A: The IRabsorption spectrum of a mineral oil dispersion of it in a calcium fluoride cell exhibits maxima only at the same wavelengths as that of a similar preparation of polyethylene glycol 3350.

B: Asolution (1in 20)responds to the tests for Sodium á191ñ,Potassium á191ñ,Bicarbonate á191ñ,Sulfate á191ñ,and Chloride á191ñ.

Mobile phase— Dilute 0.5mLof nitric acid with water to obtain 4000mLof solution.Degas,and place the solution in a suitable plastic container.Make adjustments if necessary (see System Suitabilityunder Chromatography á621ñ).

Internal standard solution— Dissolve a suitable quantity of ammonium bromide in water to obtain a solution having a concentration of about 2mg per mL.

Standard preparation— To a 100-mLvolumetric flask transfer about 90mg of potassium chloride,previously dried at 105for 2hours and accurately weighed,and about 880mg of sodium chloride,previously dried at 105for 2hours and accurately weighed,dilute with water to volume,and mix.Transfer 5.0mLof this solution to a 500-mLvolumetric flask,add 10.0mLof Internal standard solution,dilute with water to volume,and mix.Filter this solution through a 0.5-µm or finer porosity filter,and store the filtrate in a suitable plastic container.This Standard preparationcontains about 9µg (0.00012mEq)of potassium chloride and about 88µg (0.0015mEq)of sodium chloride per mL.

Assay preparation— Constitute the contents of a container of PEG3350and Electrolytes for Oral Solution with an accurately measured volume of water,as specified in the labeling.Transfer 6.0mLof this stock solution,equivalent to about 0.06mEq of potassium,to a 500-mLvolumetric flask,add 10mLof Internal standard solution,dilute with water to volume,and mix.This solution contains about 0.00012mEq of potassium and 0.0015mEq of sodium per mL.[NOTE—Reserve the remaining portion of the stock solution for the Assay for bicarbonate,and reserve the remaining portion of the Assay preparation for the Assay for chloride and sulfate and the Assay for polyethylene glycol 3350.]

Chromatographic system (see Chromatography á621ñ)—The liquid chromatograph is equipped with a conductivity detector,a 4-mm ×5-cm guard column containing packing L22,and a 4-mm ×30-cm analytical column maintained at 35±1containing packing L22.The flow rate is about 0.9mLper minute.Chromatograph the Standard preparationas directed for Procedure:the relative retention times are about 0.6for sodium,0.8for ammonium,and 1.0for potassium,the resolution,R,between the sodium and ammonium peaks is not less than 1.1and between the ammonium and potassium peaks is not less than 0.9.[NOTE—Maintain column backpressure at less than 1000pounds per square inch.Backpressure may be reduced by changing the in-line filters and frits in the columns.Column efficiency may be improved by backflushing the analytical column with 30mLof 0.1Nnitric acid or by injecting four successive 100-µLportions of 0.1Nnitric acid into the chromatograph.]

Procedure— [NOTE—Use peak heights where peak responses are indicated.]Separately inject equal volumes (about 10µL)of the Standard preparationand the Assay preparationinto the chromatograph,record the chromatograms,and measure the responses for the major peaks.Calculate the mEq of potassium per liter of constituted Oral Solution taken by the formula: in which 74.55is the molecular weight of potassium chloride,Cis the concentration,in µg per mL,of potassium chloride in the Standard preparation,and RUand RSare the peak response ratios of potassium to ammonium obtained from the Assay preparationand the Standard preparation,respectively.Calculate the mEq of sodium per liter of constituted Oral Solution taken by the formula: in which 58.44is the molecular weight of sodium chloride,Cis the concentration,in µg per mL,of sodium chloride in the Standard preparation,and RUand RSare the peak response ratios of sodium to ammonium obtained from the Assay preparationand the Standard preparation,respectively.

2.5VA,

Mobile phase— Transfer 34g of boric acid,8.6g of lithium hydroxide,23.5mLof gluconic acid solution (1:1),and 125mLof glycerin to a 1000-mLvolumetric flask,dissolve in water,dilute with water to volume,and mix.Add 15mLof this buffer solution to 865mLof water,mix,and degas.Add 120mLof acetonitrile,mix,and degas.[NOTE—Protect the Mobile phase from air to prevent absorption of carbon dioxide.]Make adjustments if necessary (see System Suitabilityunder Chromatography á621ñ).Increasing the proportion of buffer solution decreases the retention times of the analytes.

Internal standard solution— Dissolve a suitable quantity of ammonium bromide in water to obtain a solution having a concentration of about 2.2mg per mL.

Standard preparation— To a 100-mLvolumetric flask transfer about 246mg of sodium chloride (4.2mEq),previously dried at 105for 2hours and accurately weighed,and about 682mg of anhydrous sodium sulfate (9.6mEq),previously dried at 105for 2hours and accurately weighed,dilute with water to volume,and mix.Transfer 5.0mLof this solution to a 500-mLvolumetric flask,add 10.0mLof Internal standard solution,dilute with water to volume,and mix.Filter this solution through a 0.5-µm or finer porosity filter,and store the filtrate in a suitable glass container.This Standard preparationcontains about 24.6µg of sodium chloride (0.00042mEq of chloride)and about 68.2µg of sodium sulfate (0.00096mEq of sulfate)per mL.

Assay preparation— Use the Assay preparationprepared as directed in the Assay for potassium and sodium.This solution contains about 0.042mEq of chloride and 0.096mEq of sulfate per mL.

Chromatographic system (see Chromatography á621ñ)—The liquid chromatograph is equipped with a conductivity detector,a 4-mm ×5-cm guard column containing packing L23,and a 4-mm ×30-cm analytical column maintained at 35±1containing packing L23.The flow rate is about 0.9mLper minute.Chromatograph the Standard preparationas directed for Procedure:the relative retention times are about 0.25for chloride,0.4for bromide,and 1.0for sulfate,the resolution,R,between the chloride and bromide peaks is not less than 1.5and between the bromide and sulfate peaks is not less than 4.5.[NOTE—Maintain column backpressure at less than 1000pounds per square inch.Backpressure may be reduced by changing the in-line filters and frits in the columns.Column efficiency may be improved by backflushing the analytical column with 50mLof the buffer solution used to prepare the Mobile phase.]

Procedure— [NOTE—Use peak heights where peak responses are indicated.]Separately inject equal volumes (about 10µL)of the Standard preparationand the Assay preparationinto the chromatograph,record the chromatograms,and measure the responses for the major peaks.Calculate the mEq of chloride per liter of constituted Oral Solution taken by the formula: in which 58.44is the molecular weight of sodium chloride,Cis the concentration,in µg per mL,of sodium chloride in the Standard preparation,and RUand RSare the peak response ratios of chloride to bromide obtained from the Assay preparationand the Standard preparation,respectively.Calculate the mEq of sulfate per liter of constituted Oral Solution taken by the formula: in which 71.02is one-half of the molecular weight of sodium sulfate,Cis the concentration,in µg per mL,of anhydrous sodium sulfate in the Standard preparation,and RUand RSare the peak response ratios of sulfate to bromide obtained from the Assay preparationand the Standard preparation,respectively.

Salt solution— Prepare a solution in water containing 0.35mg of sodium chloride,0.18mg of potassium chloride,0.40mg of sodium bicarbonate,1.37mg of anhydrous sodium sulfate,and 0.88mg of ammonium bromide per mL.

Mobile phase— Dilute 40.0mLof Salt solutionwith water to 1000mL.Make adjustments if necessary (see System Suitabilityunder Chromatography á621ñ).

Standard preparation— Transfer about 360mg of polyethylene glycol 3350,accurately weighed,to a 500-mLvolumetric flask,add 20.0mLof Salt solutionand about 250mLof water,dissolve by swirling,dilute with water to volume,and mix.This Standard preparationcontains about 0.72mg of polyethylene glycol 3350per mL.

Assay preparation— Use the Assay preparationprepared as directed in the Assay for potassium and sodium.This solution contains about 0.72mg of polyethylene glycol 3350per mL.

Chromatographic system (see Chromatography á621ñ)—[NOTE—Use peak heights where peak responses are indicated.]The liquid chromatograph is equipped with a refractive index detector maintained at 34±0.5,a 7.8-mm ×4.5-cm guard column containing packing L25,and a 7.8-mm ×30-cm analytical column containing packing L25and maintained at ambient temperature.The flow rate is about 1mLper minute.Chromatograph the Standard preparationas directed for Procedure:the relative standard deviation for replicate injections is not more than 1.5%.[NOTE—Maintain column backpressure at less than 1000pounds per square inch.Backpressure may be reduced by cleaning the frits in the guard column or by replacing the guard column.Baseline drift may be reduced by maintaining strict control of ambient temperature,by insulating the lines,the Mobile phasereservoir,and the columns,and by increasing the time of equilibration.]

Procedure— Separately inject equal volumes (about 20µL)of the Standard preparationand the Assay preparationinto the chromatograph,record the chromatograms,and measure the responses for the major peaks.Calculate the content,in g,of polyethylene glycol 3350per liter of constituted Oral Solution taken by the formula: in which Cis the concentration,in mg per mL,of polyethylene glycol 3350in the Standard preparation,and rUand rSare the polyethylene glycol 3350peak responses obtained from the Assay preparationand the Standard preparation,respectively.