the analysis of nitrite and nitrate was less than 3.0%. This method was applied for the simultaneous determination of nitrite and nitrate in dew, rain, snow and lake water samples collected in southeast Massachusetts. Nitrate was found being present at 4.79-5.99 μg/mL in dew, 1.20-2.63 μg/mL in rain, 0.32-0.60 μg/mL in snow and 0.12-0.23 μg/mL in lake water. Nitrite was only a minor species in dew (0.62-0.83 μg/mL), rain (<0.005-0.14 μg/mL), snow (0.021-0.032 μg/mL) and lake water (0.12-0.16 μg/mL). High levels of nitrite and nitrate observed in dew water droplets may constitute an important source of hydroxyl radicals in the sunny early morning.     

A novel method for the spectrophotometric determination of cefradine by using sodium nitroprusside as chromogenic reagent

A novel method is developed for the determination of cefradine by using sodium nitroprusside as chromogenic reagent. The experiment indicates that a russety product is formed by the reaction of cefradine with sodium nitroprusside in basic solution, and the maximum absorption wavelength （λmax） of russety product is 505 rim. And the sensitization of tetradecyl benzyl dimethyl ammonium chloride for the reaction of cefradine with sodium nitroprusside is remarkable, The apparent molar absorption coefficient （5505） is 2.81 × 103 L/mol cm. The linear equation isA = 0.0657 ＋ 0.00804C （μg/mL） in the range of 1.50-55.0μg/mL of cefradine with a correlation coefficient r = 0.9992, and the detection limit is 1.38 p,g/mL. This method has been applied to determine cefradine in capsule and tablet samples.     

离子色谱法测定卷烟主流烟气中的硫化氢

建立了测定卷烟主流烟气中硫化氢含量的离子色谱法.采用玻璃纤维滤片捕集卷烟烟气粒相物,并用0.5%(体积分数)乙二胺-50 mmol/L氢氧化钠-250 mmol/L乙酸钠溶液萃取粒相物,吸收液吸收气相物中的硫化氢,合并粒相萃取液与气相吸收液,经离子色谱柱分离,以1.5 mol/L氢氧化钠-1 mol/L乙酸钠-2%(体积分数)乙二胺(40∶50∶10,体积比)为流动相,安培检测器检测并施加-100 mv的检测电位.运用方法对12种市售卷烟样品进行了测定,结果表明:方法的线性范围为0.1~5.0μg/mL,检出限为1.03μg/mL,定量限为3.41μg/mL,回收率为102.3%~107.2%,相对标准偏差小于5%.方法处理简单、准确度高,可以用于卷烟烟气中硫化氢含量的测定.     

花菁-脱氧核糖核酸的共振光散射光谱及其分析应用

研究了一种苯并噻唑阳离子花菁与脱氧核糖核酸(DNA)作用的共振光散射光谱,在pH 6.0的六次甲基四胺-HCl缓冲介质中,痕量DNA的加入使花菁在590nm的共振光散射强度显著增强。在最佳实验条件下,增强的共振光散射强度与DNA浓度具有良好的线性关系,据此建立了一种测定DNA的共振光散射光谱法。方法的线性范围为:小牛胸腺DNA(CT DNA),0～20μg/mL,鱼精子DNA(FS DNA),0～15μg/mL;检出限分别为0.005μg/mL和0.008μg/mL。该方法已用于合成样品中DNA的测定。     

Direct detection of Δ9-tetrahydrocannabinol in aqueous samples using a homogeneous increasing fluorescence immunoassay (HiFi)

The detection of the major active component of cannabis, Δ9-tetrahydrocannabinol (THC), becomes increasingly relevant due to its widespread abuse. For control purposes, some easy-to-use, sensitive and inexpensive test methods are needed. We have developed a fluorescence immunoassay utilising THC–fluorescein conjugate as tracer. Fluorescence spectroscopy of the conjugate revealed an unusual property: The relatively weak fluorescence of a dilute tracer solution was increased by a factor of up to 5 after binding of a THC-specific antibody. Fluorescence lifetime measurements in aqueous solutions suggested two different tracer conformations both associated with quenching of fluorescein fluorescence by the intramolecular THC moiety. After antibody binding, the tracer enters a third conformation in which fluorescence quenching of fluorescein is completely suppressed. Utilising this property, we established a homogeneous competitive immunoassay (homogeneous increasing fluorescence immunoassay) with low detection limits. The test requires only two reagents, the new tracer molecule and an anti-THC antibody. A single test takes only 8 min. The dynamic detection range for THC is 0.5 to 20 ng/mL in buffer, with a limit of detection (LOD) of 0.5 ng/mL. The test also works in diluted saliva samples (1:10 dilution with buffer) with an LOD of 2 ng/mL and a dynamic range of 2–50 ng/mL.