buffers (4.0, 7.0 and 10.0) were purchased from VWR (Atlanta, GA).
Aminomethylphosphonic acid (AMPA) analytical standard was purchased from Acros
Organics (Geel, Belgium). Glyphosate (PMG) analytical standards,
ethylene-diaminetetraacetic acid disodium salt dihydrate (EDTA) and acetic acid
were purchased from Sigma-Aldrich (Saint Louis, MO). HPLC grade acetone and
water + 0.1% formic acid were purchased from Fisher Scientific (Hampton, NH).
Activated carbon (AC) derived from coconut shell (mesh size: 100 – 325;
iodine number: 1100 mg/g; bulk density: 30 – 33 lbs/ft.3) was
obtained from the General Carbon Corporation (Paterson, NJ). Calcium
montmorillonite (CM) was obtained from Engelhard Corp. (Cleveland, OH). CM has
an average total surface area of 850 m2/g, an external surface area
of approximately 70 m2/g, and a cation exchange capacity of 97
cmol/kg (Grant and Phillips, 1998 (link)). CM
has a general formula of
(Ca)0.3(Al,Mg)2Si4O10(OH)2•nH2O
(Marroquin-Cardona et al., 2011 (link)).
Deionized water (18.2 MΩ) was generated in the laboratory using an
Elga™ automated filtration system (Woodridge, IL) and was used in all
experiments.