Direct Injection Of Large Volumes Research Articles

Determination of 145 pharmaceuticals and personal care products in eleven categories in water by ultra-high performance liquid chromatography-triple quadrupole mass spectrometry

Pharmaceuticals and personal care products (PPCPs) are emerging contaminants frequently detected in aquatic environments at trace levels. These chemicals have diverse structures and physicochemical properties and includes pharmaceuticals like antibiotics, antihypertensive drugs, antiviral drugs, and psychotropic drugs that are widely used in large quantities worldwide. Considering the large number of pharmaceuticals currently in usage, it is crucial to establish a priority list of PPCPs that should be monitored and/or treated first. An accurate understanding of the occurrence and levels of PPCPs in aquatic environments is essential for providing objective materials for monitoring these emerging contaminants. Therefore, accurate, efficient, sensitive, and high-throughput screening techniques need to be established for determining and quantifying PPCPs. This study developed a method for the determination of 145 PPCPs (grouped into eleven categories: antibiotics, antihypertensive drugs, antidiabetic drugs, antiviral drugs, β-receptor agonists, nitroimidazoles, H2 receptor antagonists, psychotropic drugs, hypolipidemic drugs, non-steroidal anti-inflammatory drugs, and others) in water. The method was based on large volume direct injection without sample enrichment and cleanup and used ultra-high performance liquid chromatography-triple quadrupole mass spectrometry (UHPLC-MS/MS). Water samples were collected and filtered through a 0.22-μm regenerated cellulose (RC) filter membrane. Subsequently, Na2EDTA was added to the samples to adjust their pH to 6.0-8.0. Internal standards were mixed with the solutions, and because of the addition of Na2EDTA, the interference of metal ions could be eliminated in the determination of compounds, especially for tetracycline and quinolone antibiotics. Among the six filter membranes tested in this study (PES, PFTE-Q, PFTE, MCE, GHP, and RC), RC filter membranes were screened for water sample filtration. The UHPLC-MS/MS parameters were optimized by comparing the results of various mobile phases, as well as by establishing the best instrumental conditions. The 145 PPCPs were separated using an Phenomenex Kinetex C18 column (50 mm×3 mm, 2.6 μm) via gradient elution. The mobile phases were 0.1% (v/v) formic acid aqueous solution containing 5 mmol/L ammonium formate and acetonitrile for positive ion modes, 5 mmol/L aqueous solutions of ammonium formate and acetonitrile for negative ion modes. The samples were quantified using the scheduled multiple reaction monitoring (scheduled-MRM) mode with electrospray ionization in positive and negative ion modes. A standard internal calibration procedure was used to calculate contents of sample. The established method was systematically verified, and it demonstrated a good linear relationship. The average recoveries of the 145 PPCPs at the three spiked levels were in the range of 80.4%-128% with relative standard deviations (RSDs, n=6) of 0.6%-15.6%. The method detection limits (MDLs) ranged from 0.015 to 5.515 ng/L. Finally, the optimization method was applied to analyze the 145 PPCPs in 11 surface water samples and 6 drinking water samples. Overall, 93 (64%) out of the 145 analytes were detected. The total contents of the PPCPs in surface water samples ranged from 276.9 to 2705.7 ng/L. The detection frequencies of antidiabetic, antiviral, and psychotropic drugs were 100%. The total contents of the PPCPs in drinking water samples ranged from 140.5 to 211.5 ng/L, and antibiotics, antidiabetic drugs, and antiviral drugs comprised the largest proportion of analytes (by mass concentration) in drinking water samples. Our method exhibited high analytical speed and high sensitivity. It is thus suitable for the trace analysis and determination of the 145 PPCPs in environmental water and showed improved detection efficiency for PPCPs in water, indicating that it has a high potential for practical applications. This study can extend technical support for further pollution-level analysis of PPCPs in water and provide an objective basis for environmental management.

Determination of ultra-trace level Cr(vi) in seawater using large-volume direct injection by LC-ICP-MS with in-line matrix elimination

A method to improve the sensitivity of LC-ICP-MS for the determination of hexavalent chromium (Cr(vi)) in seawater by using the large volume injection and in-line matrix elimination.

Combining chemical, bioanalytical and predictive tools to assess persistence, seasonality, and sporadic releases of organic micropollutants within the urban water cycle

Using a novel liquid chromatography-tandem mass spectrometry method with large volume direct injection and quantitation via isotope dilution, we evaluated the presence of 55 organic micropollutants in wastewater effluents, and locations within the Bow River and Elbow River watersheds in and around the city of Calgary, Alberta, Canada. In addition to establishing baseline micropollutant data for water utility operations, our study aimed to enhance our understanding of micropollutant behavior in the urban water cycle, assess the contributions of three wastewater treatment plants (WWTPs) to downstream receiving waters, explain the potential causes of total estrogenicity measured using the yeast-estrogen screen assay (YES), and prioritize a subset of substances for continuous monitoring. With data spanning 48 months and 95 river km, our results indicate the extensive persistence of metformin (antidiabetic), seasonality of N,N‑diethyl-m-toluamide (DEET, insect repellant), O-desmethylvenlafaxine (antidepressant metabolite), and sulfamethoxazole (antibiotic) in source waters, and sporadic detections of a well-known perfluoroalkyl substance (PFOA). The seasonality of pharmaceuticals at the sentinel downstream monitoring site appeared to coincide with river dilution while that of DEET was likely attributable to peak usage during the warmer months. Steroidal estrogens were rarely detected in wastewater effluents although total estrogenicity via YES was evident, suggesting the presence of less potent but more abundant non-steroidal estrogens (e.g., flame retardants, bisphenols, and phthalates). A conservative mass balance analysis suggests that the largest WWTP (serving a population of >1 million) consistently contributed the highest load of micropollutants, with the exception of metformin, which appeared to be influenced by a smaller WWTP (serving 115,000) that operates a different activated sludge process. We consider metformin, sucralose, diclofenac, and venlafaxine as more effective conservative tracers of wastewater pollution due to their notably higher concentrations and persistence in the Bow River compared to carbamazepine and caffeine, respectively. Finally, hierarchical clustering revealed a close association between E. coli and caffeine, supporting the use of caffeine as an indicator of short-term, untreated anthropogenic inputs. Overall, this study yields valuable insights on the presence, behavior, and sources of organic micropollutants in the urban water cycle and identifies indicators of anthropogenic impacts that are useful for prioritizing future monitoring campaigns in Calgary and elsewhere.

Enrichment and quantification of 18 polycyclic aromatic hydrocarbons from intermediates for plastics production by a generic liquid chromatography column switching.

The polycyclic aromatic hydrocarbon concentration in plastic products is regulated in (European Union) No. 1272/2013. However, this only covers the end products and not intermediate substances. Therefore, a generic method was developed to analyze the polycyclic aromatic hydrocarbons listed by the Environmental Protection Agency and the European Union. This method is based on direct large volume injection from solutions of plastic additives followed by liquid chromatography coupled to fluorescence detection. The additives Irganox 1010, ureido methacrylate, and cetyl methacrylate 1618F were used as examples for method development. Two serially coupled columns allowed the matrix to be removed on the first column and the analytes to be separated on the second column. The columns were connected by an intermediate valve. The valve allowed the matrix to be diverted after the first column and water to be dosed upstream of the second column via an additional pump. This allowed samples in aqueous or organic media to be focused at the column head. An injection volume of 100μl and online aqueous dilution of 1:3 led to a limit of detection below 1ng/ml for 15 polycyclic aromatic hydrocarbons. Moreover, concentrations between 1.6 and 10.3ng/ml were found in the three plastic additives.

Trace determination of disinfection by-products in drinking water by cyclic ion chromatography with large-volume direct injection.

A novel cyclic ion chromatography (IC) system was developed for the simultaneous determination of trace disinfection by-products (DBPs) in drinking water. Five DBPs (chlorite, bromate, chlorate, dichloroacetic acid, and trichloroacetic acid) were sensitively determined by large-volume direct injection, and the interferences of dominant inorganic anions present in water were eliminated online through the cyclic determination of the target analytes. Under optimized conditions, the obtained limits of detection (LODs) were in the range of 0.18-1.91 μg L-1 based on a signal-to-noise ratio (S/N) of 3 and an injection volume of 1.0 mL. The RSDs for peak area and retention time were in the range of 0.13-1.03% and 1.24-4.29%, respectively. Satisfactory recoveries between 92.3% and 106.4% were obtained by adding three concentration gradients of standards to the drinking water samples. The proposed method has advantages such as high sensitivity, facile automation, and no sample pretreatment, and might be a promising approach for routine analysis.

Determination of 42 antibiotic residues in seven categories in water using large volume direct injection by ultra high performance liquid chromatography-triple quadrupole mass spectrometry

抗生素作为新型有机污染物在自然水体中被频繁检出,检出种类多且含量水平低,为了实现更加快速、全面、准确的高通量分析,研究开发了一种利用大体积直接进样测定水中7大类(磺胺类、林可酰胺类、喹诺酮类、大环内酯类、四环素类、头孢类及氯霉素类)42种抗生素的超高效液相色谱-三重四极杆质谱法。水样经0.22 μm滤膜过滤,加入Na2EDTA并调节pH值至6.0~8.0,加入内标混匀后,采用Phenomenex Kinetex C18柱(50 mm×30 mm, 2.6 μm),以0.1%(v/v)甲酸水溶液-乙腈作为流动相进行梯度洗脱,质谱智能化分时间段-多反应选择离子监测(Schedule-MRM)模式进行检测。42种抗生素在相关线性范围内线性良好(r=0.9949~0.9995),回收率为80.1%~125%,相对标准偏差为0.8%~12.2%,方法检出限为0.015~3.561 ng/L。将该方法应用于10份水源水和5份末梢水的检测,结果显示在42种抗生素中,12种抗生素有检出,包括磺胺类、大环内酯类、林可酰胺类和氯霉素类,其在水源水中的检出率达100%;林可霉素和氯霉素是检出质量浓度最高的两种抗生素,它们的质量浓度范围分别为3.83~13.8和24.8~33.6 ng/L。该方法从检出限和回收率两方面与标准方法和文献报道进行了比较,检出限及回收率均满足要求。该方法与传统前处理方法相比具有简单、快速、绿色、精密度高、准确度高、消耗样品量小的优点,能用于地表水、地下水、末梢水等较为洁净水体中42种痕量水平的抗生素测定。

Improved protocols for large-volume injection and liquid chromatography–mass spectrometry analyses enable determination of various glycerol dialkyl glycerol tetraethers in a small amount of sediment and suspended particulate matter

Glycerol dialkyl glycerol tetraethers (GDGTs) have received considerable attention because they are useful indicators for paleoenvironment, organic matter source, and microbial community. In this study, a new simple method was developed for the analysis of GDGTs by using direct large-volume injection (LVI)–liquid chromatography (LC)–atmospheric pressure chemical ionization–mass spectrometry (APCI–MS) to reduce the usage of sediment or seawater suspended particulate matter (SPM) samples. The parameters of accelerated solvent extraction and LVI of target GDGTs were optimized. Under optimal conditions, the LVI approach (500 μL injection) coupled with LC–APCI–MS could determine various GDGTs even with 0.02–0.10 g of sediment samples or SPM samples collected from 0.2–1.0 L of marginal sea water or 10–20 L of open ocean seawater with satisfactory method precision (relative standard deviations ≤10.2%) and linearity (R2 ≥ 0.991). Compared with the classical method, the LVI–LC–APCI–MS required significantly reduced amount of sediment or SPM sample. Finally, the proposed method was applied to determine GDGTs in real sediment samples collected from hydrothermal vent sites at the Southwest Indian Ridges. Four groups of GDGTs, namely, isoprenoid GDGTs (isoGDGTs), branched GDGTs, H-GDGTs and OH-GDGTs, and archaeol, glycerol dialkanol diethers (GDDs) and glycerol monoalkanediol diethers (GMDs) were detected with only 0.02 g of sediment sample collected from Longqi and Tianzuo hydrothermal fields. The organic matter in the sediment sample from Tianzuo was significantly affected by hydrothermal activity. In addition, isoGDGTs in seawater SPM from the open area of Eastern Indian Ocean were investigated for the first time. Six common isoGDGTs were all detected in surface and subsurface SPM samples (filtering 10 L of seawater), which indicated that the LVI approach could noticeably reduce the workload of collecting seawater SPM on board and could be used to investigate conveniently the distribution of GDGTs in water column especially in open oceans and deep seas.

Quality by design optimization of a liquid chromatographic-tandem mass spectrometric method for the simultaneous analysis of structurally heterogeneous pharmaceutical compounds and its application to the rapid screening in wastewater and surface water samples by large volume direct injection

This study focused on the Analytical Quality by Design (AQbD) optimization of the chromatographic separation and mass spectrometric detection of a wide group of structurally heterogeneous model pharmaceutical compounds (PhCs) and transformation products (TPs), chosen to cover the challenging issues of the co-presence of compounds characterized by (i) a wide range of physicochemical properties, (ii) the same mass transitions, and (iii) different ionisation modes. Italian consumption of PhCs were also considered as election criteria of target analytes. Octadecyl and pentafluorophenyl stationary phases, acetonitrile/methanol ratios and acidity of the eluents, column temperature, initial organic phase percentage, and elution gradient were investigated by AQbD, aiming at optimizing critical resolutions, sensitivities, and analysis time. Statistically significant models were obtained in most cases with fitting and cross-validation coefficients in the ranges of 0.681-0.998 and 0.514-0.967, respectively. After optimization, the analysis of target analytes was performed in a single chromatographic run, adopting a mixed acquisition mode based on scheduled acquisition windows comprising both single polarity and continuous polarity switching. For most investigated analytes the method provided detection limits in the sub-ng/L to low ng/L range, meeting for macrolides the sensitivity requested by the “Watch List” 2018/840/EU. The optimized method was applied to the direct injection analysis of PhCs and TPs in four wastewater treatment plant (WWTP) effluents and surface water (SW) samples collected in the receiving water bodies. Absolute values of matrix effect were found to be far higher than 20% for most target analytes in most samples. Seventeen PhCs and two TPs were quantified in at least one sample, at the wide concentration range of about 1-3200 ng/L. The most occurring PhCs in both WWTP effluents and SWs were levofloxacin (202-1239 and 100-830 ng/L), furosemide (865-3234 and 230-880 ng/L), ketoprofen (295-1104 and 270-490 ng/L), and ibuprofen (886-3232 and 690-1440 ng/L).

Presence of Perfluoroalkyl Substances in Landfill-adjacent Surface Waters: Case Studies in Orange County and Sampson County, North Carolina

Background/Aim: Perfluoroalkyl substances (PFAS) are a synthetic class of compounds used in consumer products. Landfills have been identified as major sources of PFAS into the environment, though they are not commonly monitored in surface and groundwater near landfills in the US. This study characterized PFAS in surface waters adjacent to two landfills in North Carolina: one in Sampson County (SC) and another in Orange County (OC). The site in SC accepts PFAS-containing industrial sludge. Both sites are close to predominantly African-American neighborhoods. Landfills pose an important public health risk, especially in low-income communities and communities of color that are disproportionately sited for landfills and in rural areas where private wells may be impacted. Methods: Water samples were collected along surface water features near the landfills at points that were upstream, adjacent, downstream and downgradient. Samples were collected every 3 weeks between October 2019 and January 2020. Concentrations of thirty-four PFAS were measured using liquid chromatography with tandem mass spectroscopy (LC-MS) using the large volume direct injection method. A simple t-test was performed to determine if the average concentrations measured adjacent and downstream of the landfill were statistically significantly different from concentrations upstream of the landfill. Results: Across the 35 samples collected, we detected twelve PFAS (six novel and six legacy). Legacy PFAS were detected in surface water near both landfills, with concentrations most elevated at sampling sites adjacent to the landfill, compared to upstream sites. Novel PFAS were only detected in surface water near the SC landfill, with similar concentration profiles as the legacy PFAS. Conclusions: Offsite migration of leachate is the likely contributor of PFAS measured in landfill adjacent surface waters in SC and OC. These findings support the need for more comprehensive and more frequent water monitoring near landfills and stricter regulation regarding the landfilling of industrial materials.

Large Volume Direct Injection Ultra-High Performance Liquid Chromatography-Tandem Mass Spectrometry-Based Comparative Pharmacokinetic Study between Single and Combinatory Uses of Carthamus tinctorius Extract and Notoginseng Total Saponins.

The combination of Carthamus tinctorius extract (CTE) and notoginseng total saponins (NGTS), namely, CNP, presents a synergistic effect on myocardial ischemia protection. Herein, comparative pharmacokinetic studies between CNP and CTE/NGTS were conducted to clarify their synergistic mechanisms. A large volume direct injection ultra-high performance liquid chromatography–tandem mass spectrometry (LVDI-UHPLC-MS/MS) platform was developed for sensitively assaying the multi-component pharmacokinetic and in vitro cocktail assay of cytochrome p450 (CYP450) before and after compatibility of CTE and NGTS. The pharmacokinetic profiles of six predominantly efficacious components of CNP, including hydroxysafflor yellow A (HSYA); ginsenosides Rg1 (GRg1), Re (GRe), Rb1 (GRb1), and Rd (GRd); and notoginsenoside R1 (NGR1), were obtained, and the results disclosed that CNP could increase the exposure levels of HSYA, GRg1, GRe, GRb1, and NGR1 at varying degrees. The in vitro cocktail assay demonstrated that CNP exhibited more potent inhibition on CYP1A2 than CTE and NGTS, and GRg1, GRb1, GRd, quercetin, kaempferol, and 6-hydroxykaempferol were found to be the major inhibitory compounds. The developed pharmacokinetic interaction-based strategy provides a viable orientation for the compatibility investigation of herb medicines.

Impact of seasonality, redox conditions, travel distances and initial concentrations on micropollutant removal during riverbank filtration at four sites

Riverbank filtration (RBF) is a reliable water purification technique that has proven to be suitable for the removal of organic micropollutants. Its removal efficiency and dependency on a variety of factors such as redox conditions, temperatures, geology, travel times, level of initial micropollutant concentrations and seasonality were investigated during three seasonal sampling campaigns. Two anoxic (silty sand, Ems river) and two oxic (gravel, Ruhr river) RBF sites in Germany with different travel distances (42–633 m) were studied. Micropollutant concentrations were examined using a large-volume direct injection liquid chromatography method coupled to high-resolution mass spectrometry. Seasonal differences in micropollutant concentrations in the rivers were observed for chlorotolurone, diclofenac, terbuthylazine, mecoprop-P, MCPA (2-methyl-4-chlorophenoxyacetic acid) and propyphenazone. Redox dependencies in RBF were only found for sulfamethoxazole, propyphenazone, terbuthylazine and carbamazepine. Data for oxazepam, tramadol, N-desmethyl-tramadol, tilidin-desmethyl, carbamazepine and carbendazim indicate a required minimum travel distance of e.g. 100–200 m for the complete removal. Notably, travel time did not seem to be a substantial factor for their removal. High conductivity aquifers are also well suited for micropollutant removal. Seasonal initial concentration level variations showed no impact on the resulting abstraction well concentrations. Although the calculated removal efficiencies varied, they proved to be improper for seasonal raw water quality comparison. Knowledge of micropollutant behavior in riverbank filtration was broadened and RBF proved to be well suited for effective micropollutant reduction throughout the year, yet for a complete removal long travel distances or further technical purification steps are required.

Micelle-dominated distribution strategy for non-matrix matched calibration without an internal standard: “Extract-and-shoot” approach for analyzing hydrophilic targets in blood and cell samples

The analysis of trace hydrophilic targets in complex aqueous-rich matrices is considerably challenging, generally requiring matrix-matched calibration, internal standard, or time-and-labor-intensive sample preparation. To address this analytical bottleneck, a non-matrix-matched calibration strategy without using internal standard was reported for the first time to analyze complicated biosamples such as whole blood, plasma, serum, and cell samples. This strategy, termed micelle-dominated distribution, also aimed at realizing the simple “extract-and-shoot” analytical process for such complex matrices. The micelle–matrix interaction was found to efficiently eliminate the matrix effect by dominating phase separation and analyte distribution between the extraction and matrix phases. Thus, calibration linear curves prepared in water were applicable to the analysis of all the above-mentioned sample types. Rapid distribution equilibrium within 4 min was achieved. This strategy could tolerate direct large volume injection, thereby providing two-order-of-magnitude enhancement in the sensitivity of ion-pair chromatography. The analytical method integrated cell rupture, matrix cleanup, analyte extraction, and on-column preconcentration into a fast and high-throughput operation. The successful application to the determination of exogenous pesticides and endogenous glutathione exhibited low limits of detection (0.0085–0.015 μg mL−1 for pesticides; 0.52 μg mL−1 for glutathione), wide linear ranges (0.028–50 μg mL−1 and 0.049–50 μg mL−1 for pesticides; 1.7–1000 μg mL−1 for glutathione), good linearies (R2 = 0.9994–0.9999), excellent accuracy (recoveries of 91.3–105.2%), and good precision (0.7–6.2% at the levels of 0.028 (or 0.049), 0.1, 0.5, and 50 μg mL−1 for pesticides; 0.5–8.7% at 1.7, 500, and 1000 μg mL−1 for glutathione).

A simple, fast method for the analysis of 20 contaminants of emerging concern in river water using large-volume direct injection liquid chromatography-tandem mass spectrometry.

A fast and sensitive method for the determination of a structurally and physico-chemically diverse group of contaminants of emerging concern (CEC) based on large-volume direct injection liquid chromatography-tandem mass spectrometry was developed. The method can be used to determine 20 CECs belonging to different pollutant families (pharmaceuticals, personal care products, and pesticides) in river water at nanogram per liter. A single analytical run is required and the positive and negative ionization modes can be used simultaneously. Because of the large-volume injections of samples and the high sensitivity of the current mass spectrometers, the method has no need of a preconcentration step. The analytes are quantitated with matrix-matched calibration curves. The estimated limits of detection were in the range 0.1-5ngL-1. The accuracy of the method was in the range 86-114%, and the precision, expressed as a relative standard deviation (RSD %), was below 18% for all the analytes (n = 5, at 5, 10, and 25ngL-1). The method was applied to water samples taken from different points along the lower course of the Ebro River, Spain. A total of 12 out of the 20 target analytes were detected, and the ones at higher concentrations were caffeine and the pharmaceuticals paracetamol and ibuprofen (184.8ngL-1, 63.3ngL-1, and 23.3ngL-1, respectively).

Parallel between Offline-SPE-LC-MS and Direct Injection LC-MS Methods for Acrylamide Detection in Drinking Water at Parts Per Trillion Level

The presence of acrylamide, a potential human carcinogen, in treated drinking water has been a long-time concern for public health agencies. Due to this, acrylamide is included among the substances to be monitored in drinking water with a stated maximum admissible level of 0.1 �g/L in Europe. The necessity for ultra-trace level detection of acrylamide has led to development of an Offline-SPE-LC-MS method that involves SPE extraction of acrylamide using a strong adsorbent like activated charcoal followed by concentration. Simultaneously, a simple and rapid large volume Direct Injection LC-MS method was optimized from the previous method to detect acrylamide without the resource and time-consuming SPE step. A comprehensive comparison between the efficiency and sensitivity of the two methods is made. Optimization of LC-MS parameters (column temperature, mobile phase composition and flow, collision energy, fragmentor voltage, capillary voltage or MRM transitions) allowed high detection sensitivity. Due to Acrylamide high polarity, a Synergi Fusion-RP column with amide polar embedded groups was chosen to achieve reasonable retention and peak shape for acrylamide with a short run-time of only 3 min. The two methods provided excellent sensitivity, with reasonably low LOQ values of 2 ng/L for the Offline-SPE-LC-MS method and 30 ng/L for the Direct Injection LC-MS method. Intra-day and inter-day precision (RSD%) were 7.3 and 10.3%, for the Offline-SPE-LC-MS method and 2.4% and 6.2%, respectively for the Direct Injection LC-MS method. The analysis of acrylamide was successfully performed in drinking water from different location consumers and water treatment plants in Romania. Acrylamide was found in drinking water samples with levels between 5.2 and 35.7 ng/L using the Offline-SPE-LC-MS method. The direct injection method can only be used for acrylamide levels higher than its LOQ value (30 ng/L).

Pharmacokinetics study of 16 representative components from Baoyuan Decoction in rat plasma by LC–MS/MS with a large-volume direct injection method

BackgroundBaoyuan decoction (BYD), a well-known traditional Chinese medicine (TCM) formula, is clinically used for the treatment of aplastic anemia, chronic renal failure, coronary heart disease, etc. PurposeThe purpose of this study was to develop a large-volume direct injection liquid chromatography-mass spectrometry (LC–MS) method for simultaneous determination of 16 representative flavonoids and saponins in rat plasma after oral administration of BYD. MethodsThe rat plasma sample was injected directly into a pre-column, which was eluted firstly by 0.05% formic acid in water. Then, the accumulated components were eluted from the pre-column and transferred into a Waters BEH C18 column with acetonitrile and water system (contain 0.05% formic acid) as the mobile phase at a rate of 0.3 ml/min. The detection was accomplished in a negative mode using the schedule multiple-reaction monitoring (sMRM). ResultsThe correlation coefficients for calibration curves were all higher than 0.9920 for formononetin, ononin, calycosin, liquiritigenin, isoliquiritigenin, glycyrrhizic acid, glycyrrhetinic acid, liquiritin, isoliquiritin, liquiritin apioside, isoliquiritin apioside, ginsenoside Rb1, ginsenoside Re, ginsenoside Rd, ginsenoside Rg1 and astragaloside. The intra- and inter-day precisions (RSD) and accuracy (RE) for the investigated components were in the range of −10.9 to 13.7%. The average recoveries were in the range of 75.7–108.6%. This method was successfully applied to investigate the pharmacokinetics of 16 compounds of BYD in rats. The absorption and elimination rates of the representative saponins were significantly slower than most of the targeted-flavonoids after oral administration of BYD in rats. ConclusionThe results demonstrated that the large-volume direct injection LC–MS method provided a rapid and efficient approach for multi-components pharmacokinetics of TCM.

Direct large-volume injection analysis of polycyclic aromatic hydrocarbons in water

Due to the health risks for both humans and living beings caused by polycyclic aromatic hydrocarbons (PAHs), the monitoring of these compounds in environmental matrices is mandatory. This work proposes an analytical method for analyzing anthracene (AN) and benzo[a]pyrene (BaP), two of the most representative PAHs, at ultra-trace concentrations in water, employing direct injection of large volumes of samples coupled with reversed-phase high-performance liquid chromatography. For this purpose, principal component analysis was used to examine the behavior of AN and BaP within the chromatographic system. Results showed that AN and BaP chromatographic behavior can be described by three models representing their identification, the quantification of AN and that of BaP, respectively. The factors affecting the obtained models, such as the injection volume, column temperature, flow rate, strength of the mobile phase, and the excitation and emission wavelengths, were examined and optimized by means of design of experiments. Finally, the analytical method was validated, obtaining promising limits of detection and quantification. The developed analytical method was demonstrated to be useful for a sensitive analysis of the target analytes in relatively clean natural water matrices.

Direct residue analysis of systemic insecticides and some of their relevant metabolites in wines by liquid chromatography – mass spectrometry

A direct large volume injection (DI-LVI) high performance liquid chromatography – tandem mass spectrometry (HPLC–MS/MS) method was developed and validated for the quantitative determination of 16 systemic insecticides and their main plant metabolites. The assays were conducted on commercial red and white wines made from grapes grown in major wine-producing regions nationally and internationally. Using a 1:20 dilution and an injection volume of 800μL, a limit of quantitation (LOQ) of 1μgL−1 for all analytes was achieved. Matrix-matched standards (MM) were used for accurate quantitation. Imidacloprid (IMI) and methoxyfenozide (MET) were the most frequently detected parent insecticides in the wines reaching concentrations of 1–132μgL−1. Two important plant metabolites imidacloprid-olefin (IMI-OLE) and spirotetramat-enol (SPT-EN) were found at higher concentrations. In five samples SPT-EN was detected in the mgL−1 range with a maximum concentration of 16.3mgL−1 measured in a conventional white wine sample. Most “organic” wines contained no detectable or low insecticide residues, except for one sample, which showed the highest IMI (14.7μgL−1) and IMI-OLE (331μgL−1) concentrations. Considering the maximum residue limit (MRL) definition for the different insecticides, three “conventional” wine samples were non-compliant for SPT. This study highlights the importance to determine both parent and metabolite forms of systemic insecticides in the finished product.

Large Volume Injection of Aqueous Samples in Nano Liquid Chromatography Using Serially Coupled Columns

One of the biggest challenges in the field of water analysis is the determination of trace concentrations of emerging contaminants. These contaminants must therefore be enriched, typically by either off-line or online solid phase extraction. An alternative method is the direct large volume injection onto the separation column. In liquid chromatography, the limitation of the injection volume depends on the column dimensions, the analyte hydrophobicity, the injection solvent and the nature of the stationary phase. Exceeding of the maximum injection volume is indicated by a deterioration of peak shapes and a loss in signal intensity. By serial coupling of two stationary phases with different hydrophobicities, the focusing can be improved and the maximum injection volume can be increased. A suitable combination could be the hyphenation of a carbon-based phase like Hypercarb and a C-18 phase. This paper describes how to implement this concept based on nano-LC and UV detection. To cover a wide range of polarity, a polar, semi-polar and non-polar compound were used as model analytes. The recommended injection volume of 25 nL for a nanobore column could be successfully increased to 3,000 nL, without deterioration of peak shapes.

Fast determination of 40 drugs in water using large volume direct injection liquid chromatography–tandem mass spectrometry

This work describes a rapid analytical method based on direct sample injection of water samples for the simultaneous identification/quantification of 40 emerging compounds, including pharmaceuticals and drugs of abuse. The water samples were analyzed by ultra-high-performance liquid chromatography coupled to hybrid triple quadrupole mass spectrometer (UHPLC–MS/MS QqQ). Taking profit of the increasing sensitivity of nowadays tandem mass spectrometers, direct sample injection of large volumes has been an attractive alternative to pre-concentration steps. In this work, the developed methodology has been validated at three concentration levels (10, 100 and 1000ng/L) in 10 different water samples of different types (5 effluent wastewater and 5 surface water samples). The majority of compounds could be satisfactory validated at these concentrations, showing good recoveries and precision. With only few exceptions, the limits of quantification (LOQs), estimated from the sample chromatogram at lowest spiked level tested, were below 3ng/L. The method was applied to the analysis of 10 effluent wastewater and 10 surface water samples. Venlafaxine was the compound most frequently detected (80%) in surface water, followed by acetaminophen (70%). Regarding effluent wastewater, valsartan and 4-acetyl aminoantipyrine were detected in 9 out of 10 samples analyzed. These two compounds together with 4-formyl aminoantipyrine and naproxen showed the highest concentrations (>2000ng/L). In these cases, a dilution step was required for a correct quantification. As an additional evaluation of the method performance, the same water samples were analyzed in another laboratory by a second analytical methodology, based on on-line solid-phase-extraction coupled to LC–MS/MS (QqQ).

Determination of rifampicin in rat plasma by modified large-volume direct injection RAM-HPLC and its application to a pharmcokinetic study.

A direct large volume injection high-performance liquid chromatography (HPLC) method with homemade restricted-access media (RAM) pre-column and combined with a column-switching valve was established and developed for determination rifampicin (RIP) in rat plasma. The rat plasma samples (100 μL) were injected directly onto pre-column, where RIP was retained and pre-concentrated, while proteins were washed to waste using a methanol-water (5:95) as the mobile phase at a flow rate of 1 mL/min. Then, by rotation of the switching valve at 5 min, the RIP were eluted from the pre-column and transferred to an Luna C18 analytical column by the chromatographic mobile phase consisting of methanol-acetonitrile-10 mm ammonium format (60:5:35) at a flow rate of 1 mL/min. The total analytical run time was 15 min with UV detection wavelength at 254 nm. Carbamazepine was used as the internal standard. Excellent linear correlation (r = 0.9993) was obtained in the range of 0.25-8 µg/mL for rat plasma. The intra-day and inter-day precisions of RIP were all <5.0%. The recoveries were in the range of from 99.98-113.66% for plasma. This on-line RAM-HPLC method was successfully applied to the pharmacokinetic study of RIP in rat plasma.