Bulk analysis by IR laser ablation inductively coupled plasma atomic emission spectrometry

Two laser ablation systems dedicated to bulk analysis were evaluated for steel and PVC samples, using inductively coupled plasma atomic emission spectrometry detection. These systems were characterized by the use of a Nd:YAG laser operating at 1064 nm, the absence of observation device and a large laser spot size. The 1064 nm wavelength was selected to avoid the use of frequency-multiplying optics, and to be less critical to the sampling position. Calibration graphs and limits of detection are given for both types of materials. LODs were in the range 3-120 microg/g for steel, and in the range 0.07-15 microg/g for PVC. In the case of steel samples, similar calibration graph slopes were obtained between polished and unpolished samples.     

A Complementary Metal Oxide Semiconductor sensor array based detection system for Laser Induced Breakdown Spectroscopy: Evaluation of calibration strategies and application for manganese determination in steel

This paper describes a low cost detection system for Laser Induced Breakdown Spectroscopy based on a simple spectrograph employing a conventional diffraction grating and a non-intensified, non-gated, non-cooled 1024 pixel Complementary Metal Oxide Semiconductor linear sensor array covering the spectral range from about 250 to 390 nm. It was employed in conjunction with a 1064 nm, 5 ns pulse duration Nd:YAG laser source for analyzing steel samples using the integration of 300 analysis pulses (35 mJ each). That led to gains in the signal-to-noise ratio of approximately 3 and 16 for Mn and Fe peaks, respectively, in addition to gains in the emission intensities of about 5.3, both in comparison with the integration of just 50 analysis pulses. The acquired emission spectra were used for Mn determination, in the range from 0.214 to 0.608% m/m as previously determined by ICP OES, evaluating different univariate (at different discrete wavelengths) and multivariate (over different spectral ranges) calibration strategies. The best results, using a PLS calibration model in the spectral range from 292.9 to 294.5 nm (related to Mn emission peaks), had relative errors of prediction of the Mn concentrations, for samples not employed in the calibration, from 0.3 to 7.3%, which are similar to or better than those obtained for Mn determination in steel using higher cost detection systems. The successful analytical application of the new detection system demonstrated that the performance of low cost detection systems can be very good for specific applications and that its low resolution and sensitivity can be at least partially compensated by the use of chemometrics and the integration of analysis pulses.     

Evaluation of different sample introduction approaches for the determination of boron in unalloyed steels by inductively coupled plasma mass spectrometry

An extended study of different sampling introduction approaches using inductively coupled plasma mass spectrometry (ICP-MS) is presented for the determination of boron in steel samples. The following systems for sample introduction were applied: direct sample solution nebulization by continuous nebulization (CN) using a cross-flow nebulizer and with flow injection (FI), applied to 0.1% (m/v) and 0.5% (m/v) sample solutions, respectively; FI after iron matrix extraction, using acetylacetone–chloroform, and isotopic dilution (ID) analysis as the calibration method; FI with on-line electrolytic matrix separation; and spark ablation (SA) and laser ablation (LA) as solid sampling techniques. External calibration with matrix-matching samples was used with CN, SA, and LA, and only acid solutions (without matrix matching) with FI methods. When FI was directly applied to a sample solution, the detection limit was of 0.15 μg g⁻¹, improving by a factor of 4 that was obtained from the CN measurements. Isotopic dilution analysis, after matrix removal by solvent extraction, made it possible to analyse boron with a detection limit of 0.02 μg g⁻¹ and, with the on-line electrolytic process, the detection limit was of 0.05 μg g⁻¹. The precision for concentrations above 10 times the detection limit was better than 2% for CN, as well as for FI methods. Spark and laser ablation sampling systems, avoiding digestion and sample preparation procedures, provided detection limits at the μg g⁻¹ levels, with RSD values better than 6% in both cases. Certified Reference Materials with B contents in the range 0.5–118 μg g⁻¹ were used for validation, finding a good agreement between certified and calculated values.     

Recent trends and developments in laser ablation-ICP-mass spectrometry

The increased interest in laser technology (e.g. for micro-machining, for medical applications, light shows, CD-players) is a tremendous driving force for the development of new laser types and optical set-ups. This directly influences their use in analytical chemistry. For direct analysis of the elemental composition of solids, mostly solid state lasers, such as Nd:YAG laser systems operating at 1064 nm (fundamental wavelength), 266 nm (frequency quadrupled) and even 213 nm (frequency quintupled) have been investigated in combination with all available inductively coupled plasma mass spectrometers. The trend towards shorter wavelengths (1064 nm - 157 nm) was initiated by access to high quality optical materials which led to the incorporation of UV gas lasers, such as excimer lasers (XeCl 308 nm, KrF 248 nm, ArF 193 nm, and F2 157 nm) into laser ablation set-ups. The flexibility in laser wavelengths, output energy, repetition rate, and spatial resolution allows qualitative and quantitative local and bulk elemental analysis as well as the determination of isotope ratios. However, the ablation process and the ablation behavior of various solid samples are different and no laser wavelength was found suitable for all types of solid samples. This article highlights some of the successfully applied systems in LA-ICP-MS. The current fields of applications are explained on selected examples using 266 nm and 193 nm laser ablation systems.     

A new detection system for laser induced breakdown spectroscopy based on an acousto-optical tunable filter coupled to a photomultiplier: Application for manganese determination in steel

The development of a new detection system for laser induced breakdown spectroscopy (LIBS), based on a collinear quartz acousto-optical tunable filter (AOTF) for the ultraviolet spectral region coupled to a photomultiplier, is described. It was used in conjunction with a 1064 nm, 5 ns pulse duration neodymium-doped yttrium aluminium garnet (Nd:YAG) laser source and also employed a radio-frequency signal generator to control the AOTF and a digital delay generator to delay the start of the detection in relation to the instant of the application of the laser pulse. The detection system was optimized for highest detectivity for the manganese peak at 293.9 nm while analyzing a steel sample by LIBS. The resulting signal to background ratio at the optimal conditions of 2 µs delay time, 40 µs integration time gate and 110 mJ pulse energy was similar to that of a commercial echelle-intensified charge-coupled device (echelle-ICCD) detection system. The new detection system was then employed for manganese determination in steel samples, taking the emission signals at just 15 wavelengths, 5 related to the above mentioned manganese peak, another 5 to background emission around 296.0 nm and the others to the iron peak at 297.3 nm (internal standard). The resulting analytical curve for manganese, obtained using 5 samples in the concentration range of 0.214 to 0.939% w/w, presented a correlation coefficient of 0.979 for an exponential regression function. The relative errors of predicting the manganese concentrations, using the calibration curve, for 2 samples, containing 0.277 and 0.608% w/w, were 20.7 and − 1.9%, respectively.     

Recent trends and developments in laser ablation-ICP-mass spectrometry

The increased interest in laser technology (e.g. for micro-machining, for medical applications, light shows, CD-players) is a tremendous driving force for the development of new laser types and optical set-ups. This directly influences their use in analytical chemistry. For direct analysis of the elemental composition of solids, mostly solid state lasers, such as Nd:YAG laser systems operating at 1064 nm (fundamental wavelength), 266 nm (frequency quadrupled) and even 213 nm (frequency quintupled) have been investigated in combination with all available inductively coupled plasma mass spectrometers. The trend towards shorter wavelengths (1064 nm– 157 nm) was initiated by access to high quality optical materials which led to the incorporation of UV gas lasers, such as excimer lasers (XeCl 308 nm, KrF 248 nm, ArF 193 nm, and F₂ 157 nm) into laser ablation set-ups. The flexibility in laser wavelengths, output energy, repetition rate, and spatial resolution allows qualitative and quantitative local and bulk elemental analysis as well as the determination of isotope ratios. However, the ablation process and the ablation behavior of various solid samples are different and no laser wavelength was found suitable for all types of solid samples. This article highlights some of the successfully applied systems in LA-ICP-MS. The current fields of applications are explained on selected examples using 266 nm and 193 nm laser ablation systems.     

Studies of LA-ICP-MS on quartz glasses at different wavelengths of a Nd:YAG laser

The capability of LA-ICP-MS for determination of trace impurities in transparent quartz glasses was investigated. Due to low or completely lacking absorption of laser radiation, laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) proves difficult on transparent solids, and in particular the quantification of measurement results is problematic in these circumstances. Quartz glass reference materials of various compositions were studied by using a Nd:YAG laser system with focused laser radiation of wavelengths of 1064 nm, 532 nm and 266 nm, and an ICP-QMS (Elan 6000, Perkin Elmer). The influence of ICP and laser ablation conditions in the analysis of quartz glasses of different compositions was investigated, with the laser power density in the region of interaction between laser radiation and solid surface determining the ablation process. The trace element concentration was determined via calibration curves recorded with the aid of quartz glass reference materials. Under optimized measuring conditions the correlation coefficients of the calibration curves are in the range of 0.9–1. The relative sensitivity factors of the trace elements determined in the quartz glass matrix are 0.1–10 for most of the trace elements studied by LA-ICP-MS. The detection limits of the trace elements in quartz glass are in the low ng/g to pg/g range.     

Investigations on laser ablation–microwave induced plasma–atomic emission spectrometry using polymer samples

The potential of laser ablation–microwave induced plasma–atomic emission spectrometry (LA–MIP–AES) for the analysis of plastic materials has been investigated. A Nd/YAG laser, operated in its fundamental mode at 1064 nm, was used to ablate small amounts of various plastics. The sample atoms were transported and excited in a closely neighbored continuously running microwave induced plasma (MIP) operated in argon or helium at reduced pressure. A 0.5-m échelle spectrometer, equipped with an intensified charge coupled device (ICCD) as a detector was used for recording the spectra. The amount of ablated material was found to be strongly dependent on the matrix (10–190 ng/shot). Signals for some metals often used as additives in polymers (Al, Ca, Cu, Sb, Ti) and for the elements F, Cl, Br, J, and P in various polymers were recorded in the spectral range 250–840 nm. The estimated detection limits were found to be in the range 0.001–0.08% for metals and 0.05–0.7% for non-metals. Spectral lines of fluorine and iodine could only be measured in the helium MIP. For high concentrations of chlorine and carbon in the samples (polyvinylchloride), a memory effect was observed.     

Fast ultrasound‐assisted extraction followed by capillary gas chromatography combined with nitrogen–phosphorous selective detector for the trace determination of tebuconazole in garlic,soil and water samples

A fast and an efficient ultrasound‐assisted extraction technique using a lower density extraction solvent than water was developed for the trace‐level determination of tebuconazole in garlic, soil and water samples followed by capillary gas chromatography combined with nitrogen–phosphorous selective detector (GC–NPD). In this approach, ultrasound radiation was applied to accelerate the emulsification of the ethyl acetate in aqueous samples to enhance the extraction efficiency of tebuconazole without requiring extra partitioning or cleaning, and the use of capillary GC–NPD was a more sensitive detection technique for organonitrogen pesticides. The experimental results indicate an excellent linear relationship between peak area and concentration obtained in the range 1–50 μg/kg or μg/L. The limit of detection (S/N, 3 ± 0.5) and limit of quantification (S/N, 7.5 ± 2.5) were obtained in the range 0.2–3 and 1–10 μg/kg or μg/L. Good spiked recoveries were achieved from ranges 95.55–101.26%, 96.28–99.33% and 95.04–105.15% in garlic, Nanivaliyal soil and Par River water, respectively, at levels 5 and 20 μg/kg or μg/L, and the method precision (% RSD) was ≤5%. Our results demonstrate that the proposed technique is a viable alternative for the determination of tebuconazole in complex samples.     

ICP-AES内标法测定钢铁及其合金样品中的化学成分

建立了内标法测定钢铁样品中化学成分的ICP-OES分析方法。利用铟元素作为内标物质,消除了铁基体元素对被测元素的干扰,减少了废气、废液的产生。钢铁样品中16种被测元素的检测范围在0．001％-20．00％之间,检出限为0．001-0．030μg／mL,回收率为97％-110％。该方法减少了高纯物质的使用。     

Applicable and cost-efficient microplastic analysis by quantitative 1H-NMR spectroscopy using benchtop NMR and NoD methods

In continuation of our work on the proof-of-concept that quantitative NMR spectroscopy may be a valuable tool in microplastic (MP) analysis and quantification, we present here investigations using low-field NMR spectrometers and nondeuterated solvents for the analysis of solutions of MP particles in suitable solvents. The use of low-field NMR spectrometers (benchtop NMR) that are considerably more cost-effective in terms of purchase and operating costs compared with high-field NMR spectrometers and the use of nondeuterated solvents (NoD method) leads to an applicable and cost-efficient method for mass-based MP analysis. For benchtop 80-MHz NMR, limits of detection for polyvinylchloride (PVC), polyethylene terephthalate (PET), and polystyrene (PS) are in the same range as if a high-field 500-MHz NMR spectrometer was used for quantification (500 MHz: PET 1 μg/ml, PVC 42 μg/ml, and PS 9 μg/ml; 80 MHz: PET 4 μg/ml, PVC 19 μg/ml, and PS 21 μg/ml) for polymers being dissolved in deuterated solvents. The same is true for the corresponding limits of quantification. Moreover, it is shown for the first time that quantitative determination of the mass concentration of PET, PVC, and PS is also possible using NoD methods by evaluating the integrals of polymer-specific signals relative to an internal or external standard. Detection limits for NoD methods are in a similar range as if deuterated solvents were used (PET 2 μg/ml, PVC 39 μg/ml, and PS 8 μg/ml) using a high-field 500-MHz spectrometer or the 80-MHz spectrometer (PET 5 μg/ml).     

High Performance Liquid Chromatongraphy of ABBOTT-53385 in Dog,Rat, and Human Plasma

Abstract

A simple, sensitive and reproducible high-performance liquid chromatographic (HPLC) method was developed to monitor plasma ABBOTT-53385 (I) levels in dogs, rats and humans. The samples were first supplemented with the internal standard, then extracted on Bond Elut® extraction columns. They were analyzed by reverse-phase HPLC with UV detection at 240 nm. The calibration curve was rectilinear over the range of 0.05–2.0 μg/ml and the interday variance was less than 4%. The limit of detection for this method was about 0.03 μg/ml.     

Electrochemically controlled fiber‐in‐tube solid‐phase microextraction method for the determination of trace amounts of antipsychotic drugs in biological samples

In this study, a novel ‘fiber‐in‐tube’ configuration was applied to electrochemically controlled fiber‐in‐tube solid‐phase microextraction of antipsychotic drugs (perphenazine and chlorpromazine) from biological samples. To prepare an electrochemically controlled fiber‐in‐tube solid‐phase microextraction column, first eight stainless‐steel wires were placed into the stainless‐steel column. Then, a nanostructured Cu‐Cr‐Al ternary layered double hydroxide/polythiophene coating was prepared on the inner surface of the stainless‐steel tube and on the surfaces of the stainless‐steel wires by a facile in situ electrodeposition method. The nanostructured coating exhibited enhanced long lifetime, good mechanical stability, high porosity, and large specific surface area compared with polythiophene and Cu‐Cr‐Al layered double hydroxide coatings. Under the optimal conditions, the limits of detection were in the range of 0.07–0.8 μg/L. This method showed good linearity for perphenazine and chlorpromazine in the ranges of 0.3–300 and 0.2–300 μg/L, respectively, with coefficients of determination more than 0.9982. The inter‐ and intra‐assay precisions (RSD%, n = 3) were in the ranges of 3.0–5.1 and 2.5–4.5% at three concentration levels of 5, 25 and 50 μg/L, respectively. Finally, the method was applied for the analysis of the drugs in human urine and plasma samples.     

Continuous determination of chloroquine in plasma by laser-induced photochemical reaction and fluorescence

A flow injection fluorimetric method is proposed for the determination of chloroquine based on the photochemical derivatisation in an alkaline medium of the analyte and fluorescence generation after irradiation with a pulsed Nd:YAG laser operated at 355 nm. Chemical, hydrodynamic and laser variables were studied in order to obtain the best conditions for quantification. A linear range from 25 to 600 μg/L was achieved, with a correlation coefficient of 0.997 (n = 8), an RSD of 4.3% (n = 11) and a detection limit of 8 μg/L (3σ). The sample throughput was 10 h^–1. The method was successfully applied to the determination of chloroquine in human plasma. The increase of sensitivity with respect to the method based on monitoring the intrinsic fluorescence of chloroquine itself was 1.7 times.     

Analysis of heavy metals in soils using laser-induced breakdown spectrometry combined with laser-induced fluorescence

The investigation of a hyphenated technique combining laser-induced breakdown spectrometry (LIBS) with laser-induced fluorescence (LIF) for the analysis of heavy metals in soils is described. In order to evaluate the applicability of the technique for fast in-situ analytical purposes, measurements were performed at atmospheric pressure. The plasma radiation was detected using a Paschen–Runge spectrometer equipped with photomultipliers for the simultaneous analysis of 22 different elements. The photomultiplier signals were processed by a fast gateable multichannel integrator. Calibration curves were recorded using a set of spiked soil samples. Limits of detection were derived from these curves for As (3.3 μg/g), Cd (6 μg/g), Cr (2.5 μg/g), Cu (3.3 μg/g), Hg (84 μg/g), Ni (6.8 μg/g), Pb (17 μg/g), Tl (48 μg/g) and Zn (98 μg/g) using the LIBS signals. LIBS-LIF measurements were performed for Cd and Tl. The excitation wavelength as well as the detected fluorescence wavelength for Cd was 228.8 nm. Alternatively, Tl was excited at 276.8 nm, where the observed fluorescence wavelength was 351.9 nm. The calibration curves based on the LIF signals showed significantly improved limits of detection of 0.3 and 0.5 μg/g for Cd and Tl, respectively.     

Quasi ‘non-destructive’ laser ablation-inductively coupled plasma-mass spectrometry fingerprinting of sapphires

A homogenized 193 nm excimer laser with a flat-top beam profile was used to study the capabilities of LA-ICP-MS for ‘quasi’ non-destructive fingerprinting and sourcing of sapphires from different locations. Sapphires contain 97–99% of Al₂O₃ (corundum), with the remainder composed of several trace elements, which can be used to distinguish the origin of these gemstones. The ablation behavior of sapphires, as well as the minimum quantity of sample removal that is required to determine these trace elements, was investigated. The optimum ablation conditions were a fluency of 6 J cm⁻², a crater diameter of 120 μm, and a laser repetition rate of 10 Hz. The optimum time for the ablation was determined to be 2 s, equivalent to 20 laser pulses. The mean sample removal was 60 nm per pulse (approx. 3 ng per pulse). This allowed satisfactory trace element determination, and was found to cause the minimum amount of damage, while allowing for the fingerprinting of sapphires. More than 40 isotopes were measured using different spatial resolutions (20–120 μm) and eight elements were reproducibly detected in 25 sapphire samples from five different locations. The reproducibility of the trace element distribution is limited by the heterogeneity of the sample. The mean of five or more replicate analyses per sample was used. Calibration was carried out using NIST 612 glass reference material as external standard. The linear dynamic range of the ICP-MS (nine orders of magnitude) allowed the use of Al, the major element in sapphire, as an internal standard. The limits of detection for most of the light elements were in the μg g⁻¹ range and were better for heavier elements (mass >85), being in the 0.1 μg g⁻¹ range. The accuracy of the determinations was demonstrated by comparison with XRF analyses of the same set of samples. Using the quantitative analyses obtained using LA-ICP-MS, natural sapphires from five different origins were statistically classified using ternary plots and principal multi-component analysis.     

Studies of LA-ICP-MS on quartz glasses at different wavelengths of a Nd:YAG laser

The capability of LA-ICP-MS for determination of trace impurities in transparent quartz glasses was investigated. Due to low or completely lacking absorption of laser radiation, laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) proves difficult on transparent solids, and in particular the quantification of measurement results is problematic in these circumstances. Quartz glass reference materials of various compositions were studied by using a Nd:YAG laser system with focused laser radiation of wavelengths of 1064 nm, 532 nm and 266 nm, and an ICP-QMS (Elan 6000, Perkin Elmer). The influence of ICP and laser ablation conditions in the analysis of quartz glasses of different compositions was investigated, with the laser power density in the region of interaction between laser radiation and solid surface determining the ablation process. The trace element concentration was determined via calibration curves recorded with the aid of quartz glass reference materials. Under optimized measuring conditions the correlation coefficients of the calibration curves are in the range of 0.9-1. The relative sensitivity factors of the trace elements determined in the quartz glass matrix are 0.1-10 for most of the trace elements studied by LA-ICP-MS. The detection limits of the trace elements in quartz glass are in the low ng/g to pg/g range.     

双波长双指示剂-催化动力学光度法测定奶粉中的锌

研究发现在HCl介质中,痕量锌对H2O2氧化甲基紫和亚甲基蓝褪色具有强烈的催化作用,通过测量580 nm和668 nm处催化反应体系和非催化反应体系吸光度的变化,建立了双波长双指示剂催化动力学光度法测定痕量锌的新方法。在最佳实验条件下,线性范围为1.5~60μg/L,线性方程为ΔA=0.0169ρZn2+(μg/mL)+0.0019,r=0.9982,方法检出限为0.84μg/L。该方法可用于奶粉痕量锌的测定。     

Metal–organic framework UiO‐67‐coated fiber for the solid‐phase microextraction of nitrobenzene compounds from water

A sol–gel coating technique was applied for the preparation of a solid‐phase microextraction fiber by coating the metal–organic framework UiO‐67 onto a stainless‐steel wire. The prepared fiber was explored for the headspace solid‐phase microextraction of five nitrobenzene compounds from water samples before gas chromatography with mass spectrometric detection. The effects of the extraction temperature, extraction time, sample solution volume, salt addition, and desorption conditions on the extraction efficiency were optimized. Under the optimal conditions, the linearity was observed in the range of 0.015–12.0 μg/L for the compounds in water samples, with the correlation coefficients (r) of 0.9945–0.9987. The limits of detection of the method were 5.0–10.0 ng/L, and the recoveries of the analytes from spiked water samples for the method were in the range of 74.0–102.0%. The precision for the measurements, expressed as the relative standard deviation, was less than 11.9%.     

A high performance liquid chromatographic method for the determination of ethylenethiourea in urine and on filters

Urine samples are evaporated and pretreated with silica gel and alumina. Filters undergo ultrasonic treatment in water. Ethylenethiourea (ETU) is then determined by reversed-phase high-performance liquid chromatography with detection at 230 nm. The detection limit for ETU is 0.1 ng per injection and linear response is found for the range 0.3–110 ng; 0.2 μg 1^?1 ETU can be detected in urine. Recoveries from spiked filters (7 μg ETU/filter) varied from 79 to 94%. The methods are sensitive enough for application in occupational hygiene work.