Determination of formaldehyde in beverages using microwave-assisted derivatization and ionic liquid-based dispersive liquid-liquid microextraction followed by high-performance liquid chromatography

A simple method based on simultaneous microwave-assisted derivatization and ionic liquid-based dispersive liquid-liquid microextraction (IL-based DLLME) is proposed for the derivatization, extraction and preconcentration of formaldehyde in beverage samples prior to the determination by high-performance liquid chromatography (HPLC). Formaldehyde was in situ derivatized with 2,4-dinitrophenylhydrazine (DNPH) and simultaneously extracted and preconcentrated by using microwave-assisted derivatization and IL-based DLLME in a single step. Several experimental parameters, including type and volume of extraction solvent, type and volume of disperser, microwave power and irradiation time, volume of DNPH, pH of sample solution, and ionic strength were evaluated. When the microwave power was 120 W, formaldehyde could be derivatized and extracted simultaneously only within 90 s. Under optimal experimental conditions, good linearity was observed in the range of 0.5-50 ng/mL with the correlation coefficient of 0.9965, and the limit of detection was 0.12 ng/mL. The proposed method was applied to the analysis of different beverage samples, and the recoveries of formaldehyde obtained were in the range of 84.9-95.1% with the relative standard deviations lower than 8.4%. The results showed that the proposed method was a rapid, convenient and feasible method for the determination of formaldehyde in beverage samples.     

Towards a Non-Biased Formaldehyde Quantification in Leather: New Derivatization Conditions before HPLC Analysis of 2,4-Dinitrophenylhydrazine Derivatives

In leathers, formaldehyde is currently analyzed according to EN ISO 17226-1 standard, by reversed phase liquid chromatography after off-line precolumn derivatization with 2,4 dinitrophenylhydrazine (DNPH) in strong acidic conditions. We first demonstrate that this standard is not adapted to leather retanned with resins likely to release formaldehyde by hydrolysis. Indeed, formaldehyde content may be largely overestimated due to concomitant resin hydrolysis (in harsh acidic conditions) that releases formaldehyde during the derivatization step and during the waiting time on autosampler before analysis. Therefore, we thoroughly studied the derivatization step in order to propose new derivatization conditions. Replacing orthophosphoric acid by less acidic buffer solutions is not enough to avoid hydrolysis. A derivatization without adding acid is realized by solubilizing DNPH in acetonitrile instead of orthophosphoric acid. These conditions lead to a complete derivatization of formaldehyde in 3 h at 50 °C (in a water bath) while avoiding the hydrolysis of co-extracted dicyandiamide and melamine resins. The as-obtained leather extracts are stable over time. Formaldehyde contents found with this method agree with the formaldehyde content measured immediately at the end of derivatization reaction in standard conditions or with formaldehyde content measured by a home-designed flow injection analysis with acetylacetone online derivatization and UV detection.     

Electrochemical Study of 2,4‐Dinitrophenylhydrazine as Derivatization Reagent and Aldehydes at Carbon Glassy Electrode

A selective method based on derivatization with 2,4‐dinitrophenylhydrazine (DNPH) is described for the determination of several carbonyl compounds. The factors affecting the derivatization reaction of aldehyde and DNPH were investigated. The product of the derivatization reaction has been characterized by UV/Vis spectrophotometry, NMR, infrared spectroscopy and cyclic voltammetry. Then, an electrochemical study for the determination of aldehyde‐2.4‐dinitrophenylhydrazone was performed at glassy carbon electrode (GCE) using square wave voltammetry (SWV). After the optimization of experimental parameters, the limits of detection (at 3σ ) obtained for all aldehyde‐2,4‐DNPH were varied from 15.82 to 78.39 μmol L⁻¹ and relative standard deviations were between 1.8 and 4.5%. Finally, the proposed method was applied to determine the aldehydes concentration in drinking water and orange juice samples with satisfactory results.     

Liquid-phase microextraction with in-drop derivatization combined with microvolume fluorospectrometry for free and hydrolyzed formaldehyde determination in textile samples

A new miniaturized methodology based on the combination of headspace single drop microextraction and microvolume fluorospectrometry is proposed in this work for the determination of free and hydrolyzed formaldehyde in textile samples. The proposed method is based on the extraction and in-drop derivatization of free and hydrolyzed formaldehyde using the Hantzsch reaction. The effect of experimental variables affecting the performance of the proposed method, such as fluorescence parameters, nature of the extractant phase composition (including acetylacetone concentration, pH, ammonium acetate concentration and presence of an organic solvent), sample temperature, NaCl concentration and microextraction time was carefully investigated. Under optimized conditions, instrumental detection and quantification limits were 26 and 87 μg L⁻¹, respectively, whereas procedural detection and quantification limits were 1.0 and 3.5 mg kg⁻¹, respectively. Repeatability, expressed as relative standard deviation, was 4.6% (n = 9). The method was successfully applied to the determination of free and hydrolyzed formaldehyde in several textile samples, the found results being in good agreement with those obtained with the EN ISO 14184-1:1998 method.     

Analysis of volatile aldehyde biomarkers in human blood by derivatization and dispersive liquid–liquid microextraction based on solidification of floating organic droplet method by high performance liquid chromatography

A new dispersive liquid–liquid microextraction based on solidification of floating organic droplet method (DLLME-SFO) was developed for the determination of volatile aldehyde biomarkers (hexanal and heptanal) in human blood samples. In the derivatization and extraction procedure, 2,4-dinitrophenylhydrazine (DNPH) as derivatization reagent and formic acid as catalyzer were injected into the sample solution for derivatization with aldehydes, then the formed hydrazones was rapidly extracted by dispersive liquid–liquid microextraction with 1-dodecanol as extraction solvent. After centrifugation, the floated droplet was solidified in an ice bath and was easily removed for analysis. The effects of various experimental parameters on derivatization and extraction conditions were studied, such as the kind and volume of extraction solvent and dispersive solvent, the amount of derivatization reagent, derivatization temperature and time, extraction time and salt effect. The limit of detections (LODs) for hexanal and heptanal were 7.90 and 2.34 nmol L⁻¹, respectively. Good reproducibility and recovery of the method were also obtained. The proposed method is an alternative approach to the quantification of volatile aldehyde biomarkers in complex biological samples, being more rapid and simpler and providing higher sensitivity compared with the traditional dispersive liquid–liquid microextraction (DLLME) methods.     

HPLC-UV method development and validation for the determination of low level formaldehyde in a drug substance

A reversed-phase high-performance liquid chromatographic method (HPLC) with diode-array detection is developed and validated for the quantitative determination of formaldehyde in a drug substance. Formaldehyde (HCHO) is reacted with 2,4-dinitrophenylhydrazine (DNPH) to form a Schiff base (HCHO-DNPH derivatization product), which has an absorbing maximum (lambda max) at 360 nm. The HPLC method employs a C8, 3-microm particle size analytical column (150 mm x 4.6 mm), 15-microL injection volume, column temperature controlled at 30 degrees C, detection at 360 nm, and a water-acetonitrile (55:45, v/v) mobile phase at a flow rate of 1 mL/min. These conditions resolve the HCHO-DNPH product from unreacted DNPH, the drug substance and related impurities, as well as diluent peaks within 20 min. The retention time of the HCHO-DNPH product is approximately 6.4 min. The method is linear, accurate in the specified range (0.33-333 ppm), and robust based on analyte (HCHO-DNPH derivatization product) stability in standard and sample. Detection limit is 0.03 ng (0.1 ppm).     

丹磺酰肼衍生-高效液相色谱-荧光检测法测定包装纸中的甲醛和乙醛

建立了丹磺酰肼(DNSH)衍生-高效液相色谱-荧光检测测定包装纸中甲醛和乙醛的分析方法,并与2,4-二硝基苯肼(DNPH)衍生法进行了比较。纸张样品经衍生化试剂振荡萃取30 min,衍生化反应24 h,萃取液经PSA/C18净化管净化处理后,以Diamonsil~ C18(2)色谱柱(150 mm×4.6 mm,5μm)为固定相,用醋酸水溶液(pH2.55)-乙腈为流动相进行梯度洗脱。采用荧光检测器检测,激发波长为330 nm,发射波长为484 nm。结果表明,衍生剂、甲醛-DNSH和乙醛-DNSH在20 min内可完全分离,方法的加标回收率为81.64%~106.78%,相对标准偏差(RSD)为2.02%~5.53%(n=5),甲醛和乙醛的检出限分别为19.2μg/kg和20.7μg/kg,定量限分别为63.9μg/kg和69.1μg/kg。该法操作简单,灵敏度高,比常规方法具有更低的检出限,能很好地应用到实际样品检测中,为低含量醛类化合物的检测提供了一种新思路。     

A New Method for the Measurement of Airborne Formaldehyde Using Derivatization with 3,5-Bis(Trifluoromethyl) Phenylhydrazine and Analysis by GC-ECD and GC-MS/SIM

Abstract

A new method was developed and described for the measurement of airborne formaldehyde using derivatization with 3,5-bis(trifluoromethyl)phenylhydrazine (TFMPH) coated onto silica solid phase extraction cartridges. Analysis by GC-ECD provides a detection limit of 74 ng formaldehyde per sample. A field study was conducted to compare the use of TFMPH to 2,4-dinitrophenylhydrazine (DNPH) and NIOSH method 3500 (chromotropic acid, CTA). Samples were collected from indoor and outdoor environments known or suspected to contain formaldehyde. Use of TFMPH with GC-ECD analysis correlates well with both methods (R²=0.93, slope=1.07 vs. DNPH; R²=0.99, slope=1.06 vs. CTA). Spiked samples were shown to be stable at least 7 days when stored at –20 °C. Analysis of samples by GC-MS with selected ion monitoring (GC-MS/SIM) also proved feasible. Laboratory and field results show the use of TFMPH to be viable for quantifying airborne formaldehyde in occupational and environmental samples.     

柱前衍生-萃取阻断反应-高效液相色谱法测定化妆品中游离甲醛

建立了柱前衍生化-萃取阻断反应-高效液相色谱(HPLC)测定化妆品中甲醛的方法。化妆品中甲醛检测的难点是: 甲醛缓释剂类防腐剂在衍生过程中释放甲醛,影响游离甲醛的准确测定。以2,4-二硝基苯肼(DNPH)乙腈溶液-磷酸盐缓冲液(pH 2)(1:1, v/v)为提取溶液,于室温下快速衍生2 min后,立即加入二氯甲烷萃取,阻断衍生反应,经乙腈稀释后进行HPLC测定。以Agilent C18柱(250 mm×4.6 mm, 5 μm)为分离柱,乙腈-水(60:40, v/v)为流动相,流速为1.0 mL/min,于355 nm波长下检测。在洗发水、乳液、膏霜、洗手液、牙膏、指甲油、粉饼中分别添加50、100、500、1000 μg/g 4个浓度水平的甲醛,其回收率为81%～106%,相对标准偏差(n=6)＜5.0%。方法的定量限(以信噪比(S/N)＞10计)为50 μg/g。该方法快速、简便、重现性好,且可以有效避免甲醛缓释剂类防腐剂分解释放甲醛,适用于化妆品中游离甲醛的测定。     

Development of a novel monolith frit-based solid-phase microextraction method for determination of hexanal and heptanal in human serum samples

In this paper, a polypropylene frit with porous network structure and high area-to-thickness ratio (4.8 mm diameter, 1.6 mm thickness, 20 mm pore size) was utilized as a mould of monolith. Poly(methacrylic acid-ethlyene glycol dimethacrylate) (MAA-EGDMA) monolith was in situ synthesized in the micro-channel of frit by photopolymerization. A monolith frit-based solid-phase microextraction method (SPME) was developed for the determination of hexanal and heptanal in serum samples by combining with high-performance liquid chromatography. 2,4-Dinitrophenylhydrazine (DNPH) as the derivatizing reagent was absorbed on a monolith frit, then its derivatization reaction with aldehydes and the absorption of formed hydrazones on the monolith disk occurred simultaneously. The condition parameters for polymerization, derivatization and extraction were optimized systematically. Under the optimum conditions, rigid structure, low back-pressure and high column capacity were achieved for the monolith frit. The limits of detection for hexanal and heptanal were 1.86 and 1.38 nmol/L, respectively. The inter- and intra-day relative standard deviations were less than 7.7% (n = 6). This method was applied successfully to aldehydes analysis in human serum samples. The method possesses advantages such as simplicity, efficiency, low cost and good biocompatibility. It provides an alternative approach for quantification of aldehydes in complex biological samples.     

Determination of formaldehyde in shiitake mushroom by ionic liquid-based liquid-phase microextraction coupled with liquid chromatography

Using ionic liquid as extraction solvent and 2,4-dinitrophenylhydrazine (DNPH) as derivative agent, formaldehyde in shiitake mushroom was determined by liquid-phase microextraction coupled with high-performance liquid chromatography (HPLC). Shiitake mushroom was leached with water and filtrated, then the formaldehyde in filtrate was derivatized with DNPH and extracted simultaneously into a 10 μl drop of ionic liquid suspended on the tip of the microsyringe, and finally injected into the HPLC system for determination. The proposed procedure has a detection limit of 5 μg l⁻¹ formaldehyde in extraction solution, thus the mushroom sample filtrate could be diluted with a large ratio to eliminate the influence of sample matrix. The method has a relative standard deviation of 3.5% between days for 53.5 μg l⁻¹ formaldehyde standards. High contents of formaldehyde (119-494 μg g⁻¹ wet weight), which is harmful for human beings, were detected in shiitake mushroom. Therefore, strategies must be taken to prevent the accumulation and strictly control the content of formaldehyde in shiitake mushroom.     

Development of an automated on-line pre-column derivatization procedure for sensitive determination of histamine in food with high-performance liquid chromatography-fluorescence detection

An improved sensitive method was developed and validated for the determination of histamine in food samples by using automated on-line pre-column derivatization coupled with high performance liquid chromatography and fluorescence detection (HPLC-FLD). o-Phthaldialdehyde (OPA) was adopted as derivatization reagent, and a "sandwich" (OPA+histamine+OPA) aspiration mode for the automated on-line pre-column derivatization was found to efficiently enhance the method sensitivity and precision. Histamine in food samples was efficiently extracted with a methanol-phosphate buffer solution (50:50, v/v) at 60 degrees C for 30 min, and purified with Waters Oasis MCX solid-phase extraction (SPE) cartridge. The limit of quantification for this method is 0.2 mg/kg, which is very sensitive for histamine determination. With the "sandwich" injection program, 3.7% of relative standard deviation (RSD) was achieved by five replicative determinations of a sample blank spiked with 0.25 mg/kg histamine standard. Histamine in food samples such as fumitory skipjack and mackerel was analyzed with relative recoveries over 95% at spiking level of 150 mg/kg, as well as canned tuna fish and cheese with relative recoveries up to 98% at spiking levels of 0.50 and 5.0 mg/kg, respectively. The proposed method was validated with a sample from the Food Analysis Performance Assessment Scheme (FAPAS) as a standard certified material; and the results (140+/-6 mg/kg) agreed well with the assigned value (139 mg/kg).     

Ion chromatographic analysis of cyanate in gold processing samples containing large concentrations of copper(I) and other metallocyanide complexes

An ion chromatographic (IC) method was developed for the determination of cyanate in gold cyanidation samples containing large concentrations of metallo-cyanide complexes. The analysis was performed on a Waters HC IC-Pak A anion-exchange column with an anthranilic acid eluent, with detection achieved using indirect UV at 355 nm. Two procedures were developed for removal of the metallo-cyanide complexes prior to the IC analysis. The first was a manual off-line method which used solid-phase extraction cartridges containing a strong anion-exchange resin to trap the complexes and to then enable determination of cyanate without interference. In the second approach, an automated on-line method was developed which used an anion-exchange guard column to trap the complexes and a column switching valve to allow backflushing of the cyanate from the guard column. This enabled the total analysis to be performed in a time of 10–14 min, depending on the sample composition. Finally, a comparison of results obtained by the standard Kjeldahl nitrogen method for cyanate and the IC method revealed an interference in the Kjeldahl method for samples containing large concentrations of Cu(I)-cyanide complexes.     

复合免疫亲和柱-高效液相色谱法同时测定谷物及其制品中9种真菌毒素

建立了复合免疫亲和柱-在线光化学衍生-高效液相色谱同时测定谷物及其制品中9种真菌毒素的检测方法。以乙腈-水（80：20,v/v）混合溶液提取样品中9种真菌毒素,提取液经自制真菌毒素复合免疫亲和柱净化,采用高效液相色谱进行分离,在线光化学衍生后进入荧光检测器测定,外标法定量。结果表明,9种真菌毒素在相应浓度范围内线性关系良好,相关系数均大于0.999;在低、中、高3个不同加标浓度下,9种真菌毒素的回收率均大于80%,相对标准偏差（RSD）为1.0%~5.6%;方法的检出限（LOD）为0.02~5.00 μg/kg,定量限（LOQ）为0.07~16.70 μg/kg。该方法具有重现性好、灵敏度高、结果准确的特点,适用于谷物及其制品中9种真菌毒素残留的分析检测。     

Derivatization followed by gas chromatography-mass spectrometry for quantification of ethyl carbamate in alcoholic beverages

A sensitive and rapid analytical methodology based on derivatization followed by gas chromatography-mass spectrometry (GC-MS) was developed for the quantitative determination of the toxic contaminant ethyl carbamate (EC, urethane, C(2)H(5)OCONH(2)) in alcoholic samples. EC was extracted using liquid-liquid extraction technique, and then silylated with bis-(trimethylsilyl)trifluoroacetamide, analysed finally by GC-MS. The isopropyl carbamate was used as the internal standard for quantitative analysis of EC in alcoholic samples. In this work, the sample extraction and derivatization reaction conditions were investigated, and the optimal extraction conditions obtained were: pH 9 and solvent of ethyl acetate, and the derivatization conditions were: derivatization reaction temperature of 80°C and time duration of 30 min. With the optimal conditions, the method validations were also studied. In the validation studies, EC exhibited good linearity with a regression coefficient of 0.9999. The limit of detection and limit of quantification were 0.30 and 5.0 μg/kg, respectively. The precision was less than 8.4%. Finally, the proposed technique was successfully applied to the analysis of EC in 35 kinds of alcoholic samples. The experimental results have demonstrated that the proposed technique is a fast, reliable and low-cost method for determination of EC in alcoholic samples.     

高效液相色谱柱后衍生测定脱水蔬菜中的亚硫酸盐

建立了检测脱水蔬菜中亚硫酸盐的反相硅胶柱净化-柱后衍生-高效液相色谱方法.样品经甲醛提取,通过反相硅胶固相萃取小柱净化,采用Discover ODS-C18柱,流动相为0.005 mol/L氢氧化四丁基铵和乙腈,在碱性条件下以5,5’-二硫代双(2-硝基苯甲酸)为柱后衍生化试剂,445 nm检测.实验结果表明,在0.050～50.00 mg/L浓度范围内,相关系数为0.9987,方法的检出限和定量限分别为1 mg/kg和2 mg/kg,添加浓度在2～900mg/kg范围内,平均添加回收率为62％～88％,相对标准偏差不大于7.8％.该法能有效地避免脱水蔬菜中亚硫酸盐测定的假阳性结果,可满足实际检测工作的需要.     

络合萃取-在线衍生土壤酸性除草剂条件选择与优化

以Na4EDTA为络合剂,以五氟苄基溴为衍生试剂,采用快速溶剂萃取仪萃取,同时实现土壤酸性除草剂的络合萃取在线衍生,并以气相色谱-质谱(NCI源)进行检测。对络合条件、衍生条件、萃取条件、离子源选择进行了优化。方法的回收率为75%～95%、相对标准偏差为6.7%～13%、检测限2.8～8.4μg/Kg。     

柱前衍生-高效液相色谱法测定调制乳粉中左旋肉碱的含量

建立了柱前衍生-高效液相色谱(HPLC)测定乳制品中左旋肉碱含量的方法。试样经0.1 mol/L盐酸超声提取后,采用阳离子交换固相萃取柱净化,在三乙胺和氯甲酸丁酯的催化下与L-丙酰胺-β-萘胺发生取代反应,使用配有二极管阵列检测器(DAD)的高效液相色谱仪测定,外标法定量。该方法在0.250~50.0 mg/L范围内线性关系良好,线性方程为y=164.4x-11.3,相关系数为0.9998,加标回收率为84.3%~86.0%,相对标准偏差为1.93%~3.18%。该方法的检出限为10 mg/kg,定量限为25 mg/kg。运用该方法对国内20个实际乳粉样品中的左旋肉碱含量进行测定,20个样品中均检出了左旋肉碱,含量为53~163 mg/kg。该方法快速、简便、准确,适用于乳品中左旋肉碱含量的检测。     

直接衍生/高效液相色谱法分析水基胶中羰基化合物

建立了直接衍生/高效液相色谱分析水基胶中8种痕量羰基化合物(甲醛、乙醛、丙酮、丙烯醛、丙醛、丁烯醛、2-丁酮和丁醛)的方法.对影响分析效率的因素进行了考察,确定最佳衍生条件为:水基胶样品与2,4-二硝基苯肼衍生剂在40℃下反应20 min;最佳色谱分析条件为:采用DIONEX Acclaim Explosives E2...     

Ionic liquid-based microwave-assisted dispersive liquid-liquid microextraction and derivatization of sulfonamides in river water, honey, milk, and animal plasma

The ionic liquid-based microwave-assisted dispersive liquid-liquid microextraction (IL-based MADLLME) and derivatization was applied for the pretreatment of six sulfonamides (SAs) prior to the determination by high-performance liquid chromatography (HPLC). By adding methanol (disperser), fluorescamine solution (derivatization reagent) and ionic liquid (extraction solvent) into sample, extraction, derivatization, and preconcentration were continuously performed. Several experimental parameters, such as the type and volume of extraction solvent, the type and volume of disperser, amount of derivatization reagent, microwave power, microwave irradiation time, pH of sample solution, and ionic strength were investigated and optimized. When the microwave power was 240 W, the analytes could be derivatized and extracted simultaneously within 90 s. The proposed method was applied to the analysis of river water, honey, milk, and pig plasma samples, and the recoveries of analytes obtained were in the range of 95.0-110.8, 95.4-106.3, 95.0-108.3, and 95.7-107.7, respectively. The relative standard deviations varied between 1.5% and 7.3% (n=5). The results showed that the proposed method was a rapid, convenient and feasible method for the determination of SAs in liquid samples.