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Analytical and Bioanalytical Chemistry (v.356, #1)

Certification of fat-soluble vitamins, carotenoids, and cholesterol in human serum: Standard reference material 968b by Jeanice Brown Thomas; Margaret C. Kline; Susannah B. Schiller; Polly M. Ellerbe; Lorna T. Sniegoski; David L. Duewer; Katherine E. Sharpless (pp. 1-9).

In Standard Reference Material 968b, fat-soluble vitamins and cholesterol in human serum, certified values are provided for cholesterol, retinol, retinyl palmitate, α-tocopherol, trans-β-carotene, total β-carotene (trans plus cis isomers), total α-carotene, and lutein. Non-certified values are also reported for γ-tocopherol (includes β-tocopherol), δ-tocopherol, zeaxanthin, β-cryptoxanthin, trans-lycopene, trans-lycopene, trans-α-carotene, total lycopene, 9-cis-β-carotene, 13-plus 15-cis-β-carotene, and 15-cis-β-carotene. Both certified and non-certified values are based on the agreement among results from three different liquid Chromatographic analytical procedures developed at NIST and from an interlaboratory comparison exercise among institutions that participate in a NIST-managed Micronutrients Measurement Quality Assurance Program. Cholesterol is certified in this material using the NIST isotope dilution/mass spectrometric definitive method.

Development of a reference material for residues of chlorfluazuron and fluazuron in beef fat ACSL CRM 3 by Paul Armishaw; Jennifer Ward; Roderick G. Millar (pp. 10-12).

A beef fat sample was prepared and tested as candidate reference material for the pesticides chlor-fluazuron (CFZ) and fluazuron (FZN). An analytical method employing HPLC with UV absorbance detection was developed for homogeneity and stability testing. The material consisted of beef fat spiked with acetone solutions of CFZ and FZN to achieve concentrations close to 1.0 mg/kg for each compound. The coefficients of variation of 7 analyses carried out to test between-jar homogeneity were 1.8% and 2.3% for FZN and CFZ, respectively. No instability of CFZ was detected over a three month period. The candidate reference material was found to be suitable for certification by interlaboratory testing.

Development of a reference material for residues of chlorfluazuron and fluazuron in beef fat ACSL CRM 3 by Paul Armishaw; Jennifer Ward; Roderick G. Millar (pp. 13-16).

The certification by interlaboratory testing of a candidate reference material (ACSL CRM 3) for the concentration (mass fraction) of the pesticides chlorfluazuron (CFZ) and fluazuron (FZN) is described. The certification process was based on a two-stage nested design described in ISO Guide 35. Analysis of results reported by collaborating laboratories provided an assessment of the homogeneity of the RM. The certified values were chlorfluazuron −1.01 mg/kg and fluazuron −1.02 mg/kg. The upper and lower 95% confidence limits for CFZ and FZN were calculated to be: CFZ upper = 1.05 mg/kg, lower = 0.97 mg/kg; FZN upper = 1.08 mg/kg, lower = 0.95 mg/kg. A certificate was prepared according to guidelines set out in ISO Guide 31.

Confidence intervals for calibration with neural networks by M. Dathe; M. Otto (pp. 17-20).

Based on neural network calibration the confidence intervals of aromaticity determination from infrared reflectance spectra of raw brown coals were estimated by means of the bootstrap method, a simplified Monte Carlo Simulation. The standard deviations and the confidence intervals were estimated to characterise the analysis error. It is shown that confidence intervals of non-linear analysis methods like Back Propagation Neural Networks (BPNN) can be estimated by the bootstrap method. The estimated confidence intervals of the calibration confirm the analysis by BPNN.

Element-specific determination of chlorine in gases by Laser-Induced-Breakdown-Spectroscopy (LIBS) by C. Haisch; R. Niessner; O. I. Matveev; U. Panne; N. Omenetto (pp. 21-26).

An experimental set-up for the detection of elemental chlorine in chlorinated hydrocarbons (CHCs) is described based on a miniaturized system, which could be used for on-line monitoring of chlorinated compounds. With an optimized time-resolved detection chlorine from CHCs like CCl₄ can be determined by Laser-Induced-Breakdown-Spectroscopy (LIBS) with μg/g-detection limits in the gas phase. The application of a miniaturized Nd: YAG laser resulted only in a minor loss in performance, hence it could be used for designing a rugged and small on-line sensor. In addition, preliminary results for the detection of chlorine via the formation of CuCl in the plasma formed by focussing the laser on a copper surface are reported. Utilizing the luminescence of the CuCl D-system at 440 nm, a tenfold improvement in the detection limits was obtained. It appears that the formation of “ad hoc” selected, small molecules in a laser plasma could be a promising alternative for the selective and sensitive analysis of gaseous chlorinated and other species.

A simple and versatile PSA system for heavy metal determinations by A. Bund; J. Dittmann; D. Lordkipanidze; G. Schwitzgebel (pp. 27-30).

An easy to build potentiometric stripping analysis system for heavy metal determinations (Zn, Cd, Pb, Cu) is described which reaches good sensitivity and precision. Main components are an IBM compatible computer, an ADDA-conversion card and two selfmade electrodes, so it can be realized for one tenth of the price of complete commercial systems. A graphite pencil lead covered with a Hg-film is used as working electrode and a Ag/AgCl electrode as a combined reference/counter electrode. Reproducibility and calibration measurements are reported, heavy metal determinations on soil samples are compared with AAS results.

Optimization of ETV-ICP-MS conditions for the determination of multi-elements in semiconductor grade acids by Laly Samuel; Katsuhiro Nakagawa; Tetsuya Kimijima (pp. 31-36).

The performance of an electro thermal vaporization (ETV) unit as a sample introduction device for an inductively coupled plasma mass spectrometer (quadrupole-ICP-MS) was evaluated. The technique was found to have several advantages over the conventional nebulization method. Some features of ETV-ICP-MS for single element determination have been investigated. Attempts were made to optimize the experimental parameters such as vaporization temperature, vaporization interval and carrier gas flow rate. The study highlights on the determination of Cr, Mn, Al and Na. A compromise condition for multielement determination was suggested and tested from single-element optimum conditions obtained. 25 μL solution was used for the analysis. Results obtained for the analysis of conc. HCl samples are also reported.

Quantitative determination of F:O ratios in rare earth oxide fluorides by energy dispersive X-ray analysis by V. Marx; O. Greis; H. Strübig; T. Petzel; J. -H. Müller (pp. 37-40).

The F:O ratio in homogeneous and inhomogeneous rare earth oxide fluoride systems of compositions RO_{1 + x}F_{1 − 2x} with − 0.1 ≤ × ≤ 0.1 can be determined by energy dispersive X-ray (EDX) analysis with an accuracy of ± 0.5% if an appropriate background modelling procedure is applied and if the EDX signals of the light elements are free of overlap from the accompanying rare earth element. The latter condition holds true for R = Tb-Lu and it is shown that the calibration of the method with well-defined samples of YbO_{1 + x}F_{1 − 2x} can be transferred with only a moderate loss of accuracy to the determination of oxygen and fluorine in DyOF and ErOF. Increasing signal overlap in case of GdOF, EuOF, SmOF and especially PrOF necessitates the choice of different channels for background modelling, and the accuracy of the method is hence decreasing to ± 4% for these systems.

Improvements in the determination of eight polycyclic aromatic hydrocarbons through a stepwise interlaboratory study approach by P. de Voogt; J. Hinschberger; E. A. Maier; B. Griepink; H. Muntau; J. Jacob (pp. 41-48).

A summarising account of a systematic stepwise approach based on interlaboratory studies carried out by a number of laboratories from European Union and EFTA countries is given. This approach has been designed to improve the analytical state of the art in the determination of selected polycyclic aromatic hydrocarbons in different environmental matrices. The approach resulted in a certification exercise to produce a sewage sludge as Certified Reference Material (CRM). The results of the programme showed that HPLC and GC are equally reliable for PAH analysis at submicrogram to microgram per gram levels in various environmental matrices. Major improvements were achieved during the programme, resulting in reduced coefficients of variation and between-laboratory differences. Several recommendations emerging from the programme experience are presented.

Automatic determination of total aliphatic amines by on-line photometric liquid-liquid microextraction by J. M. López Fernández; A. Ríos; M. Valcárcel (pp. 49-51).

An automatic flow method for the determination of total aliphatic amines has been developed. Using an integrated micro extraction unit at the detection point that allows continuous on-line monitoring of small organic plug from which amines are extracted. It is based on the formation of ion-pairs between aliphatic amines and sodium 1,2-naphthoquinone-5-sulphonate that are subsequently extracted into chloroform. The gradual enrichment of the organic phase with the ionpair is continuously monitored at 460 nm. Absorbance readings at a fixed time and the slopes of absorbancetime recordings are the measured parameters used for determination purposes. The proposed method has been applied to the determination of total aliphatic amines in both synthetic and real (food) samples.

Determination of trace metal ions Co, Cu, Mo, Mn, Fe, Ti, V in reference river water and reference seawater samples by inductively coupled plasma emission spectrometry combined with the third phase preconcentration by X. J. Li; P. Schramel; H. Z. Wang; P. Grill; A. Kettrup (pp. 52-56).

A combination of DAM-SCN-third phase extraction and inductively coupled plasma emission spectrometry (ICP-AES) is used for the determination of trace metal ions in a river water and a seawater reference material. An implementation of the third phase extraction prior to ICP-AES allows a preconcentration of trace elements (Co, Cu, Mn, Fe, V, Ti, Mn) by a factor ranging from 33 to 45. A complete separation of these elements is accomplished from matrices, normally affecting the excitation characteristics of ICP and suppressing the elemental signals severely. Different factors, including pH of the solutions, amounts of reagents, matrix effects, have been investigated and optimized. Under the conditions selected, the limits of determination have been in the range of 0.02 to 0.6 μg/L. The system has been successfully applied to the determination of Cu, Mn, V in the reference river water SLRS-3 and Mo in the reference seawater NASS-3. The results were in a good agreement with the certified values.

Speciation of organolead compounds in water samples by GC-AAS after in situ butylation with tetrabutylammonium tetrabutylborate by K. Bergmann; B. Neidhart (pp. 57-61).

A simple and reliable analytical method for the determination of organolead compounds in water samples has been developed by means of a gas chromatographicatomic absorption system (GC-AAS). The derivatization of the organolead cations, necessary before their determination, was directly achieved in the water samples by the reagent tetrabutylammonium tetrabutylborate. Hexane/pentane was used to extract the butylated tetraorganolead compounds. The organic layer was dried and purified with sodium sulfate, concentrated by evaporation and injected into a GC-AAS system. The effects of various parameters on the derivatization and extraction procedures were studied and discussed.

Determination of chlorinated pesticides and PCB in pine needles — improved method for the monitoring of airborne organochlorine pollutants by H. Kylin; E. Nordstrand; A. Sjödin; S. Jensen (pp. 62-69).

A method to determine organochlorine pollutants in pine needles is described. Fresh, whole needles have been extracted for 48 h in dichloromethane to obtain the epicuticular wax fraction. The remainder has been cut into small pieces and again extracted with dichloromethane to obtain the internal lipids. Prior to gas chromatography, both the wax and the internal lipid extracts have been fractionated on two columns: first a silica gel/silica gel: sulphuric acid 2 : 1 column with dichloromethane as eluent and then a nitrophenyl silica column with hexane as eluent. Three fractions have been collected, fraction 1 containing hexachlorobenzene (HCB), fraction 2 containing polychlorinated biphenyls (PCB) and l,l-dichloro-2,2-bis(4-chlorophenyl)ethene (DDE), and fraction 3 containing the remaining, more polar, organochlorine pesticides. For some pine species, the nitrophenyl silica column has been combined with a short aminopropyl silica column to obtain chromatograms of the PCB fraction free from negative peaks. The precision is in the range of 4–12% relative standard deviation, and the overall recovery is around 65–90%.

Spectrophotometric determination of nitrite in foodstuffs by flow injection analysis by J. F. Van Staden; M. A. Makhafola (pp. 70-74).

A simple method for the determination of nitrite in foodstuffs by flow injection analysis is described. Nitrite samples are prepared in a microwave oven, treated with a 1 mol/1 NH₄Cl solution at a pH of 9 (all under nitrogen atmosphere) and are immediately analysed. Nitrite is diazotised in the FIA system with N-(l-naphthyl) ethylenediammonium dichloride to form the highly coloured azo dye, which is measured at 540 nm. The detection limit is 0.036 mg/kg for sample injections of 400 μl. The sampling rate is about 50 samples per hour and the relative standard deviation is 0.67%.

Determination of salicylate in beverages and cosmetics by use of an amperometric biosensor by M. Ehrendorfer; G. Sontag; F. Pittner (pp. 75-79).

A fast and selective enzymatic method for the determination of salicylate in beverages and cosmetics has been developed. The enzyme salicylate hydroxylase was immobilised covalently onto a glassy carbon working electrode of a wall-jet cell coupled with a flowinjection analysis system. The salicylate is enzymatically converted to catechol, which can be detected amperometrically on the glassy carbon electrode at + 0.45 V. The response of the biosensor is linearly proportional to the concentration of salicylate between 725 nmol/l and 700 μmol/l. A high sample throughput (60 h⁻¹) is possible, and the biosensor is stable for more than three months. Sample pretreatment for beverages and hair lotions is easy and fast. For creams, an extraction of salicylate is necessary. Relative standard deviations are less than 5.5% and the recoveries are between 95 and 105%.

Head-space solid phase microextraction for the GC-MS analysis of terpenoids in herb based formulations by Jacek Czerwiński; Bogdan Zygmunt; Jacek Namieśnik (pp. 80-83).

Head-Space Solid Phase Microextraction (HS-SPME) has been employed for sampling of volatile components and their volatile decomposition products occurring in herbal medicines and herb extracts with subsequent injection into a gas chromatographic column. The identification and quantification was performed by coupled gas chromatography — mass spectrometry (GC-MS) with classical splitless injection, electron impact ionization and a quadrupole mass analyzer. As fast and inexpensive technique for the isolation of organic analytes HS-SPME with GC-MS can be successfully employed for the quality control of herbal medicines and other formulations containing herb extracts. Analytical results with satisfying accuracy and precision are given.

Immobilized 2-(4-hydrazinocarbonylphenyl)-4,5-diphenylimidazole as solid phase luminophore in peroxyoxalate chemiluminescence by Einar Pontén; Patrik Appelblad; Malin Stigbrand; Knut Irgum; Kenichiro Nakashima (pp. 84-89).

A new luminophore for application in peroxyoxalate chemiluminescence is presented. An analogue of the well-known chemiluminescence compound lophine, i.e. 2-(4-hydrazinocarbonylphenyl)-4,5-diphenylimidazole (HCPI), has been covalently immobilized to controlled pore glass and a porous methacrylate resin. By using this reagent in a solid phase detection reactor, sensitive determinations of hydrogen peroxide have been demonstrated. In homogeneous solution HCPI emits poorly as a result of 1,l′-oxalyldiimidazole excitation, but when immobilized its efficiency is almost comparable to highly efficient luminophores such as 3-aminofluoranthene. Linearity extends in the single stream flow system over several orders of magnitude with both materials. The limit of detection was 1 nmol/l (10 fmole injected), when using the porous methacrylate support.

Determination of mercury in biological fluids by potentiometric stripping analysis by Maha F. Tutunji (pp. 90-95).

A method is described for the determination of mercury by potentiometric stripping analysis. The analyte, Hg²⁺, is employed for oxidizing a fixed amount of cadmium, previously reduced and amalgamated at a thin mercury film preplated on a glassy carbon electrode. The cadmium stripping signal correlates well with the amount of Hg²⁺ added. Correlation coefficients of 0.9971 and 0.9960 were obtained for the two working ranges: (25 ng–2.5 μg) and (5.0–50) μg Hg²⁺, respectively, in spiked water samples. The method was investigated with respect to precision and accuracy by spiking a natural water sample with 25 μg Hg²⁺.Nine replicate determinations gave a mean value of 24.8 μg with a standard deviation ± 0.31 μg. The 95% confidence limit of the mean suggested the absence of systematic errors. Using the highest possible sensitivity, detection limits of 2.0 ng (167ng/l) and 0.5 ng (4.2 ng/100 ml of whole blood) were obtained in water and blood samples, respectively. The applicability of the method was successfully extended to include the more complex matrices after recording a zero blank from authentic samples spiked with Cd²⁺ (25 μg).The described PSA procedure is a simple and rapid method compared with the cold-vapor technique, with a 5.2% and 4.9% RSD, respectively.

Kinetic assay of antitrypsin in human serum by a surface acoustic wave (SAW)-impedance sensor by Qingyun Cai; Wei Wei; Ronghui Wang; Lihua Nie; Shouzhuo Yao (pp. 96-97).

Antitrypsin in human serum was determined by using both the SAW-impedance sensor system and spectrophotometry, indicating that the mean value for women was significantly higher than the mean value for men; the value for acute pancreasis patients is about 2-folds of the normal values, and there is no significant difference between the acute pancreasis patients and the pancreatic cancer patients.

Cyclodextrin- and sugar-derivatives as stationary phases for the gas chromatography of semivolatiles by Bernd Märker; Karlheinz Ballschmiter (pp. 98-99).

Cyclodextrins as cyclic hexa-(α) to octa-(γ) saccharides are widely and successfully used after esterification or etherification as stationary phases in gas chromatography for the separation of chiral compounds. Their basic potential as thermostable stationary phases as such or after derivatisation offers a unique spectrum of interactions ranging from hydrogen bonding to shape selectivity. Similar properties as thermostable stationary phases are shown by long-chain saccharide ethers (chain-length C8–C20), which are normally used as non-ionic detergents.

Determination of selenite, selenate and selenomethionine by ion chromatography, microwave digestion and HGAAS by N. Ellend; C. Rohrer; M. Grasserbauer; J. A. C. Broekaert (pp. 99-101).

An on-line system for the simultaneous determination of Se(IV), Se(VI) and selenomethionine (Se-Met) in aqueous samples was developed, consisting of separation by ion chromatography, microwave digestion and detection by hydride generation atomic absorption spectrometry. 8.3 mmol/l Na₂HPO₄ (pH 9.2) was used as mobile phase for the ion chromatography, with a flow-rate of 1.5 ml/min. After the separation the sample was mixed with concentrated KBr-HCl solution and heated with microwave energy to digest Se-Met and reduce Se(VI) to Se(IV). The detection limits were 15 μg/l, 12 μg/l and 103 μg/l for Se(IV), Se(VI) and Se-Met, respectively.

Direct determination of iron in ferritin using the polarographic catalytic current by Jiang Qiu; Junfeng Song; Hong Gao (pp. 101-103).

A new method for the determination of iron in ferritin using the polarographic catalytic current has been developed. Iron is released in NaOH and triethanolamine (TEA) solution and subsequently determined based on the polarographic catalytic wave in the presence of bromate with the peak potential of −1.0 V (vs.SCE). The 2.5-derivative peak height of iron is linearly proportional to its concentration in the range of 8.0 × 10⁻⁸–1.0 × 10⁻⁶ g/ml with a correlation coefficient of 0.9991. The method has been applied to the determination of iron in human fetal liver and horse-spleen ferritin and the recovery is 95–112%.

Application of the Azomethine-H method to the determination of boron in workplace atmospheres from ceramic factories by A. F. Roig-Navarro; F. J. López; F. Hernández (pp. 103-106).

The determination of boron in airborne particulates from ceramic factories’ workplaces has been investigated. Samples containing raw or fritted material powder from ceramic factories have been digested in Erlenmeyer flasks using nitric acid as reagent. Analysis was performed by the Azomethine-H method. Recoveries for different raw materials were quantitative, whereas for fritted materials they widely depend on their composition. Relative standard deviations for all materials tested were lower than 8%. The accuracy of the procedure was tested by the addition of known amounts of boron to different types of materials. Standard addition calibrations proved that there was no influence of the matrix. In workplace atmospheres of ceramic industries boron was usually present, in the environment of enamel factories with levels higher than the recommended exposure value.

Sensitive method for the determination of different S(IV) species in cloud and fog water by Gerhard Lammel (pp. 107-108).

Suppressed ion chromatography has been applied to the determination of S(IV) species in cloud and fog water in the range 0.012–2.4 mg S(IV)-S/L. The samples have been preserved prior to storage and S(IV) species have been determined as hydroxy methanesulfonate (HMS) together with the low molecular weight carboxylic acid anions, formate and acetate. Samples have been divided and treated differently such that total S(IV) as well as the non-oxidizable fraction of S(IV) (as given by the reactivity with H₂O₂, added in surplus) could be determined. The difference between the two corresponds to the S(IV) fraction subjected to oxididation, which is of paramount interest in cloud and fogwater chemistry.

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Analytical and Bioanalytical Chemistry (v.356, #1)