A sensitive method for determining total organic carbon at microgram per liter levels in industrial, environmental, and drinking waters by thermal combustion ion chromatography was developed using tube furnace and readily accessable HPLC equipment. To achieve complete oxidation, persulfate (0.25%) was added to oxidize nonvolatile organic compounds in solution and cupric oxide heated at 900 °C to convert volatile organic compounds to CO(2), which was scrubbed in a 20 mL solution of 50 mM KOH with 10 drops of butanol added. The carbonate anion obtained was determined by nonsuppressed ion chromatography using 0.6 mM potassium hydrogen phthalate (KHP) as the eluent. Both surfactants and volatile and nonvolatile organic compounds commonly found in environmental waters give highly repeatable recoveries close to 100%. The detection limit (S/N = 2) and linear range for a 1 L water sample are 2 μg of C L(-)(1) and 10-2500 μg of C L(-)(1), respectively, and they can be adjusted using samples ranging from 100 mL to 2 L. Good repeatablity (RSD less than 10%) and close to 100% recoveries were obtained for KHP added to real samples such as deionized, mineral, tap, and river water and seawater. Compared with the ASTM D2579 method, the method developed is 3 orders of magnitude more sensitive, more accurate, and reliable in determining samples with low total organic carbon values and more flexible in adjusting the linear range and sensitivity using variable sample sizes.
A portable dehumidified and ventilated diffusive sampler (DVDS) incorporating three diffusive tubes and a domestic battery-driven fan dryer was developed to solve the problems of high humidity and stagnant air for environmental monitoring of volatile organic compounds (VOCs). Using Tenax GR as adsorbent, thermal desorption and cryogenic on-column focusing prior to capillary GC analysis with flame ionization detection, the 10 most common aromatic and halogenated VOCs were determined with the DVDS, giving linear working ranges 3.2 pg m-3-770 mg m-3 for 1 h sampling, sampling rates of 0.64-0.98 ml h-1 and RSD of 4-6%. The good repeatability is due to the use of a small-diameter diffusive tube (0.32 mm id) and reproducible ventilation in the DVDS. The optimized analytical parameters are temperature 10-40 "C, relative humidity 0-100 %, sampling time 15-480 min and storage for up to 21 days. Quality assurance procedures were developed for the calibration and preparation of the DVDS. The reliability of the method was established by parallel determinations at a given field station using both the DVDS and the active sampling method.
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