Determination of methylmercury in fish using focused microwave digestion following by Cu2+ addition, sodium tetrapropylborate derivatization, n-heptane extraction, and gas chromatography-mass spectrometry.

The analytical procedure for analysis of methylmercury in fish was developed. It involves microwave-assisted digestion with alkaline solution (tetramethylammonium hydroxide), addition of Cu2+, aqueous-phase derivatization of methylmercury with sodium tetrapropylborate, and subsequent extraction with n-heptane. The methylmercury derivative was desorbed in the splitless injection port of a gas chromatograph and subsequently analyzed by electron impact mass spectrometry. Optimum conditions allowed sample throughout to be controlled by the instrumental analysis time (near 7 min per sample) but not by the sample preparation step. At the power of 15-30, 45, and 60-75 W, sample preparation time is only 3.5, 2.5, and 1.5 min, respectively. The proposed method was finally validated by the analysis of three biological certified reference materials, BCR CRM 464 tuna fish, NRC DORM-2 dogfish muscle, and NRC DOLT-2 dogfish liver. The detection limit of the overall procedure was found to be 40 ng/g of biological tissue for methylmercury. The recovery of methylmercury was 91.2-95.3% for tuna, 89.3-94.7% for marlin, and 91.7-94.8% for shark, respectively. The detected and certified values of methylmercury of three biological certified reference materials were as follows: 5.34 +/- 0.30 microg/g (mean +/- S.D.) and 5.50 +/- 0.17 microg/g for CRM 464 tuna fish, 4.34 +/- 0.24 and 4.47 +/- 0.32 microg/g for NRC DORM-2 dogfish muscle, and 0.652 +/- 0.053 and 0.693 +/- 0.055 microg/g for NRC DOLT-2 dogfish liver, respectively. It indicated that the method was well available to quantify the methylmercury in fish.

Simultaneous quantification of glyphosate, glufosinate, and their major metabolites in rice and soybean sprouts by gas chromatography with pulsed flame photometric detector.

Procedures were developed for the simultaneous determination of glyphosate [N-(phosphonomethyl)glycine] and glufosinate [dl-homoalanin-4-yl-(methyl)phosphinic acid] and their major metabolites, aminomethylphosphonic acid (AMPA) and 3-(methylphosphinico)propionic acid (3-MPPA), in rice and soybean sprouts by gas chromatography (GC) equipped with a pulsed flame photometric detector (PFPD). Herbicides and their major metabolites were previously derivatized with TMOA (trimethyl orthoacetate (TMOA) in the presence of acetic acid, and their GC responses versus heating temperature (70-90 degrees C) and heating time (30-120 min) were optimized. It was found that increases in heating temperature and heating time were unfavorable for the derivatization of glyphosate or glufosinate, whereas high temperature and extended reaction time remarkably facilitated that of AMPA and 3-MPPA except at 90 degrees C for an extended reaction time (120 min). Combination of AG1-X8 anion-exchange chromatography with a Florisil cartridge cleanup process was favorable for the GC-PFPD analysis. Four types of derivatives spiked in rice and soybean sprout matrices were eluted, reaching a baseline separation, in a sequence of 3-MPPA, AMPA, glyphosate, and glufosinate within 14 min using a DB-608 capillary column. Recoveries of glyphosate, AMPA, glufosinate, and 3-MPPA (0.5 ppm) spiked in both sample matrices were determined to be 72-81, 71-86, 101-119, and 83-90%, respectively, whereas the coefficient of variation was determined to be <10% in three repeated determinations. The instrumental limits of detection for glyphosate, AMPA, glufosinate, and 3-MPPA in sample matrices were 0.02, 0.03, 0.02, and 0.01 ppm, respectively. The limits of quantification for glyphosate, AMPA, glufosinate, and 3-MPPA in sample matrices were 0.06, 0.10, 0.06, and 0.04 ppm, respectively.

Acrylamide content distribution and possible alternative ingredients for snack foods.

Acrylamide (AA) contents in 294 snack foods including cereal-based, root- and tuber-based, and seafood-based foods, nuts, dried beans, and dried fruits purchased in Taiwan were determined by gas chromatography-mass spectrometry in this study. The highest levels of average AA content were found in root- and tuber-based snack foods (435 µg/kg), followed by cereal-based snack foods (299 µg/kg). Rice flour-based, seafood-based, and dried fruit snack foods had the lowest average AA content (<50 µg/kg). This is the first large surveillance of AA content in snack foods in Taiwan. The results could provide important data regarding intake information from the snack foods. In addition, the results showed a great diversity of AA content in snack foods prepared from different ingredients. Rice- and seafood-based products had much lower AA than those made from other ingredients. This information could constitute a good reference for consumers to select products for healthy snacking.