Simple and sensitive determination of malondialdehyde in human urine and saliva using UHPLC-MS/MS after derivatization with 3,4-diaminobenzophenone.

Malondialdehyde has been used as a biomarker for lipid peroxidation in biological samples. An ultra-high performance liquid chromatography with tandem mass spectrometry method was developed to determine the levels of malondialdehyde in human urine and saliva samples. To select the optimum derivatization reagent from four diamino compounds, the reactivity and sensitivity of their derivatives were compared, and 3,4-diaminobenzophenone was selected. The optimum reaction conditions for malondialdehyde with 3,4-diaminobenzophenone were as follows: a reagent dosage of 50 mg/L, pH of 4, and reaction for 30 min at 50°C. The formed derivative product was analyzed using ultra-high performance liquid chromatography with tandem mass spectrometry without additional extraction or concentration steps. In the optimal conditions, the method was used to determine malondialdehyde concentration in human urine and saliva samples. The limits of quantification for malondialdehyde in biological samples were over a concentration range of 0.1-0.3 µg/L. Additionally, the calibration curve showed a linearity greater than r2  = 0.997. The method was used to analyze 14 human urine and saliva samples from healthy volunteers. Malondialdehyde was detected in the concentration range of 1.7-33.6 µg/g creatinine in all human urine samples and 0.1-1.3 µg/L in all human saliva samples.

Ultra-trace level determination of diquat and paraquat residues in surface and drinking water using ion-pair liquid chromatography with tandem mass spectrometry: a comparison of direct injection and solid-phase extraction methods.

Direct injection and solid-phase extraction methods for the determination of diquat and paraquat in surface and drinking water were developed using liquid chromatography with tandem mass spectrometry. The signal intensities of analytes based on six ion-pairing reagents were compared with each other, and 12.5 mM nonafluoropentanoic acid was selected as the best suited amongst them. A clean-up method was developed using Oasis hydrophilic-lipophilic balance; this was compared to the direct injection method, with respect to limits of detection, interference, precision, and accuracy. Limits of quantification of diquat and paraquat were 0.03 and 0.01 µg/L using the direct injection method, and 0.002 and 0.001 µg/L using the hydrophilic-lipophilic balance method. When the hydrophilic-lipophilic balance method was used to analyze target compounds in 114 surface water and 30 drinking water samples, paraquat and diquat were detected within a concentration range of 0.001-0.12 and 0.002-0.038 µg/L in surface water, respectively. When the direct injection method was used to analyze target compounds in the same samples, the detected concentrations of paraquat and diquat were within 25% in samples being >0.015 µg/L using the hydrophilic-lipophilic balance method. The liquid chromatography with tandem mass spectrometry method using direct injection can thus be used for routine monitoring of paraquat and diquat in surface and drinking water.

Simultaneous determination of non-steroidal anti-inflammatory drugs in river water by gas chromatography-mass spectrometry.

The gas chromatography/mass spectrometric assay method was developed for the determination of 13 non-steroidal anti-inflammatory drugs (NSAIDs) in river water. Extraction was achieved by a liquid-phase extraction procedure using methylene chloride. The extract was reacted for 30 min at 80°C based on the formation of methyl ester with 1.0 M HCl in methanol and extraction of the derivative with ethyl acetate, which was then measured by gas chromatography-mass spectrometry. The limit of quantification of NSAIDs was 1.0-60 ng/L and the calibration curve showed linearity being greater than r=0.997. The method was used to analyze ten river water samples from various regions in Korea. Diclofenac, indoprofen, ketoprofen and loxoprofen were detected at concentration of up to 1.29 µg/L in river water. The developed method may prove valuable for use in the national monitoring project of NSAIDs in surface water.

Simple determination of hydrazine in waste water by headspace solid-phase micro extraction and gas chromatography-tandem mass spectrometry after derivatization with trifluoro pentanedione.

A headspace solid-phase micro extraction (HS-SPME) and gas chromatography-tandem mass spectrometric (GC-MS/MS) method is described to detect hydrazine after derivatization with 1,1,1-trifluoro-2,4-pentanedione (1,1,1-TFPD) to 3-methyl-5-(trifluoromethyl) pyrazole in industrial waste water. The following optimal HS-SPME conditions were used: 85 µm-carboxen-polydimethylsiloxane fibre, 100 mg L-1 TFPD, saturated NaCl, an extraction/derivatization temperature of 80 °C, a heating time of 40 min, and a pH of 9.5. Under the established conditions, the detection and quantification limits were 0.002 µg L-1 and 0.007 µg L-1 by using 5 mL of waste water and the intra- and inter-day relative standard deviations were less than 10.2% at concentrations of 0.02 and 0.1 µg L-1. The calibration curve showed good linearity, with r2 = 0.998; the accuracy was in the range of 98.0-103%; and the precision of the assay was less than 10.2% in industrial waste water. Hydrazine was detected over a concentration range of 0.011-0.074 µg L-1 in 5 of 20 waste water samples.

Simple and sensitive determination of hydrazine in drinking water by ultra-high-performance liquid chromatography-tandem mass spectrometry after derivatization with naphthalene-2,3-dialdehyde.

An ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) method was developed to determine the level of hydrazine in drinking water. The method is based on the derivatization of hydrazine with naphthalene-2,3-dicarboxaldehyde (NDA) in water. The optimum conditions for UPLC-MS/MS detection were determined as follows: derivatization reagent dosage, 50mg/L of NDA; pH 2; and reaction time, 1min; room temperature. The formed derivative was injected into an LC system without extraction or purification procedures. Under the established conditions, the method was used to detect hydrazine in raw drinking water and chlorinated drinking water. The limits of detection and quantification for hydrazine in drinking water were 0.003µg/L and 0.01µg/L, respectively. The accuracy was in the range of 97-104%, and precision, expressed as relative standard deviation, was less than 9% in drinking water. Hydrazine was detected at a concentration of 0.13µg/L in one sample among 24 raw drinking water samples and in a range of 0.04-0.45µg/L in three samples among 24 chlorinated drinking water samples.

Identification and Quantification of Several Contaminated Compounds in Replacement Liquids of Electronic Cigarettes by Gas Chromatography-Mass Spectrometry.

Electronic cigarettes (E-cigarettes) are devices that are refilled with replacement liquids, which normally contain propylene glycol, nicotine and the desired flavor blend. Many consumers suspect that hazardous substances are present in addition to nicotine content. In this study, eight contaminated compounds in 105 replacement liquids from 11 types of E-cigarettes sold in the Republic of Korea were identified and quantified by gas chromatography-mass spectrometry. Diethyl phthalate and diethylhexyl phthalate were detected in concentration ranges of 0.01-1745.20 mg/L (47.6% detection frequency) and 0.06-81.89 mg/L (79.1% detection frequency) in the replacement liquids. Triethylene glycol, tetraethylene glycol and pentaethylene glycol were quantified in concentration ranges of 0.1-19.3 mg/L (10.5% detection frequency), 0.1-30.1 mg/L (12.4% detection frequency) and 0.1-24.9 mg/L (6.7% detection frequency) in the same samples. cis-3-Hexene-1-ol, methyl cinnamate and dodecane were quantified in concentration ranges of 0.03-3267.46 mg/L (70.5% detection frequency), 4.41-637.54 mg/L (6.7% detection frequency) and 0.01-639.96 mg/L (47.6% detection frequency) in the samples.

Sensitive determination of hydrazine in water by gas chromatography-mass spectrometry after derivatization with ortho-phthalaldehyde.

A gas chromatography-mass spectrometric (GC-MS) method has been established for the determination of hydrazine in drinking water and surface water. This method is based on the derivatization of hydrazine with ortho-phthalaldehyde (OPA) in water. The following optimum reaction conditions were established: reagent dosage, 40 mg mL(-1) of OPA; pH 2; reaction for 20 min at 70 °C. The organic derivative was extracted with methylene chloride and then measured by GC-MS. Under the established condition, the detection and the quantification limits were 0.002 µg L(-1) and 0.007 µg L(-1) by using 5.0-mL of surface water or drinking water, respectively. The calibration curve showed good linearity with r(2)=0.9991 (for working range of 0.05-100 µg L(-1)) and the accuracy was in a range of 95-106%, and the precision of the assay was less than 13% in water. Hydrazine was detected in a concentration range of 0.05-0.14 µg L(-1) in 2 samples of 10 raw drinking water samples and in a concentration range of 0.09-0.55 µg L(-1) in 4 samples of 10 treated drinking water samples.

Determination of ortho-phthalaldehyde in water by high performance liquid chromatography and gas chromatography-mass spectrometry after hydrazine derivatization.

A simple high performance liquid chromatographic (HPLC) method and a highly sensitive gas chromatography mass spectrometric (GC-MS) method have been established for the determination of ortho-phthalaldehyde (OPA) in water. These methods are based on the derivatization of OPA with hydrazine in water. The following optimum reaction conditions were established: reagent dosage, 20 mg/mL of hydrazine; pH 2; reaction for 20 min at 70 °C. The organic derivative was detected directly by HPLC or after the extraction with methylene chloride/concentration by GC-MS. The limit of detection of OPA in water was 4.0 and 0.3 µg/L by HPLC and GC-MS, respectively. The calibration curve showed good linearity with r² = 0.9993 and r² = 0.9994 by HPLC and GC-MS, respectively, the accuracy was in a range of 95-105%, and the precision of the assay was less than 13% in water. The HPLC method was simple and reproducible enough to permit the OPA content analysis in the disinfectant products, and the GC-MS method is sensitive enough to permit reliable analysis of OPA to the µg/L level in environmental water.

Rapid determination of natural steroidal hormones in saliva for the clinical diagnoses.

BACKGROUND: Saliva samples are easily collectable and non-invasive, and the monitoring of natural steroidal hormones, such as estrone (E1), 17ß-estradiol (E2), estriol (E3), progesterone (P), and testosterone (T), in saliva has attracted much attention due to its numerous potential clinical and health-related applications. Because E1, E2, E3, P and T are useful indicators in numerous clinical and health-related diagnoses, there is a need for simultaneous determination. RESULTS: A gas chromatography-mass spectrometric assay was developed for rapid simultaneous determination of E1, E2, E3, P and T in saliva for clinical diagnoses. Extraction was achieved with a liquid extraction using 3.0 mL of pentane. The extract was dried and silylated with N-methyl-N-(trimethylsilyl) trifluoroacetamide/NH4I (100:2) under a catalysis of 1.5% dithioerythritol for 10 min at 90°C. The accuracy of the analytes was in the range of 96% to 112% at concentrations of 0.05 and 0.10 µg/L (5.0 and 10.0 µg/L for E3), respectively, with relative standard deviations of less than 11%. The lowest quantification limits were from 0.002 to 0.6 µg/L for 1.0 mL of saliva. CONCLUSION: Natural steroidal hormones were detected in the concentration ranges of nd to 0.2 µg/L in human saliva. The salivary testosterone values in the patients with prostatic carcinoma were significantly lower than in normal males. The method may useful in numerous clinical and health-related diagnoses.