On a silica TLC plate for urine sugars, the glucose standard gives a round spot, but the patient lane, where 40 µL of urine was applied at once, shows a long streak. What is the most likely cause?

Overloading of the sample at the origin

Solvent level above the origin line

Tank not saturated with solvent vapour

A 12-year-old boy has recurrent kidney stones and hexagonal crystals in his urine. Which amino acids will his urine aminogram most likely show in excess?

Cystine, ornithine, arginine and lysine

Glycine, proline and hydroxyproline

Chromatography

37 Kerala PSC Lab Technician Gr II practice questions on Chromatography, part of Biochemistry. The first 25 are below; the first 5 with answers and explanations (tap Show answer after you have chosen), the rest in Learn with a free account.

Question 1 · Hard
On a silica TLC plate for urine sugars, the glucose standard gives a round spot, but the patient lane, where 40 µL of urine was applied at once, shows a long streak. What is the most likely cause?
1. AOverloading of the sample at the origin
2. BWrong locating reagent used
3. CSolvent level above the origin line
4. DTank not saturated with solvent vapour
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Answer: A · Overloading of the sample at the origin
Only the patient lane is affected, so faults that act on the whole plate, such as solvent level, tank saturation or the spray reagent, are unlikely. A large volume applied in one go makes a broad origin spot and overloads the adsorbent, so the sugar trails up the plate as a streak. Urine should be applied a few microlitres at a time, drying between applications, to keep the origin spot small. The run is repeated with a smaller, compact application.
- B: A wrong reagent would fail to show spots in every lane, including the standard.
- C: A solvent level above the origin would wash the samples of every lane into the solvent.
- D: An unsaturated tank gives an uneven front across the whole plate, not one streaked lane.
Question 2 · Medium
Gas chromatography is the method of choice for blood alcohol because ethanol is:
1. AInsoluble in water
2. BVolatile and heat stable
3. CA large charged molecule
4. DStrongly coloured
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Answer: B · Volatile and heat stable
Gas chromatography needs compounds that turn into vapour without breaking down, because the mobile phase is an inert carrier gas such as nitrogen or helium. Ethanol, methanol and other volatile alcohols are ideal, and headspace gas chromatography is the reference method for blood alcohol in medicolegal work. Large, charged or heat-labile molecules such as proteins are separated by HPLC or electrophoresis instead. Ethanol is colourless and mixes completely with water.
- A: Ethanol mixes completely with water.
- C: Ethanol is a small neutral molecule; large charged molecules suit electrophoresis or HPLC.
- D: Ethanol is colourless; it is detected by a flame ionisation detector, not by colour.
Question 3 · Hard
On a paper chromatogram the origin is 2 cm and the solvent front 17 cm from the bottom edge. A urine spot's centre is 7.7 cm from the edge. Standards (Rf): glycine 0.26, alanine 0.38, tyrosine 0.45, leucine 0.73. The spot is:
1. ALeucine
2. BGlycine
3. CTyrosine
4. DAlanine
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Answer: D · Alanine
Rf is measured from the origin, not from the edge of the paper. The spot moved 7.7 - 2 = 5.7 cm and the solvent front 17 - 2 = 15 cm, so Rf = 5.7 / 15 = 0.38, which matches alanine. Measuring both distances from the bottom edge gives 7.7 / 17 = 0.45 and wrongly suggests tyrosine. In practice standards are run on the same sheet, because Rf values change with the solvent, temperature and paper.
- A: Leucine (0.73) would need a spot about 11 cm above the origin.
- B: Glycine (0.26) would need a spot about 3.9 cm above the origin.
- C: Tyrosine (0.45) is reached only by measuring from the paper edge instead of the origin.
Question 4 · Easy
Which agent is commonly used to show lipid spots on a thin-layer plate?
1. AIodine vapour
2. BNinhydrin spray
3. CAniline phthalate spray
4. DEhrlich reagent spray
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Answer: A · Iodine vapour
Iodine dissolves in the lipid spots and stains them yellow-brown, so a closed tank with a few iodine crystals is a simple general locating method for lipids. The stain fades as the iodine evaporates, so the spots are marked with a pencil at once. Charring with sulphuric acid, or fluorescent dyes viewed under UV light, are alternatives. Ninhydrin and aniline phthalate are used for amino acids and sugars.
- B: Ninhydrin locates amino acids, which have free amino groups.
- C: Aniline phthalate locates reducing sugars.
- D: Ehrlich reagent reacts with indoles, urobilinogen and porphobilinogen.
Question 5 · Medium
A 12-year-old boy has recurrent kidney stones and hexagonal crystals in his urine. Which amino acids will his urine aminogram most likely show in excess?
1. APhenylalanine and tyrosine
2. BGlycine, proline and hydroxyproline
3. CLeucine, isoleucine and valine
4. DCystine, ornithine, arginine and lysine
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Answer: D · Cystine, ornithine, arginine and lysine
Hexagonal crystals and stones point to cystinuria, an inherited defect of the renal tubular carrier for the dibasic amino acids. Cystine, ornithine, arginine and lysine (remembered as COAL) are lost in excess and show as heavy spots on paper or thin-layer chromatography. Cystine is poorly soluble in acid urine and forms the stones; the cyanide-nitroprusside test is a quick screen. The other patterns belong to iminoglycinuria, maple syrup urine disease and tyrosinemia or liver disease.
- A: Phenylalanine and tyrosine rise in liver disease and tyrosinemia; they do not form hexagonal crystals.
- B: Glycine, proline and hydroxyproline are lost in iminoglycinuria, which causes no stones.
- C: Branched-chain amino acids are raised in maple syrup urine disease.
Question 6 · Easy
Most amino acids give which colour when a paper chromatogram is sprayed with ninhydrin and heated?
1. AGreen
2. BPurple
3. COrange
4. DYellow
Answer and explanation in LearnFree account
Question 7 · Medium
On a cation-exchange resin column, amino acids are separated mainly by which property?
1. ASolubility in organic solvent
2. BBoiling point
3. CMolecular size and shape
4. DNet charge at the buffer pH
Answer and explanation in LearnFree account
Question 8 · Medium
Thin-layer chromatography is often preferred to paper chromatography for urine sugars because it:
1. ASeparates sugars by electric charge
2. BGives the exact amount of each sugar
3. CGives faster runs with sharper spots
4. DNeeds no solvent or spray reagent
Answer and explanation in LearnFree account
Question 9 · Easy
In paper partition chromatography, what forms the stationary phase?
1. AWater held by the cellulose fibres
2. BThe organic solvent mixture
3. CThe cellulose fibres of the paper itself
4. DA thin layer of silica gel
Answer and explanation in LearnFree account
Question 10 · Easy
In high-performance liquid chromatography (HPLC), the mobile phase is driven through the column by:
1. AAn inert carrier gas
2. BA high-pressure pump
3. CGravity flow
4. DCapillary action
Answer and explanation in LearnFree account
Question 11 · Easy
In 'silica gel G' used to coat TLC plates, the letter G stands for which binder?
1. AGelatin
2. BGypsum (calcium sulphate)
3. CGlass powder
4. DGlycerol
Answer and explanation in LearnFree account
Question 12 · Medium
Serum lipids are run on a silica gel TLC plate with a hexane-ether-acetic acid solvent. Which lipid class stays nearest the origin?
1. ATriglycerides
2. BPhospholipids
3. CFree fatty acids
4. DCholesterol esters
Answer and explanation in LearnFree account
Question 13 · Medium
In ion-exchange column chromatography, proteins bound to the resin are usually eluted by:
1. AAdding a ninhydrin solution to the column
2. BUsing a longer column of the same resin
3. CRaising the salt concentration of the buffer
4. DSlowing the flow rate of the same starting buffer
Answer and explanation in LearnFree account
Question 14 · Hard
A breastfeeding mother's routine urine gives an orange Benedict test, but the glucose oxidase strip is negative and her blood glucose is normal. On TLC, the urine sugar spot runs level with the lactose standard. What is the most likely explanation?
1. ADiabetes mellitus
2. BGalactosemia
3. CRenal glycosuria
4. DLactosuria of lactation
Answer and explanation in LearnFree account
Question 15 · Easy
Chromatography was first described by which scientist, who separated plant pigments on a column of chalk?
1. AMikhail Tswett
2. BArne Tiselius
3. CArcher Martin
4. DRichard Synge
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Question 16 · Easy
Which chromatography separates a protein using a ligand fixed to the column that binds it specifically, such as an antibody?
1. AAffinity chromatography
2. BPartition chromatography
3. CIon-exchange chromatography
4. DGel filtration chromatography
Answer and explanation in LearnFree account
Question 17 · Medium
Before gas chromatography, fatty acids are usually converted to their methyl esters. Why?
1. ATo make them soluble in water
2. BTo give them a colour for detection
3. CTo give them a strong electric charge
4. DTo make them volatile enough to vaporise
Answer and explanation in LearnFree account
Question 18 · Medium
Two-dimensional paper chromatography of urine amino acids is preferred to a one-way run because it:
1. AShows the spots without ninhydrin
2. BGives the exact amount of each amino acid
3. CIs quicker and needs less urine
4. DSeparates amino acids that overlap in one solvent
Answer and explanation in LearnFree account
Question 19 · Hard
In an HPLC drug assay, a patient sample gives a drug peak area of 4,500 and an internal standard area of 2,500. A 10 µg/mL calibrator gives 6,000 and 3,000. What is the drug concentration?
1. A9.0 µg/mL
2. B18.0 µg/mL
3. C11.1 µg/mL
4. D7.5 µg/mL
Answer and explanation in LearnFree account
Question 20 · Easy
In gas chromatography, the mobile phase is:
1. AAn inert carrier gas such as nitrogen
2. BAn organic solvent pumped under pressure
3. CA buffered aqueous salt solution
4. DWater held in cellulose fibres
Answer and explanation in LearnFree account
Question 21 · Medium
A child's urine shows a generalised increase of many amino acids on chromatography, while the plasma amino acids are normal. This pattern is best described as:
1. AOverflow aminoaciduria
2. BDietary aminoaciduria
3. CPhysiological aminoaciduria
4. DRenal aminoaciduria
Answer and explanation in LearnFree account
Question 22 · Easy
The liquid that comes out of a chromatography column carrying the separated components is called the:
1. AEluent
2. BAnalyte
3. CEluate
4. DSorbent
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Question 23 · Easy
The Rf value of a substance on a paper or thin-layer chromatogram always lies between:
1. A-1 and +1
2. B0 and 1
3. C1 and 10
4. D0 and 100
Answer and explanation in LearnFree account
Question 24 · Medium
Which detector is most commonly fitted to an HPLC system for drugs and vitamins that absorb light?
1. AUltraviolet-visible absorbance detector
2. BElectron capture detector
3. CFlame ionization detector
4. DThermal conductivity detector
Answer and explanation in LearnFree account
Question 25 · Hard
Several men are admitted after drinking illicit liquor. They complain of blurred vision; one is blind. ABG: pH 7.12, HCO3 8 mmol/L, anion gap 28. Headspace gas chromatography of blood is requested. Which compound is it most likely to show?
1. AIsopropanol
2. BMethanol
3. CEthanol only
4. DEthylene glycol
Answer and explanation in LearnFree account

12 more Chromatography questions

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Study Biochemistry

Chromatography

On a silica TLC plate for urine sugars, the glucose standard gives a round spot, but the patient lane, where 40 µL of urine was applied at once, shows a long streak. What is the most likely cause?

Gas chromatography is the method of choice for blood alcohol because ethanol is:

On a paper chromatogram the origin is 2 cm and the solvent front 17 cm from the bottom edge. A urine spot's centre is 7.7 cm from the edge. Standards (Rf): glycine 0.26, alanine 0.38, tyrosine 0.45, leucine 0.73. The spot is:

Which agent is commonly used to show lipid spots on a thin-layer plate?

A 12-year-old boy has recurrent kidney stones and hexagonal crystals in his urine. Which amino acids will his urine aminogram most likely show in excess?

Most amino acids give which colour when a paper chromatogram is sprayed with ninhydrin and heated?

On a cation-exchange resin column, amino acids are separated mainly by which property?

Thin-layer chromatography is often preferred to paper chromatography for urine sugars because it:

In paper partition chromatography, what forms the stationary phase?

In high-performance liquid chromatography (HPLC), the mobile phase is driven through the column by:

In 'silica gel G' used to coat TLC plates, the letter G stands for which binder?

Serum lipids are run on a silica gel TLC plate with a hexane-ether-acetic acid solvent. Which lipid class stays nearest the origin?

In ion-exchange column chromatography, proteins bound to the resin are usually eluted by:

A breastfeeding mother's routine urine gives an orange Benedict test, but the glucose oxidase strip is negative and her blood glucose is normal. On TLC, the urine sugar spot runs level with the lactose standard. What is the most likely explanation?

Chromatography was first described by which scientist, who separated plant pigments on a column of chalk?

Which chromatography separates a protein using a ligand fixed to the column that binds it specifically, such as an antibody?

Before gas chromatography, fatty acids are usually converted to their methyl esters. Why?

Two-dimensional paper chromatography of urine amino acids is preferred to a one-way run because it:

In an HPLC drug assay, a patient sample gives a drug peak area of 4,500 and an internal standard area of 2,500. A 10 µg/mL calibrator gives 6,000 and 3,000. What is the drug concentration?

In gas chromatography, the mobile phase is:

A child's urine shows a generalised increase of many amino acids on chromatography, while the plasma amino acids are normal. This pattern is best described as:

The liquid that comes out of a chromatography column carrying the separated components is called the:

The Rf value of a substance on a paper or thin-layer chromatogram always lies between:

Which detector is most commonly fitted to an HPLC system for drugs and vitamins that absorb light?

Several men are admitted after drinking illicit liquor. They complain of blurred vision; one is blind. ABG: pH 7.12, HCO3 8 mmol/L, anion gap 28. Headspace gas chromatography of blood is requested. Which compound is it most likely to show?