GC-MS analysis of water-soluble organics in atmospheric aerosol: response surface methodology for optimizing silyl-derivatization for simultaneous analysis of carboxylic acids and sugars

This paper describes the development of a derivatization procedure — silylation using N,O-bis(trimethylsilyl)-trifluoroacetamide (BSTFA) — for the simultaneous GC–MS analysis of a wide range of water-soluble organics in atmospheric aerosols. The reaction operating conditions were optimized using the response surface methodology (RSM) including central composite design (CCD) in order to achieve the highest response for a large number of dicarboxylic acids and sugars. The factors considered were: (i) reaction temperature (50–90 °C), (ii) the reaction duration (60–120 min), (iii) reagent concentrations (10–100% of the total solution volume) and (iv) pyridine concentration (0–50% of the derivatization reagent). On the basis of RSM and experimental evidence, the optimum derivatization conditions were defined as reaction temperature of 75 °C, reaction duration of 70 min, BSTFA reagent concentration of 55% and pyridine concentration of 35%. The optimized protocol was extended to a broader range of 22 target analytes that are relevant chemical markers, i.e., 15 carboxylic acids and 7 sugars. In addition, the applicability of the optimized procedure was verified in environmental matrices from PM filters collected under different conditions, i.e., different seasons (summer vs. winter), different sampling sites (urban vs. rural), different particle size dimensions (PM_2.5 vs. PM₁).     

GC–MS analysis of low-molecular-weight dicarboxylic acids in atmospheric aerosol: comparison between silylation and esterification derivatization procedures

This paper describes methods for the determination of low-molecular-weight (LMW) dicarboxylic acids in atmospheric aerosols as important chemical tracers for source apportionment of aerosol organics and for studying atmospheric processes leading to secondary organic aerosol formation. The two derivatization procedures most widely used in GC analysis of dicarboxylic acids were compared: esterification using BF₃/alcohol reagent and silylation using N,O-bis(trimethylsilyl)-trifluoroacetamide (BSTFA). The advantages and drawbacks of the two methods are investigated and compared in terms of (1) precision and accuracy of the results and (2) sensitivity and detection limit of the procedure. The comparative investigation was performed on standard solutions containing target C₃–C₉ dicarboxylic acids and on experimental particulate matter (PM) samples. Attention was focused on low-volume sampling devices that collect small amounts of sample for organic speciation. The results show that, overall, both the techniques appear suitable for the analysis of LMW dicarboxylic acids in atmospheric aerosols since they provide low detection limits (≤4 ng m⁻³) and satisfactory reproducibility (RSD% ≤ 15%). Between them, BSTFA should be the reagent of choice under the most limiting conditions of PM filters collected by low-volume air samplers: It provides determination of all the target C₃–C₉ dicarboxylic acids with lower detection limits (≤2 ng m⁻³) and higher reproducibility (RSD% ≤ 10%)      

Optimisation of the analysis of anti-influenza drugs in wastewater and surface water

We optimised the simultaneous analysis of four analytes, namely three anti-influenza drugs (oseltamivir (OS), zanamivir (ZAN) and amantadine (AMN)) and one metabolite of OS (oseltamivir carboxylate (OC)), in sewage treatment plant (STP) influent and effluent by verifying the types and conditions of solid phase extraction (SPE) appropriate for LC-MS/MS analysis. In summary, these target analytes were extracted from aqueous samples (30–50 mL) by using strong cation-exchange SPE cartridges (500 mg adsorbent) under acidic conditions (pH 3–4). After washing of the cartridges with acidified water (pH 3.0, 3 mL) and methanol (3 mL), the analytes were eluted with a mixed solvent (2 mL) of 10% (v/v) triethylamine in a 1:1 (v/v) mixture of acetone and water. Application of this technique to the target compounds should yield a comprehensive understanding of the occurrence and fate of anti-influenza drugs in the water environment.     

Atmospheric corrosion of copper and silver influenced by particulate matter

The atmospheric corrosion of copper and silver influenced by graphite and alumina as particulate matter (PM) in an environment containing 200 μg m^?3 SO₂ + 150 μg m^?3 NO₂ at 85% RH and 25 °C was analyzed. Different proportions of PM mixture conditions were used, and the corrosion rate was followed using gravimetric analysis. Results of linear sweep voltammetry (LSV) and coulometric reduction (CR) indicated that larger corrosion rates were obtained in the presence of deposited PM. Under present exposure conditions, copper corrosion rate was larger than silver corrosion rate. X-ray diffraction (XRD) shows the presence of cuprite (Cu₂O) and brochantite (Cu₄SO₄(OH)₆) in the case of copper and achantite (Ag₂S) in the case of silver.     

Development of dynamic headspace-liquid phase microextraction method performed in a home-made extraction vessel for extraction and preconcentration of 1,4-dioxane from shampoo

In the present study, a new, simple, rapid, and environmentally friendly headspace-liquid phase microextraction method followed by gas chromatography–flame ionization detection has been developed for the extraction/preconcentration and determination of 1,4-dioxane from shampoo. The developed procedure is performed in a home-made extraction vessel, connected to a glass vial containing sample and extraction solvent. In this method, an aliquot weight of shampoo is mixed with a binary mixture of n-hexane and dichloromethane (50:50, v/v) as the extractant and the target analyte is extracted during a liquid–liquid extraction procedure. Then a home-made extraction vessel containing a few microliters of a collection/extraction solvent is contacted to a glass vial containing the organic phase obtained from the previous step. By heating 1,4-dioxane is vaporized and enriched in a μL volume of the collection/extraction solvent. Then an aliquot volume of the collected phase is injected into the separation system. The effect of several factors which may influence performance of the method, including kind and volume of the extraction solvents used in both steps, extraction temperature, extraction time, and salt addition were evaluated. Under the optimum extraction conditions, limits of detection and quantification for the target analyte were obtained 0.52 and 1.73 μg kg^?1, respectively. Enrichment factor and extraction recovery were 333 and 89 %, respectively. The method precision was evaluated at a concentration of 25 μg kg^?1 and relative standard deviation was less than 6.9 % for intra-day (n = 6) and inter-day (n = 4) precisions. Finally, the proposed method has been successfully applied in analysis of 1,4-dioxane in different shampoo samples.     

Ion Chromatography Determination of Heavy Metals in Airborne Particulate with Preconcentration and Large Volume Direct Injection

A flow injection analysis system with on-line enrichment was developed for simultaneous determination of trace levels of Cu²⁺, Ni²⁺, Zn²⁺, Co²⁺, Mn²⁺, Cd²⁺, Pb²⁺ and Fe³⁺, by high-performance ion chromatography (HPIC) with spectrophotometric detection. It is a highly sensitive and low cost alternative methodology. Ion Pac CS5A was used as the analytical column with eluent composition of sodium nitrate 160 mM and oxalic acid 36 mM. Quantification after post-column reaction with PAR allows detection limits between 0.5 and 5.0 ppb to be attained. The total analysis time is less than 30 min. The proposed procedure was compared with a large volume direct injection method using loop volumes up to 5 mL. Both procedures were applied to the analysis of heavy metals in the PM10 fraction of atmospheric particulate samples. Airborne pollutants such as nickel and cobalt can be quantified in 24 h samples of particulate matter at concentrations of a few ng m^?3.     

Validation studies for multicomponent quantitative NMR analysis: the example of apple fruit juice

Laboratories intending to work as official laboratories for food control have to be accredited according to ISO/IEC 17025. This necessitates the use of validated analytical methods. In this study, we present validation results of the recently commercialized “JuiceScreener” based on nuclear magnetic resonance (NMR) spectroscopy with apple juice as application example. The quantitative analysis included 29 compounds such as major sugars, amino acids, organic acids, as well as acetoin, arbutin, benzaldehyde, hydroxymethylfurfural, acetaldehyde, methanol, and ethanol. Limit of detection (LOD), limit of quantification (LOQ), coefficients of variation (CV) for replicated measurements, repeatability, linear range, and recoveries were determined. The LOD and LOQ values varied in the 0.48–16 mg/L and in the 1.9–122 mg/L ranges with the lowest values for shikimic acid and highest for the principal sugars. The ¹H NMR assays were linear in broad concentration ranges (R > 0.99), encompassed typical concentration in apple juices, and are sufficient to control the requirements of the code of practice of the European fruit juice association. Recoveries between 92 and 109 % on average for five separate standard additions were obtained. The average CVs were found to be 3.0 % (intraday) and 3.6 % (interday) excluding sample preparation (by measuring five time one solution) and 5.5 % (intraday) and 6.2 % (interday) including sample preparation (by preparing and analyzing five separate samples). The NMR method was judged as suitable for the simultaneous quantification of compounds in apple juice for official food control purposes. Our results show that multiparameter NMR methods can be successfully validated with standard instrumentarium and that they are fit for the purpose of official food control.     

Pressurised fluid extraction of polycyclic aromatic hydrocarbons and their polar oxidation products from atmospheric particles

An effective method utilising pressurised fluid extraction (PFE) to simultaneously extract polycyclic aromatic hydrocarbons (PAHs) and their polar oxidation products from atmospheric particulate matter (PM) is presented. The PFE method is advantageous over the traditional Soxhlet extraction due to its lower solvent consumption (9 mL compared to 90 mL) and shorter extraction time (15 min versus 18 h). Seventy compounds including PAHs and polar PAH oxidation products containing carbonyl (oxy-PAHs), hydroxyl (hydroxy-PAHs), and carboxylic acid (carboxy-PAHs) groups were targeted in the extraction of two different PM matrices: wood smoke (WS) and diesel exhaust (DE) PM. The PFE method was optimised and then compared to Soxhlet extraction for both PM matrices. The overall amounts of PAHs and their derivatives extracted from WS PM were slightly higher for the optimised PFE method (1849 ± 21 and 1863 ± 25 µg g^?1 with dichloromethane (DCM) and methanol (MeOH), respectively) than those obtained with Soxhlet extraction (1726 ± 33 and 1769 ± 22 µg g^?1 with DCM and MeOH, respectively). For DE PM (standard reference material (SRM) 2975) the overall amounts extracted by both methods were similar (average of 165 ± 6 µg g^?1), agreeing with previously published values. The detailed evaluation of extraction efficiencies for WS PM showed similar amounts for unfunctionalised PAHs (1100 µg g^?1) for both methods and solvents. For DE PM the mass yields for PAHs using PFE with DCM (62 ± 1 µg g^?1) were the highest and nearly 20% higher than those obtained with MeOH (53 ± 2 µg g^?1). The total mass yields of carboxy and hydroxy-PAHs from WS PM were also similar (412 ± 18 and 407 ± 11 µg g^?1) for PFE and Soxhlet with MeOH, and higher than when DCM was used (371 ± 5 and 379 ± 12 µg g^?1 for PFE and Soxhlet, respectively). For both matrices, the PFE yields for oxy-PAHs were higher than those obtained with Soxhlet.     

Ground level ozone (O3) associated with radon (222Rn) and particulate matter (PM) concentrations in Bucharest metropolitan area and adverse health effects

The aim of this paper is to contribute with new information in the application of ground based radon (²²²Rn) observations to atmospheric research, namely its relation with air pollution due to ground-level ozone (O₃) and particle matter in two size fractions (PM10 and PM2.5) for Bucharest metropolitan area in Romania. During January 1–December 31, 2011, ground levels of radon, ozone and particulate matter (PM) have been continuously monitored in synergy with the main meteorological parameters (air temperature, humidity and pressure), and daily global air quality indices. A systematic analysis of surface ozone observations of ground level radon, ozone and PM is presented. Observational results indicate the following yearly daily mean ground level concentrations: 40.26 ± 7.54 Bq/m³ for radon, 90.51 μg/m³ for ozone, 35.96 μg/m³ for PM2.5, and 40.91 μg/m³ for PM10. The assessment of the results showed the influence of local and meteorological conditions on the daily mean radon, ozone and PM concentrations. However, in densely populated metropolitan area of Bucharest the mean daily values of ozone, PM2.5, PM10, and attached ²²²Rn are sometimes higher than European Community limit values leading to serious public concern during the last years. Due to the high risk of increased levels of O₃, PM2.5, PM10, and attached ²²²Rn on human health respiratory function (especially for children and older persons), and urban green, the results are very useful for atmospheric, radiological protection, epidemiological and environmental studies.     

Outdoor 222Radon concentrations monitoring in relation with particulate matter levels and possible health effects

Air quality monitoring could potentially improve exposure estimates for use in epidemiological studies. We investigated air quality by monitoring concentrations of ²²²Rn near the ground and particulate matter (PM) with an aerodynamic diameter less than or equal to 10 μm (PM10) and 2.5 μm (PM2.5) for Bucharest-Magurele periurban area. Atmospheric radon concentrations have been continuously monitored near the ground at 1 m height as well as at 10 m height. This paper presents time-series of radon concentrations monitoring in air near the ground measured during 1 January 2011–1 January 2012 by use of solid state nuclear track detectors SSNTD CR-39, exposed for 10 days periods. The daily average atmospheric radon concentration near the ground registered at 1 m height was found to be in range of 40.25 ± 7.53 Bq/m³, which was comparable with the daily average radon concentration of 44.92 ± 9.94 Bq/m³ recorded for period 1 August 2011–20 December 2011 at 10 m height by AlphaGUARD Radon monitor. Also, was done a comparative analysis of spatio-temporal variations in time series of outdoor radon concentration and PM in two size fractions (PM10 and PM2.5) in Bucharest Magurele area for 2011 year. The predominant recorded component in PM10 was PM2.5. Observational results show that recorded yearly average PM2.5 and PM10 concentrations were 35.96 μg/m³ and 40.91 μg/m³, respectively. The average ratio of PM2.5/PM10 was 87.9 % at this sampling site. However, in densely populated Bucharest urban and suburban areas the mean daily EC limit values for PM10, PM2.5 and attached ²²²Rn are frequently exceeded leading to serious public concern during the last years. The ambient air pollution measurements like as PM10 and PM2.5 levels are used as a proxy for personal exposure levels. Have been investigated also meteorological effects on the temporal patterns of atmospheric radon and particle matter.     

Two-phase/Three-phase Hollow Fibre Liquid-Phase Simultaneous Microextraction Combined with HPLC for Analysis of Phenolic Acids and Flavonoids in Traditional Chinese Medicine

A two-phase/three-phase hollow fibre liquid-phase simultaneous microextraction (2p/3p-HF-LPSME) method, coupled with high-performance liquid chromatography and ultraviolet detection, was developed and introduced for simultaneous extraction and determination of phenolic acids and flavonoids in Lonicera japonica, Herba Taraxaci and Cortex Eucommiae. Several factors affecting performance were investigated and optimized, including the type of hollow fibre liquid-phase microextraction, extraction solvent, pHs of the sample and acceptor phases, extraction time, stirring rate, salt concentration in the sample solution and volume of sample phase. Under optimised conditions, the enrichment factors of 2p/3p-HF-LPSME for analytes ranged from 9 to 171, and good linearities were obtained for all analytes with regression coefficients of between 0.9939 and 0.9996. In addition, the limits of detection were between 0.3 and 4.0 ng·mL⁻¹, and satisfactory recoveries (90.0–106.3 %) and precisions (RSD 2.3–10.4 %) were also achieved. The simultaneous microextraction mechanism of the approach was also analysed and described. Experimental results show that the method is simple, sensitive, practical and effective, and it can be used for simultaneous preconcentration and determination of phenolic acids and flavonoids in traditional Chinese medicines.

     

Simultaneous Determination of Deltamethrin and Permethrin in Water Samples Using Homogeneous Liquid–Liquid Microextraction via Flotation Assistance and GC-FID

A new method was developed for the simultaneous determination of deltamethrin and permethrin in water samples with homogeneous liquid–liquid microextraction via flotation assistance and gas chromatography–flame ionization detection. A special extraction cell was designed to facilitate collection of the low density solvent extracts. The sample solution was added into the extraction cell, which contained an appropriate mixture of n-hexane (as an extraction solvent) and acetone (as a homogeneous solvent). Air flotation allowed the extraction solvent to be collected from the top of the solution. Under the optimum conditions, good linearity was observed in the range of 1.0–200 μg L^?1 with a correlation coefficient (r ²) greater than 0.9980 for both of the analytes. The limits of detection were 0.2 and 0.3 μg L^?1 for deltamethrin and permethrin, respectively (S/N = 3). The developed method was successfully applied to determine the two pesticides in three different water samples.     

Evaluation of IL-ATPS and IL-MAE for Simultaneous Determination of Herbicides and Plant Growth Regulators in Sediment

Two analytical methods, an ionic liquid/salt aqueous two-phase system (IL-ATPS) and ionic liquid-based microwave-assisted extraction procedure (IL-MAE), were evaluated for simultaneous extraction and determination of herbicides (2,4-dichlorophenoxy acetic acid, bensulfuron) and plant growth regulators (kinetin, 6-benzylaminopurine, uniconazole) in sediment followed by high-performance liquid chromatography with the diode-array detector. The experimental parameters of two methods including the volume of ionic liquid (IL), pH, the extraction temperature and the amount of salt were studied. Under the optimum conditions, the limits of detection were in the range of 0.001–0.004 µg g^?1 for IL-ATPS and 0.002–0.04 µg g^?1 for IL-MAE procedure, respectively. Relative standard deviations (RSD, n = 5) and recoveries were in the range of 2.4–4.3 % and 95–98 %, respectively for IL-ATPS, 1.0–12.0 % and 83–127 % for IL-MAE procedure except for bensulfuron. The recoveries obtained by means of IL-ATPS were higher than that by means of other methods. In addition, the IL-ATPS has the advantages of small amount of IL consumption and small systematic errors, which was applied to the simultaneous determination of the above five target analytes in actual sediment samples.     

Preparation and properties of aromatic–aliphatic copolyamides from aromatic diisocyanates and dicarboxylic acids

Aromatic–aliphatic random copolyamides of high molecular weights were prepared by the high-temperature solution polycondensation from a combination of aromatic diisocyanates, 4,4′-methylenedi(phenyl isocyanate), and 2,4-tolylene diisocyanate, and a mixture of isophthalic acid and aliphatic dicarboxylic acids with 4–10 methylene groups. Reaction conditions, such as solvent, temperature, time, and catalyst were studied to determine the optimum conditions for the preparation of high molecular weight polymers. Glass transition temperatures of the copolyamides were in the range of 131–244°C and varied with combination and composition of the diisocyanates and dicarboxylic acids used. The copolyamides prepared from 2,4-tolylene diisocyanate had greater solubility and higher glass transition temperatures than those obtained from 4,4′-methylenedi(phenyl isocyanate).     

Development of the HPLC Method for Simultaneous Determination of Lidocaine Hydrochloride and Tribenoside Along with Their Impurities Supported by the QSRR Approach

A new liquid chromatographic (LC) method for simultaneous determination of lidocaine hydrochloride (LH) and tribenoside (TR) along with their related compounds in pharmaceutical preparations is described. Satisfactory LC separation of all analytes after the liquid–liquid extraction (LLE) procedure with ethanol was performed on a C₁₈ column using a gradient elution of a mixture of acetonitrile and 0.1 % orthophosphoric acid as the mobile phase. The procedure was validated according to the ICH guidelines. The limits of detection (LOD) and quantification (LOQ) were 4.36 and 13.21 μg mL^?1 for LH, 7.60 and 23.04 μg mL^?1 for TR, and below 0.11 and 0.33 μg mL^?1 for their impurities, respectively. Intra- and inter-day precision was below 1.97 %, whereas accuracy for all analytes ranged from 98.17 to 101.94 %. The proposed method was sensitive, robust, and specific allowing reliable simultaneous quantification of all mentioned compounds. Moreover, a comparative study of the RP-LC column classification based on the quantitative structure-retention relationships (QSRR) and column selectivity obtained in real pharmaceutical analysis was innovatively applied using factor analysis (FA). In the column performance test, the analysis of LH and TR in the presence of their impurities was carried out according to the developed method with the use of 12 RP-LC stationary phases previously tested under the QSRR conditions. The obtained results confirmed that the classes of the stationary phases selected in accordance with the QSRR models provided comparable separation for LH, TR, and their impurities. Hence, it was concluded that the proposed QSRR approach could be considered a supportive tool in the selection of the suitable column for the pharmaceutical analysis.     

Determination of Six Organophosphorus Pesticides in Water by Single-Drop Microextraction Coupled with GC-NPD

A single-drop microextraction (SDME) procedure with a modified microsyringe was developed for the analysis of six organophosphorus pesticides (OPPs) in water. Microsyringe was modified by attaching a 2-mm cone onto the needle tip end. The conditions affecting SDME performance including microextraction solvent, stirring speed, extraction time, ionic strength and sample pH were optimized. Under the optimized conditions, the linear ranges of the SDME with ethion as internal standard were 0.05–50 μg L^?1 (except for dimethoate 5–5,000 μg L^?1) and limits of detection (LOD) were 0.012–0.020 μg L^?1 (except for dimethoate 0.45 μg L^?1). Recoveries of six pesticides were in the range of 70.6–107.5 % with relative standard deviation lower than 6.0 %. The modified method is simple, rapid and sensitive, and acceptable in the analysis of OPPs pesticides in water samples.     

Optimisation of caffeine and antidepressants extraction from sediments and sewage sludge using experimental designs

This study proposes a microwave-assisted method for the simultaneous extraction of highly prescribed antidepressants (citalopram, venlafaxine, fluoxetine, sertraline and amitriptyline) and caffeine from sediments and sewage sludge for subsequent HPLC-PDA analysis. Because the sludge and sediment matrices have high contents of organic material, they strongly interact with the analytes and hinder extraction. Thus, a carefully optimised analytical methodology is required for quantitative extraction. A simplex-centroid design was applied to optimise the solvent composition, and a three-factor central composite rotational design was used to optimise the extraction protocol with regards to pH, amount of solvent and processing time. Samples (in triplicates) were fortified with a standard mixed solution of all the analytes and extracted according to the experimental design in each study. The extraction steps included: 30 s vortexing, 20 s microwave heating at 10 W, cooling to room temperature (25°C) in an ultrasonic bath for 60 s, 2 min centrifugation at 2000 rpm, and filtration. Analysis of variance and lack-of-fit tests were used to assess the significance of data fitting at 95% confidence. The desirability function was the optimisation tool used to obtain the ideal extraction conditions. As a result, a binary mixture of methanol and acetonitrile in 45:55 and 53:47 (v/v) ratios was indicated as the optimum solvent composition for the simultaneous extraction of all the target drugs from the sludge and sediment, respectively. The optimised extraction conditions were: 3 extraction cycles with 4 mL of solvent at pH 3 for sewage sludge extraction and 4 extraction cycles with 3 mL of solvent at pH 11 for sediment extraction. Further, low recoveries were obtained for extractions from sediment as compared to sludge indicating strong interaction of antidepressants and caffeine with the acidic organic components of sediments. It was found that the optimisation of pH of the extraction phase was crucial for the efficient extraction of the analytes from these environmental matrices.     

Simultaneous Determination of Antibiotics in Anti-Acne Cosmetics by Rapid LC with DAD

A suitable method that allows, for the first time, the simultaneous determination of nine antibiotics which may help the therapy of acne vulgaris by rapid liquid chromatography with diode array detection in 7 min is presented in this work. An SB RP18 (50 × 4.6 mm; 1.8 μm particle size) column was used with the mobile phase consisting of a mixture of 0.1 mol L⁻¹ potassium dihydrogen phosphate (pH 2.5) and acetonitrile at the gradient elution program. The correlation coefficients were all above 0.9999 in the linear range between 4–100 μg mL⁻¹, the average spiked recoveries (n = 6) were 92.2–103.2% with RSD ranging from 0.04 to 4.5% depending on the target analytes. The method detection limits were in the range of 0.02–0.2 μg mL⁻¹ in anti-acne cosmetics. The analysis of real cosmetic preparations demonstrated the fitness for the whole analytical procedure. The proposed method appeared therefore as a sound alternative for official testing method, which could overcome the general problems of time consuming, lack of the specificity and precision difficulty.

     

Homogeneous Liquid–Liquid Microextraction Via Flotation Assistance (HLLME-FA) Method for the Pretreatment of Organochlorine Pesticides in Aqueous Samples and Determination by GC–MS

This work proposes a new, rapid and simple homogeneous liquid–liquid microextraction via flotation assistance technique for the analysis of six organochlorine pesticides in water samples. A special extraction cell was used to facilitate collection of the low-density solvent extract. No centrifugation was required in this procedure. Determination was carried using gas chromatography–mass spectrometry. The water sample solution was then added into the extraction cell containing appropriate mixture of extract and homogeneous solvents. In the first step, a homogeneous solution and then with the continuation of water sample injection, a cloudy solution was formed. Using air flotation, the organic solution was collected at the conical part of the designed cell. The optimized levels of effective parameters were found based on response surface methodology approach. Applying the optimized conditions to the system understudy, the limits of detection of all target analytes were obtained in the range of 1.4–7 ng mL^?1, while the precisions were found to be in the range of 11.08–14.87 (RSD, n = 3). The linearity of the method lay in the range of 10–150 ng mL^?1 with the coefficients of correlation (r ² ) ranging from 0.998 to 0.999.     

Simultaneous Determination of Antibiotics in Anti-Acne Cosmetics by Rapid LC with DAD

A suitable method that allows, for the first time, the simultaneous determination of nine antibiotics which may help the therapy of acne vulgaris by rapid liquid chromatography with diode array detection in 7 min is presented in this work. An SB RP18 (50 × 4.6 mm; 1.8 μm particle size) column was used with the mobile phase consisting of a mixture of 0.1 mol L^?1 potassium dihydrogen phosphate (pH 2.5) and acetonitrile at the gradient elution program. The correlation coefficients were all above 0.9999 in the linear range between 4–100 μg mL^?1, the average spiked recoveries (n = 6) were 92.2–103.2% with RSD ranging from 0.04 to 4.5% depending on the target analytes. The method detection limits were in the range of 0.02–0.2 μg mL^?1 in anti-acne cosmetics. The analysis of real cosmetic preparations demonstrated the fitness for the whole analytical procedure. The proposed method appeared therefore as a sound alternative for official testing method, which could overcome the general problems of time consuming, lack of the specificity and precision difficulty.