UGC NET — Environmental Sciences (subject code 89) · India · National Testing Agency for the University Grants Commission
Original practice questions written to the published syllabus · not past papersHow environmental samples are taken and analysed and how good the numbers are: sampling plans, gravimetric and volumetric methods, spectroscopy, chromatography, quality assurance and monitoring networks.
In the exams: UGC NET Environmental Sciences Unit 2; ICAR AIEEA-PG Physical Science Unit II (instrumental analysis); ICAR AICE Aquatic Environmental Management Unit 3
UGC NET Environmental Sciences — Unit 2 (analytical techniques)
Principles and applications of titrimetry, gravimetry, colorimetry and UV–visible spectrophotometry, AAS, ICP, chromatography (GC, HPLC, IC), mass spectrometry, electrochemical methods, isotopes, sampling and preservation, and QA/QC concepts.
How our questions for UGC NET spread across the units of Environmental Monitoring & Instrumental Analysis. Difficulty: 21 easy, 47 medium, 24 hard.
| Detection limits, accuracy, precision and calibration | 9 | |
| Quality assurance, quality control and laboratory accreditation | 9 | |
| Bioindicators and biomonitoring | 9 | |
| Monitoring objectives and network design | 8 | |
| Gas and liquid chromatography; mass spectrometry | 8 | |
| Stable and radioactive isotopes in environmental analysis | 8 | |
| Continuous and low-cost sensor monitoring | 8 | |
| Sampling and preservation of water, soil, air and biota | 7 | |
| UV-visible spectrophotometry and colorimetry | 7 | |
| Atomic absorption and ICP techniques | 7 | |
| Electrochemical methods and sensors | 7 | |
| Gravimetric and volumetric analysis | 5 |
Choose an answer, then open the working. Each explanation says why the right answer is right and why the others are not.
What does the US EPA's data quality objectives process require before sampling begins?
C. Defining the decision and tolerable errors
DQOs derive sampling design from the decision and acceptable errors, not from convenience.
Further reading: See the manual sources: Standard Methods; Harris; Skoog et al.; CPCB monitoring guidelines; ISO/IEC 17025
What is the purpose of a chain-of-custody record?
B. Documenting every sample transfer
Chain of custody proves sample integrity from collection to analysis.
Further reading: See the manual sources: Standard Methods; Harris; Skoog et al.; CPCB monitoring guidelines; ISO/IEC 17025
Mohr's method determines chloride by titration with
B. silver nitrate, chromate indicator
Red-brown silver chromate forms after all chloride precipitates as AgCl.
Further reading: See the manual sources: Standard Methods; Harris; Skoog et al.; CPCB monitoring guidelines; ISO/IEC 17025
Hexavalent chromium is commonly measured colorimetrically using
C. 1,5-diphenylcarbazide in acid
Diphenylcarbazide forms a red-violet complex with Cr(VI) at about 540 nm.
Further reading: See the manual sources: Standard Methods; Harris; Skoog et al.; CPCB monitoring guidelines; ISO/IEC 17025
Which technique gives the lowest detection limits for many trace metals and can measure isotope ratios?
B. ICP-MS
ICP-MS reaches ng/L levels and resolves isotopes; flame methods are less sensitive.
Further reading: See the manual sources: Standard Methods; Harris; Skoog et al.; CPCB monitoring guidelines; ISO/IEC 17025
Argon chloride (ArCl⁺) interferes with arsenic measurement in ICP-MS because
D. it shares nominal mass 75 with arsenic
40Ar35Cl⁺ has mass 75, like 75As⁺; collision/reaction cells remove it.
Further reading: See the manual sources: Standard Methods; Harris; Skoog et al.; CPCB monitoring guidelines; ISO/IEC 17025
Anodic stripping voltammetry measures trace metals by
C. plating them on an electrode, then stripping
Pre-concentration by electrodeposition gives very low detection limits.
Further reading: See the manual sources: Standard Methods; Harris; Skoog et al.; CPCB monitoring guidelines; ISO/IEC 17025
Biosensors based on acetylcholinesterase inhibition are used to screen for
A. organophosphate and carbamate pesticides
These pesticides inhibit acetylcholinesterase, reducing enzyme activity; results need confirmation.
Further reading: See the manual sources: Standard Methods; Harris; Skoog et al.; CPCB monitoring guidelines; ISO/IEC 17025
Why does 14C measurement distinguish fossil from modern carbon?
A. Its 14C has decayed away
Fossil fuels are millions of years old, so 14C is absent; living carbon contains atmospheric 14C.
Further reading: See the manual sources: Standard Methods; Harris; Skoog et al.; CPCB monitoring guidelines; ISO/IEC 17025
Why do low-cost optical PM sensors often overestimate PM2.5 at high relative humidity?
C. Particles absorb water and swell
Hygroscopic growth increases apparent size and scattering; correction or drying is needed.
Further reading: See the manual sources: Standard Methods; Harris; Skoog et al.; CPCB monitoring guidelines; ISO/IEC 17025
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