Determination of caffeine in solid pharmaceutical samples by FTIR spectroscopy

Fourier transform infrared spectroscopy has been used for the quantitative determination of caffeine in several pharmaceutical products: acetyl salicylic acid, paracetamol and propyphenazone. The method is simple, rapid and selective, and allows the determination of caffeine without sample pretreatment and without separation from the matrix. Two techniques for measuring the infrared spectra of caffeine are described: transmission through pellets and diffuse reflectance from powder (DRIFT). In both methods, samples were diluted (1%) with KBr. Caffeine in pharmaceutical matrices was recovered within 5% error in pellets and 10% by DRIFT. Relative standard deviations were generally 1.5% for repeated measurements on a single pellet and 5% for measurements on different pellets. DRIFT in the vacuum mode gave rather large RSDs. The limit of detection of the pellet technique was about 0.5% caffeine in the original sample.     

Determination of arsenic species in marine samples by HPLC-ICP-MS.

Arsenic speciation analysis in marine samples was performed using high performance liquid chromatography (HPLC) with ICP-MS detection. The separation of eight arsenic species viz. arsenite (As(III)), monomethylarsonic acid (MMA), dimethylarsinic acid (DMA), arsenate (As(V)), arsenobetaine, trimethylarsine oxide (TMAO), arsenocholine and tetramethylarsonium ion (TeMAs) was achieved on a Shiseido Capcell Pak C18 column by using an isocratic eluent (pH 3.0), in which condition As(III) and MMA were co-eluted. The entire separation was accomplished in 15 min. The detection limits for 8 arsenic species by HPLC/ICP-MS were in the range of 0.02 - 0.10 microg L(-1) based on 3sigma of blank response (n=9). The precision was calculated to be 3.1-7.3% (RSD) for all eight species. The method then successfully applied to several marine samples e.g., oyster, scallop, fish, and shrimps. For the extraction of arsenic species from seafood products, the low power microwave digestion was employed. The extraction efficiency was in the range of 52.9 - 112.3%. Total arsenic concentrations were analyzed by using the microwave acid digestion. The total arsenics in the certified reference materials (DORM-2 and TORT-2) were analyzed and agreed with the certified values. The concentrations of arsenics in marine samples were in the range 6.6 - 35.1 microg g(-1).     

Real-time FTIR-ATR spectroscopy of photopolymerization reactions

Real-time FTIR-ATR spectroscopy was used to study radical photo-polymerization reactions. Investigations on various acrylate systems deal with the effect of temperature on the kinetics of the polymerization reaction and the characterization of the depth profile of the conversion of double bonds. Moreover, first results on the photoinitiator-free photopolymerization of acrylates by exposure to short-wavelength UV radiation will be reported. The potential of the method will also be demonstrated in simulations of various irradiation regimes in technical UV curing processes.     

Atomic absorption spectrometric determination of copper in calcium carbonate scale and carbonate rocks by direct atomization of solid samples

Powdered samples (1 mg) are mixed with 1 mg of powdered graphite and copper is determined by atomic absorption spectrometry in a miniature graphite cup placed in a graphite crucible. Optimum conditions were drying at 200 °C (30 s), ashing at 900 °C (30 s), atomizing at 2700 °C (15 s) and cleaning at 2800 °C (10 s). Samples were powdered to 1–10 μm particle size. Magnesium, manganese and iron did not interfere. The effect of calcium carbonate was eliminated by the graphite addition. Results for copper (0.5–5 μg g^?1) in the scale and rocks agreed well with values obtained for dissolved samples. Relative standard deviations (n=10) were 4.9% for 1.2 μg g^?1 copper and 14.8% for 0.577 μg g^?1.     

Rubidium isotope measurements in solid samples by laser ablation-laser atomic absorption spectroscopy

Laser atomic absorption was used to measure the rubidium isotopes in a laser-induced plasma. An ⁸⁵Rb/⁸⁷Rb isotope ratio of 2.7±0.2 was determined in solid calcium carbonate samples. A Nd:YAG laser was used to produce the plasma on the surface of solid samples placed inside a low pressure chamber with a controlled atmosphere of 150 mtorr to 10 torr. The plasma conditions were optimized in order to provide the best sensitivity and resolution. A narrowband Ti:Sapphire laser was scanned across the 780.02-nm transition of the rubidium isotopes. The resolved isotope spectrum is shown, as well as the isotope selective calibration plots. A detection limit of 25 ppm for the individual isotopes was obtained. The optimization studies and the likely mechanisms of line broadening are discussed.     

Determination of pesticides in soil samples by solid phase extraction disks

Summary A systematic study comparing the methodology and analytical results obtained in an investigation of seven pesticide residues (Molinate, Atrazine, Carbofuran, Pirimicarb, Prometryn, Malathion and Tetrachlorvinphos) in soil samples is reported. Solid-phase extraction (SPE) using glass columns and 47 mm disks of octyl and octadecyl-bonded silica was used in the pesticide analysis. The best extraction efficiency and clearest extracts are obtained with C₈ disks. The analyses were carried out by capillary gas chromatography with nitrogen and phosphorus detection. Recovery experiments were performed at ppb levels in spiked soil samples. The average recoveries of the compounds were 53–77%. Detection limits are between 5 and 30 ng g^–1 based on 5 g moist soil sample. The method was validated by comparing it with conventional liquid-liquid extraction.     

Determination of trace elements in carbonate reference samples by instrumental neutron activation analysis

Twenty elements (Sm, U, As, Sb, La, Ce, Yb, Th, Cr, Eu, Hf, Ba, Cs, Tb, Sc, Rb, Fe, Zn, Ta, Co) have been determined by instrumental neutron activation analysis in GSJ/AIST carbonate reference samples, JCp-1 (Coral) and JCt-1 (Giant Clam), together with JLk-1 (Lake Sediment), JDo-1 (Dolomite) and JLs-1 (Limestone) reference samples.     

Determination of 226Ra in solid samples of few milligrams after mineralisation and measurement by solid scintillation

A protocol is proposed for the measurement of ²²⁶Ra on 150 mg of solid sample without radiochemistry. To evaluate the performance of this method, standard samples were used and the results were in good agreement with reference values. The detection limit obtained is about 130 Bq kg⁻¹ (dry weight) without mineralised solution concentration by evaporation. A concentration of the solution by 4 and/or an increase of sample mass by 4 in the case of microwave digestion system, allows achieving a detection limit of 30 Bq kg⁻¹ (dry weight) and thus measuring ²²⁶Ra in most soils. This method could also be used for NORM sites on soil and sediment samples.

     

冷原子荧光光谱法测定海产品中痕量镉

建立了氢化物发生-冷原子荧光光谱法测定海产品中镉(Cd)的分析方法,研究了硫脲-抗坏血酸-Co(Ⅱ)体系经KBH4还原产生Cd挥发性组分。对实验条件如载气流速、屏蔽气流速、原子化器高度、硫脲-抗坏血酸浓度、KBH4浓度及HCl浓度等进行了优化。在最优条件下,对海藻、紫菜等海产品中痕量Cd的含量进行测定。本方法中Cd的检出限为0.005μg/L,线性范围为0.02～20.0μg/L,实际样品加标回收率为94%～101%。对海藻和紫菜等国家一级标准物质进行测定,结果与标准值相符。     

Some observations on FTIR emission spectroscopy of black solid samples

Application of FTIR emission spectroscopy to the study of optically opaque polymer samples containing high levels of carbon black/carbon fibre filler is considered. The effects of reduced emission and self-absorption are discussed.ICI Films     

In-situ measurement of photochemical changes of solid samples by fourier transform infrared photoacoustic spectroscopy

Infrared spectral changes of lithographic printing plates were measuredin-situ by PAS and RAS. The advantages of PAS over RAS were discussed for the spectral measurements of organic coatings on roughened metal surface.     

Zeolite coated ATR crystals for new applications in FTIR-ATR spectroscopy

Thin silicalite-1 films were grown on ATR crystals and used for detection of low amounts of organic molecules in a gas flow by FTIR spectroscopy.     

Determination of sulfophenylcarboxylic acids in marine samples by solid-phase extraction then high-performance liquid chromatography

An analytical method is presented for the determination of sulfophenylcarboxylic acids (SPC) produced by the biodegradation of linear alkylbenzene sulfonates (LAS) in marine samples. Isolation and concentration of the compounds was by solid-phase extraction. The different factors affecting extraction efficiency packing composition, pH, clean-up, ionic strength, and elution solvents--were studied and optimized. With the proposed method C4-C13SPC and C10-C13 LAS recoveries varied between 65% and 105%, with standard deviations between 0.1 and 5, respectively, for 100-mL samples and 100 microg L(-1) concentrations of each homolog. Detection limits within the range 0.5 g L(-1) (for C4SPC) to 1.0 g L(-1) (for C12SPC) were obtained by liquid chromatography with fluorescence detection. This method is the first to be proposed that enables the simultaneous determination of monocarboxylic SPC (C>3) and LAS homologs in marine samples by a simple, sensitive, and specific method giving high recoveries and reproducibility. SPC with from three to twelve carbon atoms in the carboxyl chain have been found in marine water samples.     

Determination of silver carbonate in silver oxide(Ag2O) by infrared spectroscopy

Silver carbonate in silver oxide (Ag(2)O) is determined quantitatively by infrared spectroscopy. The deviation of the results from a mean line is +/-0.2% of Ag(2)CO(3) for samples containing only normal silver carbonate, and +/-0.4% of Ag(2)CO(3) for samples containing both normal and basic silver carbonate.     

Liquid–solid extraction of butyltin compounds from marine samples

Environmental damage due to organotins (TBT, DBT, MBT) released from antifouling paints is well documented. The concentrations of these compounds in seawater are usually at ppt (parts per 10¹²) levels. Many analytical techniques, including chromatographic and spectrophotometric ones, have been presented in the literature to detect organotins at these low levels. Liquid-liquid extraction is commonly employed as a concentration method. However, it presents some disadvantages during sampling campaigns and requires large volumes of toxic and expensive solvents. In this paper we propose an analytical method based on a liquid-solid extraction procedure that can be easily performed in the field and is characterized by good recoveries and high enrichment factors. Three different solid phases (Carbopack, LC 8 and LC 18) and five different eluting agents (methanol/tropolone, methanol, dichloromethane, hexane and diethyl ether) were evaluated. Carbopack and LC 18 were the most suitable solid phases. Inorganic tin was not retained on these solid phases and a separation of TBT from DBT and MBT was achieved, performing the elution in two steps with methanol and methanol/tropolone. In this way GF AA was suitably employed to obtain butyltin speciation data.     

Determination of selected trace elements in marine biota samples with the application of fast temperature programs and solid sampling continuous source high resolution atomic absorption spectroscopy: method validation

Analytical procedure for the determination of As, Cd, Cu, Ni, Co and Cr in marine biota samples using solid sampling high-resolution continuum source atomic absorption spectrometry (HR CS AAS) and accelerated fast temperature programmes has been developed. Calibration technique based on the use of solid certified reference materials similar to the nature of the analysed sample and statistics of regression analysis were applied. A validation approach in line with the requirements of ISO 17025 standard and Eurachem guidelines was followed. Accordingly, blanks, selectivity, calibration, linearity, working range, trueness, repeatability and reproducibility, limits of detection and quantification and expanded uncertainty for all investigated elements were assessed. The major contributors to the combined uncertainty of the analyte mass fractions were found to be the homogeneity of the samples and the microbalance precision. Traceability to the SI system of units of the obtained with the proposed analytical procedure results was also demonstrated. The potential of the proposed analytical procedure based on solid sampling HR CS AAS technique was demonstrated by direct analysis of marine reference biota samples. Overall, the use of solid sampling HR CS AAS permits obtaining significant advantages for the determination of selected trace elements in marine biota samples, such as straightforward calibration, a high sample throughput, sufficient precision, a suitable limit of detection and reduced risk of analyte loss and contamination.     

Determination of Rare earth elements in environmental samples by solid phase extraction ICP OES

A simple sample pre-treatment method for rare earth elements enrichment from environmental water samples prior to optical emission spectrometry determination with inductively coupled plasma (ICP OES) is proposed based on solid phase extraction with octadecyl silica gel modified with 1,2,5,8-tetrahydroxyanthraquinone. Optimal experimental conditions including pH of sample solution, sample volume, type, concentration and volume of eluent were investigated and established. Rare earth elements ions were quantitatively adsorbed from aqueous solution onto octadecyl silica gel modified with Quinalizarin at pH 7.0. The adsorbed ions were eluted with 1.0 mL of 2 M HNO₃ and simultaneously determined by ICP OES. Under obtained optimum conditions the calibration curves were linear with the coefficient of variation better than 0.99. The limit of detection of the method for the studied elements was in the range of 0.0004–0.01 ng/mL. The proposed method has a pre-concentration factor of 320–450 in water samples, which results in high sensitivity detection of trace ions. The developed method gave recoveries better than 80% and RSDs less than 15%.     

Determination of tetracyclines in milk samples by magnetic solid phase extraction flow injection analysis

A method is presented for magnetic solid phase extraction (MSPE) of tetracyclines in milk samples. The method involves the extraction and clean-up by silica based magnetic support dispersion on non-pretreated milk samples, followed by the magnetic isolation and desorption of the analytes by acidified methanol. The tetracyclines eluted from the magnetic support were determined simultaneously by flow injection analysis with spectrophotometric detection. Under optimal conditions, the linear range of the calibration curve ranges from 0.03 to 0.60 mg L^?1, with a limit of detection of 10 μg L^?1. Recoveries were determined for milk spiked at levels from 0.15 to 0.60 mg L^?1. Average recoveries ranged from 91.0 to 97.0%, with a precision of <5.0% in all cases. The method was validated by comparing the results with those obtained by MSPE-HPLC and SPE-HPLC. No significant differences were observed (p?<?0.05)     

顶空固相微萃取-气相色谱-质谱联用法测定海洋沉积物中的苯系物

利用顶空固相微萃取（HS-SPME）与气相色谱-质谱（GC-MS）联用建立了测定海洋沉积物中的苯、甲苯、乙苯、对二甲苯、间二甲苯、邻二甲苯以及苯乙烯等7种常见苯系物的检测分析方法。对无机盐的加入、平衡时间、萃取温度、萃取时间、解吸温度和时间等多个固相微萃取条件以及色谱条件进行了优化,内标法定量。结果表明：在0.500~20.0 ng/g范围内7种苯系物的线性关系良好,相关系数在0.995~0.999之间;方法检出限为0.0818~0.175 ng/g（干重）;日内和日间重现性较好,相对标准偏差分别为1.2%~3.6%（n=5）和0.4%~6.3%（n=3）;在每1.00 g海洋沉积物样品中2.0和15.0 ng加标水平下,平均加标回收率分别为61.7%~79.5%和77.1%~85.6%,相对标准偏差分别为5.4%~9.6%和3.9%~7.6%（n=5）。该方法快速、灵敏、简便,准确度高,重现性好,适合海洋沉积物样品中苯系物的痕量分析。     

Determination of methyl ester contents in biodiesel blends by FTIR-ATR and FTNIR spectroscopies

Partial last square regression (PLS) and artificial neural network (ANN) combined to FTIR-ATR and FTNIR spectroscopies have been used to design calibration models for the determination of methyl ester content (%, w/w) in biodiesel blends (methyl ester + diesel). Methyl esters were obtained by the methanolysis of soybean, babassu, dende, and soybean fried oils. Two sets of samples have been used: Group I, binary mixtures (diesel + one kind of methyl ester), corresponding to 96 biodiesel blends (0–100%, w/w), and Group II, quaternary mixtures (diesel + three types of methyl esters), corresponding to 60 biodiesel blends (0–100%, w/w). The PLS results have shown that the FTNIR model for Group I is more precise and accurate (±0.02 and ±0.06%, w/w). In the case of Group II the PLS models (FTIR-ATR and FTNIR) have shown the same accuracies, while the ANN/FTNIR models has presented better performance than the ANN/FTIR-ATR models. The best accuracy was achieved by the ANN/FTNIR model for diesel determination (0.14%, w/w) while the worthiest was that of dende ANN/FTIR-ATR model (0.6%, w/w). Precisions in Group II analysis ranged from 0.06 to 0.53% (w/w) and coefficients of variation were better than 3% indicating that these models are suitable for the determination of diesel–biodiesel blends composed of methyl esters derived from different vegetable oils.