Gas Chromatography-nitrogen Phosphorus Detection Research Articles

Optimization, Validation, and Application of a Quantitative GC/NPD Method for Acrylamide Determination in Yemeni Fried Fish Samples

The matrix's complexity makes measuring acrylamide in food items challenging, requiring a time-consuming extraction technique and high method sensitivity. A homemade solid phase extraction (SPE) device and a gas chromatography/nitrogen phosphorus detector (GC/NPD) were used to establish a simple and inexpensive acrylamide detection method in fried fish. Optimization and validation were used to measure acrylamide concentrations in twelve fried fish samples, four of which were home-fried and eight from Sana'a, Yemen, restaurants. The validated technique has high linearity R2 (0.995) in the 0.02–4 ppm range of acrylamide standards and good sensitivity with LOD (0.0062 ppm), substantially below the authorized level. The twelve samples had acrylamide values of 0.0583–0.4643 ppm. Due to variations in thermal treatments during frying, market-fried fish samples had greater acrylamide concentrations than home-fried fish samples. In the current study, the improved simple extraction process and GC/NPD protocol were useful for acrylamide measurement and may be employed as a prescreening tool for food sector acrylamide quantification.

Optimization, Validation and Application of Quantitative Method for the Determination of Acrylamide in Potato Chips Samples in Yemen Using GC-NPD

Over the last two decades, numerous analytical methods for determining acrylamide concentration in a wide range of food products have been developed. Some studies focused on the methods of extracting acrylamide from complex food matrices. In the present study, solid Phase Extraction (SPE) and Gas Chromatography-Nitrogen Phosphorus Detector (GC-NPD) analysis were employed to develop a simple and cost-effective acrylamide determination method. Method validation and optimization steps were carried out and used to determine acrylamide concentrations in potato chips purchased from Yemeni markets. In the concentration range of 0.1- 5 ppm, the validated method demonstrated good sensitivity within a 0.012 ppm limit of detection (LOD) and an excellent linearity of 0.996 correlation coefficient. Eighteen samples of potato chips purchased from local markets in Sana'a, Yemen, were analyzed using this method. Three of the 18 samples of interest contained various acrylamide concentration levels of 879.4, 795.6, and 754.7 ppb. These were higher than the EU Commission's indicative value for the acrylamide in potato chips (750 ppb). As a result, the optimized GC-NPD protocol proved to be useful for the acrylamide analysis, paving the way for the development of an acrylamide quantification prescreening tool in the food industry.

Categorization of Cytochrome P4502D6 Activity Score by Urinary Amphetamine/Methamphetamine Ratios.

Methamphetamine (MA) level in urine has been used for judgment in MA consumption. Metabolism and intoxication of MA are correlated with the activity of cytochrome P450 2D6 (CYP2D6). The activity score (AS) is a potential tool for predicting exposure and personalized dose of drugs metabolized by CYP2D6. Prediction of the CYP2D6 activity score might be described as MA intoxication. The objective of this study was to categorize the CYP2D6 activity score using the urinary amphetamine (AM)/MA ratio. Urine samples (n = 23,258) were collected. The levels of MA and AM were determined by a gas chromatography-nitrogen-phosphorus detector. The log AS was calculated by an AM/MA ratio and classified into four groups following the percentile position: lower than the 2.5th, the 2.5th-the 50th, the 50th-97.5th, and greater than the 97.5th percentile, respectively. The AS value for males presented was less than 0.024, 0.024-0.141, 0.141-0.836, and greater than 0.836. Meanwhile, the AS values were revealed to be lower than 0.023, 0.023-0.148, 0.148-0.850, and higher than 0.850 for females. The AS value of CYP2D6 can be applied to describe the toxicity of MA in forensic crime scenes and relapse behavior.

Chiral determination of nornicotine, anatabine and anabasine in tobacco by achiral gas chromatography with (1S)-(-)-camphanic chloride derivatization: Application to enantiomeric profiling of cultivars and curing processes.

The alkaloid enantiomers are well-known to have different physiological and pharmacological effects, and to play an important role in enantioselectivity metabolism with enzymes catalysis in tobacco plants. Here, we developed an improved method for simultaneous and high-precision determination of the individual enantiomers of nornicotine, anatabine and anabasine in four tobacco matrices, based on an achiral gas chromatography-nitrogen phosphorus detector (GCNPD) with commonly available Rtx-200 column using (1S)-(-)-camphanic chloride derivatization. The method development consists of the optimization of extraction and derivatization, screening of achiral column, analysis of the fragmentation mechanisms and evaluation of matrix effect (ME). Under the optimized experimental conditions, the current method exhibited excellent detection capability for the alkaloid enantiomers, with coefficients of determination (R2) > 0.9989 and normality test of residuals P > 0.05 in linear regression parameters. The ME can be neglected for the camphanic derivatives. The limit of detection (LOD) and limit of quantitation (LOQ) ranged from 0.087 to 0.24 μg g-1 and 0.29 to 0.81 μg g-1, respectively. The recoveries and within-laboratory relative standard deviations (RSDR) were 94.3%~104.2% and 0.51%~3.89%, respectively. The developed method was successfully applied to determine the enantiomeric profiling of cultivars and curing processes. Tobacco cultivars had a significant impact on the nornicotine, anatabine, anabasine concentration and enantiomeric fraction (EF) of (R)-nornicotine, whereas the only significant change induced by the curing processes was an increase in the EF of (R)-anabasine.

A Simple and Rapid Gas Chromatographic Method for Routine Caffeine Determination in Beverages using Nitrogen Phosphorus Detector

Caffeine is a common ingredient in beverages important to be monitored, as there are regulations worldwide. In this study, an analytical method was developed for routine caffeine determination in beverages. The sample pretreatment only takes a few minutes. Caffeine in the sample is extracted by 1 mL of ethyl acetate under sonication. The ethyl acetate phase is then dried by 0.08 g of anhydrous sodium sulfate and directly injected to gas chromatography–nitrogen phosphorus detector. The method was optimized to achieve high rate of recovery of 90.9–111.7% with RSD of <5% for fourteen real beverage samples. The method detection limit was 3.5 mg/L. Apart from the advantages of simplicity and rapidity, the method is relatively green, accurate, precise, sensitive, has a high throughput, low cost of operation and maintenance and can be recommended for the quantification of caffeine in various common beverages.

Prediction of 2-acetyl-1-pyrroline content in grains of Thai Jasmine rice based on planting condition, plant growth and yield component data using chemometrics

The aim of this research was to simultaneously investigate the effects of nitrogen (N) fertilizer and salinity (NaCl) treatments on aromatic quality of Oryza sativa L. ssp. indica cv. Pathumthani 1 (PT1) rice grain. The levels of N and NaCl were designed based on a central composite design (CCD). During the cultivation, plant growth parameters such as number of tillers, plant height and root length were recorded. After the harvest, yield components including number of grains per panicle, panicle length, plant weight, shoot and root dry weights, number of panicle per plant, number of grains per plant and thousand grain weight were collected. The concentrations of 2-acetyl-1-pyrroline (2AP), a key odor-active compound, in the grains were analyzed using gas chromatography-nitrogen phosphorus detector (GC-NPD). Using partial least squares (PLS), the root mean square error of cross validation (RMSECV) value was 0.091 with the Q2 value of 0.8470. Based on PLS coefficients and variable influence on projection (VIP) values, N, Na, the rice yield, the shoot dry weight and the number of tillers per plant were identified to have strong influence on the prediction of the 2AP content. The behaviors of the heavily influenced parameters were confirmed and visualized using self-organizing map (SOM).

소면적 재배작물 산마늘(Allium ochotense Prokh.) 중 살균제 Tebuconazole 및 Fludioxonil의 잔류특성

In recent years, Allium victorialis has been extensively used as a pharmacological agent for various diseases in the form of anti-arteriosclerotic, anti-diabetic and anti-cancer. Allium victorialis is severely affected by various fungal diseases since it naturally grow in the shady and humid environments in Korea. In this case, different types of fungicides are applied to control the fungal diseases in Allium victorialis. The present study was aimed to determine the residual characteristics of two fungicides namely tebuconazole and fludioxonil on Allium victorialis. For this study, the fungicides were drenched soil on Allium victorialis in the cultivation area Pyeongchang by the standard (two thousand fold) and double (thousand fold) dilutions. At the end of , and days samples were collected for residue analysis. Residues of tebuconazole and fludioxonil were analyzed using GC/NPD (Gas Chromatography/Nitrogen Phosphorus Detector) and their recovery were found to be 108.8~119.5% and 91.3~104.8%, respectively. The method of limits of quantification for both fungicides was . Further, the results of this study shows that the residue levels of both fungicides on Allium victorialis were and and their % ADI (% Acceptable Daily Intake) were 17.44% and 25.75%, respectively. Based on the results obtained in this study, we suggest that the residue levels of both of the fungicides on Allium victorialis are safe and these fungicides can also be used to control fungal diseases in Allium victorialis.

Superparamagnetic core–shells anchored onto graphene oxide grafted with phenylethyl amine as a nano-adsorbent for extraction and enrichment of organophosphorus pesticides from fruit, vegetable and water samples

A novel adsorbent composed of silica coated magnetic microparticles (Fe3O4@SiO2) and graphene oxide (GO) functionalized with phenylethyl amine (PEA) was synthesized and characterized using Fourier transform-infrared (FT-IR) spectroscopy, scanning electron microscopy (SEM), vibrating sample magnetometry (VSM), and CHN elemental analysis techniques. The adsorbent (Fe3O4@SiO2@GO-PEA) was then used in a magnetic solid phase extraction (MSPE) of six organophosphorous pesticides (OPPs) including methyl parathion, fenitrothion, methidathion, ethion, methyl azinphos and coumaphos prior to gas chromatography-nitrogen phosphorus detection (GC–NPD). The fabricated adsorbent combines the advantages of superior adsorption capability of modified GO and magnetic separability of magnetite microparticles to provide high adsorption capacity, and easy isolation from sample solutions. The main experimental parameters affecting the extraction recovery of OPPs including extraction time, pH, adsorbent dosage, salt concentration, and desorption conditions were investigated and optimized. Under the optimal conditions, linear responses were obtained in the concentration range of 0.06–200μgL−1 with the determination coefficients (R2) between 0.9945 and 0.9996. The limits of detection were from 0.02 to 0.1μgL−1 and the intraday and inter-day relative standard deviations (RSDs) were less than 4.8 and 6.4%, respectively. The method was successfully applied for determination of the OPPs in apple, grape, pear, bell pepper, celery and water samples. The obtained recoveries were in the range of 90.4–108.0% (RSDs=1.9–6.6%, n=3) for fruits and vegetables, and 94.6–104.2% (RSDs=2.0–4.8%, n=3) for water samples. The excellent extraction performance of the adsorbent can be attributed to its structure characteristics where the phenyl rings of PEA grafted on the GO nanosheets are accessible to interact effectively with OPPs via delocalized π-electron system.

Determination and analysis of the dissipation and residue of cyprodinil and fludioxonil in grape and soil using a modified QuEChERS method

A simple and accurate method coupled with a gas chromatography-nitrogen phosphorus detector was developed to detect cyprodinil and fludioxonil in grape and soil. The accuracy and precision of the method in detecting the two fungicides were evaluated by conducting intra- and inter-day recovery experiments. The limits of detection were 0.017 mg/kg for cyprodinil and 0.030 mg/kg for fludioxonil. The limits of quantitation were 0.05 mg/kg for cyprodinil and 0.10 mg/kg for fludioxonil in grape and soil. The recoveries of the fungicides in grape and soil were investigated at three spiked levels and were found to range from 85.81 to 102.94% for cyprodinil and from 92.00 to 106.86% for fludioxonil, with relative standard deviations below 7%. Field experiments were conducted in two experimental locations in China. The half-lives of cyprodinil were 9.6-20.8 days in grape and 5.8-15.6 day in soil, and the half-lives of fludioxonil were 6.2-7.2 days in grape and 6.0-12.1 days in soil. When the cyprodinil and fludioxonil 62% water-dispersible granule formulation was sprayed at a low dosage three times, terminal residues of cyprodinil and fludioxonil were below 1.0 mg/kg in grape 14 days after harvest. This work may serve as a reference to establish the maximum residue limits for cyprodinil and fludioxonil in grape and promote the proper and safe use of these two fungicides.

Erratum to: Detecting fludioxonil residues in brown rice and rice straw using gas chromatography-nitrogen phosphorus detector

In the present study, brown rice was steeped in 20 % wettable powder fludioxonil for 24 h, subsequently germinated, and transplanted in paddy fields. The harvested rice was tested at 156 days to detect residue levels using gas chromatography-nitrogen phosphorus detector. Validation was carried out to assess the following parameters: linearity, limit of detection and limit of quantitation (LOQ), recovery, and storage stability. Using matrix-matched calibrations, the determination coefficients were >0.999 in both matrices. Mean recoveries were 73.5–101.0 % with relative standard deviations <10 % in both matrices. The LOQ (0.006 mg/kg) was lower than the maximum residue limit (MRL = 0.02 mg/kg) set by the Ministry of Food and Drug Safety, Republic of Korea. The developed method was applied successfully, and no residues were detected in field-incurred rice and/or rice straw samples.

폴리아마이드제 등 조리기구 중 모노머의 이행에 관한 연구

국내 유통 중인 총 321건의 폴리아미드, 폴리우레탄, ABS, 아크릴 수지 재질 식품용 기구 중 이행우려가 있는 모노머인 4,4'-메틸렌디아닐린, 2,4-톨루엔디아민, 아닐린, 아크릴로니트릴 및 메틸메타크릴레이트에 대하여 이행량을 조사하고 안전성 평가를 실시하였다. 83건의 폴리아미드, ABS 및 아크릴 수지 재질 식품용 기구 검체에서 현행 식품용 기구 및 용기 포장 공전상의 용출규격 이하인 4,4'-메틸렌디아닐린, 2,4-톨루엔디아민, 아크릴로니트릴 및 메틸메타크릴레이트가 이행되었다. 이행량 결과를 토대로 안전성 평가 시나리오에 적용하여 4,4'-메틸렌디아닐린, 2,4-톨루엔디아민, 아크릴로니트릴 및 메틸메타크릴레이트의 EDI를 산출한 후 TDI와 비교하여 위해도를 평가하였다. EDI는 폴리아미드 재질 기구의 4,4'-메틸렌디아닐린과 2,4-톨루엔디아민의 경우 각각 <TEX>$2.39{\times}10^{-9}$</TEX>, 및 <TEX>$1.20{\times}10^{-9}mg/kg\;bw/day$</TEX>, ABS 재질 기구의 아크릴로니트릴의 경우 <TEX>$4.32{\times}10^{-9}mg/kg\;bw/day$</TEX>, 아크릴 수지 재질 기구 메틸메타크릴레이트의 경우 <TEX>$2.27{\times}10^{-7}mg/kg\;bw/day$</TEX>이었다. ABS 재질 기구 이행 아크릴로니트릴의 위해도는 RfD 대비 <TEX>$4.32{\times}10^{-4}%$</TEX> 수준이었고, 아크릴 수지 재질 기구 이행 메틸메타크릴레이트의 위해도는 TDI 대비 <TEX>$1.89{\times}10^{-5}%$</TEX> 수준이었다. 결론적으로 검토된 평가 항목들의 위해도는 TDI 대비 <TEX>$4.32{\times}10^{-4}%$</TEX>와 <TEX>$1.89{\times}10^{-5}%$</TEX>에 불과한 것으로 조사되어 안전한 수준인 것으로 사료되었다. 이러한 결과들은 앞으로 기구 및 용기 포장의 안전관리를 위한 과학적인 근거자료로 이용될 수 있을 것으로 판단된다. The purpose of our paper was to investigate the migration level of 4,4'-MDA(4,4'-methylenedianiline), 2,4-TDA(2,4-toluenediamine), aniline, acrylonitrile and methylmeth acrylate from plastic cookwares into food simulants and to evaluate the safety of each monomers. The test articles for monomers were PA (polyamide) items for 4,4'-MDA, 2,4-TDA and aniline, PU (polyurethane) items for 4,4'-MDA, ABS (acrylonitrile-butadiene- styrene) items for acrylonitrile, and acrylic resin items for methylmethacrylate. All the article samples of 321 intended for contact with foods were purchased in domestic market. 4,4'-MDA, 2,4-TDA and aniline were analyzed by LC-MS/MS (liquid chromatography -tandem mass spectrometer), acrylonitrile by GC-NPD (gas chromatography-nitrogen phos phorus detector) and methyl methacrylate by GC-FID (gas chromatography-flame ionization detector). The migration level of monomers were within the migration limits of Ministry of Food and Drug Safety (MFDS). As a result of safety evaluation, our results showed that the estimated daily intake (EDI, mg/kg bw/day)s were <TEX>$2.39{\times}10^{-9}$</TEX> and <TEX>$1.20{\times}10^{-9}$</TEX> for 4,4'-MDA and 2,4-TDA of PA, <TEX>$4.32{\times}10^{-9}$</TEX> for acrylonitrile of ABS and <TEX>$2.27{\times}10^{-7}$</TEX> for methylmethacrylate of acrylic resin. Reference Dose (RfD, mg/kg bw/day) of acrylonitrile and tolerable daily intake (TDI, mg/kg bw/day) of methacrylate were established respectively as 0.001 by EPA (US Environmental Protection Agency) and as 1.2 by WHO (World Health Organization). When comparing with RfD and TDI, the EDIs of acrylonitrile and methylmethacrylate accounted for <TEX>$4.32{\times}10^{-4}%$</TEX> and <TEX>$1.89{\times}10^{-5}%$</TEX> respectively.

참외(Cucumis melon var. makuwa)에 대한 Buprofezin 및 Penthiopyrad의 생산단계 잔류허용기준 설정

The present work was aimed to determine the pre-harvest residue limits (PHRLs) and the safety management of commonly used pesticides namely buprofezin and penthiopyrad on oriental melon (Cucumis melon var. makuwa). In this study, the buprofezin (diluted two thousand fold) and penthiopyrad (diluted four thousand fold) were sprayed single time on oriental melon in the cultivation areas Sangju (site 1) and Sungju (site 2). Oriental melon were randomly collected from the both areas at the end of 0 (2 hours after pesticides spaying), 1, 2, 3, 5, 7, 9 and 10 days. For analysis, each samples were partitioned twice (80 and 70 mL) with dichloromethane and purified by florisil SPE cartridge. Finally, the residual amounts of both pesticides in all samples were analyzed using gas chromatography/nitrogen phosphorus detector (GC/NPD). In this study, the method limit of quantification (MLOQ) for both buprofezin and penthiopyrad in oriental melon was found to be 0.01 mg kg and their recovery levels were 91.1~98.6% and 90.0~104.6%, respectively. Further, the calculated biological half-life for buprofezin and penthiopyrad in oriental melon were 3.9 and 3.5, and 3.0 and 2.7 days in site 1 and 2, respectively. The results of this study found that the PHRLs for buprofezin and penthiopyrad were 4.24 and 2.31 mg kg, respectively at 10 days before harvest. Consequently, the present study suggest that the residual amounts of both pesticides will be lower than the maximum residue limits (MRLs) when oriental melon is harvested.

Determination of organophosphorus pesticides in stomach contents of postmortem animals by QuEChERS and gas chromatography.

The quick, easy, cheap, effective, rugged and safe (QuEChERS) method for sample preparation was applied to determine seven organophosphorus pesticides (OPs) in stomach contents of poisoned postmortem animals. The pesticides consisted of diazinon, edifenphos, ethyl p-nitrophenyl phenylphosphonothioate, fenitrothion, monocrotophos, parathion and phosphamindon, and tested samples included stomach contents from postmortem animals of cattle, goat, dog, cat, birds, deer and rabbit. The pesticides were spiked into the samples which were found to be negative through previous pesticide poisoning analysis, and the pesticides were extracted and cleaned up based on the QuEChERS process and then they were analyzed using gas chromatography (GC)-flame photometric detector (FPD) or GC-nitrogen-phosphorus detector (NPD) with a DB-5 column. Limits of detection ranged from 0.27 to 0.41 mg/kg for the seven pesticides. The mean recoveries ranged from 80 to 99% in GC-FPD and 83 to 90% in GC-NPD. The coefficients of variation were <10% for all analytes and sample matrix combinations except for phosphamidon and edifenphos in dog stomach contents. This study demonstrated that the method using QuEChERS and GC-FPD and/or GC-NPD is very effective to analyze the OPs in the stomach contents of postmortem animals.

Analysis of etoxazole in red pepper after major modification of QuEChERS for gas chromatography–nitrogen phosphorus detection

A major modification to the QuEChERS (quick, easy, cheap, effective, rugged and safe) method was developed for the analysis of etoxazole in red pepper using gas chromatography coupled with a nitrogen-phosphorus detector. Etoxazole was extracted with acetonitrile, partitioned with magnesium sulfate and purified with a solid-phase extraction cartridge. The method showed good linearity with a determination coefficient (R(2) ) of 0.998 for the 0.02-2.0 mg/L concentration range. The method was validated using blank red pepper spiked at 0.2 and 1.0 mg/kg, and the average recovery rate was 74.4-79.1% with relative standard deviations <5% for intra- and inter-day precision. The limits of detection and quantification were 0.007 and 0.02 mg/kg, respectively. The developed method was successfully applied to field-incurred samples, and the presence of etoxazole residues was confirmed using gas chromatography/mass spectrometry.

Development of a new microextraction method based on elevated temperature dispersive liquid–liquid microextraction for determination of triazole pesticides residues in honey by gas chromatography-nitrogen phosphorus detection

In the present study, a rapid, highly efficient, and reliable sample preparation method named “elevated temperature dispersive liquid–liquid microextraction” followed by gas chromatography-nitrogen-phosphorus detection was developed for the extraction, preconcentration, and determination of five triazole pesticides (penconazole, hexaconazole, diniconazole, tebuconazole, and difenoconazole) in honey samples. In this method the temperature of high-volume aqueous phase was adjusted at an elevated temperature and then a disperser solvent containing an extraction solvent was rapidly injected into the aqueous phase. After cooling to room temperature, the phase separation was accelerated by centrifugation. Various parameters affecting the extraction efficiency such as type and volume of the extraction and disperser solvents, temperature, salt addition, and pH were evaluated. Under the optimum extraction conditions, the method resulted in low limits of detection and quantification within the range 0.05–0.21ngg−1 in honey (15–70ngL−1 in solution) and 0.15–1.1ngg−1 in honey (45–210ngL−1 in solution), respectively. Enrichment factors and extraction recoveries were in the ranges of 1943–1994 and 97–100%, respectively. The method precision was evaluated at 1.5ngg−1 of each analyte, and the relative standard deviations were found to be less than 4% for intra-day (n=6) and less than 6% for inter-days. The method was successfully applied to the analysis of honey samples and difenoconazole was determined at ngg−1 levels.

A rapid and simple determination of caffeine in teas, coffees and eight beverages

Caffeine was extracted and preconcentrated by the simple, fast and green method of dispersive liquid–liquid microextraction (DLLME) and analysed by gas chromatography–nitrogen phosphorus detection (GC–NPD). The influence of main parameters affecting the extraction efficiency investigated and optimised. Under the optimal conditions, the method was successfully applied to determination of caffeine in different real samples including five types of tea (green, black, white, oolong teas and tea bag), two kinds of coffee (Nescafe coffee and coffee), and eight beverages (regular Coca Cola, Coca Cola zero, regular Pepsi, Pepsi max, Sprite, 7up, Red Bull and Hype).The limit of detection (LOD) and limit of quantification (LOQ) were 0.02 and 0.05μgmL−1, respectively. Linear dynamic range (LDR) was 0.05–500μgmL−1 and determination coefficient (R2) was 0.9990. The relative standard deviation (RSD) was 3.2% (n=5, C=1μgmL−1).

Determination of organophosphorus pesticides and metabolites in cereal-based baby foods and wheat flour by means of ultrasound-assisted extraction and hollow-fiber liquid-phase microextraction prior to gas chromatography with nitrogen phosphorus detection

A new method based on hollow-fiber liquid-phase microextraction (HF-LPME) has been developed for the determination of a group of organophosphorus pesticides, including some of their metabolites, in two commercial cereal-based baby foods and one wheat flour prior to gas chromatography-nitrogen phosphorus detection. Samples were first extracted by ultrasound-assisted extraction with acetonitrile (ACN) containing 1.25% (v/v) of formic acid. After evaporation and reconstitution in Milli-Q water, the HF-LPME procedure, using 1-octanol as extraction solvent, was applied followed by a desorption step in ACN, which clearly improved the performance of the technique. The effects of sample pH, ionic strength, stirring rate, extraction temperature and time as well as the desorption procedure were investigated. Under the optimum conditions that involved the extraction of the analytes from 10mL of the water reconstituted extract at pH 7.0 containing 5% (w/v) of NaCl for 45min at 960rpm, the method was validated in terms of linearity, precision and accuracy. The limits of detection (LODs) were between 0.29 and 3.20μg/kg. The extraction of Milli-Q water, as an example of the applicability of the procedure to aqueous samples, allowed achieving LODs in the range 0.01–0.04μg/L. Such values, together with the ones achieved for the rest of the samples, are below or equal to the maximum residue limits specified by the European Union.

Determination of prilocaine HCl in bulk drug and pharmaceutical formulation by GC-NPD method

The novel analytical method was developed and validated for determination of prilocaine HCl in bulk drug and pharmaceutical formulation by gas chromatography-nitrogen phosphorus detection (GC-NPD). The chromatographic separation was performed using a HP-5MS column. The calibration curve was linear over the concentration range of 40-1000 ng ml-1 with a correlation coefficient of 0.9998. The limits of detection (LOD) and quantification (LOQ) of method were 10 ng ml-1 and 35 ng ml-1, respectively. The within-day and between-day precision, expressed as the percent relative standard deviation (RSD%) was less than 5.0%, and accuracy (percent relative error) was better than 4.0%. The developed method can be directly and easily applied for determination of prilocaine HCl in bulk drug and pharmaceutical formulation using internal standard methodology.

Determination of desipramine in biological samples using liquid–liquid–liquid microextraction combined with in‐syringe derivatization, gas chromatography, and nitrogen/phosphorus detection

A method was established for the determination of desipramine in biological samples using liquid-liquid-liquid microextraction followed by in-syringe derivatization and gas chromatography-nitrogen phosphorus detection. The extraction method was based on the use of two immiscible organic solvents. n-Dodecane was impregnated in the pores of the hollow fiber and methanol was placed inside the lumen of the fiber as the acceptor phase. Acetic anhydride was used as the reagent for the derivatization of the analyte inside the syringe barrel. Parameters that affect the extraction efficiency (composition of donor and acceptor phase, ionic strength, sample temperature, and extraction time) as well as derivatization efficiency (amount of acetic anhydride and reaction time and temperature) were investigated. The limit of detection was 0.02 μg/L with intra and interday RSDs of 2.6 and 7.7%, respectively. The linearity of the method was in the range of 0.2-20 μg/L (r(2) = 0.9986). The method was successfully applied to determine desipramine in human plasma and urine.

Multiple headspace solid-phase microextraction of ethyl carbamate from different alcoholic beverages employing drying agent based matrix modification

Multiple headspace solid-phase microextraction (MHS-SPME) combined with gas chromatography-nitrogen phosphorus detector is proposed to determine the toxic contaminant ethyl carbamate (EC) in various alcoholic beverages after matrix modification. The remarkable feature of this method is that matrix effect, which commonly appears in SPME-based analysis, is avoided by determining the total amount of the analyte in the sample. To increase the sensitivity of the method, a novel polyethylene glycol/hydroxy-terminated silicone oil fiber was developed by sol–gel technique and applied for the analysis. Owing to the high polarity and hydrophilia of EC, an important problem still remains because the adsorption by sample matrix causes low transport of EC to the headspace and thus invalidates MHS-SPME for quantification. Mixing with anhydrous sodium sulphate, the sensitivity of the method can be improved. A Taguchi's L 16 (4 5) orthogonal array design was employed to evaluate potentially significant factors and screen the optimum conditions for MHS-SPME of EC. Under the optimized conditions, limit of detection of 0.034 mg L −1 was obtained. Relative standard deviation of replicate samples ( n = 6) was 2.19%. The proposed method was linear in the range of 0.04–100 mg L −1, and the coefficient of determination was 0.9997. The method was used to determine EC in various alcoholic beverages. The concentrations obtained were compared with those obtained by standard addition method and no statistically significant differences were observed.