October 25, 2014

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Water Analysis and Methods

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We perform the following analyses (follow the links for a brief description of the methodology for that procedure).

Analyses

Methodology

Nitrate and Nitrite (High Range: Ref. No. 38, Low Range: Ref. No. 4 & 5, IC: Ref. No. 51)

Colorimetric analysis by the cadmium reduction method. Nitrate is reduced to nitrite in a copperized cadmium column. The nitrite ions react with sulfanilamide under acidic conditions to form a diazo compound that couples with N-1-Napthylethylenediamine dihydrochloride to form a reddish purple azo dye. The dye is subsequently measured colorimetrically at 520 nm on a Lachet 8500 FIA. Acidified samples must be neutralized to a pH between 5 and 9.

Ammonium (Ref. No. 39)

Colorimetric analysis by the salicylate/nitroprusside method. The ammonium reacts with salicylate in the presence of hypochlorite (oxidant) and nitroprusside (catalyst) to form an emerald green color measured colorimetrically on an Lachat 8500 FIA at 660 nm. The reaction takes place in a buffered alkaline medium at a pH of 12.8 – 13.0, thus acidified samples must be neutralized to a pH between 5 and 9.

Orthophosphate (Colorimetric: Ref. No. 40, IC: Ref. No. 51)

Colorimetric analysis by the molybdate-blue/ascorbic acid method. Orthophosphate reacts with ammonium molybdate and potassium antimonyl tartrate to form phosphomolybdic acid. This complex is reduced by ascorbic acid to intensely colored molybdenum blue measured colorimetrically on an Lachat 8500 FIA at 880 nm. Acidified samples must be neutralized to a pH between 5 and 9.

Total Phosphorus (TP: Ref. No. 41)

A 10 mL aliquot of a water sample is digested with sulfuric acid and HNO3 in a 75mL Folin-Wu tube. The six hour digestion takes place in an electrically heated block at 225°C. The digested sample is analyzed colorimetrically for total phosphorus as orthophosphate.

Chloride (Colorimetric: Ref. No. 43, IC: Ref. No. 51)

Colorimetric analysis by the mercury (II) thiocyanate method. Thiocyanate ion is liberated from mercuric thiocyanate through sequestration of mercury by analyte chloride ions (this forms un-ionized but soluble mercuric chloride). The liberated thiocyanate ion then forms reddish yellow ferric thiocyanate in the presence of excess ferric ions from ferric nitrate. The yellow ferric thiocyanate is measured colorimetrically on a Lachat 8500 FIA at 480nm. Alternatively, chloride can be determined by ion-chromatography on a Dionex 120 ion chromatograph.

Sulfate (IC: Ref. No. 51)

Unpreserved water samples are analyzed for sulfate on a Dionex 120 ion chromatograph.

pH (Ref. No. 45)

The pH of an unpreserved water sample is measured using Mettler Toledo seven multi pH meter equipped with the InLab Routine Pro combination electrode. 

Specific Conductance (Ref. No. 46)

The specific conductance is measured on an unpreserved water sample using a an Accumet Model 30 Conductivity Meter.

Hardness (Ref. No. 47)

Calculated from Ca and Mg concentrations (to include Fe, Al, Mn, and Zn if requested) determined by ICP-AES. Results expressed as mg/L CaCO3.

Alkalinity, Total (Ref. No. 48)

Alkalinity is determined by titration to the appropriate coloimetric endpoint [pH 4.5 (~ 500 mg/L CaCO3), 4.8 (~ 150 mg/L CaCO3), or 5.1 (~30 mg/L CaCO3)] with indicators phenolphthalein and bromcresol green using Hach reagent cartridges (0.1600 or 1.600 M H2SO4) and digital titrator.

Solids, Residue (Ref. No. 49)

Total: A well mixed sample is evaporated in a weighed porcelain dish and dried to constant weight in an oven at 180°C.
Suspended
: A well mixed sample Is filtered through a weighed standard glassfiber filter and the residue retained on the filter is dried to a constant weight at 103-105°.
Suspended, Volatile
: A well mixed sample is filtered through a glass fiber filter. The residue retained on the filter is dried at 105°C to constant weight, then is ignited at 550°C.
Total Volatile
: A well mixed sample is evaporated, then dried to constant weight at 105°C and ignited at 550°C.
Dissolved
: A well mixed sample is filtered through a standard glass fiber filter, and the filtrate is evaporated to dryness in a weighed dish and dried to constant weight at 180°C.

Multi-element, ICP (Digestion: Ref. No. 50, Analysis: Ref. No. 21)

Al, As, B, Ba, Be, Ca, Cd, Co, Cr, Cu, Fe, K, Li, Mg, Mn, Mo, Na, Ni, P, Pb, Rb, S, Si, Sr, Ti, V and Zn are determined simultaneously by Inductively Coupled Plasma (ICP) Atomic Emission Spectrometry. Samples should be acidified as soon as possible to 1% HNO3. For “dissolved” elements, samples are filtered with a 0.45m filter before analysis.  For “Total” elements the sample is digested with 5% HNO3 for one hour in a digestion block prior to analysis.

Bromide (Ref. No. 51)

Unpreserved water samples are analyzed for bromide on a Dionex 120 ion chromatograph.

Fluoride (IC: Ref. No. 51)

An unpreserved water sample is analyzed for fluoride by ion chromatography on a Dionex 120 ion chromatograph.

Total Organic Carbon (Ref No. 53)

The organic carbon is measured using a Phoenix-Dohrmann 800 Tic/Toc Analyzer. This instrument utilizes persulfate in the presence of ultraviolet light to oxidize the organic carbon to CO2. The CO2 is then measured directly by non-dispersive infrared radiation. Inorganic carbon is removed by sparging with N2 gas prior to analysis.