what factors affects the quantity/concentration of cystine using HPLC?
95900
The quantity or concentration of cystine, or any other analyte, will be dependant on the concentration in the sample, not the analytical method.
273733
Yes\n\nRemember:\n\nKsp = [Cation][Anion] (concentrations) / [Solid] (always 1)\n\nAs the concentrates of cation and anion decrease, their product decreases (making KSP smaller)
860724
The link below gives a method and chromatogram.  Bear in mind that you will need to prevent the degradation of ascorbic acid during the analysis.  This may be done by adding EDTA and HCl to the solutions, but you will have to work out the concentrations.
836016
Here is a good guide\n\nhttp://dbhs.wvusd.k12.ca.us/webdocs/Stoichiometry/Limiting-Reagent.html
471672
Depends on the method that you are using, and/or the age of the column. If the column is older than one year, or has more than 1000 hours of run time, it may be suspect. \n\nWith regards to the sample you are running, make sure that what you are running is compatible with an ODS column. Some chemistries will react with the silane groups and become permanently attached to the column. Also, make sure there are no matrix issues that could be obscuring your results. The sample might have to be washed or cleaned to remove/reduce matrix effects.\n\nWith the method you are running, make sure that you are properly cleaning the column after each run because some things may be retained on the column and not eluting.  You may have to run a stronger cleaning solvent to clean the column and then re-equilibrate with your running solvent.  Also, make sure that your running solvent stays constant and is not changing due to evaporation or any other factors. \n\nObviously to give reproducible results the methods that you use must remain as constant as possible. Check each of your method parameters to make sure nothing is changing. \n\nHope this helps without going into a treatise on HPLC theory and methodology.
580895
This is a typical sort of problem found in real life laboratories- You have differences in concentrations because, in the real world, there are errors introduced at every step of the quantitation process..tiny differences in how much stays in the tube, in the pippette tip, the accuracy of the pippette itself, etc.  However, figuring out which is more accurate is fairly easy.  First, any value that actually falls *on* your standard curve is best-that way you don't have to extrapolate. Second, in general, the more you dilute, the less accurate the reading.  The first consideration is the more important.  In sample 1, your 1:50 dilution is too low to get an accurate reading, in unknown 2, your first dilution is too high to get an accurate reading.
145956
MY ANSWER IS :\n\n18.2g  of Na2S is produced.
955885
In column chromatography, the elution of analytes is a function of both the stationary and mobile phases (among others things, like temperature).\n\nIf the analyte does not elute, then either the stationary or mobile phase was not chosen correctly.  K' might be very large without being infinite.  The compound may be moving through the column, but too slowly to elute entirely from the column.\n\nFor example:  if the stationary phase is silica gel and the compound does not elute with alcohol or water, then a basic or acidic aqueous solution might be needed to elute the compound.
617450
Some molecules absorb visible light, e.g. due to conjugation and pi to pi antibonding transitions, with the highest intensity at a particular wavelength.  One can prepare standard solutions, with accurately devised known concentrations, the measured intensities of these solutions are correlated with these standard solutions, covering a particular dynamic range.  Assuming Beer's Law, the plot will resemble a linear curve, and a least fit regression line and its equation can be obtained; also by correcting for the blank if this is has not bee accounted for by the spectrometer.  The unknown pure solution, or a matrix derived alternative method if the solution is not pure that there are significant impurities in the unknown solution, will also be measured at this wavelength and it's intensity, often the y value, will be plugged into the regression equation to estimate the concentration.
536698
Mega L-Glutathione Capsules\n250 mg, 60 capsules\nItem Catalog Number: 314 \nL-cysteine is a conditionally essential amino acid, one of only three sulfur-containing amino acids, the others being taurine (which can be produced from L-cysteine) and L-methionine from which L-cysteine can be produced in the body by a multi-step process. Cysteine plays a role in the sulfation cycle, acting as a sulfur donor in phase II detoxification and as a methyl donor in the conversion of homocysteine to methionine. Cysteine also helps synthesize glutathione, one of the body’s most important natural detoxifiers. N-acetyl-cysteine is the acetylated form of L-cysteine, which is more efficiently absorbed and used.54-64\n\nGlutathione (gamma-L-glutamyl-L-cysteinyl-glycine) is a peptide (short protein)-like molecule synthesized in the body from the three amino acids L-glutamic acid, L-cysteine, and glycine. Glutathione is one of the body’s most important and powerful antioxidants, helping to detoxify xenobiotics. A major function of vitamin C is to keep glutathione in its reduced form so that they can continue to provide free radical quenching effects.65-68\n\nEven though many published studies show that garlic, selenium, alpha-lipoic acid, L-cysteine, and N-acetyl-cysteine can boost cellular glutathione levels, people with health problems may benefit from taking high doses of glutathione.65,69-71*\n \nReferences  \nSupplement Facts \nServing Size 1 capsule\n \nServings Per Container 60\n \nAmount Per Serving \nL-glutathione\n 250 mg\n \nOther ingredients: gelatin, cellulose, purified water, magnesium stearate, silica.\n \n \nDosage and Use \n  Take one capsule daily, preferably with a meal.\n \n \nCaution \nWhen taking L-cysteine, N-acetyl-cysteine, or glutathione, it is recommended that three times as much vitamin C should be taken at the same time to prevent these amino acids from being oxidized in the body
867426
Maybe this well help...\n\nhttp://www.valueseek.com/glutathione/
970448
N = Normality...in this case the concentration of Sulfuric Acid in a solution.\n\nThe concentration of Sulfuric Acid in the 1.00 N Solution is almost 4 times as concentrated as the 0.255 N Solution.\n\nIn practice Normality is "similar" to Molarity, except Normality takes into account the actual number of protons exchanged in a reaction.  Normality = Molarity times the number of protons exchanged.  In Sulfuric Acid, two protons are available for exchange...therefore, a one molar solution would be a two normal solution.  It is useful when doing titrations to determine concentrations.
705668
the retention times are longer for everything. The gas flow rate is the only variable decider in the speed of transit through the columns. Slower flow means slower movemnt independent of column interactions\n\nThe separation should theoretically be better for everything besides the components that don't interact at all with the column. They come out at dead/void volume anyway. The other components are better separated because the slower flow rate means they have more time to interact with the stationary phase and so the differences in elution rate become more pronounced.
440553
Because you mention Rf values, I assume you're asking specifically about Thin-Layer Chromatography.  Actually the molecular weight is a fairly minor factor in the Rf value.  Intermolecular interactions between the pigment in question and the solid phase and the mobile phase are the most important.  So it really comes down to the selection of the mobile phase, how polar, how acidic or basic in relation to the analyte (your pigment in this case).  pH of the mobile phase is critically important in that your pigment may ionize to a greater or lesser extent depending upon the pH, and this drastically changes the intermolecular interactions.  Stationary phase selection is also important.
862382
Ah yes, the classic Iron Thiocyanate complexation lab.\n\nTo determine the concentrations for the first part, you need to know the concentrations of the stock solutions and the final volume of the solution you made.  You can then use the formula:\n\nC1*V1 = C2*V2\n\nWhere C is concentration and V is volume.\n\nFor the second part, I'm not really sure what you did in your lab.  Usually you use the calibration curve you constructed from the first part to measure the concentrations in the second part.  There is alot of ugly calculations to be done in there.  Check your lab packet for more information.
661226
It doesn't matter how much iron you happen to dissolve as long as you have the exact mass you dissolved for the later calculations. Use just enough sulphuric acid to dissolve all of the iron, then transfer the solution into a measuring bulb and fill up to the mark - the theoretical concentration of iron is the mass you used divided by the volume. \n\nTheoretically you need 1 mol of acid for each mol of iron, but you will want some excess acid to keep the ions in solution. Make sure that oxygen has no chance to react with your solution during dissolving and titration.\n\nTitration with potassium permanganate in acid solution will require 1 mol permanganate for each 5 moles of iron. Usual lab concentrations are 0.02 mol/l (1 ml of that solution detects 0.1 mmol iron). You will want to use roughly 20 ml permanganate solution per titration for a volume error <1%.\n\nNow we start calculating (using SI units). Iron has a molar mass of 55.8... g/mol. If you want to use about 20 ml, you will need about 0.002 mol of iron. \n\nYour iron solution will have a concentration of \n\nC = m / (M * V)\n\nm : mass of (impure) iron you dissolved, in grams\nM : molar mass of iron, in gram/mol\nV : volume of the volumetric bottle you filled your solution up with, in ml (for convenience)\n\nC : concentration of impure iron, in mol/ml\n\nDivide 0.002 by C to see (roughly) how many ml of your iron solution you want for your first titration. Take an appropriate full pipette which fits the order of magniture, or else dilute your original solution in a volumetric bottle so that you can use a full pipette you have at hand.\n\n\nNow to get percentage purity.\n\nI'll assume you can calculate a concentration from titration.\n\nWith your titration you will determine the measured concentration of iron (in small numbers of mol/ml). Divide that result by C (calculated above), and multiply by 100 to get percentiles.\n\nHave fun!
754842
thats not so hard... all you have to do is titrate it against an acidic solution of known concentration that has a mole ratio of 1:1with sls. add a indicator ( phenolphthaleine) to find the endpoint and that should do it.