Determination of biuret in urea and mixed fertilizers

A new method has been developed for the determination of biuret in urea, based on the separation of the copper-biuret complex with the aid of an anionexchanger, followed by titration of the bound copper with EDTA. This method may be used directly for the determination of biuret in solutions and in end-products of a urea factory, even with biuret contents down to 0.001%. The well-known photometric method cannot be used for less than 0.1% biuret contents; corrections are needed for the interference of urea, and ammonia and insoluble products have to be removed. Both methods are suitable for the determination of biuret in mixed fertilizers down to 0.5%, provided that cations are first removed on a cation exchanger. However, the photometric determination calls for special precautions with regard to acidity when phosphates are present.     

Integrated retention/spectrophotometric detection in flow-injection analysis : Determination of Iron in Water and Wine

An integrated retention/spectrophotometric method is proposed for the determination of iron based on the Fe (III)-thiocyanate complex. The method has good selectivity, with a determination limit of 10 ng ml^?1 and a linear range of 10–400 ng ml^?1. Different types of measurements (peak height, absorbance increment, tangent curve) are shown to have their particular advantages. The method is applied to the determination of iron in natural water and wine, with an average recovery of 100.3% and 98.8% and an average deviation of the recovery of 2.5% and 1.6%, respectively.     

Direct titrations of antibiotics with iodate solutions: Part 2. Some selected cephalosporins

A previous method for the determination of penicillins by direct titration with potassium iodate under strongly acidic conditions has been extended to the assay of some selected cephalosporins. Results are presented, including error and precision analyses, for the determination of cephaloridine, cephalothin and cephalexin. The appropriate stoichiometries are 1 mol cephalosporin to 3 mol iodate for cephalothin and cephaloridine; 1 mol to 2 mol iodate for cephalexin. An irreversible aqueous end-point technique has been compared with the chloroform layer method; the latter gives more precise results for the determination of cephaloridine and cephalothin (0.8% and 1.3% r.s.d. respectively). Comparable precision was obtained by either technique for the determination of cephalexin (1.39% r.s.d.).     

The absorptiometric determination of molybdenum as molybdenum(v) thiocyanate in steel

The absorptiometric thiocyanate method for molybdenum has been thoroughly studied with regard to the role of the following reagents: HC1, H₂SO₄, HClO₄, KSCN, SnCl₂ and Fe. A method is described, which allows the determination of 0.01–10% Mo in steel with a relative standard deviation of less than 0.5%. The only interferences (slight) are Nb and the combination V and W. The method gives better than 99.8% recoveries. Results for the determination of molybdenum in standard samples are presented.     

Use of a multichannel photometer (Multiskan MS) for determination of humic materials in soil after their dichromate oxidation

Methodology for the determination of humus and humic materials content in soil after dichromate oxidation using a multichannel automatic photometer (Multiskan MS) has been developed. The study presented here demonstrates the benefits of using this methodology for the rapid, reliable and accurate determination of humus and humic materials content in various soils. The method is characterised by good data repeatability and low labour and reagent inputs. Photometric estimation is assessed in various respects, and determination procedures are presented. We have compared the data obtained by the titrimetric method and the photometric method with the photometer Multiskan MS. The methods are well correlated. The regression equations and determination coefficients relating to the data obtained by different methods have been calculated. The best statistics of a comparison between the titrimetric ( y) and photometric ( x) methods of humus determination were obtained with a series of standards prepared from the soil samples of known humus content: R(2)=0.99; y=1.05 x-0.37; BIAS=0.24% of humus; SED=0.27% of humus.     

Application of Flow Injection Method for the Determination of Thioridazine

Abstract

A simple flow-injection spectrophotometric method for the determination of thioridazine is described. The method is based on the oxidation of thioridazine with phosphotungstic acid in hydrochloric acidic media. Concentrations of thioridazine in the range 10 – 60 ppm are determined with a relative standard deviation of 1.1%. The method was applied to the determination of thioridazine in pharmaceutical formulations.     

The titrimetric determination of carbon dioxide with special reference to the determination of carbon in organic compounds

The titrimetric barium carbonate method for the determination of. carbon in organic compounds has been examined and the various sources of error are discussed. The carbon dioxide from the combustion of the sample is absorbed in excess baryta containing 20% (w/v) barium chloride and the excess is back-titrated with hydrochloric acid in the presence of o-cresolphthalein indicator.The value of this method in conjunction with the previously described determination of water with succinyl chloride, for the simultaneous determination of carbon and hydrogen is assessed     

A fast method for the determination of plutonium in soil and sediment samples

A so-called hour method for the determination of plutonium based on extraction chromatography is validated by its application to several certified soil and sediment samples from the International Atomic Energy Agency's Seibersdorf Laboratory. The results are in good agreement with the reference values. Chemical yields range between 47%–66%, with a mean value of (56±6)%. The possible use of this method for²⁴¹Pu determination is also demonstrated.     

铜的铬、钼、钨合金中杂质氧、氮的测定方法研究

研究了铜铬、铜钨、铜钼合金中杂质氧和氮的测定方法. 针对这3种合金试样由熔点相差较大的金属组成的特点, 使用了仪器的程序升温等先进功能, 选用合适的助熔剂的预处理方法, 选择适宜的加热温度, 使用镍助熔剂、高温座坩埚和石墨粉浴进行试验, 获得了满意的测定效果. 对质量分数氧0.048%、氮0.0036%的试样, 其相对标准偏差分别为4.1%、 10.3%; 加标回收率为氧90%～109%、氮91%～117%.     

电感耦合等离子体发射光谱法(ICP-OES)测定直接法氧化锌中铝、铜、铅、铁、镉、锰

建立了电感耦合等离子体发射光谱法测定直接法氧化锌中铝、铜、铅、铁、镉、锰元素含量的分析方法。确定了溶样方法和分析谱线,对方法精密度和准确度进行了考察,结果表明,各元素的相对标准偏差在2.5%~6.5%,加标回收率在92%~105%,测定结果与其它经典分析方法测定结果一致。所建立的方法准确、快速,适用于直接法氧化锌中多元素同时测定。     

Fixed-time kinetic enthalpimetry: improved sensitivity for enthalpimetric enzyme activity determinations in homogeneous and heterogeneous systems

A fixed-time (integral) method is described for the enthalpimetric determination of enzyme activity. The method involves the determination of residual unreacted substrate after a fixed incubation time with the sample. Results are presented for the determination of cholinesterase in aqueous solution and in 0.1cm³ samples of reference sera using 30-min incubation periods. Results are correlated with a spectrophotometric procedure. A precision of 1.8% relative standard deviation is reported for serum assays. Preliminary data are also presented for the enthalpimetric determination of cholinesterase activity after immobilization onto non-porous glass beads by carbodiimide and glutaraldehyde coupling procedures.     

电感耦合等离子体质谱法(ICP-MS)测定镍钴锰三元氢氧化物中铅

研究了用电感耦合等离子体质谱法（ICP-MS）测定镍钴锰三元素氢氧化物中铅含量的测定方法。选择了仪器的最佳测量条件、元素测定的质量数,进行了基体元素的干扰等实验。方法测定结果准确、可靠,测定下限小于0.00005%,样品加标回收率在99.2%~101.0%。方法的建立为控制镍钴锰三元素氢氧化物中铅提供了检测依据。     

A sequential injection cold-vapor atomic absorption method for the determination of total mercury

A sequential injection (SI) method for the determination of mercury via cold vapor atomic absorption spectrophotometry is presented. The method differs from flow injection (FI) cold vapor methods for the determination of mercury because of the simplicity of the system required for the method: one pump, one valve, a gas-liquid separator, and an atomic absorption spectrophotometer equipped with a quartz cell. Under optimal conditions, the method has the following figures of merit: a linear ¶calibration range of 1.0 to 20 μg L^–1; a detection limit of 0.46 μg L^–1; and a precision of 0.90% RSD (8 μg L^–1). The procedure allows for a sampling rate of one injection per 80 s (excluding sample pretreatment). Results from the determination of mercury in water and fish specimens are also presented. The figures of merit of the method are compared to two other SI methods for the determination of mercury.     

Determination of anions with capillary electrophoresis and indirect ultraviolet detection

A method is validated for the determination of anions with capillary electrophoresis (CE) in combination with indirect UV detection. The method described here is used for the analysis of eight of the most common anions (fluoride, chloride, bromide, sulphate, nitrate, nitrite, thiosulphate and phosphate). Next, the method is compared with a another buffer system for the determination of anions with CE and indirect UV detection. Typical limits of detection are obtained between 1 and 3 mg/l for the above-mentioned compounds. The repeatability and reproducibility of the system differs per compound and is, with the exception of fluoride and phosphate, between 4 and 6% and 5–10%, respectively. Linearity was observed between 1 and 10 mg/l. The method is applied for the determination of anions in drinking water, serum and urine.     

Fluoroimmunoassay for tumor necrosis factor-α in human serum using Ru(bpy)3Cl2-doped fluorescent silica nanoparticles as labels

A novel fluoroimmunoassay (FIA) method was developed for the determination of tumor necrosis factor-α (TNF-α) in this study. The proposed method has the advantage of showing the specificity of immunoassays and sensitivity of fluorescent nanoparticles label technology. With the well-established inverse microemulsion polymerisation process, the tris(2′,2-bipyridyl)dichlororuthenium(II) hexahydrate (Rubpy)-doped fluorescent silica nanoparticles (RuDFSNs) were prepared. Then a RuDFSNs-labeled anti-TNF-α monoclonal antibody was prepared and used for FIA of TNF-α in human serum samples with a sandwich FIA by using the low fluorescent 96-well transparent microtiter plates. The assay response was linear from 1.0 to about 250.0 pg/mL with a detection limit of 0.1 pg/mL for TNF-α. The intra- and inter-assay precision are 4.9%, 4.4%, 4.6%; 6.1%, 5.9%, 5.3% for five parallel measurements of 2.0, 20.0, 200.0 pg/mL TNF-α respectively, and the recoveries are in the range of 96-104% for human serum sample measurements by standard-addition method. We also explored the application of fluorescence microscopy imaging in the study of the FIA for TNF-α with the fluorescent nanoparticle labels. The results demonstrate that the method offers potential advantages of sensitivity, simplicity and good reproducibility for the determination of TNF-α, and is applicable to the determination of TNF-α in serum samples and being capable of fluorescence microscopy imaging for the determination of TNF-α.     

无线磁弹性免疫传感法测定水中痕量镉

基于抗原抗体特异性结合使镉附着在免疫传感器表面导致磁弹片共振频率降低的原理,建立了应用磁弹性免疫传感法测定水中痕量镉的方法。 其共振频率变化对应于磁弹性片表面附着物的质量变化。研究了聚乙烯亚胺用量、戊二醛用量、反应时间等因素对测定的影响。在最佳条件下,测定镉的线性范围为0.90~10.0 μg/L,检出限为为0.42 μg/L。 应用本方法测定了水样中的镉,测定结果与双硫腙比色法一致,回收率为96.5%~103.6%。     

钼蓝分光光度法测定纯金中的硅

建立了钼蓝分光光度法测定纯金中硅量的方法。确定了基体的分离方法、分离条件、还原剂及其用量;考察了酸度,试剂等对测定的影响。在优化条件下对3个合成试样进行了测定,RSD10%。方法的回收率在97%~122%之间,满足测定的要求。方法适用于0.001%~0.005%的硅量的测定。     

Dosage de l'hydrogene,de l'azote et de l'oxygene dans le monocarbure d'uranium

A method is described for the determination of hydrogen, oxygen and nitrogen in uranium monocarbide. Hydrogen and oxygen are determined by the classical or modified “Platinum flux” method at 2000° with a coefficient of variation of 10%. Nitrogen is determined at 2000° by the modification of the “Platinum flux” technique. The results obtained are in agreement with those found by Kjeldahl analysis. The coefficient of variation is about 10%. A procedure for the simultaneous determination of the 3 gases is given.     

Capillary electrophoretic determination of oxalate in amniotic fluid

A capillary electrophoretic (CE) assay for oxalate has been applied to the quantitative determination of free oxalate in amniotic fluid. Indirect absorbance detection of oxalate is accomplished with a chromate-based background electrolyte modified with ethylenediaminetetraacetic acid (EDTA). Detection interference due to the presence of high levels (≈4 mg/ml) of inorganic chloride is eliminated through a direct sample clean-up procedure based on cation (Ag⁺-form) resins. Separation interference from amniotic fluid proteins is prevented through the use of a simple aqueous-based dilution procedure. This method for the determination of oxalate in amniotic fluid provides precision of ≈5% relative standard deviation (RSD). Within-day precisions for the oxalate response and migration time are better than 3% RSD and 1% RSD, respectively. Between-day precisions for the oxalate response and migration time are better than 6% RSD and 3% RSD, respectively. The analytical recovery of oxalate (1000 ng/ml) spiked into amniotic fluid was better than 96%. The limit of detection (LOD) for the method is ≈100 ng/ml oxalate. This method also shows promising results for the determination of oxalate in human blood plasma samples.     

Derivative Spectrophotometric Analysis of Oestradiol Esters,Testosterone and Progesterone in Oily Injections

Abstract

The use of derivative and difference-derivative spectrophotometry for the determination of certain drugs in oily injection is presented. The method is illustrated by the determination of oestradiol valerate, oestradiol dipropionate, oestradiol benzoate, testosterone propionate and progesterone in their oily injections. This method is simple, rapid and accurate. The results obtained are reasonably reproducible with a coefficient of variation less than 2%.