Tài liệu Drugs and Poisons in Humans - A Handbook of Practical Analysis (Part 13) pdf

1.4

© Springer-Verlag Berlin Heidelberg 2005

II.1.4 Methanol and formic acid

by Xiao-Pen Lee and Keizo Sato

Introduction

Methanol ( methyl alcohol) poisoning accidents take place most frequently by drinking it

in mistake for ethanol. Methanol poisoning is not due to the eff ect of methanol itself, but

due to toxicity of its metabolites. Methanol is rapidly absorbed into human body through

the airway mucous membranes, digestive tract mucous membranes or the skin; it is metabo￾lized into formaldehyde ( formalin, HCHO) and then formic acid (HCOOH) by the actions

of alcohol dehydrogenase and aldehyde dehydrogenase, respectively. Formic acid inhibits

cytochrome oxidase in the optic nerves, and causes visual disturbances followed by the

loss of eyesight. Th e accumulation of formic acid in the body provokes severe acidosis,

which is characteristic for methanol poisoning. Th e metabolic (oxidation) velocity for metha￾nol is about 5–10 times slower than that for ethanol. Th is is the reason why the poisoning

symptoms do not appear soon aft er its ingestion, but appear aft er a while. Formic acid can be

detected from urine for about one week aft er methanol ingestion. It is possible to diagnose

methanol poisoning by detecting methanol and/or formic acid from blood and urine

specimens.

For analysis of methanol and formic acid, GC methods with packed columns were employed

[1–5]. In this chapter, GC methods for analysis of them in blood and urine using a wide-bore

capillary column and using solid-phase microextraction (SPME) [6–9] are presented.

Analysis of methanol

Reagents and their preparation (in common with both wide-bore

capillary GC and headspace SPME-GC)

• Methanol standard solution: a 0.127 mL volume of methanol of special grade is dissolved

in 100 mL distilled water to prepare 1 mg/mL solution.

• Internal standard (IS) solution: a 0.128 mL volume of acetonitrile of special grade is dis￾solved in 100 mL distilled water to prepare 1 mg/mL solution.

Conditions for wide-bore capillary GC

Column: an Rtx-BAC2 wide-bore capillary column (30 m × 0.53 mm i.d., fi lm thickness

2.0 µm, Restek, Bellefonte, PA, USA).

GC conditions: a Shimadzu GC-14B gas chromatograph (Shimadzu Corp., Kyoto, Japan)

with an FID was used. Column (oven) temperature: 30°C (1 min)→ 20°C/min→ 210°C; injec￾tion and detector temperature: 240°C; carrier gas: He; its fl ow rate: 5.0 mL/min.