Large-volume PTV injection: Comparison of direct water injection and in-vial extraction for GC analysis of triazines

Summary The potential of large-volume PTV injection was studied for the analysis of triazine herbicides in water samples. Direct water injection and in-vial extraction were described and compared. Detection limits were between 0.01–0.02 μg L⁻¹ and relative standard deviations were <9%. Both methods are suitable for the analysis of triazines at ppt-level, although in-vial extraction is favourable for water samples with relatively large amounts of matrix components.     

Trace analysis of isothiazolinones in water samples by large-volume direct injection liquid chromatography tandem mass spectrometry

Isothiazolinones are used as preservatives, biocides and disinfectants in a variety of industrial and domestic applications. Some of the isothiazolinones are difficult to isolate from water due their high polarity. A sensitive and selective analytical method was developed and optimized for the determination of sub-μg/L levels of three isothiazolinones in water samples. Three isothiazolinones are described in this paper: 2-methyl-3-isothiazolinone, 5-chloro-2-methyl-3-isothiazolinone and 4,5-dichloro-2-methyl-3-isothiazolinone. The analytical method involves a robust large-volume direct on-column loop injection of 2 mL on an Aqua ODS HPLC column and tandem MS detection (HPLC–MS/MS). After filtration, samples are directly injected without further pretreatment. Detection limits of the individual target compounds were between 0.03 and 0.1 μg/L employing Multi-Reaction Monitoring (MRM) mass spectrometry. Based on the constant ratio of two selected product-ions together with the retention time, the identification is very selective and quantification is reliable. The method was successfully applied to real samples of membrane flushings, drinking water, surface waters and waste water. Additional investigations showed the instability of the isothiazolinones in river- and waste water. Preservation of river water and waste water samples with sodium azide (NaN₃) promotes the stability of the isothiazolines in solution. In membrane flushings, waste water, surface waters and drinking water, levels of the three isothiazolinones were all below the limit of detection. In effluents of households containing washings from normal shampoo use, isothiazolinones could be detected.     

Micro liquid-liquid extraction combined with large-volume injection gas chromatography-mass spectrometry for the determination of haloacetaldehydes in treated water

Haloacetaldehydes (HAs) are becoming the most widespread disinfection by-products (DBPs) found in drinking water, besides trihalomethanes and haloacetic acids, generated by the interaction of chemical disinfectants with organic matter naturally present in water. Because of their high potential toxicity, HAs have currently received a singular attention, especially trichloroacetaldehyde (chloral hydrate, CH), the most common and abundant compound found in treated water. The aims of this study are focused on the miniaturisation of EPA Method 551.1, including some innovations such as the use of ethyl acetate as the extracting solvent, the enhancement of HAs stability in aqueous solutions by adjusting the pH ~3.2 and the use of a large-volume sample injection (30 μL) coupled to programmed temperature vaporizer-gas chromatography-mass spectrometry to improve both sensitivity and selectivity. In optimised experimental conditions, the limits of detection for the 7 HAs studied ranged from 6 to 20 ng/L. Swimming pools have recently been recognized as an important source of exposure to DBPs and as a result, in this research for the first time, HAs have been determined in this type of water. Two HAs have been found in the analysed water: CH at concentrations between 1.2-38 and 53-340 μg/L and dichloroacetaldehyde between 0.07-4.0 and 1.8-23 μg/L in tap and swimming pool waters, respectively.     

Determination of organophosphate esters in air samples by dynamic sonication-assisted solvent extraction coupled on-line with large-volume injection gas chromatography utilizing a programmed-temperature vaporizer

An on-line method for the determination of airborne organophosphate esters based on dynamic sonication-assisted solvent extraction and large-volume injection (LVI) gas chromatography with nitrogen-phosphorous detection is introduced. The LVI is performed with a programmed-temperature vaporizer. The entire extracted fraction of 800 microl (hexane-methyl-tert.-butyl ether, 7:3, v/v) is introduced directly into the GC system without any clean-up step following extraction. The extraction and analysis step were completed in less than 15 min. The limit of detection of the investigated organophosphate esters was established to be in the range of 5-32 pg/filter. The correlation coefficients (r2) were investigated in the linear range study of the entire system and established to be approximately 0.9900 for all the investigated organophosphates esters. Applications of the method was demonstrated with the extraction of air samples collected onto glass fiber filters from different indoor environments. Six organophosphate esters were found at the levels 0.4-138 ng/m3.     

Ultra-trace analysis of pesticides by solid-phase extraction of surface water with carbopack B cartridges, combined with large-volume injection in gas chromatography

Summary A method has been developed for determination of twenty-four polar pesticides—nine organophosphorus pesticides, thirteen organonitrogen compounds, and two triazine degradation products—in surface water. It entails extraction of the target pesticides from 1-L water samples by solid-phase extraction (SPE), then gas chromatography (GC) with large-volume (40 μL) injection. Filtered surface water, from the St Lawrence River in Canada and the River Loire and its tributaries in France, was extracted on cartridges filled with 500 mg Carbopack B (120–400 mesh). Analysis was performed by gas chromatography with a thermionic specific detector (GC-TSD) and a mass spectrometric (MS) detector. Overall percentage recoveries were satisfactory (>70%) for all target pesticides, with precision below 10%. Detection limits were between 0.5 and 4 ng L⁻¹.     

A study of large-volume on-column injection GC-ECD for the ultratrace analysis of organochlorine pesticides in water

In this work, a large-volume on-column injection method for the analysis of 21 organochlorine pesticides, including HCH isomers, DDT derivatives and cyclodiene derivatives, was optimized. The solvent selected to carry out the study was ethyl acetate and the injection volume was 100 μl. Some factors were introduced in a Plackett-Burman design to determine their influence in the vaporization efficiency. The significant factors were then studied by a univariate procedure and sorted according to their importance on the response. The effect of the injection conditions on the peak resolution was also noted. The conditions selected according to sensitivity and resolution were: initial oven temperature 75 °C, injection speed 20 μl s⁻¹, solvent vapor exit (SVE) valve closure time 60 s, initial pressure 100 kPa and isothermal oven time 1 min. Analytical characteristics expressed in terms of precision, linear range, and limit of detection have been determined and compared with those obtained by splitless injection. The degradation of endrin and p,p′-DDT thermolabile pesticides was evaluated for both injection techniques. Finally the developed method was successfully applied to the ultratrace analysis of pesticides in natural waters. With this purpose a micro liquid-liquid extraction method using 2 ml of ethyl acetate to extract 10 ml of water sample was proposed. Recoveries between 69 and 107% were obtained with a very good precision (0.2-1.3%) for the studied pesticides, except for p,p′-DDD. Detection limits between 0.3 and 25 ng l⁻¹, which fulfill the limits established by the new water directive 2008/105/EC, were achieved. The MLLE method was compared with the SPE method by the analysis of some water samples using both procedures, and good concordance was obtained.     

Determination of triazine herbicides by capillary gas chromatography with large-volume on-column injection

Summary This paper describes a study of the potential of large-volume on-column injection for the determination of triazine herbicides in clean water samples (ground-water). The sensitivity of chromatographic determination has been increased by two orders of magnitude by injection of up to 200 μL of pesticide solutions and nitrogen-phosphorus detection. Analytical characteristics expressed as precision, linear range and limit of detection have been determined, the results indicating adequate analytical performance and the ruggedness of the injection technique. As an application, gas chromatography with large-volume on-column injection and nitrogen-phosphorus detection was combined with off-line liquid-liquid micro-extraction with hexane (1 mL water/1 mL hexane). The procedure was applied to spiked groundwater samples at two concentration levels (1 and 10 μg L⁻¹) with good recoveries (between 81 and 103%, except for deethylatrazine) and repeatability (better than 15% at the 1 μg L⁻¹ level). Limits of detection of the triazine herbicides studied ranged from 0.08 to 0.16 μgL⁻¹.     

Detection of s-triazine pesticides in natural waters by modified large-volume direct injection HPLC

There is a need for simple and inexpensive methods to quantify potentially harmful persistent pesticides often found in our water-ways and water distribution systems. This paper presents a simple, relatively inexpensive method for the detection of a group of commonly used pesticides (atrazine, simazine and hexazinone) in natural waters using large-volume direct injection high performance liquid chromatography (HPLC) utilizing a monolithic column and a single wavelength ultraviolet-visible light (UV-vis) detector. The best results for this system were obtained with a mobile phase made up of acetonitrile and water in a 30:70 ratio, a flow rate of 2.0 mL min⁻¹, and a detector wavelength of 230 nm. Using this method, we achieved retention times of less than three minutes, and detection limits of 5.7 μg L⁻¹ for atrazine, 4.7 μg L⁻¹ for simazine and 4.0 μg L⁻¹ for hexazinone. The performance of this method was validated with an inter-laboratory trial against a National Association of Testing Authorities (NATA) accredited liquid chromatography-mass spectrometry/mass spectrometry (LC-MS/MS) method commonly used in commercial laboratories.     

Determination of pharmaceutical residues in waters by solid-phase extraction and large-volume on-line derivatization with gas chromatography-mass spectrometry

This work presents a modified method to analyze selected pharmaceutical residues (clofibric acid, ibuprofen, carbamazepine, naproxen, ketoprofen and diclofenac) in water samples. Various solid-phase extraction cartridges were investigated. The newly developed Oasis HLB (polystyrene-divinylbenzene-N-vinyl pyrrolidone terpolymer) solid-phase extraction (SPE) cartridge provides the optimal sample extraction results. The analytes were then identified and quantitatively determined by gas chromatography-mass spectrometry (GC-MS) via on-line derivatization in the injection-port using a large-volume (10 microl) sample injection with tetrabutylammonium (TBA) salts. This injection-port derivatization technique provides sensitivity, fast and reproducible results for pharmaceutical residues analysis. Mass spectra of butylated derivatives and tentative fragmentation profiles are proposed. Molecular ions and some characteristic ions were used as the quantitation ions to obtain maximum detection sensitivity and specificity. The quantitation limits of these compounds ranged from 1.0 to 8.0 ng/l in 500 ml tap water samples. Recovery of these residues in spiked various water samples ranged from 50 to 108% while RSD ranged from 1 to 10%. The selected analytes were detected in concentrations of 30 to 420 ng/l in wastewater treatment plant effluent and river water samples.     

Water pollution screening by large-volume injection of aqueous samples and application to GC/MS analysis of a river Elbe sample

The large-volume sampling of aqueous samples in a programmed temperature vaporizer (PTV) injector was used successfully for the target and non-target analysis of real samples. In this still rarely applied method, e.g., 1 mL of the water sample to be analyzed is slowly injected direct into the PTV. The vaporized water is eliminated through the split vent. The analytes are concentrated onto an adsorbent inside the insert and subsequently thermally desorbed. The capability of the method is demonstrated using a sample from the river Elbe. By means of coupling this method with a mass selective detector in SIM mode (target analysis) the method allows the determination of pollutants in the concentration range up to 0.01 μg/L. Furthermore, PTV enrichment is an effective and time-saving method for non-target analysis in SCAN mode. In a sample from the river Elbe over 20 compounds were identified. Received: 17 June 1996 / Revised: 22 November 1996 / Accepted: 25 November 1996     

Water pollution screening by large-volume injection of aqueous samples and application to GC/MS analysis of a river Elbe sample

The large-volume sampling of aqueous samples in a programmed temperature vaporizer (PTV) injector was used successfully for the target and non-target analysis of real samples. In this still rarely applied method, e.g., 1 mL of the water sample to be analyzed is slowly injected direct into the PTV. The vaporized water is eliminated through the split vent. The analytes are concentrated onto an adsorbent inside the insert and subsequently thermally desorbed. The capability of the method is demonstrated using a sample from the river Elbe. By means of coupling this method with a mass selective detector in SIM mode (target analysis) the method allows the determination of pollutants in the concentration range up to 0.01 μg/L. Furthermore, PTV enrichment is an effective and time-saving method for non-target analysis in SCAN mode. In a sample from the river Elbe over 20 compounds were identified. Received: 17 June 1996 / Revised: 22 November 1996 / Accepted: 25 November 1996     

三氯乙酸沉淀法结合姜黄素法测定血红蛋白氧载体中残余硼

建立了一种三氯乙酸沉淀法结合姜黄素法测定血红蛋白氧载体中硼残余含量的方法.以血红蛋白氧载体:三氯乙酸=9:1(V/V)的比例用三氯乙酸沉淀血红蛋白氧载体中聚合血红蛋白,离心5000 g×10 min将溶液中的沉淀分离,获得游离硼化物,聚合血红蛋白沉淀引起体积的缺失由生理盐水补齐,依次加入硫酸冰乙酸混合酸、姜黄素冰乙酸溶...     

流动注射双安培法测定环境水样中苯酚

基于苯酚在铂电极上的氧化和不可逆电对的双安培检测原理,建立了流动注射双安培测定环境水样中苯酚的新方法。通过偶合苯酚在一支铂电极上的氧化和KMnO4在另一支铂电极上的还原这两个不可逆电对,构建双安培检测体系,在外加电位差为0V时,苯酚的氧化电流与其浓度在1.0×10-6～1.0×10-4mol/L范围内呈线性关系,检出限为5.0×10-7mol/L,连续30次测定2.0×10-5mol/L苯酚,电流值RSD为1.4%。用本方法分别对几种含酚废水样品中苯酚含量进行测量,并与4 氨基安替比啉比色法进行了对照。     

On-line multi-bed sorption trap for VOC analysis of large-volume vapor samples: injection plug width, effects of water vapor and sample decomposition

A multibed on-line sorption trap is used to preconcentrate organic vapors from air samples and inject the analytes into a GC separation column. Injection plug widths depend on the boiling point for the lipophilic compounds and on the polarity and boiling point for the polar compounds. Injection plug widths are sufficiently small (0.7-0.8 s) as to allow the direct injection of the most volatile compounds into the GC column without the need for a second focusing device. The presence of water in the samples has an effect on the retention of polar compounds by the trap. However, this effect is reproducible for a fixed water content and so can be overcome by using calibration standards under the same conditions of humidity as the samples. The thermal decomposition of many volatile organic compounds in an on-line sorption trap during the GC analysis of air samples is examined. The results show that degradation of unstable compounds is governed by the amount of heat transferred to the compounds during desorption (i.e., applied temperature and pulse duration). The use of an on-line trap results in the immediate transfer of desorbed compounds to the analytical column, which can reduce the formation of artifacts.     

Determination of PAHs in airborne particles by accelerated solvent extraction and large-volume injection-gas chromatography-mass spectrometry

A sensitive and automated method is presented for the determination of polycyclic aromatic hydrocarbons (PAHs) in airborne particulate matter. The procedure includes extraction of PM10-bound PAHs by accelerated solvent extraction (ASE) followed by gel permeation chromatography (GPC) clean-up, and large-volume programmable temperature vaporizer (PTV-LV) injection coupled to GC-MS. The limit of detection (LOD) of the whole method, based on a signal-to-noise ratio (S/N) of 3:1, ranged from 0.26 pg m⁻³ to 3 pg m⁻³ when air volumes of 760 m³ are collected.The hexane-acetone mixture (1:1, v/v) gave the best recoveries when ASE parameters were fixed at 125 °C, 1500 psi, and a total time of 10 min. The recoveries for all PAHs tested ranged from 96% to 103%, rates similar to those obtained by the Soxhlet reference method.To improve the sensitivity, 70 μL were injected. The PTV-LV injection settings were optimized using a statistical design of experiments, including a screening 2⁴ full factorial design and a further central composite design. A sensitivity increase from 10 to 50 times was achieved as compared with the conventional 2 μL splitless injection.The method was validated with the standard reference material SRM 1649a and applied to real PM10 samples from the monitoring network of the Regional Valencia Government (Spain).The analytical performance of the method shows that it is appropriate to monitor PAHs levels in ambient air according to European Union Directives. In addition, the method can be used when a high sensitivity is required.     

Studies of the heat of vaporization of water associated with cellulose fibers characterized by thermal analysis

The heat of vaporization (H _vap) of water associated with cellulose fibers versus moisture ratio was determined using modulated differential scanning calorimetry. A steep increase in the H _vap for decreasing moisture ratio was observed at low moisture ratios (0.0–0.3 g/g), indicating a higher energy required to evaporate water interacting with the cellulose. The water molecules with elevated H _vap correspond to non-freezing bound water. This may be attributed to (a) energy to break mono and/or multilayer sorption and (b) energy to overcome capillary forces. For polypropylene and glass fibers, H _vap was constant versus moisture ratio, in agreement with no non-freezing bound water existing in these systems. It is suggested that non-freezing bound water could be used as an indicator of H _vap, and vice versa, at low moisture ratios.     

The effect of gas injection on a thermal argon plasma flow in a water-cooled tube

The effect of gas injection on an atmospheric thermal argon plasma flow in a water-cooled tube was investigated experimentally and numerically. The injection gas is argon, helium, or nitrogen. The static pressure with helium injection increases greatly because of its high thermal conductivity, while little increase occurs for nitrogen injection because of the dissociation. The increasing rate of the static pressure depends on the ratio of the momentum term to the viscosity term. The heat flux to the tube wall with gas injection changes less than that without injection. The numerical results showed variations similar to the experimental ones.     

Development of an environment-friendly microextraction method for the determination of aliphatic and aromatic aldehydes in water

Aldehydes are produced in water disinfected primarily by ozone treatment, and are generally present in treated water below the limit of detection (<5 μg L⁻¹) of commonly proposed methods. Formaldehyde is the most studied along with acetaldehyde due to their mutagenic character, and because it causes chromosomal aberrations. This paper reports the first miniaturised system for the simultaneous determination of thirteen aldehydes (aliphatic and aromatic) which are selected based on their frequent or suspected presence in water, mainly as disinfection by-products (DBPs). The micro liquid–liquid extraction (MLLE) method is a miniaturisation of EPA Method 556.1 for carbonyl compounds that includes some innovations, such as performing the derivatising reaction in a strong acidic medium (pH 1.1), and the addition of magnesium sulphate to the aqueous layer as the heating agent, which allows to carry out the whole simultaneous derivatisation/microextraction process in only 1 min. Large-volume sample injection (50 μL) coupled to programmed temperature vaporiser–gas chromatography–mass spectrometry is also used to improve both sensitivity and selectivity. The MLLE method demonstrated high extraction efficiency (96%) with low limits of detection, between 0.7 and 80 ng L⁻¹, and good precision (RSD below 10%, n = 11). The proposed method was evaluated by determining aldehydes in water. Our study demonstrated that the selection of the target aldehydes was appropriate since all were found (at average concentrations from 8.0 to 1.4 μg L⁻¹ for aliphatic and aromatic aldehydes, respectively) in swimming pool waters as DBPs.     

顺序注射阻抑动力学光度法测定环境水样中的间苯二酚

在酸性条件下,利用间苯二酚能抑制罗丹明B和溴酸根反应速率的原理,联用顺序注射技术建立了非平衡态快速测定痕量间苯二酚的新方法.优化了顺序注射流路参数、试剂用量,考察了共存物的影响.在最佳条件下,该法测定间苯二酚的线性范围为0.20～3.00 μg/mL,检出限为0.09 μg/mL,每小时可测定40个样.     

The use of thermal desorption GC/MS to study weight loss in thermogravimetric analysis of di-acid salts

Thermal desorption gas chromatograph mass spectrometry (TD GC/MS) was used to study weight loss in thermogravimetric analysis (TGA). The technique of thermal desorption utilizes the same temperature heating rate as the TGA to thermally desorb volatiles from solid sample matrices. Volatiles were cryo-trapped at −60 °C. After thermal desorption is complete, the trapped volatiles are separated by a GC capillary column and identified by mass spectrometry. In this study, the TD GC/MS was applied in pharmaceutical development to understand the chemical reactions attributed to the weight loss in the thermal decomposition of two dicarboxylic acid salts of a drug substance. These two salts exhibited different thermal stabilities. The thermally induced chemical reactions obtained from these two salts included dehydration and decarboxylation. Thermal degradation compounds were identified and reaction pathways for decomposition were proposed. The stability of the salts is dependent on the identity of the dicarboxylic acids from which they were generated. The information obtained from TD GC/MS helps better understand the weight loss process in thermogravimetric analysis.