Substoichiometric preconcentration in radioanalytical methods

The application of substoichiometric (with respect to interfering elements) separation as a method of preliminary concentration is suggested in order to decrease the contents of interfering elements to permissible levels in the methods of determination. The equations for the calculations of enrichment factors and isolated fractions of test elements are derived and the corresponding dependences are plotted. The combination of substoichiometric concentration with some new radioanalytical methods allows comparatively simple determinations of micro amounts of one element to be made in the presence of macro amounts of other elements with similar chemical properties.     

Assay of p-aminobenzenesulphonamides with chloramine-T

New spectrophotometric and titrimetric methods for the assay of p-aminobenzenesulphonamides with chloramine-T have been developed. They are simple, reproducible and accurate within the limits described (+/-3%) and are useful at high concentration levels. These methods are also applicable to the assay of p-aminobenzenesulphonamides in rat urine.     

Measurement of total protein in urine: Comparison of two dye-binding procedures with a gel filtration/modified biuret method

Two dye-binding methods for the determination of urinary total protein concentration have been compared to a biuret-based procedure requiring a preliminary gel filtration step. The biuret-based procedure is claimed to be both specific and sensitive for the measurement of protein in urine. With those urines having relatively low protein concentrations, the dye-binding methods provide values about one-half of those given by the modified biuret procedure. This difference disappears when urines containing high levels of protein are measured. The lower results obtained at normal protein levels are most likely caused by the inability of dye-binding methods to measure proteins of high carbohydrate content (such as uromucoid) accurately. In spite of this limitation, both dye-binding methods appear suitable for routine use. In contrast to the biuret-based procedure, we found the dye-binding methods to be free from interferences by compounds known to appear in urine in high concentrations.     

Fluorimetry compared to spectrophotometry for uranium evaluation in liquid waste

Uranium concentration levels in surface waters are of great importance because uranium presents both chemical and radiological hazard to the environment. The subject of this article is to establish that spectrophotometric method for uranium evaluation in effluents collected from liquid waste treatment generated during fabrication of nuclear fuel elements could be replaced by the optical fluorimetric technique. Both methods are briefly described. The comparison of the two methods was carried out with regard to international standards and national regulations offering from a statistical point of view a useful approach to compare two analytical measurement techniques. This methodology can be applied to any other measurement procedures. A discussion about the compliance of the fluorimetric analytical method with the mandatory discharge level of uranium concentration in surface waters is also presented.     

The analysis of high-purity noble metals and their salts by ICP-MS

Ongoing work is being carried out at Mintek to establish methods for the determination of trace levels of impurities in high-purity noble metals and their salts. The sample-preparation methods are outlined, and the optimum instrumental parameters that were established are tabulated. Spectral interferences arising from the presence of a matrix element at high concentration levels, including abundance sensitivity overlap and the formation of noble-metal oxides, are discussed. Accuracy was established by the comparison of the results with those obtained by a DC-arc method, and by spike recovery tests. The precision of measurement was found to vary from 0.72 to 49% S(r) for concentrations of between 15 and 0.5 gmg/g, respectively.     

Techniques and procedures for preparation of aquatic samples for chromatographic analyses

The measurement of low levels of organic compounds in environmental samples presents the researcher with a number of possible pathways to effectively obtain and analyze samples. Numerous sampling methods, sample preparation techniques, and extraction procedures are available. A number of different approaches to sampling strategy, isolation, concentration, cleanup and fractionation will be discussed. Objectives for collecting environmental samples differ from those for many other types of samples because reliable measurements at very low levels are frequently required. Often, specific analytes need to be measured at the μg/kg and even ng/kg levels in complex matrices. Advances in analytical methodology continue to lower the levels at which reliable measurements can be made. At these levels, many factors that are of little or no concern in other analytical measurements are of critical importance in influencing the outcome and reliability of environmental analyses. Analytical measurements are used for determining the composition and the quantities of analytes in the defined system at various concentration levels. Environmental analytical measurements provide data about the transportation and transformation of an environmental contraminant and for determination of its concentration in a sample.     

Boron Determination—A Review of Analytical Methods

This paper reviews published methods of sample preparation, determinand purification, and the determination of boron concentration and isotopic composition in a sample. The most common methods for the determination of B concentration are spectrophotometric and plasma-source spectrometric methods. Although most spectrophotometric methods are based on colorimetric reactions of B with azomethine-H, curcumin, or carmine, other colorimetric and fluorometric methods have also been used to some extent. These methods, in general, suffer from numerous interferences and have low sensitivity and precision. Application of nuclear reaction and atomic emission/absorption spectrometric (AES/AAS) methods has remained limited because these methods have poor sensitivity and suffer from serious memory effects and interferences. Among a large number of published nuclear reaction methods only prompt-γ spectrometry has been of practical use. The prompt-γ method can determine B concentration in intact samples, which makes this method especially useful for some medical applications, including boron neutron capture therapy. However, this is a time-consuming method and not suitable for detection of low levels of B. Inductively coupled plasma optical emission spectrometry (ICP-OES) created a new dimension in B determination because of its simplicity, sensitivity, and multielement capability. However, it suffers interferences and is not adequately sensitive for some nutritional and medical applications involving animal tissues that are naturally low in B. All methods involving the measurement of B isotopic composition require a mass spectrometer. Thermal ionization mass spectrometry (TIMS) and secondary ion mass spectrometry (SIMS) have been used to measure isotopic composition of B; however, these methods are time consuming and require extensive sample preparation and purification. Development of inductively coupled plasma mass spectrometry (ICP-MS) not only overcame most of the drawbacks of earlier methods, but also its capabiltiy of measuring B isotopes made possible (1) B concentration determination by isotope dilution, (2) verification of B concentration by isotope fingerprinting in routine analysis, and (3) determination of total B concentration and B isotope ratio for biological tracer studies in the same run. Therefore, plasma source MS appears to be the method of choice among present-day technologies.     

Detection of traces of formaldehyde in pure air by gas chromatography and helium ionization detection

The sensitive helium ionization detector (HID) was used for the direct determination of ppm to ppb levels of formaldehyde in air. Two methods to generate formaldehyde in an air stream were evaluated. The first method utilized a paraformaldehyde permeation tube and the second utilized a motor driven syringe and a dilute solution of formaldehyde. The two methods were evaluated using gas chromatography with HID and spectrophotometry. The paraformaldehyde permeation tube generates only about 60% of the theoretical value, while the motor driven syringe was accurate for levels below 2 ppm; however, at a concentration of 13 ppm or above, oligomers or other chemical forms of CH2O are formed to decrease the concentration of gaseous CH2O produced.     

Fast gas chromatography for pesticide residues analysis

The importance of method development in the area of pesticide residues analysis is apparent from legislative requirements continuously decreasing the maximum acceptable concentration levels in food and water. This covers also contribution in the science in the field of ultra-trace analysis of organic pollutants in complex mixtures. Analysis time is one of the most important aspects that should be considered in the choice of analytical methods for routine application. With this fact, fast gas chromatography (GC) has acquired a real importance in the pesticide residue analysis. This paper provides an overview of fast GC methods for analysis of pesticide residues in variety of matrices at ultra-trace concentration levels. Emphasis is put on the development in the last 6 years.     

高效毛细管电泳分离的优化策略

本文提出一种新的优化策略，综合分析表面活性剂浓度、缓冲液ＰＨ值、有机添加剂浓度，缓冲溶液浓度及操作电压等实验因素对高效毛细管电泳分离的影响，用多种优化目标函数考察分离度和峰分布均匀性。     

Assessment of photosensitizer dosimetry and tissue damage assay for photodynamic therapy in advanced-stage tumors

Photodynamic therapy (PDT) efficacy is a complex function of tissue sensitivity, photosensitizer (PS) uptake, tissue oxygen concentration, delivered light dose and some other parameters. To better understand the mechanisms and optimization of PDT treatment, we assessed two techniques for quantifying tissue PS concentration and two methods for quantifying pathological tumor damage. The two methods used to determine tissue PS concentration kinetic were in vivo fluorescence probe and ex vivo chemical extraction. Both methods show that the highest tumor to normal tissue PS uptake ratio appears 4 h after PS administration. Two different histopathologic techniques were used to quantify tumor and normal tissue damage. A planimetry assessment of regional tumor necrosis demonstrated a linear relationship with increasing light dose. However, in large murine tumors this finding was complicated by the presence of significant spontaneous necrosis. A second method (densitometry) assessed cell death by nuclear size and density. With some exceptions the densitometry method generally supported the planimetry results. Although the densitometry method is potentially more accurate, it has greater potential subjectivity. Finally, our research suggests that the tools or methods we are studying for quantifying PS levels and tissue damage are necessary for the understanding of PDT effect and therapeutic ratio in experimental in vivo tumor research.     

Determination of caffeine and caffeine-related metabolites in ephedra-containing standard reference materials using liquid chromatography with absorbance detection and tandem mass spectrometry

The concentrations of caffeine and caffeine-related compounds in 2 ephedra-containing reference materials have been determined by 3 independent methods with measurements performed by the National Institute of Standards and Technology (NIST) and a collaborating laboratory. Results from the 3 methods were used for value assignment of caffeine, theobromine, and theophylline in these Standard Reference Materials (SRMs). The methods used at NIST to determine the concentration levels of caffeine, theobromine, and theophylline in SRM 3243 Ephedra-Containing Solid Oral Dosage Form and SRM 3244 Ephedra-Containing Protein Powder used reversed-phase liquid chromatography with absorbance detection and tandem mass spectrometry. These reference materials are part of the first suite in a series of NIST SRMs that provide concentration values for multiple components in dietary supplements. These SRMs are primarily intended for method validation and for use as control materials to support the analysis of dietary supplements and similar materials.     

Measurement of240Pu/239Pu ratio by fission track method and inductively coupled plasma mass spectrometry

Fission track /FT/ method and inductively coupled plasma mass spectrometry /ICP-MS/, that is a new analytical technique for the analysis of trace element, were used for the measurement of²⁴⁰Pu/²³⁹Pu ratios in environmental samples. The results obtained by both methods are in agreement within the relative deviation of 9–13%. The precision in ICP-MS was found to be better than in it the FT-method. These methods are applicable to measure the Pu isotopes ratio at low concentration levels in environmental samples.     

Extraction,separation, and fluorometric analysis of selected environmental contaminants

Teratogenic, carcinogenic, and pervasive endocrine disrupting compounds (EDCs) in suspect water systems present an immediate threat to both the environment and potable water supplies. The US Environmental Protection Agency mandated research regarding suspect EDCs, personal care products, and pesticide pollution requires the use of suitable methods of analysis that can perform extraordinarily well in the field and show low “cost to benefit” ratios. Such methods must increasingly address the need for enhanced sensitivity and selectivity in interrogating complex mixtures. Here, several device and method optimization strategies, specific for these classes of compounds, are discussed and include, among others, the preconcentration of field samples utilizing high performance extraction disk cartridges. Matrix interferences and undetectable concentration levels are eliminated by the way of an RP extraction technique that is vital to obtaining detectable concentrations of target analytes in the ppb range. Established capillary EKC methods are modified and implemented on a short capillary for low nanoliter discrete injections, efficient separations, and detection with LIF of analyte mixtures. Efficient separations were achieved with plate counts ranging from 10³ to 10⁴. Analytes spiked into real sample matrices at ppb levels were easily separated and detected via LIF using a He/Cd laser operating at 325 nm. The presented techniques are valuable in determining both the presence and concentration of suspect contaminates in different water systems. The methods presented here could easily be extended to microfluidic platforms with little to no optimization for on‐site testing.     

食品中主要霉菌毒素分析方法的研究进展

食品中霉菌毒素的检测面临基质复杂、污染浓度水平低的困扰,研发选择性高、富集能力强的样品前处理方法和高灵敏的分析方法对于提升食品中霉菌毒素的检测能力、保障食品安全具有重要意义。该文综述了近年来食品中霉菌毒素分析方法的研究进展,并对其发展方向作总结和展望。     

Creatinine determination in urine samples by batchwise kinetic procedure and flow injection analysis using the Jaffé reaction: chemometric study

The classical Jaffé reaction for the determination of creatinine in urine samples is tested. A comparative study of the main analytical characteristics focussed to minimize the bias error and improve the precision, for the batchwise and flow injection (FI) methods is realized. Also, the effect of the albumin concentration in the determination of creatinine has been studied. Different analytical signals were studied. Absorbance increments at different times permit to estimate the creatinine concentration free from bias error in urine by the batchwise method using the calibration graph obtained with creatinine standards and no measurement of the blank solution is needed. The lineal interval was 0.92-50 mg l(-1) and seven samples can be processed per hour by an operator. No previous treatment of the urine sample is necessary. The FI method provides also good results. The lineal interval was 30-100 mg l(-1) and the sample rate was around 20 samples per hour. If increased albumin levels are detected in the urine, standard addition method or the calibration graphs with standards in presence of albumin are needed in order to obtain accurate results when FI method is employed. The obtained accuracy of the both methods allows its application as diagnostic tool to establish the urinary creatinine levels.     

Creatinine determination in urine samples by batchwise kinetic procedure and flow injection analysis using the Jaffé reaction: chemometric study

The classical Jaffé reaction for the determination of creatinine in urine samples is tested. A comparative study of the main analytical characteristics focussed to minimize the bias error and improve the precision, for the batchwise and flow injection (FI) methods is realized. Also, the effect of the albumin concentration in the determination of creatinine has been studied. Different analytical signals were studied. Absorbance increments at different times permit to estimate the creatinine concentration free from bias error in urine by the batchwise method using the calibration graph obtained with creatinine standards and no measurement of the blank solution is needed. The lineal interval was 0.92–50 mg l⁻¹ and seven samples can be processed per hour by an operator. No previous treatment of the urine sample is necessary. The FI method provides also good results. The lineal interval was 30–100 mg l⁻¹ and the sample rate was around 20 samples per hour. If increased albumin levels are detected in the urine, standard addition method or the calibration graphs with standards in presence of albumin are needed in order to obtain accurate results when FI method is employed. The obtained accuracy of the both methods allows its application as diagnostic tool to establish the urinary creatinine levels.     

Geostandards and geochemical analysis

Progress in geochemical analysis depends on progress in geostandards. The present state of the availability and quality of the geostandards is reviewed for major and trace elements. The several geochemical methods employed are evaluated by their performances in the characterization of geostandards. Signs of progress are visible in the quality of geostandards for major and “common” trace elements. There are also new developments in geoanalytical methods. It is hoped that optical emission inductively coupled plasma spectrometry will play an increasing role in the characterization of trace elements which are normally present in less than 10 ppm concentration levels.Like it or not, progress in geochemical analysis is intimately tied up with the quality of geochemical reference samples (GRS). The converse is true as well; therefore, how well and to what extent international geochemical reference samples are characterized for their chemical composition reflect in a way the current status of geoanalytical methods employed the world over.     

Analytical methods for determination of free metal ion concentration, labile species fraction and metal complexation capacity of environmental waters: A review

Different experimental approaches have been suggested in the last few decades to determine metal species in complex matrices of unknown composition as environmental waters. The methods are mainly focused on the determination of single species or groups of species.The more recent developments in trace elements speciation are reviewed focusing on methods for labile and free metal determination.Electrochemical procedures with low detection limit as anodic stripping voltammetry (ASV) and the competing ligand exchange with adsorption cathodic stripping voltammetry (CLE-AdCSV) have been widely employed in metal distribution studies in natural waters. Other electrochemical methods such as stripping chronopotentiometry and AGNES seem to be promising to evaluate the free metal concentration at the low levels of environmental samples. Separation techniques based on ion exchange (IE) and complexing resins (CR), and micro separation methods as the Donnan membrane technique (DMT), diffusive gradients in thin-film gels (DGT) and the permeation liquid membrane (PLM), are among the non-electrochemical methods largely used in this field and reviewed in the text. Under appropriate conditions such techniques make possible the evaluation of free metal ion concentration.