Tài liệu Drugs and Poisons in Humans - A Handbook of Practical Analysis (Part 61) docx

7. 4 7. 4 © Springer-Verlag Berlin Heidelberg 2005 II.7.4 Carbamate pesticides by Kiyoshi Ameno Introduction Among many carbamate pesticides commercially available in Japan, those with relatively high toxicities are shown in > Table 4.1 [1]. Carbamate pesticides are generally classi ed into N-methylcarbamate insecticides and N-allylcarbamate herbicides in view of their chemical structures and biological actions.  e number of fatalities due to poisoning by carbamate pes- ticides is 50–100 every year in Japan; many of them are poisoned by methomyl [2]. According to statics reported by National Research Institute of Police Science of Japan, the number of fatalities is highest with paraquat plus diquat, followed by organophosphates and then carba- mates among pesticides.  e toxicity of carbamate pesticides is due to inhibition of acetylcho- linesterase (AchE) by their binding with the active site of the enzyme; the inhibition of the hydrolysis reaction of acetylcholine (Ach) results in the accumulation of Ach, provoking poisoning symptoms, such as miosis, lacrimation, sweating, hypersalivation and convulsion of extremities.  e binding of carbamate pesticides to AchE is much weaker than that of organo- phosphorus pesticides, and the former pesticides are easily decomposed a in mammalian bodies.  erefore, the damages of organs by carbamate pesticides have not been reported. For analysis of carbamate pesticides, methods by GC [3–7], GC/MS [5, 7, 8–10], HPLC [11] and LC/MS [10] were reported. In this chapter, the extraction procedures and analytical methods using the above 4 instruments are described for this group of pesticides. Reagents and their preparation •  e authentic standards of compounds listed in > Table 4.1 and ethion can be purchased from Wako Pure Chemical Industries, Ltd., Osaka, Japan. A standard mixture of seven N-methylcarbamate pesticides can be obtained from Kanto Chemicals (Tokyo, Japan) b . Carbofuran, carbaryl and ethion are separately dissolved in acetone to prepare 100 µg/mL solutions as stock solutions for internal standards (ISs) c . Carbendazole (Aldrich, Milwau- kee, WI, USA) is dissolved in distilled water to prepare 100 µg/mL solution. o-Methoxyl- phenol can be also obtained from Aldrich. • Sep-Pak C 18 and Oasis MCX cartridges are purchased from Waters (Milford, MA, USA). •  e solutions to be prepared are: n-hexane/ethyl acetate (1:1, v/v); acetonitrile/distilled water (1:1, v/v); methanol/distilled water (5:59, v/v); 0.1 M HCl solution; and 2 % NaCl solution. • 0.1 M Phosphate bu er solution (pH 7.0): 6.81 g of KH 2 PO 4 is dissolved in 400 mL distilled water, and the pH of the solution is adjusted to 7.0 with 1.0 M NaOH solution; the  nal volume is adjusted to 500 mL with distilled water. • 5 % Ammonia/methanol solution: 2.5 mL of 3 M NH 4 OH solution is mixed with 47.5 mL methanol. • HPLC mobile phases: methanol/distilled water (65:35, v/v); acetonitrile/2 mM ammonium formate (30:70 and 80:20, v/v, pH 3.0). 560 Carbamate pesticides ⊡ Table 4.1 Structures, properties and toxicities of carbamate pesticides Name, MF, MW, property and structure Use Acute oral LD 50 (rat, mg/kg) bendiocarb C 11 H 13 NO 4 MW: 223.2 MP: 125 ~ 129 insecticide 40 ~ 156 benfuracarb C 20 H 30 N 2 O 5 S MW: 410.5 MP: 110 insecticide 223 205 carbaryl C 12 H 15 NO 2 MW: 201.2 MP: 142 insecticide 850 500 carbofuran C 12 H 15 NO 3 MW: 221.3 MP: 153 ~ 154 insecticide 8 carbosulfan C 20 H 32 N 3 O 3 S MW: 380.5 BP: 124 ~ 128 insecticide 623 657 ethiofencarb C 11 H 15 NO 2 S MW:: 225.3 MP: 33.4 insecticide 200 approx. fenobucarb C 12 H 17 NO 2 MW: 207.3 MP: 31 ~ 32 insecticide 250 185 furathiocarb C 18 H 26 N 2 O 5 S MW: 382.5 BP: 250< insecticide 53 561Carbamate pesticides ⊡ Table 4.1 (continued) isoprocarb C 11 H 15 NO 2 MW: 225.3 MP: 93 ~ 96 insecticide 450 metolcarb C 9 H 11 NO 2 MW: 162.2 MP: 76 ~ 77 insecticide 580 498 methomyl C 5 H 13 N 2 O 2 S MW: 162.2 MP: 78 ~ 79 insecticide 17 24 oxamyl C 7 H 13 N 3 O 3 S MW: 219.3 MP: 100 ~ 102 insecticide 5.4 pirimicarb C 11 H 18 N 4 O 2 MW: 238.3 MP: 90.5 insecticide 147 propoxur C 11 H 15 NO 3 MW: 209.2 MP: 90 insecticide 50 thiodicarb C10H18N4O4S3 MW: 354.5 MP: 173 ~ 174 insecticide 66 XMC C 10 H 13 NO 2 MW: 179.2 MP: 99 insecticide 542 xylylcarb C 10 H 13 NO 2 MW: 179.2 MP: 79 ~ 80 insecticide 375 325 MF: molecular formula; MW: molecular weight; MP (°C): melting point; BP (°C): boiling point. 562 Carbamate pesticides Extraction methods It is absolutely necessary to extract carbamate pesticides from crude biomedical specimens containing many impurity compounds as pretreatments before instrumental analysis. As spec- imens, body  uids (whole blood, serum and urine), tissues and stomach contents are objects for analyses.  e whole blood should be completely hemolyzed before extraction. Homogeni- zation is needed for tissues (organs) specimens; for stomach contents, the supernatant fraction a er their centrifugation should be used. Liquid-liquid extraction i. A 2-g aliquot of specimens (blood, tissues and stomach contents d ) is mixed with 10 mL acetonitrile (containing an appropriate IS), homogenized with a Polytron homogenizer and centrifuged at 3,000 rpm for 5 min to obtain clear supernatant solution. ii. For the sediment, the above i) step of extraction is repeated two times. iii.  e three acetonitrile supernatant solutions thus obtained are combined and mixed with 80 mL of 2 % NaCl solution and 25 mL of n-hexane/ethyl acetate (1:1, v/v) in a 250-mL volume separating funnel e . iv.  e funnel is shaken for 10 min (with a shaking machine). v.  e n-hexane/ethyl acetate layer is obtained. vi.  e layer is evaporated to dryness under reduced pressure in a rotary evaporator at room temperature. vii.  e residue is dissolved in 100 µL methanol. viii. A 2-µL aliquot of it is injected into GC or GC/MS; a 20-µL aliquot into HPLC. ix. For quantitation, each calibration curve is constructed using peak area ratios of a target compound to IS. A ratio obtained from a specimen is applied to the curve to calculate its concentration. Solid-phase extraction-1 [4] i. A Sep-Pak C 18 cartridge f is washed and activated by passing chloroform, acetonitrile, acetonitrile/distilled water (1:1) and distilled water, 10 mL each, successively. ii. A 1-mL volume of a specimen (blood, serum or urine) is mixed with 9 mL distilled water, stirred well g and poured into the Sep-Pak C 18 cartridge. iii. It is washed with 10 mL distilled water. iv. A target compound and IS are eluted with 3 mL chloroform. v. A small amount of aqueous layer (upper) of the eluate is carefully removed with a Pasteur pipette h . vi.  e above organic extract is dehydrated with anhydrous Na 2 SO 4 i . vii. It is evaporated to dryness under a stream of nitrogen at room temperature. viii.  e residue is dissolved in 100 µL methanol j . ix. A 2-µL aliquot of it is injected into GC or GC/MS; a 20-µL aliquot into HPLC or LC/MS. 563 Solid-phase extraction-2 [10] i. An Oasis MCX cartridge k is activated by passing 1 mL methanol and 1 mL of 0.1 M phos- phate bu er solution (pH 7) through it. ii. A 1-mL volume of serum is mixed well with 100 µL of IS (for example carbendazole) so- lution and poured into the cartridge. iii.  e cartridge is washed with 1 mL distilled water. iv.  e  rst elution is made by passing 1 mL methanol through it. v.  e cartridge is washed with 1 mL of 0.1 M HCl solution. vi.  e second elution is made by passing 1 mL methanol again. vii.  e third elution is made by passing 1 mL of 5 % ammonia/methanol. viii.  e three eluates obtained at the steps iv, vi and vii are combined l , and evaporated to dry- ness under a stream of nitrogen. ix.  e residue is dissolved in 100 µL methanol for GC or GC/MS analysis; an appropriate amount is injected into GC (/MS). For HPLC (/MS), the residue is dissolved in 100 µL of a mobile phase to be used and injected into HPLC (/MS). GC and GC/MS analysis GC conditions GC columns m : DB-5 and DB-1 fused silica capillary columns (30 m × 0.25 mm i.d.,  lm thick- ness 0.25 µm, J&W Scienti c, Folsom, CA, USA). GC conditions; instrument: Shimadzu GC14B (Shimadzu Corp., Kyoto, Japan); detector:  ame thermionic ionization detector (FTD) n ; column temperature: 50 °C → 20 °C/min → 120 °C → 5 °C/min → 260 °C(10 min); injection and detector temperature o : 230 °C; carrier gas: He (13 kPa). GC/MS conditions GC column: a DB-5MS fused silica capillary column (30 m × 0.25 mm i.d.,  lm thickness 0.25 µm, J&W Scienti c). GC/MS; instrument: Shimadzu GC-MS5000 (Shimadzu Corp.); column temperature: 120 °C (1 min) → 20 °C/min → 240 °C (8 min); injection and separator temperature: 230 °C; carrier gas: He (2.0 mL/min); ionization mode: EI (70 eV). Assessment of the method For GC analysis of carbamate pesticides, an FTD detector is recommendable, because it is speci c and sensitive, and is not in uenced by impurities and organic solvents appreciably. Qualitative analysis only with a single column is insu cient; multiple columns of di erent properties should be used for testing an identity of a compound. > Table 4.2 shows retention GC and GC/MS analysis 564 Carbamate pesticides ⊡ Table 4.2 Retention times of carbamate pesticides obtained by GC* Carbamate Retention time (min) Carbamate Retention time (min) oxamyl 5.9 bendiocarb 15.1 methomyl-oxime 7.1 carbofuran 16.5 propamocarb 9.3 ethiofencarb 18.8 metolcarb (MTMC) 11.2 pirimicarb 18.8 isoprocarb 12.2 carbaryl 19.7 methomyl 12.2 methiocarb 20.7 XMC 12.6 benthiocarb 21.1 xylylcarb (MPMC) 13.3 diethofencarb 21.4 propoxur (PHC) 13.6 furathiocarb 31.5 fenobucarb 13.7 benfuracarb 33.6 * Detection limits were 0.5–1.0 ng on-column. Data were obtained in cooperation with Dr. S. Hatta (environmental chemist). Column: a DB-5 fused silica capillary column (30 m × 0.25 mm i. d., film thickness 0.25 µm). ⊡ Table 4.3 EI mass spectra of carbamate pesticides Carbamate Mass spectral ions (m/z) M + Base Others oxamyl 162 72 98 145 115 propamocarb 188 58 129 143 70 metolcarb (MTMC) 165 108 77 58 107 isoprocarb 193* 121 136 91 103 methomyl-oxime 105 88 58 methomyl 162* 105 58 88 103 XMC 179 122 107 91 77 xylylcarb (MPMC) 179 122 107 91 77 propoxur (PHC) 209* 110 152 81 58 fenobucarb 207* 121 150 91 77 bendiocarb 223 151 166 126 108 carbofuran 221 164 149 122 131 ethiofencarb 225 107 168 77 57 pirimicarb 238 166 72 132 152 carbaryl 201 144 115 116 145 methiocarb 225 168 153 109 91 benthiocarb 257 100 82 125 89 diethofencarb 267 151 225 207 124 furathiocarb 382* 163 135 194 325 benfuracarb 410* 190 163 135 102 APC 274 160 217 176 190 M + : molecular ion; Base: base peak; *: very small peak or not detectable. 565 times of carbamate pesticides, when a DB-5 fused silica capillary column was used for GC analysis. > Table 4.3 shows principal ions (5 peaks each including a molecular ion) observed in EI mass spectra for carbamate pesticides obtained by GC/MS [4, 9].  e intensities of molecular ions are generally low; there are compounds without appearance of molecular ions p . Su cient qualitative analysis is achieved by measuring retention times and mass spectra of compounds tested.  e sensitive quantitation analysis can be made using the selected ion monitoring (SIM). Methomyl can be analyzed by GC (/MS) in its underivatized from; but a method using the conversion of methomyl into methomyl-oxime by alkali, followed by silylation (TMS) for GC/ MS, was reported [8].  is method is aimed to overcome the thermolability of underivatized methomyl, and a good mass spectrum including the molecular ion can be obtained for the methomyl-oxime-TMS (M.W. 177); the mass spectrum shows ions at m/z 177 (molecular ion), 162, 130, 121 and 105. Chemical ionization (CI) mode is preferably used for quantitation, because it gives the base peaks at m/z 178 and 197 of protonated ions of methomyl-oxime-TMS and o-methoxyphenol-TMS (IS).  e quantitation can be made with peak area ratios of the ion at m/z 178 to that at m/z 197.  e quantitative range is reported to be 0.1–6 µg/mL; the details of the method can be obtained from the reference [8]. HPLC and LC/MS analysis HPLC conditions [11] HPLC column q : Finepak SIL C 18 (25 cm × 4.6 mm i.d., particle size 5 µm, Nihonbunko, Tokyo, Japan). HPLC conditions; instrument: Shimadzu HPLC10A (Shimadzu Corp.); detector: UV (wavelength, 254 nm); mobile phase: methanol/distilled water (65:35, v/v); its  ow rate: 1 mL/ min. LC/MS conditions [10] LC column: NucleosilC18 5 µm (15 cm × 1.0 mm i.d., Polymer Laboratories, Marseille, France). LC/MS conditions; MS instrument: PE-Biosystems AP100 (PE Biosystems, Marseille, France); HPLC pump: Shimadzu LC10AD (Shimadzu Corp.); autosampler: Series 200 Perkin- Elmer (Perkin-Elmer, Courtaboeuf, France); mobile phase: gradient 30–80 % acetonitrile/2 mM ammonium formate (pH 3); its  ow rate: 50 µL/min; ionization mode: ion spray (+ 5 keV). Assessment of the method  e analysis of carbamate pesticides by HPLC is much inferior to that by capillary GC in reso- lution ability, but does not su er from decomposition of analytes by heat. In HPLC analysis of HPLC and LC/MS analysis 566 Carbamate pesticides methomyl and methomyl-oxime, the peaks are frequently interfered with by a solvent peak; to avoid the problem, the ratio of water content of the mobile phase is increased to about 50 %.  ere are various detectors commercially available for HPLC; they are useful for improving speci city r and sensitivity s . > Table 4.4 shows retention times and detection limits for carbamate pesticides obtained under the above HPLC-UV conditions.  e analysis by LC/MS has been established recently; it requires no concern about the decomposition by heat and also give mass spectra.  e method is very useful for qualitative analysis and enables sensitive quantitation in the SIM mode. > Table 4.5 shows ions selected ⊡ Table 4.4 Retention times and detection limits (on-column) of carbamate pesticides obtained by HPLC Carbamate Retention time (min) Detection limit (ng) methomyl-oxime 3.5 35 methomyl 4.0 54 metolcarb (MTMC) 5.4 10 propoxur (PHC) 5.5 16 carbaryl (NAC) 6.3 45 ethiofencarb 6.4 12 xylylcarb (MPMC) 6.5 11 XMC (macball) 6.8 6 isoprocarb (MIPC) 6.9 11 EMPC 7.1 35 fenobucarb 8.6 9 terbucarb 23.0 2 allyxycarb (APC) 25.0 7 ⊡ Table 4.5 Selected ions for qualitative and quantitative LC/MS analysis of carbamate pesticides Carbamate Selected ion (m/z) Quantitative Qualitative aldicarb 89 116 ethiofencarb 107 – methomyl 88 106 carbaryl 145 155 carbofuran 123 165 chlorpropham 172 126 methiocarb 121 169 pirimicarb 239 182 formetanate 110 93 fenoxycarb 302 88 propham 138 120 567 for qualitative and quantitative analyses.  e sensitivity obtained by SIM of LC/MS is as high as that of GC/MS. Toxic and fatal concentrations Although the number of fatalities due to carbamate pesticide poisoning is not small in the world, the reports on their concentrations in blood and organs are not many.  e concen- trations reported in literature and measured in the author’s laboratories are summarized in > Table 4.6.  e blood methomyl concentrations in fatalities by its poisoning is 0.6–57 µg/mL (mean concentration in 13 cases, 20 µg/mL) [3, 8, 12–14]. When the blood methomyl concentrations of survived subjects, a er ingestion followed by treatments, are also taken into consideration, the fatal blood concentration of methomyl is estimated not lower than 1.0 µg/mL.  e respective blood concentrations of carbofuran, benfuracarb and furathiocarb a er their ingestion for suicidal purposes are as follows.  e blood carbofuran concentrations in 7 fatality cases a er ingestion of the pesticide only were 0.32–29.3 µg/mL (n = 7, average 9.2 µg/mL) [7, 10, 15, 16].  e blood benfuracarb concentrations a er its ingestion were 0.30– 2.32 µg/mL (n = 3, average 0.98 µg/mL) and the blood concentrations of carbofuran, the metabolite of benfuracarb, were not lower than 1.45 µg/mL [6], suggesting that benfuracarb is rapidly metabolized into carbofuran in human bodies. A er furathiocarb ingestion, its blood concentrations were 0.1–21.6 µg/mL (n = 7, average 3.6 µg/mL); but carbofuran, also the meta- bolite of furathiocarb, has never been analyzed simultaneously t [5]. As shown in > Table 4.1, the acute toxicities of furathiocarb and benfuracarb in rats are 8–30 times less than that of carbofuran; the both compounds are metabolized into a highly toxic metabolite carbofuran in mammals. In furathiocarb and benfuracarb poisoning cases, carbofuran should be analyzed simultaneously. In fatal cases of propoxur poisoning, its blood concentrations were 0.3–41.1 µg/mL (n = 6, average 10.7 µg/mL) [17] and ethanol was also detected from blood in many cases.  is sug- gests that ethanol enhances the toxicity of propoxur. Notes a) Many of carbamate pesticides are generally decomposed by alkali and occasionally by strong acids.  e contact of carbamate pesticides with strongly alkaline and acidic com- pounds should be avoided. Carbosulfan is decomposed even by weak acids.  e metabo- lism of carbamate pesticides is rapid and gives unstable intermediate metabolites [1]. In this chapter, the methods for analysis of the metabolites are not dealt with. b)  e standard metabolic solution contains aldicarb, ethiofencarb, oxamyl, carbaryl, fenobu- carb, bendiocarb and methiocarb (10 µg/mL each). It is useful for the testing of retention times and as the standards for quantitative analysis. c) In GC and GC/MS analysis, one or two of carbofuran, carbaryl and ethion (an organophos- phorus compound) are used as IS(s) according to retention time(s) of target compound(s).  e peak of ethion appears at about 27 min by GC analysis (DB-5).  e solutions of the above ISs should be prepared at the  nal concentration of 5 or 20 µg/mL. Toxic and fatal concentrations 568 Carbamate pesticides ⊡ Table 4.6 Blood concentrations of carbamate pesticides in their fatal poisoning cases Carbamate Subject No. Blood conc. (µg/mL) Ref. methomyl 1 2 3 4 5 6 7 8 9 10 11 12 13 average 0.7 1.4 44.0 (1 h) 0.6 35.0 4.0 (Al) 57.0 3.2 (Al) 8.0 0.5 (Al) 5.6 28.0 4.8 19.1 12.8 43.2 20.0 [3] [8] [12] [13] [14] carbofuran 1 2 3 4 5 6 7 average 8.0 29.3 11.6 10.0 4.0 0.32 1.5 9.2 [15] [16] [7] [10] benfuracarb 1 2 3 average 2.32 (NA) 0.31 1.47 (CA) 0.30 1.45 (CA) 0.98 1.46 (CA) [6] furathiocarb 1 2 3 4 5 6 7 average 21.6 0.7 0.1 1.0 0.4 0.32 0.8 3.6 [5] propoxur 1 2 3 4 5 6 average 1.3 0.10 (Al) 13.6 2.26 (Al) 0.6 1.67 (Al) 7.5 0.04 (Al) 41.1 1.38 (Al) 0.3 0.07 (Al) 10.7 [17] NA: not analyzed; CA: carbofuran (µg/mL); Al: ethanol (mg/mL); 1 h: 1 h after ingestion. [...]... sulfone, oxamyl, methomyl, 3-hydroxycarbofuran, 569 570 Carbamate pesticides aldicarb, propoxur, carbofuran, carbaryl and methiocarb can be analyzed at ppb levels simultaneously t) Carbofuran as a metabolite of furathiocarb has never been analyzed This does not mean “not detectable”, but means “not determined” If it is analyzed, an appreciable amount of carbofuran seems to be detected References 1) Tomlin... with that of the authentic one s) When N-methylcarbamate pesticides are heated in NaOH solution, methylamine is produced The methylamine can react with o-phthalaldehyde and 2-mercaptoethanol to form a highly fluorescent compound Various HPLC systems equipped with the post-column labelling method are commercially available from various manufacturers Using this method, aldicarb-sulfoxide, aldicarb- sulfone,... implication of acute fatal poisoning cases due to benfuracarb ingestion Int J Legal Med 112:268–270 7) Ameno K, Lee SK, In SW et al (2001) Blood carbofuran concentrations in suicidal ingestion cases Forensic Sci Int 116:59–61 8) Miyazaki T, Yashiki M, Kojima T et al (1989) Fatal and non-fatal methomyl intoxication in an attempted double suicide Forensic Sci Int 42:263–270 9) Tsunoda N, Kishi T (1988) Mass... spectra of pesticides 4 N-Methylcarbamate pesticides Rep Natl Res Inst Police Sci 41:85–91 (in Japanese) 10) Lacassie R, Marquet P, Gaulier J-M et al (2001) Sensitive and specific multiresidue methods for the determination of pesticides of various classes in clinical and forensic toxicology Forensic Sci Int 121:116–123 11) Tsunoda N (1985) Analysis of N-methylcarbamate pesticides by high-performance... Pesticide Manual 11th edn British Corp Protection Council, Surrey 2) National Research Institute of Police Science (ed) (1997–2001) Annual Case Reports of Drug and Toxic Poisoning in Japan, Nos 38–43 National Police Agency, Tokyo, (in Japanese) 3) Araki M, Yonemitsu K, Kambe T et al (1982) Forensic toxicological investigations on fatal cases of carbamate pesticide methomyl (Lannate®) poisoning Jpn J Legal... 36:584–588 (in Japanese with an English abstract) 4) Suzuki O, Hattori H, Liu J et al (1990) Positive -and negative-ion mass spectrometry and rapid clean-up of some carbamate pesticides Forensic Sci Int 46:169–180 5) Lee SK, Ameno K, In SW et al (1999) Acute fatal poisoning cases due to furathiocarb ingestion Forensic Sci Int 101:65–70 6) Lee SK, Ameno K, Yang JY et al (1999) Forensic toxicological implication... recovery rates are about 100 % An Oasis HLB cartridge (Waters) with a polymer-resin base does not give low recoveries due to drying up According to a report by Waters, an Oasis HLB cartridge is activated by passing t-butyl methyl ether, methanol and distilled water, 3 mL each, through it A specimen solution diluted with buffer solution at pH 3 containing a carbamate pesticide is poured into the cartridge,... chromatography Forensic Toxicol News 3 (3):33–34 (in Japanese) 12) Driskell WJ, Groce DF, Hill RH Jr et al (1991) Methomyl in the blood of a pilot who crashed during aerial spraying J Anal Toxicol 5:339–340 13) Tsatsakis AM, Tsakalof AK, Siatitsas Y et al (1996) Acute poisoning with carbamate pesticides: the Cretan experience Sci Justice 36:35–39 14) Tsatsakis AM (1998) More fatal methomyl poisoning in. .. protonated molecular peaks can be obtained in the CI mode [4, 9] q) Even with the similar ODS columns, the retention times are greatly different according to manufacturers and lots, and should be confirmed using the authentic standard for each column r) Using a photodiode array detector (DAD), it is possible to make tentative identification of a compound by comparing the absorption spectrum of a test... for HPLC analysis, the dehydration is not necessary, because the mobile phase contains water j) Acetonitrile acts to shorten the life span of the FTD and should not be used k) There is no lowering of recovery rates due to drying up of the Oasis MCX cartridge l) For GC and GC/MS analysis, anhydrous Na2SO4 should be added for dehydration of the combined eluates m) Fused silica wide-bore capillary columns . compounds are metabolized into a highly toxic metabolite carbofuran in mammals. In furathiocarb and benfuracarb poisoning cases, carbofuran should be analyzed. 3-hydroxycarbofuran, Toxic and fatal concentrations 570 Carbamate pesticides aldicarb, propoxur, carbofuran, carbaryl and methiocarb can be analyzed at ppb