Patai S., Rappoport Z. 1996 The chemistry of functional groups. The chemistry of amino, nitroso, nitro and related groups. Part 2 / 1041 1168

Supplement F2: The Chemistry of Amino, Nitroso, Nitro and Related Groups.

Edited by Saul Patai Copyright 1996 John Wiley & Sons, Ltd.

ISBN: 0-471-95171-4

CHAPTER 24

Analytical aspects of amino, quaternary ammonium, nitro, nitroso and related functional groups

JACOB ZABICKY and SHMUEL BITTNER
Institutes for Applied Research and Department of Chemistry,
Ben-Gurion University of the Negev, Beer-Sheva, Israel
Fax: [phone]; e-mail: [e-mail]
	[e-mail]
I. ABBREVIATIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .		1042
II. INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .		1044
III. ELEMENTAL ANALYSIS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .		1045
A. Automatic Organic Elemental Analysis (CHNOS) . . . . . . . . . . . . . .		1045
1.	General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	1045
2.	Nitrogen . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	1045
3.	Oxygen . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	1046
B. Digestion Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .		1046
C. Nitrogen Responsive Detectors for GC . . . . . . . . . . . . . . . . . . . . .		1047
D. Stable Isotope Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .		1048
IV. AMINES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .		1049
A. General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .		1049
B. Isotope Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .		1059
C. Gas Chromatography . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .		1060
D. Liquid Chromatography . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .		1067
1.	General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	1067
2.	Underivatized analytes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	1068
3.	Pre-column and post-column derivatization . . . . . . . . . . . . . . . .	1076
	a. Reaction with dicarboxaldehydes . . . . . . . . . . . . . . . . . . . . .	1077
	b. Oxazole derivatives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	1080
	c. N-Acylation and N-sulfonation . . . . . . . . . . . . . . . . . . . . . .	1080
	d. Reaction with isothiocyanates . . . . . . . . . . . . . . . . . . . . . . .	1084

1041

1042		Jacob Zabicky and Shmuel Bittner
	e. N-Arylation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .		1085
	f. Schiff bases . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .		1085
g. Miscellaneous reactions . . . . . . . . . . . . . . . . . . . . . . . . . . .			1086
4.	Chiral purity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .		1089
5.	Fossil dating . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .		1092
E. Electrophoresis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .			1093
F. Spectrophotometric Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . .			1096
G. Enzymatic Biosensors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .			1102
H. Miscellaneous Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .			1105
I. Derivatization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .			1109
V. QUATERNARY AMMONIUM COMPOUNDS . . . . . . . . . . . . . . . . .			1114
A. Chromatography . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .			1116
B. Miscellaneous Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .			1118
VI. NITRO COMPOUNDS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .			1122
A. General . .		. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	1122
B. Aromatic Nitro Compounds . . . . . . . . . . . . . . . . . . . . . . . . . . . .			1125
1.	General	. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	1125
2.	Monocyclic arenes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .		1127
3.	Polycyclic aromatic hydrocarbons (PAH) . . . . . . . . . . . . . . . . . .		1129
4.	Phenols	. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	1133
	a. HPLC and GC without derivatization . . . . . . . . . . . . . . . . . .		1133
b. HPLC and GC with precolumn derivatization . . . . . . . . . . . . .			1134
	c. Miscellaneous methods . . . . . . . . . . . . . . . . . . . . . . . . . . .		1134
5.	Aromatic amines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .		1135
6.	Miscellaneous aromatic compounds . . . . . . . . . . . . . . . . . . . . .		1137
C. Nitrofurans . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .			1139
D. Miscellaneous Heterocyclic Compounds . . . . . . . . . . . . . . . . . . . .			1140
E. Aliphatic Compounds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .			1141
F. Nitrates . .		. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	1142
G. Nitramines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .			1142
VII. NITROSO COMPOUNDS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .			1143
A. General . .		. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	1143
B. Nitrosoarenes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .			1143
C. Nitrosamines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .			1144
1.	Gas chromatography . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .		1144
2.	Liquid chromatography . . . . . . . . . . . . . . . . . . . . . . . . . . . . .		1146
3.	Miscellaneous methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . .		1148
D. Tobacco .		. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	1150
VIII. HYDROXYLAMINES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .			1151
A. Quantitative Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .			1151
B. Structural Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .			1152
C. Derivatization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .			1152
IX. AMINO-OXYLS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .			1153
X. REFERENCES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .			1154
		I. ABBREVIATIONS
AAS		atomic absorption spectroscopy
AED		atomic emission detector(ion)
AFID		alkali FID
AOAC		Association of Official Analytical Chemists

					24. Analytical aspects	1043
CE	capillary electrophoresis
CI-MS	chemical ionization MS
CLD	chemiluminescence detector(ion)
CLND	chemiluminescence nitrogen detector(ion)
CMC	critical concentration for micelle formation
CZE	capillary zone electrophoresis
DON	dissolved organic nitrogen
DSC	differential scanning calorimetry
DTA	differential thermal analysis
ECD	electron capture detector(ion)
EI-MS	electron impact MS
ELCD	electrolytic conductivity detector(ion)
ELISA	enzyme-linked immunosorbed assay
ELS	evaporative light scattering
EPA	Environmental Protection Agency (USA)
FAB	fast atom bombardment
FASD	flameless alkali-sensitized detector(ion)
FIA	flow injection analysis
FID	flame ionization detector(ion)
FLD	fluorescence detector(ion)
FPD	flame photometric detector(ion)
GC-. . .	gas chromatography combined with special detectors
GCE	glassy carbon electrode
HPTLC	high-performance TLC
ICP	inductively coupled plasma
IEC	ion-exchange chromatography
LIF	laser-induced fluorescence
LLE	liquid		liquid extraction
LOD	limit(s) of detection
LOQ	limit(s) of quantation
MEKC	micellar electrokinetic chromatography
MSTS	mainstream tobacco smoke
NAA	nitroso amino acids
NDIR	nondispersive infrared
NICI-MS	negative ion chemical ionization MS
NIOSH	National Institute for Occupational Safety and Health (USA)
NOC	nitroso organic compounds (nitrosamines)
NPD	nitrogen				phosphorus detector(ion)
OFID	oxygen FID
OSHA	Occupational Safety and Health Administration (USA)
PAH	polycyclic aromatic hydrocarbon(s)
PON	particular organic nitrogen
PSP-MS	plasma-spray MS (discharge-assisted TSP-MS)
RIA	radioimmunoassay
RID	refractive index detector(ion)
RP-. . .	reversed-phase combined with other items
RSD	relative standard deviation

1044	Jacob Zabicky and Shmuel Bittner
RTECS	Registry of Toxic Effects of Chemical Substances (NIOSH/OSHA)
SCE	standard calomel electrode
SFE	supercritical fluid extraction
SIM	selected-ion monitoring mode of MS
SIMS	secondary ion MS
SNR	signal-to-noise ratio
SPE	solid-phase extraction
SPME	solid-phase microextraction
SSTS	sidestream tobacco smoke
TCD	thermal conductivity detector(ion)
TDN	total dissolved nitrogen
TEA	thermal energy analyzer
TGA	thermogravimetric analysis
TOF	time of flight
TSD	thermionic specific detector(ion)
TSNA	tobacco-specific N-nitrosamines
TSP-MS	thermospray MS
USP	US Pharmacopea
UVD	UVV photometric detector(ion)
UVV	ultraviolet-visible
VNOC	volatile NOC
XPS	X-ray photoelectron spectroscopy
XRD	X-ray diffractometry

II. INTRODUCTION

The present chapter deals with amino, nitro and nitroso groups, quaternary ammonium compounds, and with several minor related functional groups. Analytical aspects concerning these functional groups were reviewed in the past to various extents1 3. The present chapter will deal with certain general aspects and especially with advancements that took place in the last few years.

The technological importance of organic compounds containing amino and nitro groups is outstanding, both as chemical intermediates and as products that are used in other manufacturing industries, agriculture and medicine. They have found application as drugs, dyestuffs, pesticides, explosives, additives, modifiers and others. Manufacture of these chemicals requires development of analytical methods for process and quality control. Examples of such compounds that have found industrial application are listed in various tables below.

Automatization of all stages of the analytical process is a trend that can be discerned in the development of modern analytical methods for chemical manufacture, to various extents depending on reliability and cost-benefit considerations. Among the elements of reliability one counts conformity of the accuracy and precision of the method to the specifications of the manufacturing process, stability of the analytical system and closeness to real-time analysis. The latter is a requirement for feedback into automatic processcontrol systems. Since the investment in equipment for automatic online analysis may be high, this is frequently replaced by monitoring a property that is easy and inexpensive to measure and correlating that property with the analyte of interest. Such compromise is usually accompanied by a collection of samples that are sent to the analytical laboratory for determination, possibly at a lower cost.

A different approach is required in biological research, pharmacology, forensic investigations, occupational hygiene and environmental protection. Often one confronts samples that are difficult to deal with because of their small size, unstability, the low concentration

24. Analytical aspects

1045

of analyte or the nature of the matrix. Many advances of modern analysis are concerned with pushing down the limits of detection and quantation (LOD, LOQ) using smaller and smaller samples, frequently in the mM or nM range, with only picomoles or even femtomoles of analyte. These advancements are the result of improved selectivity of reagents and media, development of sensors with increased sensitivity that are backed-up by reliable electronic system and optimization of the analytical methodology. Some advances are concerned with making the analytical equipment cheaper, easier to handle and more time efficient (see, for example, Reference 4).

It should be pointed out that the LOD and LOQ concepts are used rather loosely in the literature and are sometimes interchanged. Furthermore, LOD are given in extensive as well as intensive terms (e.g. mmol vs nM/mL). Except for cases where sample size was reported and a lower limit concentration could be discerned, extensive LOD are given as reported.

The present chapter is subdivided according to the nature of the various analytical methods, emphasizing the importance of chromatography including the various detection methods. Structural analysis is treated only briefly here and is left mostly to other chapters dealing with spectral properties.

III. ELEMENTAL ANALYSIS

Compounds bearing the functional groups of the present chapter are usually analyzed for the characteristic N heteroatom and less frequently for O. In this section some recent advances in the analysis of these heteroatoms are presented. A critical review appeared of the analysis of the nutrient elements C, N, P and Si, and their speciation in environmental waters, including sample collection and preservation, sample preparation and methods for end analysis5.

A. Automatic Organic Elemental Analysis (CHNOS)

1. General

A recent brief review showed the working principles of various automatic analyzers6. A modified account of N and O analysis will be presented here. Today there exist in the market instruments that perform organic elemental analyses in a few minutes. The ease and speed of such analyses enable the use of such instruments for routine analysis. Although some operational details vary from model to model and between one manufacturer and another, all these instruments can be considered as exalted versions of the classical Pregl determination of C and H by conversion to CO2 and H2O, together with Dumas’ method for N by conversion to N2, the calorimetric bomb method for S by conversion to SO2 and SO3 and Schultzes’ method for O by conversion to CO. This is combined with modern electronic control, effective catalysts and instrumental measuring methods such as IR detectors and GC analyzers.

A method for rapid organic C and N analysis in natural particulate materials consists of eliminating carbonates with HCl solution and determining these elements in an automatic analyzer7.

2. Nitrogen

Instruments are available for determination of N alone, CHN, CNS and CHNS. N determination in one of the CHN models involves removal of all nonnitrogenous combustion products, including halogens and various oxides, reduction of N oxides to N2, removal of excess oxygen, dilution with helium and measurement with a thermal conductivity

1046	Jacob Zabicky and Shmuel Bittner

detector (TCD)8. In a simultaneous CHNS analyzer the combustion gases are reduced to a mixture of N2, CO2, H2O and SO2, carried in a helium stream and determined by GC-TCD9.

Automatic Dumas determinations of N in plant tissue were consistently higher than the corresponding Kjeldahl determination in a comparative study. A correlation between both results was proposed10. Significantly higher values were also obtained from a LECO FP428 nitrogen analyzer when comparing the results with those of the Kjeldahl method for the determination of N in various oil-bearing seeds. The automatic analyzer was adopted for routine analysis of these materials11. The same instrument was fitted with a liquid injector for determination of total N in milk. The intense production of steam resulted in poor N recoveries. This was improved by slow injection and filling the combustion tube with CeO2. Results were about 6.7% higher than by the Kjeldahl method12.

A dual-channel analyzer for the determination of N in water was developed, based on chemiluminescence detectors (CLD). One channel is for total dissolved N (TDN) and the other for Nox (e.g. NO2 , NO3 ). The difference between the two channels is taken as organic N. Total N analysis of waste waters takes 2 4 min, in manual or automatic mode; operational range: 10 ppb to 200 ppm N as Nox, 60 ppb to 200 ppm total N and 90 ppb to 200 ppm organic N13.

3. Oxygen

Oxygen elemental analyzers are usually sold as adaptation kits for the CHN analyzers. In one commercial model all the oxygen-containing compounds are converted to CO, which is measured with a nondispersive infrared (NDIR) photometer8. A recent development in GC is the oxygen flame ionization detector (OFID), incorporating a reactor in which the C of organic matter is retained and O appears ultimately as methane and is measured by FID. The OFID exhibits over 105 O-to-C selectivity14.

B. Digestion Methods

Nitrogen in forest soil extracts and surface waters may belong dominantly to the socalled dissolved organic nitrogen (DON), which is difficult to measure by the Kjeldahl method. An accurate, fast, simple and inexpensive alternative is based on persulfate oxidation followed by conductometric measurement of the nitrate ion15. Nitrogen in sediments can be determined by persulfate oxidation in a strongly alkaline environment in a bomb at high temperature and pressure. End analysis of the resulting nitrates is by ion-exchange chromatography (IEC)16.

Determination of DON and dissolved organic phosphorus was carried out in a flow injection analysis (FIA) system by oxidation promoted by UV light, successively in acid and alkaline media. At the 2 40 mM level, recovery was 60 100% for spiked deionized water and 40 80% for seawater17. A method for TDN in water is based on photooxidation of inorganic and organic nitrogen with alkaline peroxodisulfate. The nitrate formed is reduced by Cd to nitrite. The latter participates in diazotation and coupling reactions, followed by spectrophotometric determination at 540 nm. The FIA method is relatively fast and inexpensive; LOD 0.03 mg N/L with linearity up to 3 mg/L18. The alkaline peroxodisulfate digestion of TDN in a bomb may yield nitrate as the sole product. End analysis can be by ion chromatography. The method showed a recovery higher than 90%, relative standard deviation (RSD) 4.62% for urea and ammonium chloride and 3.62% for natural water samples19. Determination of total particulate organic nitrogen (PON) and phosphorus is based on the standard persulfate digestion method at 120 °C, yielding nitrate and phosphate for end analysis. The modification is efficient for cell cultures and natural

24. Analytical aspects

1047

seawater and is suitable for routine analysis in shipboard laboratories20. PON was determined by persulfate oxidation using 0.2 mm Teflon membrane filters. The results obtained for seawater were 20 90% higher than those obtained with the coarser glass fiber filters, so it was concluded that submicron particles contribute significantly to PON21. Possible interferences in the analysis of TDN in seawater by the persulfate oxidation stem from the presence of bromide ions. These are eliminated by reducing the bromate ion product to bromide, oxidizing to bromine and expelling the latter from the solution22.

A review of the Kjeldahl method has appeared23. A Cu catalyst was investigated instead of the standard Hg catalyst for the Kjeldahl determination of N in meat products, according to AOAC Method 928.0824. Microwave drying was demonstrated for rice leaves and did not affect the N analysis25. The presence of organic nitrogen interferes with the determination of ammonium ions in organic fertilizers when ammonia is distilled off from suspensions alkalinized with NaOH. No such interference was noted when MgO was used as the base. The specific ammonium electrode was found to be unsatisfactory for the end analysis of ammonia. The residue left after distilling off ammonia could be used for Kjeldahl determination of organic N26.

Total nitrogen determinations in barley and malt gave slightly higher results by the Dumas than by the Kjeldahl method. The Dumas method was adopted as the reference method by the Analysis Committee of the Institute of Brewing27. Comparison of the results obtained by the Kjeldahl method with those of automatic N analyzers is mentioned in Section III.A.2 above.

Pyrochemiluminescence was adopted by AOAC International, as a method for determination of total N in urine. The reaction of ozone with the products of oxidative pyrolysis is measured with a CLD; average recovery of total N in urine in a collaborative study of twelve laboratories was 99.9% with RSD ranging from 3.66 to 9.57%28.

C. Nitrogen Responsive Detectors for GC

Gas chromatography is idealy suited for identification and determination of individual compounds, but samples with overlapping and coincidental peaks may confuse the analysis. Combinations such as GC-MS or GC-FTIR are now commonplace; however, these instruments may be unwieldy for most routine analyses. In such cases element-specific detectors may be of help, as they greatly simplify complex chromatograms. These detectors have been reviewed6,29,30 including ones that respond specifically to nitrogen-containing species: Alkali flame ionization detector (AFID)31 33, flameless alkali-sensitized detector (FASD)34 38, chemiluminescence detector (CLD)39 42, electrolytic conductivity detector (ELCD)43,44 and electron capture detector (ECD)45 49. A nitrogen-specific chemiluminescence detector (CLND) is based on total conversion of N to NO, which undergoes a chemiluminescent reaction with ozone. This was applied to the analysis of nitrosamines, pesticide residues, food flavoring compounds, pharmaceuticals and petroleum distillates50. A new thermionic ionization chemiluminescence-measuring device is sensitive to S, N and P. In this detector sulfur-containing compounds produce SO and the chemiluminescence produced on mixing this species with O3 is measured. Independent response channels lead to chromatograms for the S channel and for the NP channel51. Recent examples of GC analysis using specific response detectors for N are mentioned also in Sections IV.C and VI.A.

Atrazine (1a) was determined in freeze-dried water samples containing simazine (1b) by GC combined with a nitrogen phosphorus detector (NPD). This method and direct rapid-magnetic particle-based enzyme-linked immunosorbed assay (ELISA) gave comparable results at levels between 0.1 to 5 mg/L of water. A clean-up step before ELISA was advantageous52. Organophosphorus and nitrogen-containing pesticides,

1048	Jacob Zabicky and Shmuel Bittner

EtNH N Cl

(a) R = i-Pr

(b) R = Et

N N

NHR

(1)

e.g. simazine (1b), in ground and drinking water were determined after concentration by solid-phase extraction (SPE) and elution with an organic solvent. Recovery was 75 90% from 1 2.5 L samples containing 0.1 5 mg/L of analytes. GC-NPD and GC-MS in selected-ion monitoring (SIM) mode were compared, the latter being more sensitive; LOD 0.08 0.60 mg/L vs 0.03 0.13 mg/L, respectively53.

2-Methoxy-3-alkylpyrazines (2) were determined in carrots by combining a selective stripping method with GC-NPD. Concentrations of 2a as low as 0.029 ng/g were measured54. Traces of aldicarb (3a) and its metabolites (3b c) were determined in oranges by extraction with aqueous solvents, partitioning with dichloromethane and a combination of reversed phase (RP) HPLC, using a gradient mobile phase, GC-NPD and GC combined with a flame photometric detector (FPD); LOD 0.4, 0.8 and 0.4 ppb for 3a, b and c, respectively55.

N

OMe

(a) R = i-Pr

Me

(a) Y = S

(b) R = i-Bu

MeY

C

CH

N

O2 CNHMe (b) Y = SO

R

(c) R = s-Bu

(c) Y = SO2

N

Me

(2)

(3)

Nitrogen-containing components of gasoline were determined by simulated distillation (a GC procedure) using a CLND56. The effect of SPE was studied on analytical reproducibility in the determination of thirteen drugs by GC-NPD in whole blood. Reproducibility was good as long as limiting factors such as volatility or chromatographic behavior did not interfere57. A study was made of the effectiveness of SPE with a C18 adsorbent for P- and N-containing pesticides, using GC-NPD for the end analysis. Recoveries varied from 0 to 91%, depending on the physicochemical properties of the analyte58.

D. Stable Isotope Analysis

A comparative study was made between determinations of the 15N content of plant and soil samples, using the methods of the International Atomic Energy Agency Laboratories, based on MS, a novel automatic N analyzer coupled to a mass spectrometer and a microprocessor-controlled emission spectrometer. Although the latter instrument is fast, its precision may be insufficient to determine 15N in soil59.

Enrichment of the 15N content has become part of various powerful research techniques. For example, uniform labeling with 15N was used for sequence-specific assignments and secondary structure determination of certain proteins by NMR60 and tracing of complicated processes including the increase of DON in soil61,62.

An inexpensive piston-action ball mill for the rapid preparation of plant and soil material for automated 15N and 13C analysis enables one to process 150 samples per hour to

24. Analytical aspects

1049

particle sizes that are at least 50% under 105 mm. This allows a precision better than 1% for the determination of 15N isotope enrichment in an automated, continuous flow, N and C isotope-ratio mass spectrometer63. A method for purification of nanomole quantities of N prior to determination of the isotope ratio was described, based on the absorption of various impurities on calcium oxide and copper at high temperature64. Problems arose with ammonia diffusion techniques for concentration of low N-content samples, before 15N analysis, such as nonquantitative recovery and isotopic fractionation, to which no solutions were found. Therefore, evaluation of the ammonia diffusion technique for representative sample types and use of standard curves are recommended for overcoming such problems65.

Some elemental analysis methods involve conversion to N2 and a direct method that does not require standards was developed based on the (2,0) band of the second positive system emitted by the N2 molecule in a high-frequency discharge. The band heads of 14N14N and 14N15N molecules were resolved in a monochromator and the peak intensities measured; RSD <4% in the 15N concentration range of 0.36 to 24%66. The precision of these molecular spectroscopy measurements has been limited by the variability of the spectral background. Imaging of the isotopic bandhead region with a diode array allowed making corrections for the spectral background and increasing the analytical precision67.

A study was made of the effects of derivatization on the 13C analysis of amino acid enantiomers. Conventional isotope ratio MS and GC-isotope ratio MS were used. The latter method requires volatilization of the analytes, which was accomplished by introducing O-isopropyl and N-trifluoroacetyl groups, causing a change in the 13C analysis of the original analytes. It was proposed to use a set of known standards for such analyses, which are applied in geological studies68.

IV. AMINES

A. General

Amines, including the amino acids, peptides and proteins, are mentioned in this Section. Tables 1 3 list primary, secondary and tertiary amines of industrial relevance. Compounds

TABLE 1. Examples of environmental, occupational and quality control protocols for industrial primary amines

Compound and CAS registry			Various
number a	Safetyb	Spectrac	protocolsd
Amino group attached to saturated aliphatic carbon
1-Adamantanamine [768-94-5]	117D	I(3)409D, N(1)276C	YD1925000, USP
L-Alanine [56-41-7]	83D	I(1)571B	USP
Amikacine			USP
2-Aminoethanol [141-43-5]	1547B	I(3)423D, N(1)291B	KJ5775000
2-(2-Aminoethylamino)ethanol	168B	I(3)437D, N(1)304C	KJ6300000
[111-41-1]f
1-(2-Aminoethyl)piperazine	172B	I(3)437D, N(1)330C	TK8050000
[140-31-8]f
2-Amino-2-ethyl-1,3-propanediol		I(1)348B
[115-70-8]
2-Aminoheptane [123-82-0]	177C	I(3)374A, N(1)490C	MQ5425000, USP
6-Aminohexanoic acid [60-32-2]	149B	I(1)578D, N(1)247C	MO6300000, USP

(continued overleaf )

1050	Jacob Zabicky and Shmuel Bittner
TABLE 1.	(continued)
Compound and CAS registry				Various
number a		Safetyb	Spectrac	protocolsd
2-Amino-2-methyl-1-propanol		194B	I(3)425D, N(1)294B	UA5950000
[124-68-5]
1-Amino-2-propanol [78-96-6]		215D	I(3)425A, N(1)293B	UA5775000
Amphetamine sulfate [60-13-9] (28)				SI1750000, USP
Amphotericin B [1397-89-3]				BU2625000, USP
Ampicillin [69-53-4]		247A		XH8350000, USP
L-Arginine [74-79-3] (8)		302D	I(1)786A, N(1)658B	CF1934200, USP
Bacampicillin hydrochloride				SH8490000, USP
[37661-08-8]
n-Butylamine [109-73-9]		302D	I(3)364D, N(1)239B	EO2975000
s-Butylamine [13952-84-6;		615B	I(3)368B, N(1)243A	EO3325000
33966-50-6]g
t-Butylamine [65-64-9]		615C	I(3)369B, N(1)244A	EO3330000
Capreomycin sulfate [1405-37-4]e				USP
(R)-(C)-Cycloserine [68-41-7]			I(1)810D, N(1)678C	NY2975000, USP
Cyclohexylamine [108-91-8]		970C	I(3)402A, N(1)270C	GX0700000
L-Cysteine hydrochloride		1000C	I(1)592A, N(1)499B	HA2275000, USP
monohydrate [7048-09-6] (115)
Diethylenetriamine [111-40-0]e,f		1207D	I(1)396A, N(1)266B	IE1225000
L-DOPA [59-92-7]			I(2)257B	AY5600000, USP
Dopamine [62-31-7] (19b)			I(1)1294A, N(1)1098B	UX1092000, USP
Doxorubicin hydrochloride		1499A		Q19295900, USP
[25316-40-9]
Ethylamine [75-04-7]		1569C	I(3)364B, N(1)237D	KH2100000
Ethylenediamine [107-15-3]e		1604B	I(3)374D, N(1)248A	KH8575000, USP
L-Glutamic acid [56-86-0] (34b)		1776A	I(1)590A, N(1)497B	LZ9700000
Glycine [56-40-6]		1786D	I(1)563A, N(1)481A	MB7600000, USP
Histamine phosphate [51-74-1] (6)		1877C		NI5425000, USP
L-Histidine [71-00-1]		1877D	I(2)621D, N(2)493B	MS3070000, USP
L-Isoleucine [73-32-5]		2024A	I(1)575D, N(1)489C	NR4705000, USP
Isopropylamine [75-31-0]		2031B	I(3)368A, N(1)242C	NT8400000
Kanamycin sulfate [133-92-6;				NZ3225000, USP
25389-94-0]e
L-Leucine [61-90-5]		2116D	I(1)575B, N(1)489B	OH2850000, USP
L-Lysine monohydrochloride		2172B	I(1)588B, N(1)495B	OL5650000, USP
[657-27-2] (144)e
L-Methionine [63-68-3]		2232D	I(1)594C, N(1)501B	PD0457000, USP
Methylamine [74-89-5]		2283D	I(3)363D	PF6300000
˛-Methyl-L-DOPA [41372-08-1]			I(2)258D	AY5950000, USP
Natamycin [7681-93-8]		2838C		TK3325000, USP
(š)-Norephedrine hydrochloride		2624C	I(1)1273A, N(1)1079D	DN4200000, USP
[154-41-6] (79)
D-Penicillamine [52-67-5]		2689b	I(1)592C, N(1)500A	YV9425000, USP
DL-Phenylalanine [150-30-1]		2755D	I(2)250C, N(2)248B
L-Phenylalanine [63-91-2] (45)		2756B	I(2)251A, N(2)248C	AY7535000, USP
2-Phenylethylamine [64-04-0] (33)		2741C	I(3)1164C, N(1)1075C	SG8750000
Pimaricin [7681-93-8]g		2838C		TK3325000
Primaquine phosphate (148)		2942C	I(2)864B, N(2)741A	VA9660000, USP
[63-45-6]f